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Wu Y, Zhang J, Wang B, Zhang Y, Li H, Liu Y, Yin J, He D, Luo H, Gan F, Tang B, Tang XF. Dissecting the Arginine and Lysine Biosynthetic Pathways and Their Relationship in Haloarchaeon Natrinema gari J7-2 via Endogenous CRISPR-Cas System-Based Genome Editing. Microbiol Spectr 2023; 11:e0028823. [PMID: 37347159 PMCID: PMC10433800 DOI: 10.1128/spectrum.00288-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 06/07/2023] [Indexed: 06/23/2023] Open
Abstract
The evolutionary relationship between arginine and lysine biosynthetic pathways has been well established in bacteria and hyperthermophilic archaea but remains largely unknown in haloarchaea. Here, the endogenous CRISPR-Cas system was harnessed to edit arginine and lysine biosynthesis-related genes in the haloarchaeon Natrinema gari J7-2. The ΔargW, ΔargX, ΔargB, and ΔargD mutant strains display an arginine auxotrophic phenotype, while the ΔdapB mutant shows a lysine auxotrophic phenotype, suggesting that strain J7-2 utilizes the ArgW-mediated pathway and the diaminopimelate (DAP) pathway to synthesize arginine and lysine, respectively. Unlike the ArgD in Escherichia coli acting as a bifunctional aminotransferase in both the arginine biosynthesis pathway and the DAP pathway, the ArgD in strain J7-2 participates only in arginine biosynthesis. Meanwhile, in strain J7-2, the function of argB cannot be compensated for by its evolutionary counterpart ask in the DAP pathway. Moreover, strain J7-2 cannot utilize α-aminoadipate (AAA) to synthesize lysine via the ArgW-mediated pathway, in contrast to hyperthermophilic archaea that employ a bifunctional LysW-mediated pathway to synthesize arginine (or ornithine) and lysine from glutamate and AAA, respectively. Additionally, the replacement of a 5-amino-acid signature motif responsible for substrate specificity of strain J7-2 ArgX with that of its hyperthermophilic archaeal homologs cannot endow the ΔdapB mutant with the ability to biosynthesize lysine from AAA. The in vitro analysis shows that strain J7-2 ArgX acts on glutamate rather than AAA. These results suggest that the arginine and lysine biosynthetic pathways of strain J7-2 are highly specialized during evolution. IMPORTANCE Due to their roles in amino acid metabolism and close evolutionary relationship, arginine and lysine biosynthetic pathways represent interesting models for probing functional specialization of metabolic routes. The current knowledge with respect to arginine and lysine biosynthesis is limited for haloarchaea compared to that for bacteria and hyperthermophilic archaea. Our results demonstrate that the haloarchaeon Natrinema gari J7-2 employs the ArgW-mediated pathway and the DAP pathway for arginine and lysine biosynthesis, respectively, and the two pathways are functionally independent of each other; meanwhile, ArgX is a key determinant of substrate specificity of the ArgW-mediated pathway in strain J7-2. This study provides new clues about haloarchaeal amino acid metabolism and confirms the convenience and efficiency of endogenous CRISPR-Cas system-based genome editing in haloarchaea.
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Affiliation(s)
- Yi Wu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Jia Zhang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Bingxue Wang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Yanyan Zhang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Huai Li
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Yang Liu
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Jing Yin
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
| | - Dan He
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Hongyi Luo
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
| | - Fei Gan
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Wuhan, China
| | - Bing Tang
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, China
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Wuhan, China
| | - Xiao-Feng Tang
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan University, Wuhan, China
- Cooperative Innovation Center of Industrial Fermentation (Ministry of Education & Hubei Province), Wuhan, China
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Adams JD, Sander KB, Criddle CS, Arkin AP, Clark DS. Engineering osmolysis susceptibility in Cupriavidus necator and Escherichia coli for recovery of intracellular products. Microb Cell Fact 2023; 22:69. [PMID: 37046248 PMCID: PMC10091555 DOI: 10.1186/s12934-023-02064-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 03/16/2023] [Indexed: 04/14/2023] Open
Abstract
BACKGROUND Intracellular biomacromolecules, such as industrial enzymes and biopolymers, represent an important class of bio-derived products obtained from bacterial hosts. A common key step in the downstream separation of these biomolecules is lysis of the bacterial cell wall to effect release of cytoplasmic contents. Cell lysis is typically achieved either through mechanical disruption or reagent-based methods, which introduce issues of energy demand, material needs, high costs, and scaling problems. Osmolysis, a cell lysis method that relies on hypoosmotic downshock upon resuspension of cells in distilled water, has been applied for bioseparation of intracellular products from extreme halophiles and mammalian cells. However, most industrial bacterial strains are non-halotolerant and relatively resistant to hypoosmotic cell lysis. RESULTS To overcome this limitation, we developed two strategies to increase the susceptibility of non-halotolerant hosts to osmolysis using Cupriavidus necator, a strain often used in electromicrobial production, as a prototypical strain. In one strategy, C. necator was evolved to increase its halotolerance from 1.5% to 3.25% (w/v) NaCl through adaptive laboratory evolution, and genes potentially responsible for this phenotypic change were identified by whole genome sequencing. The evolved halotolerant strain experienced an osmolytic efficiency of 47% in distilled water following growth in 3% (w/v) NaCl. In a second strategy, the cells were made susceptible to osmolysis by knocking out the large-conductance mechanosensitive channel (mscL) gene in C. necator. When these strategies were combined by knocking out the mscL gene from the evolved halotolerant strain, greater than 90% osmolytic efficiency was observed upon osmotic downshock. A modified version of this strategy was applied to E. coli BL21 by deleting the mscL and mscS (small-conductance mechanosensitive channel) genes. When grown in medium with 4% NaCl and subsequently resuspended in distilled water, this engineered strain experienced 75% cell lysis, although decreases in cell growth rate due to higher salt concentrations were observed. CONCLUSIONS Our strategy is shown to be a simple and effective way to lyse cells for the purification of intracellular biomacromolecules and may be applicable in many bacteria used for bioproduction.
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Affiliation(s)
- Jeremy David Adams
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA
| | - Kyle B Sander
- Department of Bioengineering, University of California, Berkeley, CA, 94720, USA
| | - Craig S Criddle
- Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Adam P Arkin
- Department of Bioengineering, University of California, Berkeley, CA, 94720, USA
- Environmental Genomics and Systems Biology Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - Douglas S Clark
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA.
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA.
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Nagler M, Podmirseg SM, Mayr M, Ascher-Jenull J, Insam H. The masking effect of extracellular DNA and robustness of intracellular DNA in anaerobic digester NGS studies: A discriminatory study of the total DNA pool. Mol Ecol 2020; 30:438-450. [PMID: 33219564 PMCID: PMC7839673 DOI: 10.1111/mec.15740] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Revised: 11/06/2020] [Accepted: 11/13/2020] [Indexed: 01/08/2023]
Abstract
Most commonly, next generation sequencing-based microbiome studies are performed on the total DNA (totDNA) pool; however, this consists of extracellular- (exDNA) and intracellular (iDNA) DNA fractions. By investigating the microbiomes of different anaerobic digesters over time, we found that totDNA suggested lower species richness considering all and/or only common species and yielded fewer unique reads as compared to iDNA. Additionally, exDNA-derived sequences were more similar to those from totDNA than from iDNA and, finally, iDNA showed the best performance in tracking temporal changes in microbial communities. We postulate that abundant sequences present within the exDNA fraction mask the overall results of totDNA and provide evidence that exDNA has the potential to qualitatively bias microbiome studies at least in the anaerobic digester environment as it contains information about cells that were lysed hours or days ago. iDNA, however, was found to be more appropriate in providing reliable genetic information about potentially alive as well as rare microbes within the target habitat.
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Affiliation(s)
- Magdalena Nagler
- Institute of Microbiology, Universität Innsbruck, Innsbruck, Austria
| | | | - Markus Mayr
- Institute of Microbiology, Universität Innsbruck, Innsbruck, Austria
| | | | - Heribert Insam
- Institute of Microbiology, Universität Innsbruck, Innsbruck, Austria
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Methanogenesis inhibitors used in bio-electrochemical systems: A review revealing reality to decide future direction and applications. BIORESOURCE TECHNOLOGY 2020; 319:124141. [PMID: 32977094 DOI: 10.1016/j.biortech.2020.124141] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 09/11/2020] [Accepted: 09/13/2020] [Indexed: 02/08/2023]
Abstract
Microbial fuel cell (MFC) is a robust technology capable of treating real wastewaters by utilizing mixed anaerobic microbiota as inoculum for producing electricity from oxidation of the biodegradable matters. However, these mixed microbiota comprises of both electroactive microorganisms (EAM) and substrate/electron scavenging microorganisms such as methanogens. Hence, in order to maximize bioelectricity from MFC, different physio-chemical techniques have been applied in past investigations to suppress activity of methanogens. Interestingly, recent investigations exhibit that methanogens can produce electricity in MFC and possess the cellular machinery like cytochrome c and Type IV pili to perform extracellular electron transfer (EET) in the presence of suitable electron acceptors. Hence, in this review, in-depth analysis of versatile behaviour of methanogens in both MFC and natural anaerobic conditions with different inhibition techniques is explored. This review also discusses the future research directions based on the latest scientific evidence on role of methanogens for EET in MFC.
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Jung MY, Islam MA, Gwak JH, Kim JG, Rhee SK. Nitrosarchaeum koreense gen. nov., sp. nov., an aerobic and mesophilic, ammonia-oxidizing archaeon member of the phylum Thaumarchaeota isolated from agricultural soil. Int J Syst Evol Microbiol 2018; 68:3084-3095. [PMID: 30124400 DOI: 10.1099/ijsem.0.002926] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A mesophilic, chemolithoautotrophic, neutrophilic and aerobic ammonia-oxidizing archaeon, designated strain MY1T, was isolated from agricultural soil. Microscopic observation revealed short, rod-shaped cells with a diameter of 0.3-0.5 µm and length of 0.6-1.0 µm. The isolate had no flagella and pili, and possessed no genes associated with archaeal flagella synthesis. The major membrane lipids consisted mainly of the glycerol dibiphytanyl glycerol tetraether (GDGT) lipids GDGT-0 to GDGT-4 and crenarchaeol. The major intact polar lipids (IPLs) were determined as hexose plus phosphohexose IPL and dihexose IPL. Strain MY1T obtains energy by aerobically oxidizing ammonia and carbon by fixing CO2. An optimal growth was observed at 25 °C, at pH 7 and with 0.2-0.4 % (w/v) salinity that corresponds with its terrestrial habitat. The addition of α-keto acids was necessary to stimulate growth. The strain tolerated ammonium and nitrite concentrations up to 10 and 5 mM, respectively. The MY1T genome has a DNA G+C content of 32.7 mol%. Phylogenetic analysis based on the 16S rRNA gene showed that strain MY1T belongs to the family Nitrosopumilaceaeof the phylum Thaumarchaeota, sharing the highest 16S rRNA gene sequence similarity (96.6-97.1 %) with marine isolates of the genus Nitrosopumilus. The average nucleotide identity was 78 % between strain MY1T and Nitrosopumilus maritimus SCM1T, indicating distant relatedness. Based on the phenotypic, phylogenetic and genomic analyses, it was concluded that strain MY1T belongs to the novel genus Nitrosarchaeum, under which the name Nitrosarchaeum koreense sp. nov. is proposed as the type species. The type strain is MY1T (=JCM 31640T=KCTC 4249T).
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Affiliation(s)
- Man-Young Jung
- 1Department of Microbiology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea.,2Department of Microbiology and Ecosystem Science, Division of Microbial Ecology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria
| | - Md Arafat Islam
- 1Department of Microbiology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
| | - Joo-Han Gwak
- 1Department of Microbiology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
| | - Jong-Geol Kim
- 1Department of Microbiology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
| | - Sung-Keun Rhee
- 1Department of Microbiology, Chungbuk National University, 1 Chungdae-ro, Seowon-Gu, Cheongju 28644, Republic of Korea
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Methods for Collection and Characterization of Samples From Icy Environments. METHODS IN MICROBIOLOGY 2018. [DOI: 10.1016/bs.mim.2018.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Fei YY, Gai JY, Zhao TJ. Identification of regulated genes conferring resistance to high concentrations of glyphosate in a new strain of Enterobacter. FEMS Microbiol Lett 2013; 349:135-43. [PMID: 24237416 DOI: 10.1111/1574-6968.12306] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Accepted: 10/17/2013] [Indexed: 11/29/2022] Open
Abstract
Glyphosate is a widely used herbicide that inhibits 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) activity. Most plants and microbes are sensitive to glyphosate. However, transgenic-resistant crops that contain a modified epsps obtained from the resistant microbes have been commercially successful and therefore, new resistance genes and their adaptive regulatory mechanisms are of great interest. In this study, a soil-borne, glyphosate-resistant bacterium was selected and identified as Enterobacter. The EPSPS in this strain was found to have been altered to a resistant one. A total of 42 differentially expressed genes (DEGs) in the glyphosate were screened using microarray techniques. Under treatment, argF, sdhA, ivbL, rrfA-H were downregulated, whereas the transcripts of speA, osmY, pflB, ahpC, fusA, deoA, uxaC, rpoD and a few ribosomal protein genes were upregulated. Data were verified by quantitative real-time PCR on selected genes. All transcriptional changes appeared to protect the bacteria from glyphosate and associated osmotic, acidic and oxidative stresses. Many DEGs may have the potential to confer resistance to glyphosate alone, and some may be closely related to the shikimate pathway, reflecting the complex gene interaction network for glyphosate resistance.
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Affiliation(s)
- Yun-Yan Fei
- Soybean Research Institute/National Center for Soybean, Improvement/National Key Laboratory for Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing, China
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Engelhardt H. Mechanism of osmoprotection by archaeal S-layers: a theoretical study. J Struct Biol 2007; 160:190-9. [PMID: 17888677 DOI: 10.1016/j.jsb.2007.08.004] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/29/2007] [Accepted: 08/02/2007] [Indexed: 11/19/2022]
Abstract
Many Archaea possess protein surface layers (S-layers) as the sole cell wall component. S-layers must therefore integrate the basic functions of mechanical and osmotic cell stabilisation. While the necessity is intuitively clear, the mechanism of structural osmoprotection by S-layers has not been elucidated yet. The theoretical analysis of a model S-layer-membrane assembly, derived from the typical cell envelope of Crenarchaeota, explains how S-layers impart lipid membranes with increased resistance to internal osmotic pressure and offers a quantitative assessment of S-layer stability. These considerations reveal the functional significance of S-layer symmetry and unit cell size and shed light on the rationale of S-layer architectures.
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Affiliation(s)
- Harald Engelhardt
- Abteilung Molekulare Strukturbiologie, Max-Planck-Institut für Biochemie, Am Klopferspitz 18, D-82152 Martinsried, Germany.
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9
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Garcia JL, Patel BK, Ollivier B. Taxonomic, phylogenetic, and ecological diversity of methanogenic Archaea. Anaerobe 2007; 6:205-26. [PMID: 16887666 DOI: 10.1006/anae.2000.0345] [Citation(s) in RCA: 376] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- J L Garcia
- Laboratoire de Microbiologie IRD, Université de Provence, ESIL case 925, 163 Avenue de Luminy, 13288, Marseille cedex 9, France
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Abstract
A range of surface proteins is anchored to the cell walls of Gram-positive pathogens such as Staphylococcus aureus by the transpeptidase sortase. Until now, sortase-like proteins and their substrates appeared to be limited mainly to such pathogens. However, by searching for sortase homologues among complete and incomplete genome sequences, we have found them to be present in almost all Gram-positives, a single Gram-negative bacterium and an archaean. There is usually more than one sortase-like protein encoded in each Gram-positive genome, and the genes encoding the sortase-like proteins are often clustered with genes encoding their likely substrates.
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Affiliation(s)
- M J Pallen
- Department of Microbiology and Immunobiology, Queen's University Belfast, Belfast, UK BT12 6BN.
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Affiliation(s)
- T J Beveridge
- Canadian Bacterial Disease Network, and Department of Microbiology, College of Biological Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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12
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Gupta RS. Protein phylogenies and signature sequences: A reappraisal of evolutionary relationships among archaebacteria, eubacteria, and eukaryotes. Microbiol Mol Biol Rev 1998; 62:1435-91. [PMID: 9841678 PMCID: PMC98952 DOI: 10.1128/mmbr.62.4.1435-1491.1998] [Citation(s) in RCA: 380] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The presence of shared conserved insertion or deletions (indels) in protein sequences is a special type of signature sequence that shows considerable promise for phylogenetic inference. An alternative model of microbial evolution based on the use of indels of conserved proteins and the morphological features of prokaryotic organisms is proposed. In this model, extant archaebacteria and gram-positive bacteria, which have a simple, single-layered cell wall structure, are termed monoderm prokaryotes. They are believed to be descended from the most primitive organisms. Evidence from indels supports the view that the archaebacteria probably evolved from gram-positive bacteria, and I suggest that this evolution occurred in response to antibiotic selection pressures. Evidence is presented that diderm prokaryotes (i.e., gram-negative bacteria), which have a bilayered cell wall, are derived from monoderm prokaryotes. Signature sequences in different proteins provide a means to define a number of different taxa within prokaryotes (namely, low G+C and high G+C gram-positive, Deinococcus-Thermus, cyanobacteria, chlamydia-cytophaga related, and two different groups of Proteobacteria) and to indicate how they evolved from a common ancestor. Based on phylogenetic information from indels in different protein sequences, it is hypothesized that all eukaryotes, including amitochondriate and aplastidic organisms, received major gene contributions from both an archaebacterium and a gram-negative eubacterium. In this model, the ancestral eukaryotic cell is a chimera that resulted from a unique fusion event between the two separate groups of prokaryotes followed by integration of their genomes.
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Affiliation(s)
- R S Gupta
- Department of Biochemistry, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.
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Beveridge TJ, Pouwels PH, Sára M, Kotiranta A, Lounatmaa K, Kari K, Kerosuo E, Haapasalo M, Egelseer EM, Schocher I, Sleytr UB, Morelli L, Callegari ML, Nomellini JF, Bingle WH, Smit J, Leibovitz E, Lemaire M, Miras I, Salamitou S, Béguin P, Ohayon H, Gounon P, Matuschek M, Koval SF. Functions of S-layers. FEMS Microbiol Rev 1997; 20:99-149. [PMID: 9276929 DOI: 10.1111/j.1574-6976.1997.tb00305.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Although S-layers are being increasingly identified on Bacteria and Archaea, it is enigmatic that in most cases S-layer function continues to elude us. In a few instances, S-layers have been shown to be virulence factors on pathogens (e.g. Campylobacter fetus ssp. fetus and Aeromonas salmonicida), protective against Bdellovibrio, a depository for surface-exposed enzymes (e.g. Bacillus stearothermophilus), shape-determining agents (e.g. Thermoproteus tenax) and nucleation factors for fine-grain mineral development (e.g. Synechococcus GL 24). Yet, for the vast majority of S-layered bacteria, the natural function of these crystalline arrays continues to be evasive. The following review up-dates the functional basis of S-layers and describes such diverse topics as the effect of S-layers on the Gram stain, bacteriophage adsorption in lactobacilli, phagocytosis by human polymorphonuclear leukocytes, the adhesion of a high-molecular-mass amylase, outer membrane porosity, and the secretion of extracellular enzymes of Thermoanaerobacterium. In addition, the functional aspect of calcium on the Caulobacter S-layer is explained.
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Affiliation(s)
- T J Beveridge
- Department of Microbiology, College of Biological Science, University of Guelph, Canada.
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