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Lv Y, Chang J, Zhang W, Dong H, Chen S, Wang X, Zhao A, Zhang S, Alam MA, Wang S, Du C, Xu J, Wang W, Xu P. Improving Microbial Cell Factory Performance by Engineering SAM Availability. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:3846-3871. [PMID: 38372640 DOI: 10.1021/acs.jafc.3c09561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Methylated natural products are widely spread in nature. S-Adenosyl-l-methionine (SAM) is the secondary abundant cofactor and the primary methyl donor, which confer natural products with structural and functional diversification. The increasing demand for SAM-dependent natural products (SdNPs) has motivated the development of microbial cell factories (MCFs) for sustainable and efficient SdNP production. Insufficient and unsustainable SAM availability hinders the improvement of SdNP MCF performance. From the perspective of developing MCF, this review summarized recent understanding of de novo SAM biosynthesis and its regulatory mechanism. SAM is just the methyl mediator but not the original methyl source. Effective and sustainable methyl source supply is critical for efficient SdNP production. We compared and discussed the innate and relatively less explored alternative methyl sources and identified the one involving cheap one-carbon compound as more promising. The SAM biosynthesis is synergistically regulated on multilevels and is tightly connected with ATP and NAD(P)H pools. We also covered the recent advancement of metabolic engineering in improving intracellular SAM availability and SdNP production. Dynamic regulation is a promising strategy to achieve accurate and dynamic fine-tuning of intracellular SAM pool size. Finally, we discussed the design and engineering constraints underlying construction of SAM-responsive genetic circuits and envisioned their future applications in developing SdNP MCFs.
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Affiliation(s)
- Yongkun Lv
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Jinmian Chang
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Weiping Zhang
- Bloomage Biotechnology Corporation Limited, 678 Tianchen Street, Jinan, Shandong 250101, China
| | - Hanyu Dong
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Song Chen
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Xian Wang
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Anqi Zhao
- School of Life Sciences, Zhengzhou University, No. 100 Science Avenue, Zhengzhou, 450001, China
| | - Shen Zhang
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Md Asraful Alam
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Shilei Wang
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Chaojun Du
- Nanyang Research Institute of Zhengzhou University, Nanyang Institute of Technology, No. 80 Changjiang Road, Nanyang 473004, China
| | - Jingliang Xu
- School of Chemical Engineering, Zhengzhou University, No. 100 Science Avenue, Zhengzhou 450001, China
- National Key Laboratory of Biobased Transportation Fuel Technology, No. 100 Science Avenue, Zhengzhou 450001, China
| | - Weigao Wang
- Department of Chemical Engineering, Stanford University, 443 Via Ortega, Palo Alto, California 94305, United States
| | - Peng Xu
- Department of Chemical Engineering, Guangdong Technion-Israel Institute of Technology (GTIIT), Shantou, Guangdong 515063, China
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2
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Ozturk TN, Coumoundouros C, Culham DE, Wood JM. Structural Determinants and Functional Significance of Dimerization for Osmosensing Transporter ProP in Escherichia coli. Biochemistry 2023; 62:118-133. [PMID: 36516499 DOI: 10.1021/acs.biochem.2c00393] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Osmosensing transporter ProP forestalls cellular dehydration by detecting environments with high osmotic pressure and mediating the accumulation of organic osmolytes by bacterial cells. It is composed of 12 transmembrane helices with cytoplasmic N- and C-termini. In Escherichia coli, dimers form when the C-terminal domains of ProP molecules form homodimeric, antiparallel, α-helical coiled coils. No dominant negative effect was detected when inactive and active ProP molecules formed heterodimers in vivo. Purification of ProP in detergent dodecylmaltoside yielded monomers, which were functional after reconstitution in proteoliposomes. With other evidence, this suggests that ProP monomers function independently whether in the monomeric or dimeric state. Amino acid replacements that disrupted or reversed the coiled coil did not prevent in vivo dimerization of ProP detected with a bacterial two-hybrid system. Maleimide labeling detected no osmolality-dependent variation in the reactivities of cysteine residues introduced to transmembrane helix (TM) XII. In contrast, coarse-grained molecular dynamic simulations detected deformation of the lipid around TMs III and VI, on the lipid-exposed protein surface opposite to TM XII. This suggests that the dimer interface of ProP includes the surfaces of TMs III and VI, not of TM XII as previously suggested by crosslinking data. Homology modeling suggested that coiled-coil formation and dimerization via such an interface are not mutually exclusive. In previous work, alterations to the C-terminal coiled coil blocked co-localization of ProP with phospholipid cardiolipin at E. coli cell poles. Thus, dimerization may contribute to ProP targeting, adjust its lipid environment, and hence indirectly modify its osmotic stress response.
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Affiliation(s)
- Tugba N Ozturk
- Department of Biochemistry and Molecular Biophysics, Washington University in Saint Louis, Saint Louis, Missouri63110, United States.,Theoretical Molecular Biophysics Laboratory, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland20814, United States
| | - Chelsea Coumoundouros
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, CanadaN1G 2 W1
| | - Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, CanadaN1G 2 W1
| | - Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, CanadaN1G 2 W1
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3
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Proline Transport and Growth Changes in Proline Transport Mutants of Staphylococcus aureus. Microorganisms 2022; 10:microorganisms10101888. [DOI: 10.3390/microorganisms10101888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/19/2022] [Accepted: 09/21/2022] [Indexed: 11/16/2022] Open
Abstract
Staphylococcus aureus is a major cause of skin/soft tissue infections and more serious infections in humans. The species usually requires the importation of proline to be able to survive. Previous work has shown that single mutations in genes that encode for proline transporters affect the ability of S. aureus to survive in vitro and in vivo. To better understand proline transport in S. aureus, double and triple gene mutant strains were created that targeted the opuD, proP, and putP genes. Single gene mutants had some effect on proline transport, whereas double mutants exhibited significantly lower proline transport. An opuD prop putP triple gene mutant displayed the lowest proline transport under low- and high-affinity conditions. To assess growth differences caused by the mutations, the same mutants were grown in brain heart infusion (BHI) broth and defined staphylococcal medium (DSM) with various concentrations of proline. The triple mutant did not grow in DSM with a low concentration of proline and grew poorly in both DSM with a high proline concentration and BHI broth. These results show that S. aureus has multiple mechanisms to import proline into the cell and knocking out three of the main proline transporters significantly hinders S. aureus growth.
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Kumar S, Paul D, Bhushan B, Wakchaure GC, Meena KK, Shouche Y. Traversing the "Omic" landscape of microbial halotolerance for key molecular processes and new insights. Crit Rev Microbiol 2020; 46:631-653. [PMID: 32991226 DOI: 10.1080/1040841x.2020.1819770] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Post-2005, the biology of the salt afflicted habitats is predominantly studied employing high throughput "Omic" approaches comprising metagenomics, transcriptomics, metatranscriptomics, metabolomics, and proteomics. Such "Omic-based" studies have deciphered the unfamiliar details about microbial salt-stress biology. The MAGs (Metagenome-assembled genomes) of uncultured halophilic microbial lineages such as Nanohaloarchaea and haloalkaliphilic members within CPR (Candidate Phyla Radiation) have been reconstructed from diverse hypersaline habitats. The study of MAGs of such uncultured halophilic microbial lineages has unveiled the genomic basis of salt stress tolerance in "yet to culture" microbial lineages. Furthermore, functional metagenomic approaches have been used to decipher the novel genes from uncultured microbes and their possible role in microbial salt-stress tolerance. The present review focuses on the new insights into microbial salt-stress biology gained through different "Omic" approaches. This review also summarizes the key molecular processes that underlie microbial salt-stress response, and their role in microbial salt-stress tolerance has been confirmed at more than one "Omic" levels.
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Affiliation(s)
- Satish Kumar
- National Centre for Microbial Resource, National Centre for Cell Science, Pune, India.,ICAR-National Institute of Abiotic Stress Management, Baramati, Pune, India
| | - Dhiraj Paul
- National Centre for Microbial Resource, National Centre for Cell Science, Pune, India
| | - Bharat Bhushan
- ICAR-National Bureau of Plant Genetic Resources, New Delhi, India
| | - G C Wakchaure
- ICAR-National Institute of Abiotic Stress Management, Baramati, Pune, India
| | - Kamlesh K Meena
- ICAR-National Institute of Abiotic Stress Management, Baramati, Pune, India
| | - Yogesh Shouche
- National Centre for Microbial Resource, National Centre for Cell Science, Pune, India
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Ozturk TN, Culham DE, Tempelhagen L, Wood JM, Lamoureux G. Salt-Dependent Interactions between the C-Terminal Domain of Osmoregulatory Transporter ProP of Escherichia coli and the Lipid Membrane. J Phys Chem B 2020; 124:8209-8220. [PMID: 32838524 DOI: 10.1021/acs.jpcb.0c03935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Osmosensing transporter ProP detects the increase in cytoplasmic cation concentration associated with osmotically induced cell dehydration and mediates osmolyte uptake into bacteria. ProP is a 12-transmembrane helix protein with an α-helical, cytoplasmic C-terminal domain (CTD) linked to transmembrane helix XII (TM XII). It has been proposed that the CTD helix associates with the anionic membrane surface to lock ProP in an inactive conformation and that the release of the CTD may activate ProP. To investigate this possible activation mechanism, we have built and simulated a structural model in which the CTD was anchored to the membrane by TM XII and the CTD helix was associated with the membrane surface. Molecular dynamics simulations showed specific intrapeptide salt bridges forming when the CTD associated with the membrane. Experiments supported the presence of the salt bridge Lys447-Asp455 and suggested a role for these residues in osmosensing. Simulations performed at different salt concentrations showed weakened CTD-lipid interactions at 0.25 M KCl and gradual stiffening of the membrane with increasing salinity. These results suggest that salt cations may affect CTD release and activate ProP by increasing the order of membrane phospholipids.
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Affiliation(s)
- Tugba N Ozturk
- Department of Physics, Concordia University, Montreal QC H4B 1R6, Canada.,Centre for Research in Molecular Modeling, Concordia University, Montreal, Quebec H4B 1R6, Canada
| | - Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Laura Tempelhagen
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Guillaume Lamoureux
- Centre for Research in Molecular Modeling, Concordia University, Montreal, Quebec H4B 1R6, Canada.,Department of Chemistry and Center for Computational and Integrative Biology, Rutgers University, Camden, New Jersey 08102, United States
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6
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Abstract
For bacteria, maintaining higher internal solute concentrations than those present in the environment allows cells to take up water. As a result, survival is challenging in high-osmolarity environments. To investigate how bacteria adapt to high-osmolarity environments, we maintained Escherichia coli in a variety of high-osmolarity solutions for hundreds of generations. We found that the evolved populations adopted different strategies to improve their growth rates depending on the osmotic passaging condition, either generally adapting to high-osmolarity conditions or better metabolizing the osmolyte as a carbon source. Single-cell imaging demonstrated that enhanced fitness was coupled to faster growth, and metagenomic sequencing revealed mutations that reflected growth trade-offs across osmolarities. Our study demonstrated the utility of long-term evolution experiments for probing adaptation occurring during environmental stress. Bacteria must maintain a cytosolic osmolarity higher than that of their environment in order to take up water. High-osmolarity environments therefore present formidable stress to bacteria. To explore the evolutionary mechanisms by which bacteria adapt to high-osmolarity environments, we selected Escherichia coli in media with a variety of osmolytes and concentrations for 250 generations. Adaptation was osmolyte dependent, with sorbitol stress generally resulting in increased fitness under conditions with higher osmolarity, while selection in high concentrations of proline resulted in increased fitness specifically on proline. Consistent with these phenotypes, sequencing of the evolved populations showed that passaging in proline resulted in specific mutations in an associated metabolic pathway that increased the ability to utilize proline for growth, while evolution in sorbitol resulted in mutations in many different genes that generally resulted in improved growth under high-osmolarity conditions at the expense of growth at low osmolarity. High osmolarity decreased the growth rate but increased the mean cell volume compared with growth on proline as the sole carbon source, demonstrating that osmolarity-induced changes in growth rate and cell size follow an orthogonal relationship from the classical Growth Law relating cell size and nutrient quality. Isolates from a sorbitol-evolved population that captured the likely temporal sequence of mutations revealed by metagenomic sequencing demonstrated a trade-off between growth at high osmolarity and growth at low osmolarity. Our report highlights the utility of experimental evolution for dissecting complex cellular networks and environmental interactions, particularly in the case of behaviors that can involve both specific and general metabolic stressors.
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7
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Hu X, Li D, Qiao Y, Song Q, Guan Z, Qiu K, Cao J, Huang L. Salt tolerance mechanism of a hydrocarbon-degrading strain: Salt tolerance mediated by accumulated betaine in cells. JOURNAL OF HAZARDOUS MATERIALS 2020; 392:122326. [PMID: 32092654 DOI: 10.1016/j.jhazmat.2020.122326] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 02/15/2020] [Accepted: 02/15/2020] [Indexed: 06/10/2023]
Abstract
Rhodococcus sp. HX-2 could degrade diesel oil in the presence of 1%-10 % NaCl. The compatible solute betaine accumulated in cells with increasing NaCl concentration, and this was found to be the main mechanism of resistance of HX-2 to high salt concentration. Exogenously added betaine can be transported into cells, which improved cell growth and the percentage degradation of diesel oil in the presence of high [NaCl] in solution and in soil. Scanning electron microscopy data suggested that addition of exogenous betaine facilitated salt tolerance by stimulating exopolysaccharide production. Fourier-transform infrared analysis suggested that surface hydroxyl, amide and phosphate groups may be related to tolerance of high-salt environments. Four betaine transporter-encoding genes (H0, H1, H3, H5) and the betaine producer gene betB were induced in Rhodococcus sp. HX-2 by NaCl stress. The maximal induction of H0, H1, H3 and H5 transcription depended on high salinity plus the presence of betaine. These results demonstrate that salt tolerance is mediated by accumulated betaine in Rhodococcus sp. HX-2 cells, and the potential of this strain for application in bioremediation of hydrocarbon pollution in saline environments.
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Affiliation(s)
- Xin Hu
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China
| | - Dahui Li
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China
| | - Yue Qiao
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China
| | - Qianqian Song
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China
| | - Zhiguo Guan
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China
| | - Kaixuan Qiu
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China
| | - Jiachang Cao
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China
| | - Lei Huang
- College of Chemistry and Chemical Engineering, Tianjin Key Laboratory of Organic Solar Cells and Photochemical Conversion, Tianjin Key Laboratory of Drug Targeting and Bioimaging, Tianjin University of Technology, Tianjin, 300384, China.
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8
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Distinct metabolic states of a cell guide alternate fates of mutational buffering through altered proteostasis. Nat Commun 2020; 11:2926. [PMID: 32522991 PMCID: PMC7286901 DOI: 10.1038/s41467-020-16804-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 05/27/2020] [Indexed: 12/29/2022] Open
Abstract
Metabolic changes alter the cellular milieu; can this also change intracellular protein folding? Since proteostasis can modulate mutational buffering, if change in metabolism has the ability to change protein folding, arguably, it should also alter mutational buffering. Here we find that altered cellular metabolic states in E. coli buffer distinct mutations on model proteins. Buffered-mutants have folding problems in vivo and are differently chaperoned in different metabolic states. Notably, this assistance is dependent upon the metabolites and not on the increase in canonical chaperone machineries. Being able to reconstitute the folding assistance afforded by metabolites in vitro, we propose that changes in metabolite concentrations have the potential to alter protein folding capacity. Collectively, we unravel that the metabolite pools are bona fide members of proteostasis and aid in mutational buffering. Given the plasticity in cellular metabolism, we posit that metabolic alterations may play an important role in cellular proteostasis. Changes in osmotic homeostasis alter metabolites and therefore chemical milieu of the cells. Here, the authors show that altering metabolites in E. coli also change the cellular capacity for buffering mutations that impair protein folding and influences proteostasis irrespective of molecular chaperones
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9
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Tempelhagen L, Ayer A, Culham DE, Stocker R, Wood JM. Cultivation at high osmotic pressure confers ubiquinone 8–independent protection of respiration on Escherichia coli. J Biol Chem 2020. [DOI: 10.1016/s0021-9258(17)49909-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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10
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Tempelhagen L, Ayer A, Culham DE, Stocker R, Wood JM. Cultivation at high osmotic pressure confers ubiquinone 8-independent protection of respiration on Escherichia coli. J Biol Chem 2019; 295:981-993. [PMID: 31826918 DOI: 10.1074/jbc.ra119.011549] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 12/11/2019] [Indexed: 11/06/2022] Open
Abstract
Ubiquinone 8 (coenzyme Q8 or Q8) mediates electron transfer within the aerobic respiratory chain, mitigates oxidative stress, and contributes to gene expression in Escherichia coli In addition, Q8 was proposed to confer bacterial osmotolerance by accumulating during growth at high osmotic pressure and altering membrane stability. The osmolyte trehalose and membrane lipid cardiolipin accumulate in E. coli cells cultivated at high osmotic pressure. Here, Q8 deficiency impaired E. coli growth at low osmotic pressure and rendered growth osmotically sensitive. The Q8 deficiency impeded cellular O2 uptake and also inhibited the activities of two proton symporters, the osmosensing transporter ProP and the lactose transporter LacY. Q8 supplementation decreased membrane fluidity in liposomes, but did not affect ProP activity in proteoliposomes, which is respiration-independent. Liposomes and proteoliposomes prepared with E. coli lipids were used for these experiments. Similar oxygen uptake rates were observed for bacteria cultivated at low and high osmotic pressures. In contrast, respiration was dramatically inhibited when bacteria grown at the same low osmotic pressure were shifted to high osmotic pressure. Thus, respiration was restored during prolonged growth of E. coli at high osmotic pressure. Of note, bacteria cultivated at low and high osmotic pressures had similar Q8 concentrations. The protection of respiration was neither diminished by cardiolipin deficiency nor conferred by trehalose overproduction during growth at low osmotic pressure, but rather might be achieved by Q8-independent respiratory chain remodeling. We conclude that osmotolerance is conferred through Q8-independent protection of respiration, not by altering physical properties of the membrane.
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Affiliation(s)
- Laura Tempelhagen
- Department of Molecular and Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, Ontario N1G 2W1, Canada
| | - Anita Ayer
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia.,St. Vincent's Clinical School, University of New South Wales Medicine, Kensington, New South Wales 2050, Australia
| | - Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, Ontario N1G 2W1, Canada
| | - Roland Stocker
- Vascular Biology Division, Victor Chang Cardiac Research Institute, Darlinghurst, New South Wales 2010, Australia.,St. Vincent's Clinical School, University of New South Wales Medicine, Kensington, New South Wales 2050, Australia
| | - Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, Ontario N1G 2W1, Canada
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Calatrava V, Hom EFY, Llamas Á, Fernández E, Galván A. OK, thanks! A new mutualism between Chlamydomonas and methylobacteria facilitates growth on amino acids and peptides. FEMS Microbiol Lett 2019; 365:4828328. [PMID: 29385570 DOI: 10.1093/femsle/fny021] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Accepted: 01/24/2018] [Indexed: 12/15/2022] Open
Abstract
Nitrogen is a key nutrient for land plants and phytoplankton in terrestrial and aquatic ecosystems. The model alga Chlamydomonas reinhardtii can grow efficiently on several inorganic nitrogen sources (e.g. ammonium, nitrate, nitrite) as well as many amino acids. In this study, we show that Chlamydomonas is unable to use proline, hydroxyproline and peptides that contain these amino acids. However, we discovered that algal growth on these substrates is supported in association with Methylobacterium spp., and that a mutualistic carbon-nitrogen metabolic exchange between Chlamydomonas and Methylobacterium spp. is established. Specifically, the mineralization of these amino acids and peptides by Methylobacterium spp. produces ammonium that can be assimilated by Chlamydomonas, and CO2 photosynthetically fixed by Chlamydomonas yields glycerol that can be assimilated by Methylobacterium. As Chlamydomonas is an algal ancestor to land plants and Methylobacterium is a plant growth-promoting bacterium, this new model of mutualism may facilitate insights into the ecology and evolution of plant-bacterial interactions and design principles of synthetic ecology.
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Affiliation(s)
- Victoria Calatrava
- Departamento de Bioquímica y Biología Molecular, Campus de Rabanales y Campus Internacional de Excelencia Agroalimentario (CeiA3), Edif. Severo Ochoa, Universidad de Córdoba, Córdoba, 14071-Córdoba, Spain
| | - Erik F Y Hom
- Department of Biology, University of Mississippi, University, MS 38677, USA
| | - Ángel Llamas
- Departamento de Bioquímica y Biología Molecular, Campus de Rabanales y Campus Internacional de Excelencia Agroalimentario (CeiA3), Edif. Severo Ochoa, Universidad de Córdoba, Córdoba, 14071-Córdoba, Spain
| | - Emilio Fernández
- Departamento de Bioquímica y Biología Molecular, Campus de Rabanales y Campus Internacional de Excelencia Agroalimentario (CeiA3), Edif. Severo Ochoa, Universidad de Córdoba, Córdoba, 14071-Córdoba, Spain
| | - Aurora Galván
- Departamento de Bioquímica y Biología Molecular, Campus de Rabanales y Campus Internacional de Excelencia Agroalimentario (CeiA3), Edif. Severo Ochoa, Universidad de Córdoba, Córdoba, 14071-Córdoba, Spain
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12
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Jechalke S, Schierstaedt J, Becker M, Flemer B, Grosch R, Smalla K, Schikora A. Salmonella Establishment in Agricultural Soil and Colonization of Crop Plants Depend on Soil Type and Plant Species. Front Microbiol 2019; 10:967. [PMID: 31156568 PMCID: PMC6529577 DOI: 10.3389/fmicb.2019.00967] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 04/16/2019] [Indexed: 12/20/2022] Open
Abstract
Human pathogenic bacteria, such as Salmonella enterica, are able to colonize crop plants. So far, not much is known about biotic and abiotic factors influencing this colonization in field soil. This understanding, however, is imperative for the provision of safe fresh produce to the consumer. In this study, we investigated the effects of soil type, organic fertilization, plant species and the way of Salmonella entry into the plant production system, on the survival of S. enterica in soil as well as the colonization of plants. The selected S. enterica serovar Typhimurium strain 14028s, S. Typhimurium strain LT2 and S. Senftenberg were able to persist in soil for several weeks. Salmonella's persistence in soil was prolonged in loamy, if compared to sandy soil, and when applied together with organic fertilizer. The leaves of lettuce and corn salad were colonized by S. enterica providing evidence for internalization from the soil via the root. Colonization rates were affected by soil type, plant species and S. enterica strain. Overall, S. enterica was detected in leaves of 0.5-0.9% of the plants, while lettuce was more frequently colonized than corn salad. Plants grown in sandy soil were more often colonized than plants grown in loamy soil. After spray inoculation, S. enterica could be detected on and in leaves for several weeks by cultivation-depending methods, confirmed by confocal microscopy using GFP-labeled S. Typhimurium 14028s. On the one hand, transcriptome data from S. Typhimurium 14028s assessed in response to lettuce medium or lettuce root exudates showed an upregulation of genes associated with biofilm formation and virulence. On the other hand, lettuce inoculated with S. Typhimurium 14028s showed a strong upregulation of genes associated with plant immune response and genes related to stress response. In summary, these results showed that organic fertilizers can increase the persistence of Salmonella in soil and that soil type and plant species play a crucial role in the interactions between human pathogens and crop plants. This understanding is therefore a starting point for new strategies to provide safe food for the consumer.
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Affiliation(s)
- Sven Jechalke
- Institute for Phytopathology, Justus Liebig University Giessen, Gießen, Germany
| | - Jasper Schierstaedt
- Leibniz Institute of Vegetable and Ornamental Crops, Plant-Microbe Systems, Großbeeren, Germany
| | - Marlies Becker
- Federal Research Centre for Cultivated Plants, Julius Kühn-Institut (JKI), Institute for Epidemiology and Pathogen Diagnostics, Braunschweig, Germany
| | - Burkhardt Flemer
- Leibniz Institute of Vegetable and Ornamental Crops, Plant-Microbe Systems, Großbeeren, Germany
| | - Rita Grosch
- Leibniz Institute of Vegetable and Ornamental Crops, Plant-Microbe Systems, Großbeeren, Germany
| | - Kornelia Smalla
- Federal Research Centre for Cultivated Plants, Julius Kühn-Institut (JKI), Institute for Epidemiology and Pathogen Diagnostics, Braunschweig, Germany
| | - Adam Schikora
- Federal Research Centre for Cultivated Plants, Julius Kühn-Institut (JKI), Institute for Epidemiology and Pathogen Diagnostics, Braunschweig, Germany
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Christgen SL, Becker DF. Role of Proline in Pathogen and Host Interactions. Antioxid Redox Signal 2019; 30:683-709. [PMID: 29241353 PMCID: PMC6338583 DOI: 10.1089/ars.2017.7335] [Citation(s) in RCA: 65] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 10/26/2017] [Accepted: 11/14/2017] [Indexed: 01/20/2023]
Abstract
SIGNIFICANCE Proline metabolism has complex roles in a variety of biological processes, including cell signaling, stress protection, and energy production. Proline also contributes to the pathogenesis of various disease-causing organisms. Understanding the mechanisms of how pathogens utilize proline is important for developing new strategies against infectious diseases. Recent Advances: The ability of pathogens to acquire amino acids is critical during infection. Besides protein biosynthesis, some amino acids, such as proline, serve as a carbon, nitrogen, or energy source in bacterial and protozoa pathogens. The role of proline during infection depends on the physiology of the host/pathogen interactions. Some pathogens rely on proline as a critical respiratory substrate, whereas others exploit proline for stress protection. CRITICAL ISSUES Disruption of proline metabolism and uptake has been shown to significantly attenuate virulence of certain pathogens, whereas in other pathogens the importance of proline during infection is not known. Inhibiting proline metabolism and transport may be a useful therapeutic strategy against some pathogens. Developing specific inhibitors to avoid off-target effects in the host, however, will be challenging. Also, potential treatments that target proline metabolism should consider the impact on intracellular levels of Δ1-pyrroline-5-carboxylate, a metabolite intermediate that can have opposing effects on pathogenesis. FUTURE DIRECTIONS Further characterization of how proline metabolism is regulated during infection would provide new insights into the role of proline in pathogenesis. Biochemical and structural characterization of proline metabolic enzymes from different pathogens could lead to new tools for exploring proline metabolism during infection and possibly new therapeutic compounds.
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Affiliation(s)
- Shelbi L. Christgen
- Department of Biochemistry, Redox Biology Center, University of Nebraska−Lincoln, Lincoln, Nebraska
| | - Donald F. Becker
- Department of Biochemistry, Redox Biology Center, University of Nebraska−Lincoln, Lincoln, Nebraska
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14
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Culham DE, Marom D, Boutin R, Garner J, Ozturk TN, Sahtout N, Tempelhagen L, Lamoureux G, Wood JM. Dual Role of the C-Terminal Domain in Osmosensing by Bacterial Osmolyte Transporter ProP. Biophys J 2018; 115:2152-2166. [PMID: 30448037 PMCID: PMC6289098 DOI: 10.1016/j.bpj.2018.10.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 10/22/2018] [Accepted: 10/29/2018] [Indexed: 11/23/2022] Open
Abstract
ProP is a member of the major facilitator superfamily, a proton-osmolyte symporter, and an osmosensing transporter. ProP proteins share extended cytoplasmic carboxyl terminal domains (CTDs) implicated in osmosensing. The CTDs of the best characterized, group A ProP orthologs, terminate in sequences that form intermolecular, antiparallel α-helical coiled coils (e.g., ProPEc, from Escherichia coli). Group B orthologs lack that feature (e.g., ProPXc, from Xanthomonas campestris). ProPXc was expressed and characterized in E. coli to further elucidate the role of the coiled coil in osmosensing. The activity of ProPXc was a sigmoid function of the osmolality in cells and proteoliposomes. ProPEc and ProPXc attained similar activities at the same expression level in E. coli. ProPEc transports proline and glycine betaine with comparable high affinities at low osmolality. In contrast, proline weakly inhibited high-affinity glycine-betaine uptake via ProPXc. The KM for proline uptake via ProPEc increases dramatically with the osmolality. The KM for glycine-betaine uptake via ProPXc did not. Thus, ProPXc is an osmosensing transporter, and the C-terminal coiled coil is not essential for osmosensing. The role of CTD-membrane interaction in osmosensing was examined further. As for ProPEc, the ProPXc CTD co-sedimented with liposomes comprising E. coli phospholipid. Molecular dynamics simulations illustrated association of the monomeric ProPEc CTD with the membrane surface. Comparison with the available NMR structure for the homodimeric coiled coil formed by the ProPEc-CTD suggested that membrane association and homodimeric coiled-coil formation by that peptide are mutually exclusive. The membrane fluidity in liposomes comprising E. coli phospholipid decreased with increasing osmolality in the range relevant for ProP activation. These data support the proposal that ProP activates as cellular dehydration increases cytoplasmic cation concentration, releasing the CTD from the membrane surface. For group A orthologs, this also favors α-helical coiled-coil formation that stabilizes the transporter in an active form.
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Affiliation(s)
- Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - David Marom
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Rebecca Boutin
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Jennifer Garner
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada; Centre for Research in Molecular Modeling, Concordia University, Montréal, Québec, Canada
| | - Tugba Nur Ozturk
- Centre for Research in Molecular Modeling, Concordia University, Montréal, Québec, Canada; Department of Physics, Concordia University, Montréal, Québec, Canada
| | - Naheda Sahtout
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Laura Tempelhagen
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Guillaume Lamoureux
- Centre for Research in Molecular Modeling, Concordia University, Montréal, Québec, Canada; Department of Physics, Concordia University, Montréal, Québec, Canada; Department of Chemistry and Biochemistry, Concordia University, Montréal, Québec, Canada
| | - Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada.
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15
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Romantsov T, Gonzalez K, Sahtout N, Culham DE, Coumoundouros C, Garner J, Kerr CH, Chang L, Turner RJ, Wood JM. Cardiolipin synthase A colocalizes with cardiolipin and osmosensing transporter ProP at the poles of Escherichia coli cells. Mol Microbiol 2018; 107:623-638. [PMID: 29280215 DOI: 10.1111/mmi.13904] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 11/09/2017] [Accepted: 12/19/2017] [Indexed: 11/29/2022]
Abstract
Osmosensing by transporter ProP is modulated by its cardiolipin (CL)-dependent concentration at the poles of Escherichia coli cells. Other contributors to this phenomenon were sought with the BACterial Two-Hybrid System (BACTH). The BACTH-tagged variants T18-ProP and T25-ProP retained ProP function and localization. Their interaction confirmed the ProP homo-dimerization previously established by protein crosslinking. YdhP, YjbJ and ClsA were prominent among the putative ProP interactors identified by the BACTH system. The functions of YdhP and YjbJ are unknown, although YjbJ is an abundant, osmotically induced, soluble protein. ClsA (CL Synthase A) had been shown to determine ProP localization by mediating CL synthesis. Unlike a deletion of clsA, deletion of ydhP or yjbJ had no effect on ProP localization or function. All three proteins were concentrated at the cell poles, but only ClsA localization was CL-dependent. ClsA was shown to be N-terminally processed and membrane-anchored, with dual, cytoplasmic, catalytic domains. Active site amino acid replacements (H224A plus H404A) inactivated ClsA and compromised ProP localization. YdhP and YjbJ may be ClsA effectors, and interactions of YdhP, YjbJ and ClsA with ProP may reflect their colocalization at the cell poles. Targeted CL synthesis may contribute to the polar localization of CL, ClsA and ProP.
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Affiliation(s)
- Tatyana Romantsov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Karen Gonzalez
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Naheda Sahtout
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Chelsea Coumoundouros
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Jennifer Garner
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Craig H Kerr
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Limei Chang
- Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
| | - Raymond J Turner
- Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada
| | - Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
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16
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Wholly Rickettsia! Reconstructed Metabolic Profile of the Quintessential Bacterial Parasite of Eukaryotic Cells. mBio 2017; 8:mBio.00859-17. [PMID: 28951473 PMCID: PMC5615194 DOI: 10.1128/mbio.00859-17] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Reductive genome evolution has purged many metabolic pathways from obligate intracellular Rickettsia (Alphaproteobacteria; Rickettsiaceae). While some aspects of host-dependent rickettsial metabolism have been characterized, the array of host-acquired metabolites and their cognate transporters remains unknown. This dearth of information has thwarted efforts to obtain an axenic Rickettsia culture, a major impediment to conventional genetic approaches. Using phylogenomics and computational pathway analysis, we reconstructed the Rickettsia metabolic and transport network, identifying 51 host-acquired metabolites (only 21 previously characterized) needed to compensate for degraded biosynthesis pathways. In the absence of glycolysis and the pentose phosphate pathway, cell envelope glycoconjugates are synthesized from three imported host sugars, with a range of additional host-acquired metabolites fueling the tricarboxylic acid cycle. Fatty acid and glycerophospholipid pathways also initiate from host precursors, and import of both isoprenes and terpenoids is required for the synthesis of ubiquinone and the lipid carrier of lipid I and O-antigen. Unlike metabolite-provisioning bacterial symbionts of arthropods, rickettsiae cannot synthesize B vitamins or most other cofactors, accentuating their parasitic nature. Six biosynthesis pathways contain holes (missing enzymes); similar patterns in taxonomically diverse bacteria suggest alternative enzymes that await discovery. A paucity of characterized and predicted transporters emphasizes the knowledge gap concerning how rickettsiae import host metabolites, some of which are large and not known to be transported by bacteria. Collectively, our reconstructed metabolic network offers clues to how rickettsiae hijack host metabolic pathways. This blueprint for growth determinants is an important step toward the design of axenic media to rescue rickettsiae from the eukaryotic cell. A hallmark of obligate intracellular bacteria is the tradeoff of metabolic genes for the ability to acquire host metabolites. For species of Rickettsia, arthropod-borne parasites with the potential to cause serious human disease, the range of pilfered host metabolites is unknown. This information is critical for dissociating rickettsiae from eukaryotic cells to facilitate rickettsial genetic manipulation. In this study, we reconstructed the Rickettsia metabolic network and identified 51 host metabolites required to compensate patchwork Rickettsia biosynthesis pathways. Remarkably, some metabolites are not known to be transported by any bacteria, and overall, few cognate transporters were identified. Several pathways contain missing enzymes, yet similar pathways in unrelated bacteria indicate convergence and possible novel enzymes awaiting characterization. Our work illuminates the parasitic nature by which rickettsiae hijack host metabolism to counterbalance numerous disintegrated biosynthesis pathways that have arisen through evolution within the eukaryotic cell. This metabolic blueprint reveals what a Rickettsia axenic medium might entail.
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17
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Fuentealba P, Aros C, Latorre Y, Martínez I, Marshall S, Ferrer P, Albiol J, Altamirano C. Genome-scale metabolic reconstruction for the insidious bacterium in aquaculture Piscirickettsia salmonis. BIORESOURCE TECHNOLOGY 2017; 223:105-114. [PMID: 27788423 DOI: 10.1016/j.biortech.2016.10.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 10/04/2016] [Accepted: 10/11/2016] [Indexed: 06/06/2023]
Abstract
Piscirickettsia salmonis is a fish bacterium that causes the disease piscirickettsiosis in salmonids. This pathology is partially controlled by vaccines. The lack of knowledge has hindered its culture on laboratory and industrial scale. The study describes the metabolic phenotype of P. salmonis in culture. This study presents the first genome-scale model (iPF215) of the LF-89 strain of P. salmonis, describing the central metabolic pathway, biosynthesis and molecule degradation and transport mechanisms. The model was adjusted with experiment data, allowing the identification of the capacities that were not predicted by the automatic annotation of the genome sequences. The iPF215 model is comprised of 417 metabolites, 445 reactions and 215 genes, was used to reproduce the growth of P. salmonis (μmax 0.052±0.005h-1). The metabolic reconstruction of the P. salmonis LF-89 strain obtained in this research provides a baseline that describes the metabolic capacities of the bacterium and is the basis for developing improvements to its cultivation for vaccine formulation.
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Affiliation(s)
- Pablo Fuentealba
- Doctorado en Biotecnología, Pontificia Universidad Católica de Valparaíso - Universidad Federico Santa María, Valparaíso, Chile; Laboratorio of Cultivos Celulares, Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Camila Aros
- Laboratorio of Cultivos Celulares, Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Yesenia Latorre
- Laboratorio of Cultivos Celulares, Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Irene Martínez
- Laboratorio of Cultivos Celulares, Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile
| | - Sergio Marshall
- Laboratorio of Genética e Inmunología Molecular, Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Curauma, Chile
| | - Pau Ferrer
- Laboratorio de Biología de Sistemas, Departamento Ingeniería Química, Universidad Autónoma de Barcelona, Barcelona, Spain
| | - Joan Albiol
- Laboratorio de Biología de Sistemas, Departamento Ingeniería Química, Universidad Autónoma de Barcelona, Barcelona, Spain
| | - Claudia Altamirano
- Laboratorio of Cultivos Celulares, Escuela de Ingeniería Bioquímica, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile; CREAS CONICYT Regional GORE Valparaíso R0GI1004, Av. Universidad, Curauma, Chile.
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18
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Romantsov T, Culham DE, Caplan T, Garner J, Hodges RS, Wood JM. ProP‐ProP and ProP‐phospholipid interactions determine the subcellular distribution of osmosensing transporter ProP inEscherichia coli. Mol Microbiol 2016; 103:469-482. [DOI: 10.1111/mmi.13569] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/27/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Tatyana Romantsov
- Department of Molecular and Cellular BiologyUniversity of GuelphGuelph ON CanadaN1G2W1
| | - Doreen E. Culham
- Department of Molecular and Cellular BiologyUniversity of GuelphGuelph ON CanadaN1G2W1
| | - Tavia Caplan
- Department of Molecular and Cellular BiologyUniversity of GuelphGuelph ON CanadaN1G2W1
| | - Jennifer Garner
- Department of Molecular and Cellular BiologyUniversity of GuelphGuelph ON CanadaN1G2W1
| | - Robert S. Hodges
- Department of Biochemistry and Molecular GeneticsUniversity of Colorado Denver, School of MedicineP.O. Box 6511, Mail Stop 8101Aurora CO80045, USA
| | - Janet M. Wood
- Department of Molecular and Cellular BiologyUniversity of GuelphGuelph ON CanadaN1G2W1
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19
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Schwan WR, Wetzel KJ. Osmolyte transport in Staphylococcus aureus and the role in pathogenesis. World J Clin Infect Dis 2016; 6:22-27. [PMID: 27429907 PMCID: PMC4943863 DOI: 10.5495/wjcid.v6.i2.22] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Revised: 02/18/2016] [Accepted: 04/11/2016] [Indexed: 02/06/2023] Open
Abstract
Osmolyte transport is a pivotal part of bacterial life, particularly in high salt environments. Several low and high affinity osmolyte transport systems have been identified in various bacterial species. A lot of research has centered on characterizing the osmolyte transport systems of Gram-negative bacteria, but less has been done to characterize the same transport systems in Gram-positive bacteria. This review will focus on the previous work that has been done to understand the osmolyte transport systems in the species Staphylococcus aureus and how these transporters may serve dual functions in allowing the bacteria to survive and grow in a variety of environments, including on the surface or within humans or other animals.
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20
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Zou H, Chen N, Shi M, Xian M, Song Y, Liu J. The metabolism and biotechnological application of betaine in microorganism. Appl Microbiol Biotechnol 2016; 100:3865-76. [PMID: 27005411 DOI: 10.1007/s00253-016-7462-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 11/29/2022]
Abstract
Glycine betaine (betaine) is widely distributed in nature and can be found in many microorganisms, including bacteria, archaea, and fungi. Due to its particular functions, many microorganisms utilize betaine as a functional chemical and have evolved different metabolic pathways for the biosynthesis and catabolism of betaine. As in animals and plants, the principle role of betaine is to protect microbial cells against drought, osmotic stress, and temperature stress. In addition, the role of betaine in methyl group metabolism has been observed in a variety of microorganisms. Recent studies have shown that betaine supplementation can improve the performance of microbial strains used for the fermentation of lactate, ethanol, lysine, pyruvate, and vitamin B12, during which betaine can act as stress protectant or methyl donor for the biosynthesis of structurally complex compounds. In this review, we summarize the transport, synthesis, catabolism, and functions of betaine in microorganisms and discuss potential engineering strategies that employ betaine as a methyl donor for the biosynthesis of complex secondary metabolites such as a variety of vitamins, coenzymes, and antibiotics. In conclusion, the biocompatibility, C/N ratio, abundance, and comprehensive metabolic information of betaine collectively indicate that this molecule has great potential for broad applications in microbial biotechnology.
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Affiliation(s)
- Huibin Zou
- College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, 266042, China. .,CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
| | - Ningning Chen
- College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, 266042, China
| | - Mengxun Shi
- College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, 266042, China
| | - Mo Xian
- CAS Key Laboratory of Bio-based Materials, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
| | - Yimin Song
- College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, 266042, China
| | - Junhong Liu
- College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, 266042, China
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21
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Culham DE, Shkel IA, Record MT, Wood JM. Contributions of Coulombic and Hofmeister Effects to the Osmotic Activation of Escherichia coli Transporter ProP. Biochemistry 2016; 55:1301-13. [PMID: 26871755 DOI: 10.1021/acs.biochem.5b01169] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Osmosensing transporters mediate osmolyte accumulation to forestall cellular dehydration as the extracellular osmolality increases. ProP is a bacterial osmolyte-H(+) symporter, a major facilitator superfamily member, and a paradigm for osmosensing. ProP activity is a sigmoid function of the osmolality. It is determined by the osmolality, not the magnitude or direction of the osmotic shift, in cells and salt-loaded proteoliposomes. The activation threshold varies directly with the proportion of anionic phospholipid in cells and proteoliposomes. The osmosensory mechanism was probed by varying the salt composition and concentration outside and inside proteoliposomes. Data analysis was based on the hypothesis that the fraction of maximal transporter activity at a particular luminal salt concentration reflects the proportion of ProP molecules in an active conformation. ProP attained the same activity at the same osmolality when diverse, membrane-impermeant salts were added to the external medium. Contributions of Coulombic and/or Hofmeister salt effects to ProP activation were examined by varying the luminal salt cation (K(+) and Na(+)) and anion (chloride, phosphate, and sulfate) composition and then systematically increasing the luminal salt concentration by increasing the external osmolality. ProP activity increased with the sixth power of the univalent cation concentration, independent of the type of anion. This indicates that salt activation of ProP is a Coulombic, cation effect resulting from salt cation accumulation and not site-specific cation binding. Possible origins of this Coulombic effect include folding or assembly of anionic cytoplasmic ProP domains, an increase in local membrane surface charge density, and/or the juxtaposition of anionic protein and membrane surfaces during activation.
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Affiliation(s)
- Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, ON N1G 2W1, Canada
| | - Irina A Shkel
- Departments of Biochemistry and Chemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
| | - M Thomas Record
- Departments of Biochemistry and Chemistry, University of Wisconsin , Madison, Wisconsin 53706, United States
| | - Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph , Guelph, ON N1G 2W1, Canada
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22
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Abstract
Escherichia coli and Salmonella encounter osmotic pressure variations in natural environments that include host tissues, food, soil, and water. Osmotic stress causes water to flow into or out of cells, changing their structure, physics, and chemistry in ways that perturb cell functions. E. coli and Salmonella limit osmotically induced water fluxes by accumulating and releasing electrolytes and small organic solutes, some denoted compatible solutes because they accumulate to high levels without disturbing cell functions. Osmotic upshifts inhibit membrane-based energy transduction and macromolecule synthesis while activating existing osmoregulatory systems and specifically inducing osmoregulatory genes. The osmoregulatory response depends on the availability of osmoprotectants (exogenous organic compounds that can be taken up to become compatible solutes). Without osmoprotectants, K+ accumulates with counterion glutamate, and compatible solute trehalose is synthesized. Available osmoprotectants are taken up via transporters ProP, ProU, BetT, and BetU. The resulting compatible solute accumulation attenuates the K+ glutamate response and more effectively restores cell hydration and growth. Osmotic downshifts abruptly increase turgor pressure and strain the cytoplasmic membrane. Mechanosensitive channels like MscS and MscL open to allow nonspecific solute efflux and forestall cell lysis. Research frontiers include (i) the osmoadaptive remodeling of cell structure, (ii) the mechanisms by which osmotic stress alters gene expression, (iii) the mechanisms by which transporters and channels detect and respond to osmotic pressure changes, (iv) the coordination of osmoregulatory programs and selection of available osmoprotectants, and (v) the roles played by osmoregulatory mechanisms as E. coli and Salmonella survive or thrive in their natural environments.
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23
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Lang S, Cressatti M, Mendoza KE, Coumoundouros CN, Plater SM, Culham DE, Kimber MS, Wood JM. YehZYXW of Escherichia coli Is a Low-Affinity, Non-Osmoregulatory Betaine-Specific ABC Transporter. Biochemistry 2015; 54:5735-47. [DOI: 10.1021/acs.biochem.5b00274] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shenhui Lang
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
| | - Marisa Cressatti
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
| | - Kris E. Mendoza
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
| | - Chelsea N. Coumoundouros
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
| | - Samantha M. Plater
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
| | - Doreen E. Culham
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
| | - Matthew S. Kimber
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
| | - Janet M. Wood
- Department
of Molecular and
Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, ON N1G
2W1, Canada
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24
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Stability of the osmoregulated promoter-derived proP mRNA is posttranscriptionally regulated by RNase III in Escherichia coli. J Bacteriol 2015; 197:1297-305. [PMID: 25645556 DOI: 10.1128/jb.02460-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
UNLABELLED The enzymatic activity of Escherichia coli endo-RNase III determines the stability of a subgroup of mRNA species, including bdm, betT, and proU, whose protein products are associated with the cellular response to osmotic stress. Here, we report that the stability of proP mRNA, which encodes a transporter of osmoprotectants, is controlled by RNase III in response to osmotic stress. We observed that steady-state levels of proP mRNA and ProP protein are inversely correlated with cellular RNase III activity and, in turn, affect the proline uptake capacity of the cell. In vitro and in vivo analyses of proP mRNA revealed RNase III cleavage sites in a stem-loop within the 5' untranslated region present only in proP mRNA species synthesized from the osmoregulated P1 promoter. Introduction of nucleotide substitutions in the cleavage site identified inhibited the ribonucleolytic activity of RNase III on proP mRNA, increasing the steady-state levels and half-life of the mRNA. In addition, decreased RNase III activity coincided with a significant increase in both the half-life and abundance of proP mRNA under hyperosmotic stress conditions. Analysis of the RNA bound to RNase III via in vivo cross-linking and immunoprecipitation indicated that this phenomenon is related to the decreased RNA binding capacity of RNase III. Our findings suggest the existence of an RNase III-mediated osmoregulatory network that rapidly balances the expression levels of factors associated with the cellular response to osmotic stress in E. coli. IMPORTANCE Our results demonstrate that RNase III activity on proP mRNA degradation is downregulated in Escherichia coli cells under osmotic stress. In addition, we show that the downregulation of RNase III activity is associated with decreased RNA binding capacity of RNase III under hyperosmotic conditions. In particular, our findings demonstrate a link between osmotic stress and RNase III activity, underscoring the growing importance of posttranscriptional regulation in modulating rapid physiological adjustment to environmental changes.
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25
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Feeney A, Johnston CD, Lucid A, O'Mahony J, Coffey A, Lucey B, Sleator RD. The role of the Cronobacter sakazakii ProP C-terminal coiled coil domain in osmotolerance. Gut Pathog 2014; 6:46. [PMID: 25530808 PMCID: PMC4272814 DOI: 10.1186/s13099-014-0046-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 11/25/2014] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND We investigate the role of the C-terminal coiled coil of the secondary proline porter ProP in contributing to Cronobacter sakazakii osmotolerance. FINDINGS The extended C-terminal domain of ProP1 (encoded by ESA_02131) was spliced onto the truncated C-terminal end of ProP2 (encoded by ESA_01706); creating a chimeric protein (ProPc) which exhibits increased osmotolerance relative to the wild type. CONCLUSIONS It appears that the C-terminal coiled coil domain tunes ProP at low osmolality, whereas ProP transporters lacking the coiled coil domain are more active at a higher osmolality range.
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Affiliation(s)
- Audrey Feeney
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork Ireland
| | - Christopher D Johnston
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork Ireland
| | - Alan Lucid
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork Ireland
| | - Jim O'Mahony
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork Ireland
| | - Aidan Coffey
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork Ireland
| | - Brigid Lucey
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork Ireland
| | - Roy D Sleator
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork Ireland
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26
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Feeney A, Johnston CD, Govender R, O’Mahony J, Coffey A, Sleator RD. Analysis of the role of the Cronobacter sakazakii ProP homologues in osmotolerance. Gut Pathog 2014; 6:15. [PMID: 24910715 PMCID: PMC4047261 DOI: 10.1186/1757-4749-6-15] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 05/14/2014] [Indexed: 01/06/2023] Open
Abstract
Bacteria respond to elevated osmolality by the accumulation of a range of low molecular weight molecules, known as compatible solutes (owing to their compatibility with the cells' normal physiology at high internal concentrations). The neonatal pathogen Cronobacter sakazakii is uniquely osmotolerant, surviving in powdered infant formula (PIF) which typically has a water activity (aw) of 0.2 - inhospitable to most micro-organisms. Mortality rates of up to 80% in infected infants have been recorded making C. sakazakii a serious cause for concern. In silico analysis of the C. sakazakii BAA-894 genome revealed seven copies of the osmolyte uptake system ProP. Herein, we test the physiological role of each of these homologues following heterologous expression against an osmosensitive Escherichia coli host.
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Affiliation(s)
- Audrey Feeney
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland
| | - Christopher D Johnston
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland
| | - Rodney Govender
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland
| | - Jim O’Mahony
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland
| | - Aidan Coffey
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland
| | - Roy D Sleator
- Department of Biological Sciences, Cork Institute of Technology, Rossa Avenue, Bishopstown, Cork, Ireland
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27
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Culligan EP, Marchesi JR, Hill C, Sleator RD. Combined metagenomic and phenomic approaches identify a novel salt tolerance gene from the human gut microbiome. Front Microbiol 2014; 5:189. [PMID: 24808895 PMCID: PMC4010731 DOI: 10.3389/fmicb.2014.00189] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 04/07/2014] [Indexed: 12/13/2022] Open
Abstract
In the current study, a number of salt-tolerant clones previously isolated from a human gut metagenomic library were screened using Phenotype MicroArray (PM) technology to assess their functional capacity. PM's can be used to study gene function, pathogenicity, metabolic capacity and identify drug targets using a series of specialized microtitre plate assays, where each well of the microtitre plate contains a different set of conditions and tests a different phenotype. Cellular respiration is monitored colorimetrically by the reduction of a tetrazolium dye. One clone, SMG 9, was found to be positive for utilization/transport of L-carnitine (a well-characterized osmoprotectant) in the presence of 6% w/v sodium chloride (NaCl). Subsequent experiments revealed a significant growth advantage in minimal media containing NaCl and L-carnitine. Fosmid sequencing revealed putative candidate genes responsible for the phenotype. Subsequent cloning of two genes did not replicate the L-carnitine-associated phenotype, although one of the genes, a σ54-dependent transcriptional regulator, did confer salt tolerance to Escherichia coli when expressed in isolation. The original clone, SMG 9, was subsequently found to have lost the original observed phenotype upon further investigation. Nevertheless, this study demonstrates the usefulness of a phenomic approach to assign a functional role to metagenome-derived clones.
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Affiliation(s)
- Eamonn P Culligan
- Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork Cork, Ireland ; School of Microbiology, University College Cork Cork, Ireland
| | - Julian R Marchesi
- Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork Cork, Ireland ; Cardiff School of Biosciences, Cardiff University Cardiff, UK ; Department of Surgery and Cancer, Centre for Digestive and Gut Health, Imperial College London London, UK
| | - Colin Hill
- Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork Cork, Ireland ; School of Microbiology, University College Cork Cork, Ireland
| | - Roy D Sleator
- Alimentary Pharmabiotic Centre, Biosciences Institute, University College Cork Cork, Ireland ; Department of Biological Sciences, Cork Institute of Technology Cork, Ireland
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28
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Culham DE, Meinecke M, Wood JM. Impacts of the osmolality and the lumenal ionic strength on osmosensory transporter ProP in proteoliposomes. J Biol Chem 2012; 287:27813-22. [PMID: 22740696 DOI: 10.1074/jbc.m112.387936] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
H(+) symporter ProP serves as a paradigm for the study of osmosensing. ProP attains the same activity at the same osmolality when the medium outside cells or proteoliposomes is supplemented with diverse, membrane-impermeant solutes. The osmosensory mechanism of ProP has been probed by varying the solvent within membrane vesicles and proteoliposomes. ProP activation was not ion specific, did not require K(+), and could be elicited by large, uncharged solutes polyethylene glycols (PEGS). We hypothesized that ProP is an ionic strength sensor and lumenal macromolecules activate ProP by altering ion activities. The attainable range of lumenal ionic strength was expanded by lowering the phosphate concentration within proteoliposomes. ProP activity at high osmolality, but not the osmolality, yielding half-maximal activity (Π(1/2)/RT), decreased with the lumenal phosphate concentration. This was attributed to acidification of the proteoliposome lumen due to H(+)-proline symport. The ionic strength yielding half-maximal ProP activity was more anion-dependent than Π(1/2)/RT for proteoliposomes loaded with citrate, sulfate, phosphate, chloride, or iodide. The anion effects followed the Hofmeister series. Lumenal bovine serum albumin (BSA) lowered the lumenal ionic strength at which ProP became active. Osmolality measurements documented the non-idealities of solutions including potassium phosphate and other solutes. The impacts of PEGS and BSA on ion activities did not account for their impacts on ProP activity. The effects of the tested solutes on ProP appear to be non-coulombic in nature. They may arise from effects of preferential interactions and macromolecular crowding on the membrane or on ProP.
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Affiliation(s)
- Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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29
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Culligan EP, Sleator RD, Marchesi JR, Hill C. Functional metagenomics reveals novel salt tolerance loci from the human gut microbiome. ISME JOURNAL 2012; 6:1916-25. [PMID: 22534607 DOI: 10.1038/ismej.2012.38] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Metagenomics is a powerful tool that allows for the culture-independent analysis of complex microbial communities. One of the most complex and dense microbial ecosystems known is that of the human distal colon, with cell densities reaching up to 10(12) per gram of faeces. With the majority of species as yet uncultured, there are an enormous number of novel genes awaiting discovery. In the current study, we conducted a functional screen of a metagenomic library of the human gut microbiota for potential salt-tolerant clones. Using transposon mutagenesis, three genes were identified from a single clone exhibiting high levels of identity to a species from the genus Collinsella (closest relative being Collinsella aerofaciens) (COLAER_01955, COLAER_01957 and COLAER_01981), a high G+C, Gram-positive member of the Actinobacteria commonly found in the human gut. The encoded proteins exhibit a strong similarity to GalE, MurB and MazG. Furthermore, pyrosequencing and bioinformatic analysis of two additional fosmid clones revealed the presence of an additional galE and mazG gene, with the highest level of genetic identity to Akkermansia muciniphila and Eggerthella sp. YY7918, respectively. Cloning and heterologous expression of the genes in the osmosensitive strain, Escherichia coli MKH13, resulted in increased salt tolerance of the transformed cells. It is hoped that the identification of atypical salt tolerance genes will help to further elucidate novel salt tolerance mechanisms, and will assist our increased understanding how resident bacteria cope with the osmolarity of the gastrointestinal tract.
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Affiliation(s)
- Eamonn P Culligan
- Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
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30
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Gasper BJ, McCreight JC, Banschbach K, Bustion A, Davis C, Divecha R, Donoho M, Elmore AG, Garrison CM, Glenn S, Goeman DC, Haby M, Hooks T, Korman AM, Kowal J, Kuschke S, Mellencamp JE, Meyer M, Myers AN, Nichols MF, Pfeifer A, Porucznik A, Qu X, Ramos-Miller M, Reed RR, Sagintayev A, Singel JM, Smith A, Valle ME, Venderley A, Weber CA, Zaffino AJ, Csonka LN, Gardner SM. Isolation and preliminary characterization of amino acid substitution mutations that increase the activity of the osmoregulated ProP protein of Salmonella enterica serovar Typhimurium. DNA Cell Biol 2012; 31:956-67. [PMID: 22360681 DOI: 10.1089/dna.2011.1510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In Enterobacteriaceae, the ProP protein, which takes up proline and glycine betaine, is subject to a post-translational control mechanism that increases its activity at high osmolarity. In order to investigate the osmoregulatory mechanism of the Salmonella enterica ProP, we devised a positive selection for mutations that conferred increased activity on this protein at low osmolarity. The selection involved the isolation of mutations in a proline auxotroph that resulted in increased accumulation of proline via the ProP system in the presence of glycine betaine, which is a competitive inhibitor of proline uptake by this permease. This selection was performed by first-year undergraduates in two semesters of a research-based laboratory course. The students generated sixteen mutations resulting in six different single amino acids substitutions. They determined the effects of the mutations on the growth rates of the cells in media of high and low osmolarity in the presence of low concentrations of proline or glycine betaine. Furthermore, they identified the mutations by DNA sequencing and displayed the mutated amino acids on a putative three-dimensional structure of the protein. This analysis suggested that all six amino acid substitutions are residues in trans-membrane helices that have been proposed to contribute to the formation of the transport pore, and, thus, may affect the substrate binding site of the protein.
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Affiliation(s)
- Brittany J Gasper
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-1392, USA
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31
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A Rickettsia genome overrun by mobile genetic elements provides insight into the acquisition of genes characteristic of an obligate intracellular lifestyle. J Bacteriol 2011; 194:376-94. [PMID: 22056929 DOI: 10.1128/jb.06244-11] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We present the draft genome for the Rickettsia endosymbiont of Ixodes scapularis (REIS), a symbiont of the deer tick vector of Lyme disease in North America. Among Rickettsia species (Alphaproteobacteria: Rickettsiales), REIS has the largest genome sequenced to date (>2 Mb) and contains 2,309 genes across the chromosome and four plasmids (pREIS1 to pREIS4). The most remarkable finding within the REIS genome is the extraordinary proliferation of mobile genetic elements (MGEs), which contributes to a limited synteny with other Rickettsia genomes. In particular, an integrative conjugative element named RAGE (for Rickettsiales amplified genetic element), previously identified in scrub typhus rickettsiae (Orientia tsutsugamushi) genomes, is present on both the REIS chromosome and plasmids. Unlike the pseudogene-laden RAGEs of O. tsutsugamushi, REIS encodes nine conserved RAGEs that include F-like type IV secretion systems similar to that of the tra genes encoded in the Rickettsia bellii and R. massiliae genomes. An unparalleled abundance of encoded transposases (>650) relative to genome size, together with the RAGEs and other MGEs, comprise ~35% of the total genome, making REIS one of the most plastic and repetitive bacterial genomes sequenced to date. We present evidence that conserved rickettsial genes associated with an intracellular lifestyle were acquired via MGEs, especially the RAGE, through a continuum of genomic invasions. Robust phylogeny estimation suggests REIS is ancestral to the virulent spotted fever group of rickettsiae. As REIS is not known to invade vertebrate cells and has no known pathogenic effects on I. scapularis, its genome sequence provides insight on the origin of mechanisms of rickettsial pathogenicity.
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32
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Conformational changes of the betaine transporter BetP from Corynebacterium glutamicum studied by pulse EPR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:359-66. [PMID: 22051018 DOI: 10.1016/j.bbamem.2011.10.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 10/13/2011] [Accepted: 10/18/2011] [Indexed: 10/15/2022]
Abstract
The betaine transporter BetP from Corynebacterium glutamicum is activated by hyperosmotic stress critically depending on the presence and integrity of its sensory C-terminal domain. The conformational properties of the trimeric BetP reconstituted in liposomes in the inactive state and during osmotic activation were investigated by site-directed spin labeling and electron paramagnetic resonance (EPR) spectroscopy. Comparison of intra- and intermolecular inter spin distance distributions obtained by double electron-electron resonance (DEER) EPR with the crystal structure of BetP by means of a rotamer library analysis suggest a rotation of BetP protomers within the trimer by about 15° as compared to the X-ray structure. Furthermore, we observed conformational changes upon activation of BetP, which are reflected in changes of the distances between positions 545 and 589 of different protomers in the trimer. Introduction of proline at positions 550 and 572, both leading to BetP variants with a permanent (low level) transport activity, caused changes of the DEER data similar to those observed for the activated and inactivated state, respectively. This indicates that not only displacements of the C-terminal domain in general but also concomitant interactions of its primary structure with surrounding protein domains and/or lipids are crucial for the activity regulation of BetP.
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33
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Stincone A, Daudi N, Rahman AS, Antczak P, Henderson I, Cole J, Johnson MD, Lund P, Falciani F. A systems biology approach sheds new light on Escherichia coli acid resistance. Nucleic Acids Res 2011; 39:7512-28. [PMID: 21690099 PMCID: PMC3177180 DOI: 10.1093/nar/gkr338] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 04/20/2011] [Accepted: 04/25/2011] [Indexed: 11/16/2022] Open
Abstract
In order to develop an infection, diarrhogenic Escherichia coli has to pass through the stomach, where the pH can be as low as 1. Mechanisms that enable E. coli to survive in low pH are thus potentially relevant for pathogenicity. Four acid response systems involved in reducing the concentration of intracellular protons have been identified so far. However, it is still unclear to what extent the regulation of other important cellular functions may be required for survival in acid conditions. Here, we have combined molecular and phenotypic analysis of wild-type and mutant strains with computational network inference to identify molecular pathways underlying E. coli response to mild and strong acid conditions. The interpretative model we have developed led to the hypothesis that a complex transcriptional programme, dependent on the two-component system regulator OmpR and involving a switch between aerobic and anaerobic metabolism, may be key for survival. Experimental validation has shown that the OmpR is responsible for controlling a sizeable component of the transcriptional programme to acid exposure. Moreover, we found that a ΔompR strain was unable to mount any transcriptional response to acid exposure and had one of the strongest acid sensitive phenotype observed.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Francesco Falciani
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
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34
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Wetzel KJ, Bjorge D, Schwan WR. Mutational and transcriptional analyses of the Staphylococcus aureus low-affinity proline transporter OpuD during in vitro growth and infection of murine tissues. ACTA ACUST UNITED AC 2011; 61:346-55. [PMID: 21231964 DOI: 10.1111/j.1574-695x.2011.00781.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Staphylococcus aureus continues to be a major health problem. This species' requirement for proline and proline transport from the extracellular environment is not well understood. Here, we identify a S. aureus low-affinity proline transport gene (opuD) with homology to the OpuD protein of Bacillus subtilis. Mutation of the opuD gene caused a significant decline in proline uptake under low-affinity conditions as compared with wild type, but the opuD mutant strain showed no significant attenuation in a murine abscess model of infection. The S. aureus opuD gene was transcriptionally activated during growth in moderate osmolarity media with high levels of proline or glycine betaine independent of SigB. In murine abscesses, the opuD gene was activated at a later time point, whereas the opuD expression dropped over the course of an 18-h period within murine urinary tracts. Transcriptional regulation of opuD in S. aureus appears to be coordinated within this species when grown in moderate to high NaCl environments, but the level of extracellular proline had a marked effect on expression of this proline transport gene. The differential regulation of proline transport genes in S. aureus may be an adaptation for life in a variety of environments, including survival within the human body.
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Affiliation(s)
- Keith J Wetzel
- Department of Microbiology, University of Wisconsin-La Crosse, La Crosse, WI, USA
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35
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Keates RAB, Culham DE, Vernikovska YI, Zuiani AJ, Boggs JM, Wood JM. Transmembrane helix I and periplasmic loop 1 of Escherichia coli ProP are involved in osmosensing and osmoprotectant transport. Biochemistry 2010; 49:8847-56. [PMID: 20828170 DOI: 10.1021/bi101281f] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Osmoregulatory transporters stimulate bacterial growth by mediating osmoprotectant uptake in response to increasing osmotic pressure. The ProP protein of Escherichia coli transports proline and other osmoprotectants. Like LacY, ProP is a member of the major facilitator superfamily and a H(+)-solute symporter. ProP is regulated by osmotic pressure via a membrane potential-dependent mechanism. A homology model predicts that ionizable and polar residues, highly conserved among ProP homologues, cluster deep within the N-terminal helix bundle of ProP. Chemical labeling of introduced cysteine (Cys) residues supported the homology model by confirming the predicted positions of transmembrane helix I (TMI) and periplasmic loop 1. Replacements of residues in the putative polar cluster impaired or altered ProP function, suggesting that they are important for osmosensing and may interact with the transport substrates. Asn34, Glu37, Phe41, Tyr44, and Ala48 line the most polar face of TMI; Tyr44 is on the periplasmic side of the putative polar cluster, and Ala59 is in periplasmic loop 1. The N-ethylmaleimide reactivities of Cys introduced at positions 41, 44, 48, and 59 increased with osmotic pressure, whereas the reactivities of those at cytoplasm-proximal positions 34 and 37 did not. Replacements of polar cluster residues that blocked transport also affected the NEM reactivity of Cys44 and its osmolality dependence. This report and previous work suggest that conformational changes associated with osmosensing may shift the equilibria between outward- and inward-facing transport pathway intermediates.
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Affiliation(s)
- Robert A B Keates
- Department of Molecular and Cellular Biology, University of Guelph, 488 Gordon Street, Guelph, Ontario, Canada
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36
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Identification, source, and metabolism of N-ethylglutamate in Escherichia coli. J Bacteriol 2010; 192:5437-40. [PMID: 20709899 DOI: 10.1128/jb.00721-10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
N-Ethylglutamate (NEG) was detected in Escherichia coli BL21 cells grown on LB broth, and it was found to occur at a concentration of ∼4 mM in these cells under these conditions. The same cells grown on M9 glucose medium contained no detectable amount of NEG. Analysis of the LB broth showed the presence of NEG, a compound never before reported as a natural product. Isotope dilution analysis showed that it occurred at a concentration of 160 μM in LB broth. Analyses of yeast extract and tryptone, the organic components of LB broth, both showed the presence NEG. It was demonstrated that NEG can be generated during the autolysis of the yeast used in the preparation of the yeast extract. Growth of these E. coli cells in LB broth prepared in deuterated water showed no incorporation of deuterium into NEG, demonstrating that E. coli cells did not generate the NEG. Cell growth rates were not affected by the addition of 5 mM NEG to either LB or M9 glucose medium. l-[ethyl-(2)H(4)]NEG was found to be readily incorporated into the cells and metabolized by the cells. From these results, it was concluded that all of the NEG present in the cells was taken up from the medium. NEG could serve as the sole nitrogen source for E. coli when grown on M9 glucose medium in the presence of glucose but could not serve as the sole carbon source on M9 medium in the absence of glucose.
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37
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Lambert C, Erdmann A, Eikmanns M, Kramer R. Triggering Glutamate Excretion in Corynebacterium glutamicum by Modulating the Membrane State with Local Anesthetics and Osmotic Gradients. Appl Environ Microbiol 2010; 61:4334-42. [PMID: 16535186 PMCID: PMC1388651 DOI: 10.1128/aem.61.12.4334-4342.1995] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Corynebacterium glutamicum can be triggered to excrete glutamate by the addition of local anesthetics, particularly tetracaine. Glutamate efflux is a carrier-mediated process and not due to unspecific membrane permeabilization. The concentration of local anesthetics triggering optimum excretion depended on the type of anesthetic and varied, ranging from 0.1 (chlorpromazine), 1.3 (tetracaine), and 2.6 mM (butacaine) to 15 mM (benzocaine), in close resemblance to the order of efficiency in anesthetic effect. The onset of glutamate excretion was not correlated to a change in the viscosity or fluidity of the membrane, as measured by electron spin resonance spectroscopy, nor was it related to an action of the anesthetic as an uncoupler. Tetracaine-triggered glutamate excretion was sensitive to changes in the transmembrane osmotic gradient, although an osmotic gradient alone could not trigger glutamate excretion. Tetracaine-triggered glutamate efflux was inhibited by an external rise in osmolality and stimulated by a corresponding decrease. The effects of osmotic gradients and the addition of local anesthetics on glutamate excretion were mutually exchangeable, indicating similar modes of action. We suggest that this common principle is a change in the membrane strain. C. glutamicum cells which excrete glutamate without manipulation of the membrane, e.g., biotin-limited cells or glutamate production mutants, were not stimulated by the addition of tetracaine.
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38
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Crawford JM, Kontnik R, Clardy J. Regulating alternative lifestyles in entomopathogenic bacteria. Curr Biol 2010; 20:69-74. [PMID: 20022247 DOI: 10.1016/j.cub.2009.10.059] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 10/16/2009] [Accepted: 10/20/2009] [Indexed: 02/01/2023]
Abstract
Bacteria belonging to the genera Photorhabdus and Xenorhabdus participate in a trilateral symbiosis in which they enable their nematode hosts to parasitize insect larvae. The bacteria switch from persisting peacefully in a nematode's digestive tract to a lifestyle in which pathways to produce insecticidal toxins, degrading enzymes to digest the insect for consumption, and antibiotics to ward off bacterial and fungal competitors are activated. This study addresses three questions: (1) What molecular signal triggers antibiotic production in the bacteria? (2) What small molecules are regulated by the signal? And (3), how do the bacteria recognize the signal? Differential metabolomic profiling in Photorhabdus luminescens TT01 and Xenorhabdus nematophila revealed that L-proline in the insect's hemolymph initiates a metabolic shift. Small molecules known to be crucial for virulence and antibiosis in addition to previously unknown metabolites are dramatically upregulated by L-proline, linking the recognition of host environment to bacterial metabolic regulation. To identify the L-proline-induced signaling pathway, we deleted the proline transporters putP and proU in P. luminescens TT01. Studies of these strains support a model in which acquisition of L-proline both regulates the metabolic shift and maintains the bacterial proton motive force that ultimately regulates the downstream bacterial pathways affecting virulence and antibiotic production.
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Affiliation(s)
- Jason M Crawford
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
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39
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Protein localization in Escherichia coli cells: comparison of the cytoplasmic membrane proteins ProP, LacY, ProW, AqpZ, MscS, and MscL. J Bacteriol 2009; 192:912-24. [PMID: 20008071 DOI: 10.1128/jb.00967-09] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Fluorescence microscopy has revealed that the phospholipid cardiolipin (CL) and FlAsH-labeled transporters ProP and LacY are concentrated at the poles of Escherichia coli cells. The proportion of CL among E. coli phospholipids can be varied in vivo as it is decreased by cls mutations and it increases with the osmolality of the growth medium. In this report we compare the localization of CL, ProP, and LacY with that of other cytoplasmic membrane proteins. The proportion of cells in which FlAsH-labeled membrane proteins were concentrated at the cell poles was determined as a function of protein expression level and CL content. Each tagged protein was expressed from a pBAD24-derived plasmid; tagged ProP was also expressed from the chromosome. The osmosensory transporter ProP and the mechanosensitive channel MscS concentrated at the poles at frequencies correlated with the cellular CL content. The lactose transporter LacY was found at the poles at a high and CL-independent frequency. ProW (a component of the osmoregulatory transporter ProU), AqpZ (an aquaporin), and MscL (a mechanosensitive channel) were concentrated at the poles in a minority of cells, and this polar localization was CL independent. The frequency of polar localization was independent of induction (at arabinose concentrations up to 1 mM) for proteins encoded by pBAD24-derived plasmids. Complementation studies showed that ProW, AqpZ, MscS, and MscL remained functional after introduction of the FlAsH tag (CCPGCC). These data suggest that CL-dependent polar localization in E. coli cells is not a general characteristic of transporters, channels, or osmoregulatory proteins. Polar localization can be frequent and CL independent (as observed for LacY), frequent and CL dependent (as observed for ProP and MscS), or infrequent (as observed for AqpZ, ProW, and MscL).
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Boroujerdi AFB, Vizcaino MI, Meyers A, Pollock EC, Huynh SL, Schock TB, Morris PJ, Bearden DW. NMR-based microbial metabolomics and the temperature-dependent coral pathogen Vibrio coralliilyticus. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:7658-7664. [PMID: 19921875 DOI: 10.1021/es901675w] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Coral bleaching occurs when the symbioses between coral animals and their zooxanthellae is disrupted, either as part of a natural cycle or as the result of unusual events. The bacterium Vibrio coralliilyticus (type strain ATCC BAA-450) has been linked to coral disease globally (for example in the Mediterranean, Red Sea, Indian Ocean, and Great Barrier Reef) and like many other Vibrio species exhibits a temperature-dependent pathogenicity. The temperature-dependence of V. corallillyticus in regard to its metabolome was investigated. Nuclear magnetic resonance (NMR) spectra were obtained of methanol-water extracts of intracellula rmetabolites (endometabolome) from multiple samples of the bacteria cultured into late stationary phase at 27 degrees C (virulent form) and 24 degrees C (avirulent form). The spectra were subjected to principal components analysis (PCA), and significant temperature-based separations in PC1, PC2, and PC3 dimensions were observed. Betaine, succinate, and glutamate were identified as metabolites that caused the greatest temperature-based separations in the PC scores plots. With increasing temperature, betaine was shown to be down regulated, while succinate and glutamate were up regulated.
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Affiliation(s)
- Arezue F B Boroujerdi
- Analytical Chemistry Division, National Institute of Standards and Technology, Hollings Marine Laboratory, Charleston, South Carolina 29412, USA
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Romantsov T, Guan Z, Wood JM. Cardiolipin and the osmotic stress responses of bacteria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2092-100. [PMID: 19539601 DOI: 10.1016/j.bbamem.2009.06.010] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 06/07/2009] [Accepted: 06/10/2009] [Indexed: 11/29/2022]
Abstract
Cells control their own hydration by accumulating solutes when they are exposed to high osmolality media and releasing solutes in response to osmotic down-shocks. Osmosensory transporters mediate solute accumulation and mechanosensitive channels mediate solute release. Escherichia coli serves as a paradigm for studies of cellular osmoregulation. Growth in media of high salinity alters the phospholipid headgroup and fatty acid compositions of bacterial cytoplasmic membranes, in many cases increasing the ratio of anionic to zwitterionic lipid. In E. coli, the proportion of cardiolipin (CL) increases as the proportion of phosphatidylethanolamine (PE) decreases when osmotic stress is imposed with an electrolyte or a non-electrolyte. Osmotic induction of the gene encoding CL synthase (cls) contributes to these changes. The proportion of phosphatidylglycerol (PG) increases at the expense of PE in cls(-) bacteria and, in Bacillus subtilis, the genes encoding CL and PG synthases (clsA and pgsA) are both osmotically regulated. CL is concentrated at the poles of diverse bacterial cells. A FlAsH-tagged variant of osmosensory transporter ProP is also concentrated at E. coli cell poles. Polar concentration of ProP is CL-dependent whereas polar concentration of its paralogue LacY, a H(+)-lactose symporter, is not. The proportion of anionic lipids (CL and PG) modulates the function of ProP in vivo and in vitro. These effects suggest that the osmotic induction of CL synthesis and co-localization of ProP with CL at the cell poles adjust the osmolality range over which ProP activity is controlled by placing it in a CL-rich membrane environment. In contrast, a GFP-tagged variant of mechanosensitive channel MscL is not concentrated at the cell poles but anionic lipids bind to a specific site on each subunit of MscL and influence its function in vitro. The sub-cellular locations and lipid dependencies of other osmosensory systems are not known. Varying CL content is a key element of osmotic adaptation by bacteria but much remains to be learned about its roles in the localization and function of osmoregulatory proteins.
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Affiliation(s)
- Tatyana Romantsov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
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42
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Culham DE, Vernikovska Y, Tschowri N, Keates RAB, Wood JM, Boggs JM. Periplasmic loops of osmosensory transporter ProP in Escherichia coli are sensitive to osmolality. Biochemistry 2009; 47:13584-93. [PMID: 19049385 DOI: 10.1021/bi801576x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
ProP is an osmosensory transporter. The activities of ProP and ProP*, a cysteine-less, His(6)-tagged ProP variant, increase with osmotic pressure in cells and proteoliposomes. In proteoliposomes, ProP activity is osmolality-dependent only if the magnitude of the membrane potential (DeltaPsi) exceeds 100 mV. Some amino acid replacements rendered ProP activity osmolality-insensitive [e.g., Y44M in transmembrane segment 1 (TMI); S62C in periplasmic loop 1 (loop P1)], whereas others elevated the osmolality at which ProP activates (e.g., A59C). This suggested that the environments and/or conformations of TMI and loop P1 might be osmolality-dependent. This report correlates structural dynamics of ProP with osmoregulation of its transport activity. Residues in periplasmic loops were replaced with Cys, and changes in their environments were detected by monitoring their reactivities with N-ethylmaleimide (NEM). Increasing osmolality markedly increased the NEM reactivity of some Cys residues (e.g., C59, loop P1; C415-C418, loop P6) but not others (e.g., C293, loop P4; C348, loop P5). The NEM reactivity of C62 was insensitive to osmolality, as expected. Substitution Y44M rendered the transport activities of ProP*-A59C and ProP*-Q415C, and the NEM reactivities of the introduced Cys, osmolality-insensitive. Furthermore, osmolality did not affect the reactivity of C59 in cells lacking a protonmotive force, consistent with evidence that DeltaPsi is required for osmosensing by ProP. These results indicate that the osmotically induced increases in NEM reactivity of C59 and C415 in energized bacteria are due to a conformational change of ProP in response to osmolality. They therefore constitute the first direct evidence of an osmotically induced conformational change associated with osmosensing by a transporter.
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Affiliation(s)
- Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
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43
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Culham DE, Romantsov T, Wood JM. Roles of K+, H+, H2O, and DeltaPsi in solute transport mediated by major facilitator superfamily members ProP and LacY. Biochemistry 2008; 47:8176-85. [PMID: 18620422 DOI: 10.1021/bi800794z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
H (+)-solute symporters ProP and LacY are members of the major facilitator superfamily. ProP mediates osmoprotectant (e.g., proline) accumulation, whereas LacY transports the nutrient lactose. The roles of K (+), H (+), H 2O, and DeltaPsi in H (+)-proline and H (+)-lactose symport were compared using right-side-out cytoplasmic membrane vesicles (MVs) from bacteria expressing both transporters and proteoliposomes (PRLs) reconstituted with pure ProP-His 6. ProP activity increased as LacY activity decreased when osmotic stress (increasing osmolality) was imposed on MVs. The activities of both transporters decreased to similar extents when Na (+) replaced K (+) in MV preparations. Thus, K (+) did not specifically control ProP activity. As with LacY, an increasing extravesicular pH stimulated ProP-mediated proline efflux much more than ProP-mediated proline exchange from de-energized MVs. In contrast to that of LacY, ProP-mediated exchange was only 2-fold faster than ProP-mediated efflux and was inhibited by respiration. In the absence of the protonmotive force (Deltamu H (+) ), efflux of lactose from MVs was much more sensitive to increasing osmolality than lactose exchange. Thus, H 2O may be directly involved in proton transport via LacY. In the absence of Deltamu H (+) , proline efflux and exchange from MVs were osmolality-independent. In PRLs with a DeltapH of 1 (lumen alkaline), ProP-His 6 was inactive when the membrane potential (DeltaPsi) was zero, was active but insensitive to osmolality when DeltaPsi was -100 mV, and became osmolality-sensitive as DeltaPsi increased further to -137 mV. ProP-His 6 had the same membrane orientation in PRLs as in cells and MVs. ProP switches among "off", "on", and "osmolality-sensitive" states as the membrane potential increases. Kinetic parameters determined in the absence of Deltamu H (+) represent a ProP population that is predominantly off.
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Affiliation(s)
- Doreen E Culham
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
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Romantsov T, Stalker L, Culham DE, Wood JM. Cardiolipin controls the osmotic stress response and the subcellular location of transporter ProP in Escherichia coli. J Biol Chem 2008; 283:12314-23. [PMID: 18326496 DOI: 10.1074/jbc.m709871200] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The phospholipid composition of the membrane and transporter structure control the subcellular location and function of osmosensory transporter ProP in Escherichia coli. Growth in media of increasing osmolality increases, and entry to stationary phase decreases, the proportion of phosphatidate in anionic lipids (phosphatidylglycerol (PG) plus cardiolipin (CL)). Both treatments increase the CL:PG ratio. Transporters ProP and LacY are concentrated with CL (and not PG) near cell poles and septa. The polar concentration of ProP is CL-dependent. Here we show that the polar concentration of LacY is CL-independent. The osmotic activation threshold of ProP was directly proportional to the CL content of wild type bacteria, the PG content of CL-deficient bacteria, and the anionic lipid content of cells and proteoliposomes. CL was effective at a lower concentration in cells than in proteoliposomes, and at a much lower concentration than PG in either system. Thus, in wild type bacteria, osmotic induction of CL synthesis and concentration of ProP with CL at the cell poles adjust the osmotic activation threshold of ProP to match ambient conditions. ProP proteins linked by homodimeric, C-terminal coiled-coils are known to activate at lower osmolalities than those without such structures and coiled-coil disrupting mutations raise the osmotic activation threshold. Here we show that these mutations also prevent polar concentration of ProP. Stabilization of the C-terminal coiled-coil by covalent cross-linking of introduced Cys reverses the impact of increasing CL on the osmotic activation of ProP. Association of ProP C termini with the CL-rich membrane at cell poles may raise the osmotic activation threshold by blocking coiled-coil formation. Mutations that block coiled-coil formation may also block association of the C termini with the CL-rich membrane.
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Affiliation(s)
- Tatyana Romantsov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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Tsatskis Y, Kwok SC, Becker E, Gill C, Smith MN, Keates RAB, Hodges RS, Wood JM. Core Residue Replacements Cause Coiled-Coil Orientation Switching in Vitro and in Vivo: Structure−Function Correlations for Osmosensory Transporter ProP. Biochemistry 2007; 47:60-72. [DOI: 10.1021/bi7018173] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yonit Tsatskis
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
| | - Stanley C. Kwok
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
| | - Elisabeth Becker
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
| | - Chad Gill
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
| | - Michelle N. Smith
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
| | - Robert A. B. Keates
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
| | - Robert S. Hodges
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
| | - Janet M. Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada, and Department of Biochemistry and Molecular Genetics, University of Colorado Denver, School of Medicine, P.O. Box 6511, Mail Stop 8101, Aurora, Colorado 80045
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Romantsov T, Helbig S, Culham DE, Gill C, Stalker L, Wood JM. Cardiolipin promotes polar localization of osmosensory transporter ProP in Escherichia coli. Mol Microbiol 2007; 64:1455-65. [PMID: 17504273 DOI: 10.1111/j.1365-2958.2007.05727.x] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The osmolality required to activate osmosensory transporter ProP and the proportion of cardiolipin (CL) among the phospholipids of Escherichia coli rise with growth medium osmolality. Most CL synthesis has been attributed to the cls gene product. Transcription of cls increased with osmolality. The proportion of CL was low and osmolality-independent in cls(-) bacteria. It increased more dramatically on the transition to stationary phase in cls(-) than cls(+) bacteria. Thus, Cls is responsible for osmoregulated CL synthesis and other enzymes may contribute to CL accumulation during stationary phase. The proportion of phosphatidylglycerol (PG) was elevated and it increased with medium osmolality in cls(-) bacteria. A cls defect impaired growth of E. coli on solid and in liquid media at low and, more strongly, at high osmolality. Bacteria cultured at high osmolality without osmoprotectant were shorter and rounder than those cultured at low osmolality or with glycine betaine. Fluorescence microscopy showed that CL and ProP colocalize at the poles and near the septa of dividing E. coli cells. The polar localization of ProP was independent of its expression level but correlated with the proportion and polar localization of CL. Association with CL (and not PG) may be required for polar ProP localization.
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Affiliation(s)
- Tatyana Romantsov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON N1G 2W1, Canada
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47
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Liu F, Culham DE, Vernikovska YI, Keates RAB, Boggs JM, Wood JM. Structure and Function of Transmembrane Segment XII in Osmosensor and Osmoprotectant Transporter ProP ofEscherichia coli. Biochemistry 2007; 46:5647-55. [PMID: 17441691 DOI: 10.1021/bi062198r] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Escherichia coli transporter ProP acts as both an osmosensor and an osmoregulator. As medium osmolality rises, ProP is activated and mediates H+-coupled uptake of osmolytes like proline. A homology model of ProP with 12-transmembrane (TM) helices and cytoplasmic termini was created, and the protein's topology was substantiated experimentally. Residues 468-497, at the end of the C-terminal domain and linked to TM XII, form an intermolecular, homodimeric alpha-helical coiled-coil that tunes the transporter's response to osmolality. We aim to further define the structure and function of ProP residues Q415-E440, predicted to include TM XII. Each residue was replaced with cysteine (Cys) in a histidine-tagged, Cys-less ProP variant (ProP*). Cys at positions 415-418 and 438-440 were most reactive with Oregon Green Maleimide (OGM), suggesting that residues 419 through 437 are in the membrane. Except for V429-I433, reactivity of those Cys varied with helical periodicity. Cys predicted to face the interior of ProP were more reactive than Cys predicted to face the lipid. The former may be exposed to hydrated polar residues in the protein interior, particularly on the periplasmic side. Intermolecular cross-links formed when ProP* variants with Cys at positions 419, 420, 422, and 439 were treated with DTME. Thus TM XII can participate, along its entire length, in the dimer interface of ProP. Cys substitution E440C rendered ProP* inactive. All other variants retained more than 30% of the proline uptake activity of ProP* at high osmolality. Most variants with Cys substitutions in the periplasmic half of TM XII activated at lower osmolalities than ProP*. Variants with Cys substitutions on one face of the cytoplasmic half of TM XII required a higher osmolality to activate. They included elements of a GXXXG motif that are predicted to form the interface of TM XII with TM VII. These studies define the position of ProP TM XII within the membrane, further support the predicted structure of ProP, reveal the dimerization interface, and show that the structure of TM XII influences the osmolality at which ProP activates.
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Affiliation(s)
- Feng Liu
- Department of Structural Biology and Biochemistry, Hospital for Sick Children, Toronto M5G 1X8, ON Canada
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48
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Abstract
Cells faced with dehydration because of increasing extracellular osmotic pressure accumulate solutes through synthesis or transport. Water follows, restoring cellular hydration and volume. Prokaryotes and eukaryotes possess arrays of osmoregulatory genes and enzymes that are responsible for solute accumulation under osmotic stress. In bacteria, osmosensing transporters can detect increasing extracellular osmotic pressure and respond by mediating the uptake of organic osmolytes compatible with cellular functions ("compatible solutes"). This chapter reviews concepts and methods critical to the identification and study of osmosensing transporters. Like some experimental media, cytoplasm is a "nonideal" solution so the estimation of key solution properties (osmotic pressure, osmolality, water activity, osmolarity, and macromolecular crowding) is essential for studies of osmosensing and osmoregulation. Because bacteria vary widely in osmotolerance, techniques for its characterization provide an essential context for the elucidation of osmosensory and osmoregulatory mechanisms. Powerful genetic, molecular biological, and biochemical tools are now available to aid in the identification and characterization of osmosensory transporters, the genes that encode them, and the osmoprotectants that are their substrates. Our current understanding of osmosensory mechanisms is based on measurements of osmosensory transporter activity performed with intact cells, bacterial membrane vesicles, and proteoliposomes reconstituted with purified transporters. In the quest to elucidate the structural mechanisms of osmosensing and osmoregulation, researchers are now applying the full range of available biophysical, biochemical, and molecular biological tools to osmosensory transporter prototypes.
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Affiliation(s)
- Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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Laloknam S, Tanaka K, Buaboocha T, Waditee R, Incharoensakdi A, Hibino T, Tanaka Y, Takabe T. Halotolerant cyanobacterium Aphanothece halophytica contains a betaine transporter active at alkaline pH and high salinity. Appl Environ Microbiol 2006; 72:6018-26. [PMID: 16957224 PMCID: PMC1563673 DOI: 10.1128/aem.00733-06] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Aphanothece halophytica is a halotolerant alkaliphilic cyanobacterium which can grow in media of up to 3.0 M NaCl and pH 11. This cyanobacterium can synthesize betaine from glycine by three-step methylation using S-adenosylmethionine as a methyl donor. To unveil the mechanism of betaine uptake and efflux in this alkaliphile, we isolated and characterized a betaine transporter. A gene encoding a protein (BetT(A. halophytica)) that belongs to the betaine-choline-carnitine transporter (BCCT) family was isolated. Although the predicted isoelectric pH of a typical BCCT family transporter, OpuD of Bacillus subtilis, is basic, 9.54, that of BetT(A. halophytica) is acidic, 4.58. BetT(A. halophytica) specifically catalyzed the transport of betaine. Choline, gamma-aminobutyric acid, betaine aldehyde, sarcosine, dimethylglycine, and amino acids such as proline did not compete for the uptake of betaine by BetT(A. halophytica). Sodium markedly enhanced betaine uptake rates, whereas potassium and other cations showed no effect, suggesting that BetT(A. halophytica) is a Na(+)-betaine symporter. Betaine uptake activities of BetT(A. halophytica) were high at alkaline pH values, with the optimum pH around 9.0. Freshwater Synechococcus cells overexpressing BetT(A. halophytica) showed NaCl-activated betaine uptake activities with enhanced salt tolerance, allowing growth in seawater supplemented with betaine. Kinetic properties of betaine uptake in Synechococcus cells overexpressing BetT(A. halophytica) were similar to those in A. halophytica cells. These findings indicate that A. halophytica contains a Na(+)-betaine symporter that contributes to the salt stress tolerance at alkaline pH. BetT(A. halophytica) is the first identified transporter for compatible solutes in cyanobacteria.
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Affiliation(s)
- Surasak Laloknam
- Research Institute of Meijo University, Tenpaku-ku, Nagoya 468-8502, Japan
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Abstract
Osmosensors are proteins that sense environmental osmotic pressure. They mediate or direct osmoregulatory responses that allow cells to survive osmotic changes and extremes. Bacterial osmosensing transporters sense high external osmotic pressure and respond by mediating organic osmolyte uptake, hence cellular rehydration. Detailed studies of osmosensing transporters OpuA, BetP, and ProP suggest that they sense and respond to different osmotic pressure-dependent cellular properties. These studies also suggest that each protein has a cytoplasmic osmosensory or osmoregulatory domain, but that these domains differ in structure and function. It is not yet clear whether each transporter represents a distinct osmosensory mechanism or whether different research groups are approaching the same mechanism by way of different paths. Principles emerging from this research will apply to other osmosensors, including those that initiate signal transduction cascades in prokaryotes and eukaryotes.
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Affiliation(s)
- Janet M Wood
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
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