1
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Spiers AJ, Dorfmueller HC, Jerdan R, McGregor J, Nicoll A, Steel K, Cameron S. Bioinformatics characterization of BcsA-like orphan proteins suggest they form a novel family of pseudomonad cyclic-β-glucan synthases. PLoS One 2023; 18:e0286540. [PMID: 37267309 DOI: 10.1371/journal.pone.0286540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 05/18/2023] [Indexed: 06/04/2023] Open
Abstract
Bacteria produce a variety of polysaccharides with functional roles in cell surface coating, surface and host interactions, and biofilms. We have identified an 'Orphan' bacterial cellulose synthase catalytic subunit (BcsA)-like protein found in four model pseudomonads, P. aeruginosa PA01, P. fluorescens SBW25, P. putida KT2440 and P. syringae pv. tomato DC3000. Pairwise alignments indicated that the Orphan and BcsA proteins shared less than 41% sequence identity suggesting they may not have the same structural folds or function. We identified 112 Orphans among soil and plant-associated pseudomonads as well as in phytopathogenic and human opportunistic pathogenic strains. The wide distribution of these highly conserved proteins suggest they form a novel family of synthases producing a different polysaccharide. In silico analysis, including sequence comparisons, secondary structure and topology predictions, and protein structural modelling, revealed a two-domain transmembrane ovoid-like structure for the Orphan protein with a periplasmic glycosyl hydrolase family GH17 domain linked via a transmembrane region to a cytoplasmic glycosyltransferase family GT2 domain. We suggest the GT2 domain synthesises β-(1,3)-glucan that is transferred to the GH17 domain where it is cleaved and cyclised to produce cyclic-β-(1,3)-glucan (CβG). Our structural models are consistent with enzymatic characterisation and recent molecular simulations of the PaPA01 and PpKT2440 GH17 domains. It also provides a functional explanation linking PaPAK and PaPA14 Orphan (also known as NdvB) transposon mutants with CβG production and biofilm-associated antibiotic resistance. Importantly, cyclic glucans are also involved in osmoregulation, plant infection and induced systemic suppression, and our findings suggest this novel family of CβG synthases may provide similar range of adaptive responses for pseudomonads.
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Affiliation(s)
- Andrew J Spiers
- School of Applied Sciences, Abertay University, Dundee, United Kingdom
| | - Helge C Dorfmueller
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Robyn Jerdan
- School of Applied Sciences, Abertay University, Dundee, United Kingdom
| | - Jessica McGregor
- Nuffield Research Placement Students, School of Applied Sciences, Abertay University, Dundee, United Kingdom
| | - Abbie Nicoll
- Nuffield Research Placement Students, School of Applied Sciences, Abertay University, Dundee, United Kingdom
| | - Kenzie Steel
- Nuffield Research Placement Students, School of Applied Sciences, Abertay University, Dundee, United Kingdom
| | - Scott Cameron
- School of Applied Sciences, Abertay University, Dundee, United Kingdom
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2
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Müller M, Spiers AJ, Tan A, Mujahid A. Investigating quorum-quenching marine bacilli as potential biocontrol agents for protection of shrimps against Early Mortality Syndrome (EMS). Sci Rep 2023; 13:4095. [PMID: 36907954 PMCID: PMC10008827 DOI: 10.1038/s41598-023-31197-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 03/07/2023] [Indexed: 03/14/2023] Open
Abstract
Early Mortality Syndrome (EMS) has been a major problem for shrimp aquaculture in Southeast Asia due to its epizootic prevalence within the region since the first reported case in 2009. This study explores the application of halophilic marine bacilli isolated from coral mucus and their quorum-quenching abilities as potential biocontrol agents in aquaculture systems to combat the causative agent of EMS, Vibrio parahaemolyticus. N-acylhomoserine lactone (AHL)-degrading (AiiA) activity was first screened by PCR then confirmed by bio-reporter assay, and a combination of 16S rDNA sequence analysis and quantitative phenotype assays including biofilm-formation and temperature-growth responses were used to demonstrate diversity amongst these quorum-quenching isolates. Three phenotypically distinct strains showing notable potential were chosen to undergo co-cultivation as a method for strain improvement via long term exposure to the pathogenic V. parahaemolyticus. The novel approach taken led to significant improvements in antagonism and quorum quenching activities as compared to the ancestral wild-type strains and offers a potential solution as well as pathway to improve existing beneficial microbes for one of the most pressing issues in shrimp aquacultures worldwide.
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Affiliation(s)
- Moritz Müller
- Faculty of Engineering, Computing and Science, Swinburne University of Technology Sarawak, 93350, Kuching, Malaysia.
| | - Andrew J Spiers
- School of Science, Engineering and Technology, Abertay University, Dundee, DD1 1HG, UK
| | - Angelica Tan
- Faculty of Engineering, Computing and Science, Swinburne University of Technology Sarawak, 93350, Kuching, Malaysia
| | - Aazani Mujahid
- Institute of Biodiversity and Environmental Conservation (IBEC), Universiti Malaysia Sarawak, 93400, Kota Samarahan, Sarawak, Malaysia
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3
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Moshynets OV, Pokholenko I, Iungin O, Potters G, Spiers AJ. eDNA, Amyloid Fibers and Membrane Vesicles Identified in Pseudomonas fluorescens SBW25 Biofilms. Int J Mol Sci 2022; 23:ijms232315096. [PMID: 36499433 PMCID: PMC9738004 DOI: 10.3390/ijms232315096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 11/25/2022] [Accepted: 11/26/2022] [Indexed: 12/03/2022] Open
Abstract
Pseudomonas fluorescens SBW25 is a model soil- and plant-associated bacterium capable of forming a variety of air-liquid interface biofilms in experimental microcosms and on plant surfaces. Previous investigations have shown that cellulose is the primary structural matrix component in the robust and well-attached Wrinkly Spreader biofilm, as well as in the fragile Viscous Mass biofilm. Here, we demonstrate that both biofilms include extracellular DNA (eDNA) which can be visualized using confocal laser scanning microscopy (CLSM), quantified by absorbance measurements, and degraded by DNase I treatment. This eDNA plays an important role in cell attachment and biofilm development. However, exogenous high-molecular-weight DNA appears to decrease the strength and attachment levels of mature Wrinkly Spreader biofilms, whereas low-molecular-weight DNA appears to have little effect. Further investigation with CLSM using an amyloid-specific fluorophore suggests that the Wrinkly Spreader biofilm might also include Fap fibers, which might be involved in attachment and contribute to biofilm strength. The robust nature of the Wrinkly Spreader biofilm also allowed us, using MALDI-TOF mass spectrometry, to identify matrix-associated proteins unable to diffuse out of the structure, as well as membrane vesicles which had a different protein profile compared to the matrix-associated proteins. CLSM and DNase I treatment suggest that some vesicles were also associated with eDNA. These findings add to our understanding of the matrix components in this model pseudomonad, and, as found in other biofilms, biofilm-specific products and material from lysed cells contribute to these structures through a range of complex interactions.
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Affiliation(s)
- Olena V. Moshynets
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine
| | - Ianina Pokholenko
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine
| | - Olga Iungin
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine
- Department of Biotechnology, Leather and Fur, Kyiv National University of Technologies and Design, 01011 Kyiv, Ukraine
| | - Geert Potters
- Antwerp Maritime Academy, 2030 Antwerp, Belgium
- Department of Bioscience Engineering, University of Antwerp, 2000 Antwerp, Belgium
- Correspondence:
| | - Andrew J. Spiers
- School of Applied Sciences, Abertay University, Dundee DD1 1HG, UK
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4
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Moshynets OV, Baranovskyi TP, Cameron S, Iungin OS, Pokholenko I, Jerdan R, Kamyshnyi A, Krikunov AA, Potochilova VV, Rudnieva KL, Spiers AJ. Azithromycin possesses biofilm–inhibitory activity and potentiates non-bactericidal colistin methanesulfonate (CMS) and polymyxin B against Klebsiella pneumonia. PLoS One 2022; 17:e0270983. [PMID: 35776759 PMCID: PMC9249213 DOI: 10.1371/journal.pone.0270983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 06/21/2022] [Indexed: 11/30/2022] Open
Abstract
Novel antibiotic combinations may act synergistically to inhibit the growth of multidrug-resistant bacterial pathogens but predicting which combination will be successful is difficult, and standard antimicrobial susceptibility testing may not identify important physiological differences between planktonic free-swimming and biofilm-protected surface-attached sessile cells. Using a nominally macrolide-resistant model Klebsiella pneumoniae strain (ATCC 10031) we demonstrate the effectiveness of several macrolides in inhibiting biofilm growth in multi-well plates, and the ability of azithromycin (AZM) to improve the effectiveness of the antibacterial last-agent-of-choice for K. pneumoniae infections, colistin methanesulfonate (CMS), against biofilms. This synergistic action was also seen in biofilm tests of several K. pneumoniae hospital isolates and could also be identified in polymyxin B disc-diffusion assays on azithromycin plates. Our work highlights the complexity of antimicrobial-resistance in bacterial pathogens and the need to test antibiotics with biofilm models where potential synergies might provide new therapeutic opportunities not seen in liquid culture or colony-based assays.
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Affiliation(s)
- Olena V. Moshynets
- Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
- * E-mail: (OVM); (AJS)
| | - Taras P. Baranovskyi
- Shupyk National Healthcare University of Ukraine, Kyiv, Ukraine
- Kyiv Regional Clinical Hospital, Kyiv, Ukraine
| | - Scott Cameron
- School of Applied Sciences, Abertay University, Dundee, United Kingdom
| | - Olga S. Iungin
- Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
- Kyiv National University of Technologies and Design, Kyiv, Ukraine
| | - Ianina Pokholenko
- Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine
| | - Robyn Jerdan
- School of Applied Sciences, Abertay University, Dundee, United Kingdom
| | | | | | | | | | - Andrew J. Spiers
- School of Applied Sciences, Abertay University, Dundee, United Kingdom
- * E-mail: (OVM); (AJS)
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5
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Moshynets OV, Baranovskyi TP, Iungin OS, Kysil NP, Metelytsia LO, Pokholenko I, Potochilova VV, Potters G, Rudnieva KL, Rymar SY, Semenyuta IV, Spiers AJ, Tarasyuk OP, Rogalsky SP. eDNA Inactivation and Biofilm Inhibition by the PolymericBiocide Polyhexamethylene Guanidine Hydrochloride (PHMG-Cl). Int J Mol Sci 2022; 23:ijms23020731. [PMID: 35054915 PMCID: PMC8775615 DOI: 10.3390/ijms23020731] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 01/03/2022] [Accepted: 01/03/2022] [Indexed: 01/05/2023] Open
Abstract
The choice of effective biocides used for routine hospital practice should consider the role of disinfectants in the maintenance and development of local resistome and how they might affect antibiotic resistance gene transfer within the hospital microbial population. Currently, there is little understanding of how different biocides contribute to eDNA release that may contribute to gene transfer and subsequent environmental retention. Here, we investigated how different biocides affect the release of eDNA from mature biofilms of two opportunistic model strains Pseudomonas aeruginosa ATCC 27853 (PA) and Staphylococcus aureus ATCC 25923 (SA) and contribute to the hospital resistome in the form of surface and water contaminants and dust particles. The effect of four groups of biocides, alcohols, hydrogen peroxide, quaternary ammonium compounds, and the polymeric biocide polyhexamethylene guanidine hydrochloride (PHMG-Cl), was evaluated using PA and SA biofilms. Most biocides, except for PHMG-Cl and 70% ethanol, caused substantial eDNA release, and PHMG-Cl was found to block biofilm development when used at concentrations of 0.5% and 0.1%. This might be associated with the formation of DNA–PHMG-Cl complexes as PHMG-Cl is predicted to bind to AT base pairs by molecular docking assays. PHMG-Cl was found to bind high-molecular DNA and plasmid DNA and continued to inactivate DNA on surfaces even after 4 weeks. PHMG-Cl also effectively inactivated biofilm-associated antibiotic resistance gene eDNA released by a pan-drug-resistant Klebsiella strain, which demonstrates the potential of a polymeric biocide as a new surface-active agent to combat the spread of antibiotic resistance in hospital settings.
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Affiliation(s)
- Olena V. Moshynets
- Biofilm Study Group, Department of Cell Regulatory Mechanisms, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 150 Zabolotnoho Str., 03680 Kiev, Ukraine; (O.S.I.); (I.P.); (S.Y.R.)
- Correspondence: (O.V.M.); (S.P.R.)
| | - Taras P. Baranovskyi
- Department of Dermatovenerology, Allergology, Clinical and Laboratory Immunology, Shupyk National Healthcare University of Ukraine, 9 Dorohozhytska Str., 03680 Kiev, Ukraine;
- Kyiv Regional Clinical Hospital, 1 Baggovutivska Street, 04107 Kiev, Ukraine; (V.V.P.); (K.L.R.)
| | - Olga S. Iungin
- Biofilm Study Group, Department of Cell Regulatory Mechanisms, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 150 Zabolotnoho Str., 03680 Kiev, Ukraine; (O.S.I.); (I.P.); (S.Y.R.)
- Department of Biotechnology, Leather and Fur, Faculty of Chemical and Biopharmaceutical Technologies, Kyiv National University of Technologies and Design, Nemyrovycha-Danchenka Street, 2, 01011 Kiev, Ukraine
| | - Nadiia P. Kysil
- National Children’s Specialized Hospital “Okhmatdyt”, 28/1 Chornovola Str., 01135 Kiev, Ukraine;
| | - Larysa O. Metelytsia
- V. P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Science of Ukraine, 50 Kharkivske Schose, 01135 Kiev, Ukraine; (L.O.M.); (I.V.S.); (O.P.T.)
| | - Ianina Pokholenko
- Biofilm Study Group, Department of Cell Regulatory Mechanisms, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 150 Zabolotnoho Str., 03680 Kiev, Ukraine; (O.S.I.); (I.P.); (S.Y.R.)
| | - Viktoria V. Potochilova
- Kyiv Regional Clinical Hospital, 1 Baggovutivska Street, 04107 Kiev, Ukraine; (V.V.P.); (K.L.R.)
| | - Geert Potters
- Antwerp Maritime Academy, Noordkasteel Oost 6, 2030 Antwerp, Belgium;
- Department of Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
| | - Kateryna L. Rudnieva
- Kyiv Regional Clinical Hospital, 1 Baggovutivska Street, 04107 Kiev, Ukraine; (V.V.P.); (K.L.R.)
| | - Svitlana Y. Rymar
- Biofilm Study Group, Department of Cell Regulatory Mechanisms, Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 150 Zabolotnoho Str., 03680 Kiev, Ukraine; (O.S.I.); (I.P.); (S.Y.R.)
| | - Ivan V. Semenyuta
- V. P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Science of Ukraine, 50 Kharkivske Schose, 01135 Kiev, Ukraine; (L.O.M.); (I.V.S.); (O.P.T.)
| | - Andrew J. Spiers
- School of Applied Sciences, Abertay University, Bell Street, Dundee DD1 1HG, UK;
| | - Oksana P. Tarasyuk
- V. P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Science of Ukraine, 50 Kharkivske Schose, 01135 Kiev, Ukraine; (L.O.M.); (I.V.S.); (O.P.T.)
| | - Sergiy P. Rogalsky
- V. P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Science of Ukraine, 50 Kharkivske Schose, 01135 Kiev, Ukraine; (L.O.M.); (I.V.S.); (O.P.T.)
- Correspondence: (O.V.M.); (S.P.R.)
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6
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Koza A, Jerdan R, Cameron S, Spiers AJ. Three biofilm types produced by a model pseudomonad are differentiated by structural characteristics and fitness advantage. Microbiology (Reading) 2020; 166:707-716. [PMID: 32520698 DOI: 10.1099/mic.0.000938] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Model bacterial biofilm systems suggest that bacteria produce one type of biofilm, which is then modified by environmental and physiological factors, although the diversification of developing populations might result in the appearance of adaptive mutants producing altered structures with improved fitness advantage. Here we compare the air-liquid (A-L) interface viscous mass (VM) biofilm produced by Pseudomonas fluorescens SBW25 and the wrinkly spreader (WS) and complementary biofilm-forming strain (CBFS) biofilm types produced by adaptive SBW25 mutants in order to better understand the link between these physical structures and the fitness advantage they provide in experimental microcosms. WS, CBFS and VM biofilms can be differentiated by strength, attachment levels and rheology, as well as by strain characteristics associated with biofilm formation. Competitive fitness assays demonstrate that they provide similar advantages under static growth conditions but respond differently to increasing levels of physical disturbance. Pairwise competitions between biofilms suggest that these strains must be competing for at least two growth-limiting resources at the A-L interface, most probably O2 and nutrients, although VM and CBFS cells located lower down in the liquid column might provide an additional fitness advantage through the colonization of a less competitive zone below the biofilm. Our comparison of different SBW25 biofilm types illustrates more generally how varied biofilm characteristics and fitness advantage could become among adaptive mutants arising from an ancestral biofilm-forming strain and raises the question of how significant these changes might be in a range of medical, biotechnological and industrial contexts where diversification and change may be problematic.
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Affiliation(s)
- Anna Koza
- School of Applied Sciences, Abertay University, Bell Street, Dundee DD1 1HG, UK
| | - Robyn Jerdan
- School of Applied Sciences, Abertay University, Bell Street, Dundee DD1 1HG, UK
| | - Scott Cameron
- School of Applied Sciences, Abertay University, Bell Street, Dundee DD1 1HG, UK
| | - Andrew J Spiers
- School of Applied Sciences, Abertay University, Bell Street, Dundee DD1 1HG, UK
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7
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Jerdan R, Kuśmierska A, Petric M, Spiers AJ. Penetrating the air-liquid interface is the key to colonization and wrinkly spreader fitness. Microbiology (Reading) 2020; 165:1061-1074. [PMID: 31436522 DOI: 10.1099/mic.0.000844] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In radiating populations of Pseudomonas fluorescens SBW25, adaptive wrinkly spreader (WS) mutants are able to gain access to the air-liquid (A-L) interface of static liquid microcosms and achieve a significant competitive fitness advantage over other non-biofilm-forming competitors. Aerotaxis and flagella-based swimming allows SBW25 cells to move into the high-O2 region located at the top of the liquid column and maintain their position by countering the effects of random cell diffusion, convection and disturbance (i.e. physical displacement). However, wild-type cells showed significantly lower levels of enrichment in this region compared to the archetypal WS, indicating that WS cells employ an additional mechanism to transfer to the A-L interface where displacement is no longer an issue and a biofilm can develop at the top of the liquid column. Preliminary experiments suggest that this might be achieved through the expression of an as yet unidentified surface active agent that is weakly associated with WS cells and alters liquid surface tension, as determined by quantitative tensiometry. The effect of physical displacement on the colonization of the high-O2 region and A-L interface was reduced through the addition of agar or polyethylene glycol to increase liquid viscosity, and under these conditions the competitive fitness of the WS was significantly reduced. These observations suggest that the ability to transfer to the A-L interface from the high-O2 region and remain there without further expenditure of energy (through, for example, the deployment of flagella) is a key evolutionary innovation of the WS, as it allows subsequent biofilm development and significant population increase, thereby affording these adaptive mutants a competitive fitness advantage over non-biofilm-forming competitors located within the liquid column.
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Affiliation(s)
- Robyn Jerdan
- School of Applied Sciences, Abertay University, Dundee DD1 1HG, UK
| | - Anna Kuśmierska
- Department of Industrial Microbiology and Biotechnology, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland.,School of Applied Sciences, Abertay University, Dundee DD1 1HG, UK
| | - Marija Petric
- School of Applied Sciences, Abertay University, Dundee DD1 1HG, UK
| | - Andrew J Spiers
- School of Applied Sciences, Abertay University, Dundee DD1 1HG, UK
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8
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Jerdan R, Cameron S, Donaldson E, Iungin O, Moshynets OV, Spiers AJ. Community biofilm-formation, stratification and productivity in serially-transferred microcosms. FEMS Microbiol Lett 2020; 367:5989696. [PMID: 33206951 DOI: 10.1093/femsle/fnaa187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/16/2020] [Indexed: 12/13/2022] Open
Abstract
The establishment of O2 gradients in liquid columns by bacterial metabolic activity produces a spatially-structured environment. This produces a high-O2 region at the top that represents an un-occupied niche which could be colonised by biofilm-competent strains. We have used this to develop an experimental model system using soil-wash inocula and a serial-transfer approach to investigate changes in community-based biofilm-formation and productivity. This involved 10 transfers of mixed-community or biofilm-only samples over a total of 10-60 days incubation. In all final-transfer communities the ability to form biofilms was retained, though in longer incubations the build-up of toxic metabolites limited productivity. Measurements of microcosm productivity, biofilm-strength and attachment levels were used to assess community-aggregated traits which showed changes at both the community and individual-strain levels. Final-transfer communities were stratified with strains demonstrating a plastic phenotype when migrating between the high and low-O2 regions. The majority of community productivity came from the O2-depleted region rather than the top of the liquid column. This model system illustrates the complexity we expect to see in natural biofilm-forming communities. The connection between biofilms and the liquid column seen here has important implications for how these structures form and respond to selective pressure.
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Affiliation(s)
- Robyn Jerdan
- School of Applied Sciences, Abertay University, Bell Street, Dundee, DD1 1HG, UK
| | - Scott Cameron
- School of Applied Sciences, Abertay University, Bell Street, Dundee, DD1 1HG, UK
| | - Emily Donaldson
- School of Applied Sciences, Abertay University, Bell Street, Dundee, DD1 1HG, UK
| | - Olga Iungin
- Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, IMBG - '150 Zabolotnogo Street, Kiev 03143', Ukraine.,Kyiv National University of Technologies and Design, Tech & Design - 'Nemyrovycha-Danchenka Steet, Kiev 01011', Ukraine
| | - Olena V Moshynets
- Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, IMBG - '150 Zabolotnogo Street, Kiev 03143', Ukraine
| | - Andrew J Spiers
- School of Applied Sciences, Abertay University, Bell Street, Dundee, DD1 1HG, UK
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9
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Moshynets OV, Babenko LM, Rogalsky SP, Iungin OS, Foster J, Kosakivska IV, Potters G, Spiers AJ. Priming winter wheat seeds with the bacterial quorum sensing signal N-hexanoyl-L-homoserine lactone (C6-HSL) shows potential to improve plant growth and seed yield. PLoS One 2019; 14:e0209460. [PMID: 30802259 PMCID: PMC6388923 DOI: 10.1371/journal.pone.0209460] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Accepted: 02/07/2019] [Indexed: 01/07/2023] Open
Abstract
Several model plants are known to respond to bacterial quorum sensing molecules with altered root growth and gene expression patterns and induced resistance to plant pathogens. These compounds may represent novel elicitors that could be applied as seed primers to enhance cereal crop resistance to pathogens and abiotic stress and to improve yields. We investigated whether the acyl-homoserine lactone N-hexanoyl-L-homoserine lactone (C6-HSL) impacted winter wheat (Triticum aestivum L.) seed germination, plant development and productivity, using two Ukrainian varieties, Volodarka and Yatran 60, in both in vitro experiments and field trials. In vitro germination experiments indicated that C6-HSL seed priming had a small but significant positive impact on germination levels (1.2x increase, p < 0.0001), coleoptile and radicle development (1.4x increase, p < 0.0001). Field trials over two growing seasons (2015–16 and 2016–17) also demonstrated significant improvements in biomass at the tillering stage (1.4x increase, p < 0.0001), and crop structure and productivity at maturity including grain yield (1.4–1.5x increase, p < 0.0007) and quality (1.3x increase in good grain, p < 0.0001). In some cases variety effects were observed (p ≤ 0.05) suggesting that the effect of C6-HSL seed priming might depend on plant genetics, and some benefits of priming were also evident in F1 plants grown from seeds collected the previous season (p ≤ 0.05). These field-scale findings suggest that bacterial acyl-homoserine lactones such as C6-HSL could be used to improve cereal crop growth and yield and reduce reliance on fungicides and fertilisers to combat pathogens and stress.
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Affiliation(s)
- Olena V. Moshynets
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, Kiev, Ukraine
- * E-mail: (OM); (AS)
| | - Lidia M. Babenko
- M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Sergiy P. Rogalsky
- V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Olga S. Iungin
- D.K. Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Jessica Foster
- School of Science, Engineering and Technology, Abertay University, Dundee, United Kingdom
| | - Iryna V. Kosakivska
- M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, Kiev, Ukraine
| | - Geert Potters
- Antwerp Maritime Academy, Antwerp, Belgium
- Department of Bioscience Engineering, University of Antwerp, Antwerp, Belgium
| | - Andrew J. Spiers
- School of Science, Engineering and Technology, Abertay University, Dundee, United Kingdom
- * E-mail: (OM); (AS)
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Koza A, Kusmierska A, McLaughlin K, Moshynets O, Spiers AJ. Adaptive radiation of Pseudomonas fluorescens SBW25 in experimental microcosms provides an understanding of the evolutionary ecology and molecular biology of A-L interface biofilm formation. FEMS Microbiol Lett 2018; 364:3850210. [PMID: 28535292 DOI: 10.1093/femsle/fnx109] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/22/2017] [Indexed: 12/17/2022] Open
Abstract
Combined experimental evolutionary and molecular biology approaches have been used to investigate the adaptive radiation of Pseudomonas fluorescens SBW25 in static microcosms leading to the colonisation of the air-liquid interface by biofilm-forming mutants such as the Wrinkly Spreader (WS). In these microcosms, the ecosystem engineering of the early wild-type colonists establishes the niche space for subsequent WS evolution and colonisation. Random WS mutations occurring in the developing population that deregulate diguanylate cyclases and c-di-GMP homeostasis result in cellulose-based biofilms at the air-liquid interface. These structures allow Wrinkly Spreaders to intercept O2 diffusing into the liquid column and limit the growth of competitors lower down. As the biofilm matures, competition increasingly occurs between WS lineages, and niche divergence within the biofilm may support further diversification before system failure when the structure finally sinks. A combination of pleiotropic and epistasis effects, as well as secondary mutations, may explain variations in WS phenotype and fitness. Understanding how mutations subvert regulatory networks to express intrinsic genome potential and key innovations providing a selective advantage in novel environments is key to understanding the versatility of bacteria, and how selection and ecological opportunity can rapidly lead to substantive changes in phenotype and in community structure and function.
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Affiliation(s)
- Anna Koza
- School of Science, Engineering and Technology, Abertay University, Dundee DD1 1HG, UK
| | - Anna Kusmierska
- School of Science, Engineering and Technology, Abertay University, Dundee DD1 1HG, UK
| | - Kimberley McLaughlin
- School of Science, Engineering and Technology, Abertay University, Dundee DD1 1HG, UK
| | - Olena Moshynets
- Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine, Kiev 03143, Ukraine
| | - Andrew J Spiers
- School of Science, Engineering and Technology, Abertay University, Dundee DD1 1HG, UK
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11
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Kabir K, Deeni YY, Hapca SM, Moore L, Spiers AJ. Uncovering behavioural diversity amongst high-strength Pseudomonas spp. surfactants at the limit of liquid surface tension reduction. FEMS Microbiol Lett 2018; 365:4810749. [DOI: 10.1093/femsle/fny008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 01/15/2018] [Indexed: 11/15/2022] Open
Affiliation(s)
- Kamaluddeen Kabir
- School of Science, Engineering and Technology, Abertay University, Bell Street, Dundee, DD1 1HG, UK
| | - Yusuf Y Deeni
- School of Science, Engineering and Technology, Abertay University, Bell Street, Dundee, DD1 1HG, UK
| | - Simona M Hapca
- School of Science, Engineering and Technology, Abertay University, Bell Street, Dundee, DD1 1HG, UK
| | - Luke Moore
- School of Science, Engineering and Technology, Abertay University, Bell Street, Dundee, DD1 1HG, UK
| | - Andrew J Spiers
- School of Science, Engineering and Technology, Abertay University, Bell Street, Dundee, DD1 1HG, UK
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Harrison E, Hall JPJ, Paterson S, Spiers AJ, Brockhurst MA. Conflicting selection alters the trajectory of molecular evolution in a tripartite bacteria-plasmid-phage interaction. Mol Ecol 2017; 26:2757-2764. [PMID: 28247474 PMCID: PMC5655702 DOI: 10.1111/mec.14080] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 02/08/2017] [Accepted: 02/08/2017] [Indexed: 01/21/2023]
Abstract
Bacteria engage in a complex network of ecological interactions, which includes mobile genetic elements (MGEs) such as phages and plasmids. These elements play a key role in microbial communities as vectors of horizontal gene transfer but can also be important sources of selection for their bacterial hosts. In natural communities, bacteria are likely to encounter multiple MGEs simultaneously and conflicting selection among MGEs could alter the bacterial evolutionary response to each MGE. Here, we test the effect of interactions with multiple MGEs on bacterial molecular evolution in the tripartite interaction between the bacterium, Pseudomonas fluorescens, the lytic bacteriophage, SBW25φ2, and conjugative plasmid, pQBR103, using genome sequencing of experimentally evolved bacteria. We show that individually, both plasmids and phages impose selection leading to bacterial evolutionary responses that are distinct from bacterial populations evolving without MGEs, but that together, plasmids and phages impose conflicting selection on bacteria, constraining the evolutionary responses observed in pairwise interactions. Our findings highlight the likely difficulties of predicting evolutionary responses to multiple selective pressures from the observed evolutionary responses to each selective pressure alone. Understanding evolution in complex microbial communities comprising many species and MGEs will require that we go beyond studies of pairwise interactions.
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Affiliation(s)
- Ellie Harrison
- Department of Animal and Plant SciencesUniversity of SheffieldSheffieldS10 2TNUK
| | - James P. J. Hall
- Department of Animal and Plant SciencesUniversity of SheffieldSheffieldS10 2TNUK
| | - Steve Paterson
- Institute of Integrative BiologyUniversity of LiverpoolLiverpoolL69 7ZBUK
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13
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Harrison E, Dytham C, Hall JPJ, Guymer D, Spiers AJ, Paterson S, Brockhurst MA. Rapid compensatory evolution promotes the survival of conjugative plasmids. Mob Genet Elements 2016; 6:e1179074. [PMID: 27510852 PMCID: PMC4964889 DOI: 10.1080/2159256x.2016.1179074] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 04/08/2016] [Accepted: 04/12/2016] [Indexed: 12/14/2022] Open
Abstract
Conjugative plasmids play a vital role in bacterial adaptation through horizontal gene transfer. Explaining how plasmids persist in host populations however is difficult, given the high costs often associated with plasmid carriage. Compensatory evolution to ameliorate this cost can rescue plasmids from extinction. In a recently published study we showed that compensatory evolution repeatedly targeted the same bacterial regulatory system, GacA/GacS, in populations of plasmid-carrying bacteria evolving across a range of selective environments. Mutations in these genes arose rapidly and completely eliminated the cost of plasmid carriage. Here we extend our analysis using an individual based model to explore the dynamics of compensatory evolution in this system. We show that mutations which ameliorate the cost of plasmid carriage can prevent both the loss of plasmids from the population and the fixation of accessory traits on the bacterial chromosome. We discuss how dependent the outcome of compensatory evolution is on the strength and availability of such mutations and the rate at which beneficial accessory traits integrate on the host chromosome.
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Affiliation(s)
| | - Calvin Dytham
- Department of Biology, University of York , York, UK
| | | | - David Guymer
- Department of Biology, University of York , York, UK
| | | | - Steve Paterson
- Institute of Integrative Biology, University of Liverpool , Liverpool, UK
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14
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Abstract
Coevolution with bacteriophages is a major selective force shaping bacterial populations and communities. A variety of both environmental and genetic factors has been shown to influence the mode and tempo of bacteria–phage coevolution. Here, we test the effects that carriage of a large conjugative plasmid, pQBR103, had on antagonistic coevolution between the bacterium Pseudomonas fluorescens and its phage, SBW25ϕ2. Plasmid carriage limited bacteria–phage coevolution; bacteria evolved lower phage-resistance and phages evolved lower infectivity in plasmid-carrying compared with plasmid-free populations. These differences were not explained by effects of plasmid carriage on the costs of phage resistance mutations. Surprisingly, in the presence of phages, plasmid carriage resulted in the evolution of high frequencies of mucoid bacterial colonies. Mucoidy can provide weak partial resistance against SBW25ϕ2, which may have limited selection for qualitative resistance mutations in our experiments. Taken together, our results suggest that plasmids can have evolutionary consequences for bacteria that go beyond the direct phenotypic effects of their accessory gene cargo.
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Affiliation(s)
- Ellie Harrison
- Department of Biology, University of York, York YO10 5DD, UK
| | - Julie Truman
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Rosanna Wright
- Department of Biology, University of York, York YO10 5DD, UK
| | | | - Steve Paterson
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
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15
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Harrison E, Guymer D, Spiers AJ, Paterson S, Brockhurst MA. Parallel compensatory evolution stabilizes plasmids across the parasitism-mutualism continuum. Curr Biol 2015; 25:2034-9. [PMID: 26190075 DOI: 10.1016/j.cub.2015.06.024] [Citation(s) in RCA: 153] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 05/25/2015] [Accepted: 06/10/2015] [Indexed: 11/16/2022]
Abstract
Plasmids drive genomic diversity in bacteria via horizontal gene transfer [1, 2]; nevertheless, explaining their survival in bacterial populations is challenging [3]. Theory predicts that irrespective of their net fitness effects, plasmids should be lost: when parasitic (costs outweigh benefits), plasmids should decline due to purifying selection [4-6], yet under mutualism (benefits outweigh costs), selection favors the capture of beneficial accessory genes by the chromosome and loss of the costly plasmid backbone [4]. While compensatory evolution can enhance plasmid stability within populations [7-15], the propensity for this to occur across the parasitism-mutualism continuum is unknown. We experimentally evolved Pseudomonas fluorescens and its mercury resistance mega-plasmid, pQBR103 [16], across an environment-mediated parasitism-mutualism continuum. Compensatory evolution stabilized plasmids by rapidly ameliorating the cost of plasmid carriage in all environments. Genomic analysis revealed that, in both parasitic and mutualistic treatments, evolution repeatedly targeted the gacA/gacS bacterial two-component global regulatory system while leaving the plasmid sequence intact. Deletion of either gacA or gacS was sufficient to completely ameliorate the cost of plasmid carriage. Mutation of gacA/gacS downregulated the expression of ∼17% of chromosomal and plasmid genes and appears to have relieved the translational demand imposed by the plasmid. Chromosomal capture of mercury resistance accompanied by plasmid loss occurred throughout the experiment but very rarely invaded to high frequency, suggesting that rapid compensatory evolution can limit this process. Compensatory evolution can explain the widespread occurrence of plasmids and allows bacteria to retain horizontally acquired plasmids even in environments where their accessory genes are not immediately useful.
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Affiliation(s)
- Ellie Harrison
- Department of Biology, University of York, York YO10 5DD, UK
| | - David Guymer
- Department of Biology, University of York, York YO10 5DD, UK
| | | | - Steve Paterson
- Institute of Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK
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16
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Hall JPJ, Harrison E, Lilley AK, Paterson S, Spiers AJ, Brockhurst MA. Environmentally co-occurring mercury resistance plasmids are genetically and phenotypically diverse and confer variable context-dependent fitness effects. Environ Microbiol 2015; 17:5008-22. [PMID: 25969927 PMCID: PMC4989453 DOI: 10.1111/1462-2920.12901] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/20/2015] [Accepted: 05/05/2015] [Indexed: 01/26/2023]
Abstract
Plasmids are important mobile elements that can facilitate genetic exchange and local adaptation within microbial communities. We compared the sequences of four co‐occurring pQBR family environmental mercury resistance plasmids and measured their effects on competitive fitness of a Pseudomonas fluorescens
SBW25 host, which was isolated at the same field site. Fitness effects of carriage differed between plasmids and were strongly context dependent, varying with medium, plasmid status of competitor and levels of environmental mercury. The plasmids also varied widely in their rates of conjugation and segregational loss. We found that few of the plasmid‐borne accessory genes could be ascribed functions, although we identified a putative chemotaxis operon, a type IV pilus‐encoding cluster and a region encoding putative arylsulfatase enzymes, which were conserved across geographically distant isolates. One plasmid, pQBR55, conferred the ability to catabolize sucrose. Transposons, including the mercury resistance Tn5042, appeared to have been acquired by different pQBR plasmids by recombination, indicating an important role for horizontal gene transfer in the recent evolution of pQBR plasmids. Our findings demonstrate extensive genetic and phenotypic diversity among co‐occurring members of a plasmid community and suggest a role for environmental heterogeneity in the maintenance of plasmid diversity.
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Affiliation(s)
- James P J Hall
- Department of Biology, Wentworth Way, University of York, York, UK
| | - Ellie Harrison
- Department of Biology, Wentworth Way, University of York, York, UK
| | - Andrew K Lilley
- Pharmaceutical Science Research Division, King's College London, London, UK
| | - Steve Paterson
- Institute of Integrative Biology, University of Liverpool, Liverpool, UK
| | - Andrew J Spiers
- The SIMBIOS Centre, School of Science, Engineering and Technology, Abertay University, Dundee, UK
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17
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Udall YC, Deeni Y, Hapca SM, Raikes D, Spiers AJ. The evolution of biofilm-forming Wrinkly Spreaders in static microcosms and drip-fed columns selects for subtle differences in wrinkleality and fitness. FEMS Microbiol Ecol 2015; 91:fiv057. [DOI: 10.1093/femsec/fiv057] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/20/2015] [Indexed: 12/30/2022] Open
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18
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Vinoj G, Vaseeharan B, Thomas S, Spiers AJ, Shanthi S. Quorum-quenching activity of the AHL-lactonase from Bacillus licheniformis DAHB1 inhibits Vibrio biofilm formation in vitro and reduces shrimp intestinal colonisation and mortality. Mar Biotechnol (NY) 2014; 16:707-715. [PMID: 25060960 DOI: 10.1007/s10126-014-9585-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Accepted: 07/02/2014] [Indexed: 06/03/2023]
Abstract
Vibrio parahaemolyticus is a significant cause of gastroenteritis resulting from the consumption of undercooked sea foods and often cause significant infections in shrimp aquaculture. Vibrio virulence is associated with biofilm formation and is regulated by N-acylated homoserine lactone (AHL)-mediated quorum sensing. In an attempt to reduce vibrio colonisation of shrimps and mortality, we screened native intestinal bacilli from Indian white shrimps (Fenneropenaeus indicus) for an isolate which showed biofilm-inhibitory activity (quorum quenching) against the pathogen V. parahaemolyticus DAHP1. The AHL-lactonase (AiiA) expressed by one of these, Bacillus licheniformis DAHB1, was characterised as having a broad-spectrum AHL substrate specificity and intrinsic resistance to the acid conditions of the shrimp intestine. Purified recombinant AiiA inhibited vibrio biofilm development in a cover slip assay and significantly attenuated infection and mortality in shrimps reared in a recirculation aquaculture system. Investigation of intestinal samples also showed that AiiA treatment also reduced vibrio viable counts and biofilm development as determined by confocal laser scanning microscopy (CLSM) imaging. These findings suggest that the B. licheniformis DAHB1 quorum-quenching AiiA might be developed for use as a prophylactic treatment to inhibit or reduce vibrio colonisation and mortality of shrimps in aquaculture.
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Affiliation(s)
- G Vinoj
- Crustacean Molecular Biology and Genomics Laboratory, Department of Animal Health and Management, Alagappa University, Science Block, 4th Floor, Burma Colony, Karaikudi, 630 004, Tamil Nadu, India
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19
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Mohammed IU, Deeni Y, Hapca SM, McLaughlin K, Spiers AJ. Predicting the minimum liquid surface tension activity of pseudomonads expressing biosurfactants. Lett Appl Microbiol 2014; 60:37-43. [PMID: 25256441 DOI: 10.1111/lam.12331] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 09/12/2014] [Accepted: 09/19/2014] [Indexed: 11/28/2022]
Abstract
UNLABELLED Bacteria produce a variety of biosurfactants capable of significantly reducing liquid (aqueous) surface tension (γ) with a range of biological roles and biotechnological uses. To determine the lowest achievable surface tension (γMin ), we tested a diverse collection of Pseudomonas-like isolates from contaminated soil and activated sludge and identified those expressing biosurfactants by drop-collapse assay. Liquid surface tension-reducing ability was quantitatively determined by tensiometry, with 57 isolates found to significantly lower culture supernatant surface tensions to 24·5-49·1 mN m(-1) . Differences in biosurfactant behaviour determined by foaming, emulsion and oil-displacement assays were also observed amongst isolates producing surface tensions of 25-27 mN m(-1) , suggesting that a range of structurally diverse biosurfactants were being expressed. Individual distribution identification (IDI) analysis was used to identify the theoretical probability distribution that best fitted the surface tension data, which predicted a γMin of 24·24 mN m(-1) . This was in agreement with predictions based on earlier work of published mixed bacterial spp. data, suggesting a fundamental limit to the ability of bacterial biosurfactants to reduce surface tensions in aqueous systems. This implies a biological restriction on the synthesis and export of these agents or a physical-chemical restriction on their functioning once produced. SIGNIFICANCE AND IMPACT OF THE STUDY Numerous surveys of biosurfactant-producing bacteria have been conducted, but only recently has an attempt been made to predict the minimum liquid surface tension these surface-active agents can achieve. Here, we determine a theoretical minimum of 24 mN m(-1) by statistical analysis of tensiometry data, suggesting a fundamental limit for biosurfactant activity in bacterial cultures incubated under standard growth conditions. This raises a challenge to our understanding of biosurfactant expression, secretion and function, as well as being of interest to biotechnology where they are used in an increasingly wide range of applications.
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Affiliation(s)
- I U Mohammed
- SIMBIOS Centre & School of Science, Engineering and Technology, Abertay University, Dundee, UK
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20
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Downie HF, Valentine TA, Otten W, Spiers AJ, Dupuy LX. Transparent soil microcosms allow 3D spatial quantification of soil microbiological processes in vivo. Plant Signal Behav 2014; 9:e970421. [PMID: 25482802 PMCID: PMC4622970 DOI: 10.4161/15592316.2014.970421] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Revised: 07/08/2014] [Accepted: 07/09/2014] [Indexed: 05/04/2023]
Abstract
The recently developed transparent soil consists of particles of Nafion, a polymer with a low refractive index (RI), which is prepared by milling and chemical treatment for use as a soil analog. After the addition of a RI-matched solution, confocal imaging can be carried out in vivo and without destructive sampling. In a previous study, we showed that the new substrate provides a good approximation of plant growth conditions found in natural soils. In this paper, we present further development of the techniques for detailed quantitative analysis of images of root-microbe interactions in situ. Using this system it was possible for the first time to analyze bacterial distribution along the roots and in the bulk substrate in vivo. These findings indicate that the coupling of transparent soil with light microscopy is an important advance toward the discovery of the mechanisms of microbial colonisation of the rhizosphere.
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Affiliation(s)
- Helen F Downie
- The James Hutton Institute; Invergowrie, Dundee, UK
- The SIMBIOS Center; Abertay University; Dundee, UK
- Current affiliation: Williamson Research Center for Molecular Environmental Science; University of Manchester; Manchester, UK
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21
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Abstract
Understanding of soil processes is essential for addressing the global issues of food security, disease transmission and climate change. However, techniques for observing soil biology are lacking. We present a heterogeneous, porous, transparent substrate for in situ 3D imaging of living plants and root-associated microorganisms using particles of the transparent polymer, Nafion, and a solution with matching optical properties. Minerals and fluorescent dyes were adsorbed onto the Nafion particles for nutrient supply and imaging of pore size and geometry. Plant growth in transparent soil was similar to that in soil. We imaged colonization of lettuce roots by the human bacterial pathogen Escherichia coli O157:H7 showing micro-colony development. Micro-colonies may contribute to bacterial survival in soil. Transparent soil has applications in root biology, crop genetics and soil microbiology.
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Affiliation(s)
- Helen Downie
- The James Hutton Institute, Invergowrie, Dundee, United Kingdom
- The SIMBIOS Centre, University of Abertay Dundee, Bell Street, Dundee, United Kingdom
| | - Nicola Holden
- The James Hutton Institute, Invergowrie, Dundee, United Kingdom
| | - Wilfred Otten
- The SIMBIOS Centre, University of Abertay Dundee, Bell Street, Dundee, United Kingdom
| | - Andrew J. Spiers
- The SIMBIOS Centre, University of Abertay Dundee, Bell Street, Dundee, United Kingdom
| | | | - Lionel X. Dupuy
- The James Hutton Institute, Invergowrie, Dundee, United Kingdom
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Fechtner J, Koza A, Sterpaio PD, Hapca SM, Spiers AJ. Surfactants expressed by soil pseudomonads alter local soil-water distribution, suggesting a hydrological role for these compounds. FEMS Microbiol Ecol 2011; 78:50-8. [DOI: 10.1111/j.1574-6941.2011.01141.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Silby MW, Cerdeño-Tárraga AM, Vernikos GS, Giddens SR, Jackson RW, Preston GM, Zhang XX, Moon CD, Gehrig SM, Godfrey SAC, Knight CG, Malone JG, Robinson Z, Spiers AJ, Harris S, Challis GL, Yaxley AM, Harris D, Seeger K, Murphy L, Rutter S, Squares R, Quail MA, Saunders E, Mavromatis K, Brettin TS, Bentley SD, Hothersall J, Stephens E, Thomas CM, Parkhill J, Levy SB, Rainey PB, Thomson NR. Genomic and genetic analyses of diversity and plant interactions of Pseudomonas fluorescens. Genome Biol 2009; 10:R51. [PMID: 19432983 PMCID: PMC2718517 DOI: 10.1186/gb-2009-10-5-r51] [Citation(s) in RCA: 324] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 04/21/2009] [Accepted: 05/11/2009] [Indexed: 11/14/2022] Open
Abstract
Comparison of the genome sequences of three Pseudomonas fluorescens strains reveals a heterogeneity reminiscent of a species complex rather than a single species Background Pseudomonas fluorescens are common soil bacteria that can improve plant health through nutrient cycling, pathogen antagonism and induction of plant defenses. The genome sequences of strains SBW25 and Pf0-1 were determined and compared to each other and with P. fluorescens Pf-5. A functional genomic in vivo expression technology (IVET) screen provided insight into genes used by P. fluorescens in its natural environment and an improved understanding of the ecological significance of diversity within this species. Results Comparisons of three P. fluorescens genomes (SBW25, Pf0-1, Pf-5) revealed considerable divergence: 61% of genes are shared, the majority located near the replication origin. Phylogenetic and average amino acid identity analyses showed a low overall relationship. A functional screen of SBW25 defined 125 plant-induced genes including a range of functions specific to the plant environment. Orthologues of 83 of these exist in Pf0-1 and Pf-5, with 73 shared by both strains. The P. fluorescens genomes carry numerous complex repetitive DNA sequences, some resembling Miniature Inverted-repeat Transposable Elements (MITEs). In SBW25, repeat density and distribution revealed 'repeat deserts' lacking repeats, covering approximately 40% of the genome. Conclusions P. fluorescens genomes are highly diverse. Strain-specific regions around the replication terminus suggest genome compartmentalization. The genomic heterogeneity among the three strains is reminiscent of a species complex rather than a single species. That 42% of plant-inducible genes were not shared by all strains reinforces this conclusion and shows that ecological success requires specialized and core functions. The diversity also indicates the significant size of genetic information within the Pseudomonas pan genome.
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Affiliation(s)
- Mark W Silby
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Centre for Adaptation Genetics and Drug Resistance, Boston, MA 02111, USA.
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Koza A, Hallett PD, Moon CD, Spiers AJ. Characterization of a novel air-liquid interface biofilm of Pseudomonas fluorescens SBW25. Microbiology (Reading) 2009; 155:1397-1406. [PMID: 19383709 DOI: 10.1099/mic.0.025064-0] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Pseudomonads are able to form a variety of biofilms that colonize the air-liquid (A-L) interface of static liquid microcosms, and differ in matrix composition, strength, resilience and degrees of attachment to the microcosm walls. From Pseudomonas fluorescens SBW25, mutants have evolved during prolonged adaptation-evolution experiments which produce robust biofilms of the physically cohesive class at the A-L interface, and which have been well characterized. In this study we describe a novel A-L interface biofilm produced by SBW25 that is categorized as a viscous mass (VM)-class biofilm. Several metals were found to induce this biofilm in static King's B microcosms, including copper, iron, lead and manganese, and we have used iron to allow further examination of this structure. Iron was demonstrated to induce SBW25 to express cellulose, which provided the matrix of the biofilm, a weak structure that was readily destroyed by physical disturbance. This was confirmed in situ by a low (0.023-0.047 g) maximum deformation mass and relatively poor attachment as measured by crystal violet staining. Biofilm strength increased with increasing iron concentration, in contrast to attachment levels, which decreased with increasing iron. Furthermore, iron added to mature biofilms significantly increased strength, suggesting that iron also promotes interactions between cellulose fibres that increase matrix interconnectivity. Whilst weak attachment is important in maintaining the biofilm at the A-L interface, surface-interaction effects involving cellulose, which reduced surface tension by approximately 3.8 mN m(-1), may also contribute towards this localization. The fragility and viscoelastic nature of the biofilm were confirmed by controlled-stress amplitude sweep tests to characterize critical rheological parameters, which included a shear modulus of 0.75 Pa, a zero shear viscosity of 0.24 Pa s(-1) and a flow point of 0.028 Pa. Growth and morphological data thus far support a non-specific metal-associated physiological, rather than mutational, origin for production of the SBW25 VM biofilm, which is an example of the versatility of bacteria to inhabit optimal niches within their environment.
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Affiliation(s)
- Anna Koza
- SIMBIOS Centre, Level 5 Kydd Building, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, UK
| | - Paul D Hallett
- Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Christina D Moon
- AgResearch Limited, Grasslands Research Centre, Private Bag 11008, Palmerston North, New Zealand
| | - Andrew J Spiers
- SIMBIOS Centre, Level 5 Kydd Building, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, UK
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25
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Huang WE, Singer AC, Spiers AJ, Preston GM, Whiteley AS. Characterizing the regulation of the Pu promoter in Acinetobacter baylyi ADP1. Environ Microbiol 2008; 10:1668-80. [DOI: 10.1111/j.1462-2920.2008.01583.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Malone JG, Williams R, Christen M, Jenal U, Spiers AJ, Rainey PB. The structure-function relationship of WspR, a Pseudomonas fluorescens response regulator with a GGDEF output domain. Microbiology (Reading) 2007; 153:980-994. [PMID: 17379708 DOI: 10.1099/mic.0.2006/002824-0] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The GGDEF response regulator WspR couples the chemosensory Wsp pathway to the overproduction of acetylated cellulose and cell attachment in the Pseudomonas fluorescens SBW25 wrinkly spreader (WS) genotype. Here, it is shown that WspR is a diguanylate cyclase (DGC), and that DGC activity is elevated in the WS genotype compared to that in the ancestral smooth (SM) genotype. A structure-function analysis of 120 wspR mutant alleles was employed to gain insight into the regulation and activity of WspR. Firstly, 44 random and defined pentapeptide insertions were produced in WspR, and the effects determined using assays based on colony morphology, attachment to surfaces and cellulose production. The effects of mutations within WspR were interpreted using a homology model, based on the crystal structure of Caulobacter crescentus PleD. Mutational analyses indicated that WspR activation occurs as a result of disruption of the interdomain interface, leading to the release of effector-domain repression by the N-terminal receiver domain. Quantification of attachment and cellulose production raised significant questions concerning the mechanisms of WspR function. The conserved RYGGEEF motif of WspR was also subjected to mutational analysis, and 76 single amino acid residue substitutions were tested for their effects on WspR function. The RYGGEEF motif of WspR is functionally conserved, with almost every mutation abolishing function.
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Affiliation(s)
- J G Malone
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
- Division of Molecular Microbiology, Biozentrum, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland
| | - R Williams
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - M Christen
- Division of Molecular Microbiology, Biozentrum, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland
| | - U Jenal
- Division of Molecular Microbiology, Biozentrum, Klingelbergstrasse 50-70, CH-4056 Basel, Switzerland
| | - A J Spiers
- Centre for Ecology and Hydrology, Mansfield Road, Oxford OX1 3SR, UK
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - P B Rainey
- School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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Abstract
In this article, an overview of some of the latest developments in the field of cerebral cortex to computer interfacing (CCCI) is given. This is posed in the more general context of Brain-Computer Interfaces in order to assess advantages and disadvantages. The emphasis is clearly placed on practical studies that have been undertaken and reported on, as opposed to those speculated, simulated or proposed as future projects. Related areas are discussed briefly only in the context of their contribution to the studies being undertaken. The area of focus is notably the use of invasive implant technology, where a connection is made directly with the cerebral cortex and/or nervous system. Tests and experimentation which do not involve human subjects are invariably carried out a priori to indicate the eventual possibilities before human subjects are themselves involved. Some of the more pertinent animal studies from this area are discussed. The paper goes on to describe human experimentation, in which neural implants have linked the human nervous system bidirectionally with technology and the internet. A view is taken as to the prospects for the future for CCCI, in terms of its broad therapeutic role.
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Affiliation(s)
- K Warwick
- Department of Cybernetics, University of Reading, Reading, UK.
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Spiers AJ. Wrinkly-Spreader fitness in the two-dimensional agar plate microcosm: maladaptation, compensation and ecological success. PLoS One 2007; 2:e740. [PMID: 17710140 PMCID: PMC1939736 DOI: 10.1371/journal.pone.0000740] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Accepted: 07/10/2007] [Indexed: 11/19/2022] Open
Abstract
Bacterial adaptation to new environments often leads to the establishment of new genotypes with significantly altered phenotypes. In the Wrinkly Spreader (WS), ecological success in static liquid microcosms was through the rapid colonisation of the air-liquid interface by the production of a cellulose-based biofilm. Rapid surface spreading was also seen on agar plates, but in this two-dimensional environment the WS appears maladapted and rapidly reverts to the ancestral smooth (SM)-like colony genotype. In this work, the fitness of WS relative to SM in mixed colonies was found to be low, confirming the WS instability on agar plates. By examining defined WS mutants, the maladaptive characteristic was found to be the expression of cellulose. SM-like revertants had a higher growth rate than WS and no longer expressed significant amounts of cellulose, further confirming that the expression of this high-cost polymer was the basis of maladaptation and the target of compensatory mutation in developing colonies. However, examination of the fate of WS-founded populations in either multiple-colony or single mega-colony agar plate microcosms demonstrated that the loss of WS lineages could be reduced under conditions in which the rapid spreading colony phenotype could dominate nutrient and oxygen access more effectively than competing SM/SM-like genotypes. WS-like isolates recovered from such populations showed increased WS phenotype stability as well as changes in the degree of colony spreading, confirming that the WS was adapting to the two-dimensional agar plate microcosm.
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Affiliation(s)
- Andrew J Spiers
- Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
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29
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Tett A, Spiers AJ, Crossman LC, Ager D, Ciric L, Dow JM, Fry JC, Harris D, Lilley A, Oliver A, Parkhill J, Quail MA, Rainey PB, Saunders NJ, Seeger K, Snyder LAS, Squares R, Thomas CM, Turner SL, Zhang XX, Field D, Bailey MJ. Sequence-based analysis of pQBR103; a representative of a unique, transfer-proficient mega plasmid resident in the microbial community of sugar beet. ISME J 2007; 1:331-40. [PMID: 18043644 PMCID: PMC2656933 DOI: 10.1038/ismej.2007.47] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The plasmid pQBR103 was found within Pseudomonas populations colonizing the leaf and root surfaces of sugar beet plants growing at Wytham, Oxfordshire, UK. At 425 kb it is the largest self-transmissible plasmid yet sequenced from the phytosphere. It is known to enhance the competitive fitness of its host, and parts of the plasmid are known to be actively transcribed in the plant environment. Analysis of the complete sequence of this plasmid predicts a coding sequence (CDS)-rich genome containing 478 CDSs and an exceptional degree of genetic novelty; 80% of predicted coding sequences cannot be ascribed a function and 60% are orphans. Of those to which function could be assigned, 40% bore greatest similarity to sequences from Pseudomonas spp, and the majority of the remainder showed similarity to other gamma-proteobacterial genera and plasmids. pQBR103 has identifiable regions presumed responsible for replication and partitioning, but despite being tra+ lacks the full complement of any previously described conjugal transfer functions. The DNA sequence provided few insights into the functional significance of plant-induced transcriptional regions, but suggests that 14% of CDSs may be expressed (11 CDSs with functional annotation and 54 without), further highlighting the ecological importance of these novel CDSs. Comparative analysis indicates that pQBR103 shares significant regions of sequence with other plasmids isolated from sugar beet plants grown at the same geographic location. These plasmid sequences indicate there is more novelty in the mobile DNA pool accessible to phytosphere pseudomonas than is currently appreciated or understood.
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Affiliation(s)
- Adrian Tett
- Centre for Ecology and Hydrology-Oxford, Oxford, UK
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Ude S, Bailey MJ, Huang WE, Spiers AJ. The environmental plasmid pQBR103 alters the single-cell Raman spectral profile of Pseudomonas fluorescens SBW25. Microb Ecol 2007; 53:494-7. [PMID: 17431708 DOI: 10.1007/s00248-006-9191-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Revised: 11/08/2006] [Accepted: 11/26/2006] [Indexed: 05/14/2023]
Abstract
Although plasmids are ubiquitous amongst phytosphere pseudomonads, the advantage and costs of plasmids for the bacterial host remain unclear. The application of single-cell Raman spectral analysis to plasmid-bacterial systems under different environmental conditions offers a new means of determining the impact of plasmids on host cell physiology, metabolic status, and response to stress.
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Affiliation(s)
- Susanne Ude
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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Huang WE, Ude S, Spiers AJ. Pseudomonas fluorescens SBW25 biofilm and planktonic cells have differentiable Raman spectral profiles. Microb Ecol 2007; 53:471-4. [PMID: 17345138 DOI: 10.1007/s00248-006-9190-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Revised: 11/08/2006] [Accepted: 11/26/2006] [Indexed: 05/14/2023]
Abstract
Biofilms, and other bacterial aggregations, are of significance in both environmental microbiology and in plant and human pathogenesis. Comparative single-cell Raman spectral analysis can differentiate between planktonic bacteria and those recovered from biofilms and appears to offer a new means by which to investigate bacterial cell physiology, metabolic status, and stress under different environmental conditions.
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Affiliation(s)
- Wei E Huang
- Molecular Microbiology Ecology Section, CEH-Oxford, Mansfield Road, Oxford, OX1 3SR, UK
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Huang WE, Bailey MJ, Thompson IP, Whiteley AS, Spiers AJ. Single-cell Raman spectral profiles of Pseudomonas fluorescens SBW25 reflects in vitro and in planta metabolic history. Microb Ecol 2007; 53:414-25. [PMID: 17334857 DOI: 10.1007/s00248-006-9138-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Accepted: 07/10/2006] [Indexed: 05/14/2023]
Abstract
Single-cell Raman microspectroscopy has the potential to report on the whole-cell chemical composition of bacteria, reflecting metabolic status as well as growth history. This potential has been demonstrated through the discriminant functional analysis of Raman spectral profiles (RSP) obtained from the soil and plant-associated bacterium Pseudomonas fluorescens SBW25, grown in vitro using defined media, and in planta using 3-month-old sugar beets (Beta vulgaris var. Roberta). SBW25 in vitro RSP data showed significant variation between those cells grown on different amino acids, sugars, TCA cycle intermediates, rich King's B, and culture media derived from the sugar beet phytosphere. Raman analysis was also able to follow the transition of SBW25 starved of carbon over a period of days, and SBW25 in planta RSP data also showed variation with significant differences between bacteria recovered from soil and the rhizosphere. SBW25 whole-cell chemical composition, and therefore growth and metabolic history, could be interpreted by coanalyzing in vitro and in planta RSP data. SBW25 recovered from the phytosphere was found to be more similar to SBW25 grown in vitro on Fru or Asp, rather than on Glc or Arg, and quite dissimilar to that resulting from carbon starvation. This suggests that SBW25 growth in the phytosphere is generally neither carbon-catabolite-repressed nor carbon-limited. These findings demonstrate that the analysis of single-cell RSP can differentiate between isogenic populations of bacteria with different metabolic histories or after recovery from different parts of their natural environment. In addition, Raman analysis is also capable of providing biologically relevant biochemical inferences, which might then be tested to uncover the mechanistic basis (biochemical-metabolic-genetic) differentiating bacteria growing in complex environments and exposed to different conditions.
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Affiliation(s)
- Wei E Huang
- Molecular Microbiology Ecology and Environmental Biotechnology Sections, CEH Oxford, Mansfield Road, Oxford, OX1 3SR, UK
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33
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Bantinaki E, Kassen R, Knight CG, Robinson Z, Spiers AJ, Rainey PB. Adaptive divergence in experimental populations of Pseudomonas fluorescens. III. Mutational origins of wrinkly spreader diversity. Genetics 2007; 176:441-53. [PMID: 17339222 PMCID: PMC1893022 DOI: 10.1534/genetics.106.069906] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Understanding the connections among genotype, phenotype, and fitness through evolutionary time is a central goal of evolutionary genetics. Wrinkly spreader (WS) genotypes evolve repeatedly in model Pseudomonas populations and show substantial morphological and fitness differences. Previous work identified genes contributing to the evolutionary success of WS, in particular the di-guanylate cyclase response regulator, WspR. Here we scrutinize the Wsp signal transduction pathway of which WspR is the primary output component. The pathway has the hallmarks of a chemosensory pathway and genetic analyses show that regulation and function of Wsp is analogous to the Che chemotaxis pathway from Escherichia coli. Of significance is the methyltransferase (WspC) and methylesterase (WspF) whose opposing activities form an integral feedback loop that controls the activity of the kinase (WspE). Deductions based on the regulatory model suggested that mutations within wspF were a likely cause of WS. Analyses of independent WS genotypes revealed numerous simple mutations in this single open reading frame. Remarkably, different mutations have different phenotypic and fitness effects. We suggest that the negative feedback loop inherent in Wsp regulation allows the pathway to be tuned by mutation in a rheostat-like manner.
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Affiliation(s)
- Eleni Bantinaki
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
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34
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Abstract
The ability to form biofilms is seen as an increasingly important colonization strategy among both pathogenic and environmental bacteria. A survey of 185 plant-associated, phytopathogenic, soil and river Pseudomonas isolates resulted in 76% producing biofilms at the air-liquid (A-L) interface after selection in static microcosms. Considerable variation in biofilm phenotype was observed, including waxy aggregations, viscous and floccular masses, and physically cohesive biofilms with continuously varying strengths over 1500-fold. Calcofluor epifluorescent microscopy identified cellulose as the matrix component in biofilms produced by Pseudomonas asplenii, Pseudomonas corrugata, Pseudomonas fluorescens, Pseudomonas marginalis, Pseudomonas putida, Pseudomonas savastanoi and Pseudomonas syringae isolates. Cellulose expression and biofilm formation could be induced by the constitutively active WspR19 mutant of the cyclic-di-GMP-associated, GGDEF domain-containing response regulator involved in the P. fluorescens SBW25 wrinkly spreader phenotype and cellular aggregation in Pseudomonas aeruginosa PA01. WspR19 could also induce P. putida KT2440, which otherwise did not produce a biofilm or express cellulose, as well as Escherichia coli K12 and Salmonella typhimurium LT2, both of which express cellulose yet lack WspR homologues. Statistical analysis of biofilm parameters suggest that biofilm development is a more complex process than that simply described by the production of attachment and matrix components and bacterial growth. This complexity was also seen in multivariate analysis as a species-ecological habitat effect, underscoring the fact that in vitro biofilms are abstractions of those surface and volume colonization processes used by bacteria in their natural environments.
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Affiliation(s)
- Susanne Ude
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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35
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Huang WE, Spiers AJ. Consideration of Future Requirements for Raman Microbiology as an Examplar for the Ab Initio Development of Informatics Frameworks for Emergent OMICS Technologies. OMICS: A Journal of Integrative Biology 2006; 10:238-41. [PMID: 16901232 DOI: 10.1089/omi.2006.10.238] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Raman spectroscopy of single bacteria provides an OMIC-like view of the chemical status of individual cells, reporting on metabolism, cell stress and growth, and is likely to become a significant tool in environmental and medical microbiology. We advocate the early development of integrated data models and informatics frameworks, in parallel with the development of Raman hardware and experimental protocols, in order to maximize the benefits of this emerging OMIC technology to the research community.
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Affiliation(s)
- Wei E Huang
- Molecular Microbiology Ecology and Environmental Biotechnology Sections, Oxford, United Kingdom
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36
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Goymer P, Kahn SG, Malone JG, Gehrig SM, Spiers AJ, Rainey PB. Adaptive divergence in experimental populations of Pseudomonas fluorescens. II. Role of the GGDEF regulator WspR in evolution and development of the wrinkly spreader phenotype. Genetics 2006; 173:515-26. [PMID: 16624907 PMCID: PMC1526540 DOI: 10.1534/genetics.106.055863] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Wrinkly spreader (WS) genotypes evolve repeatedly in model Pseudomonas populations undergoing adaptive radiation. Previous work identified genes contributing to the evolutionary success of WS. Here we scrutinize the GGDEF response regulator protein WspR and show that it is both necessary and sufficient for WS. Activation of WspR occurs by phosphorylation and different levels of activation generate phenotypic differences among WS genotypes. Five alleles of wspR, each encoding a protein with a single amino acid substitution, were generated by mutagenesis. Two alleles are constitutively active and cause the ancestral genotype to develop a WS phenotype; the phenotypic effects are allele specific and independent of phosphorylation. Three alleles contain changes in the GGDEF domain and when overexpressed in WS cause reversion to the ancestral phenotype. Ability to mimic this effect by overexpression of a liberated N-terminal domain shows that in WS, regulatory components upstream of WspR are overactive. To connect changes at the nucleotide level with fitness, the effects of variant alleles were examined in both structured and unstructured environments: alleles had adaptive and deleterious effects with trade-offs evident across environments. Despite the proclivity of mutations within wspR to generate WS, sequence analysis of wspR from 53 independently obtained WS showed no evidence of sequence change in this gene.
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Spiers AJ, Rainey PB. The Pseudomonas fluorescens SBW25 wrinkly spreader biofilm requires attachment factor, cellulose fibre and LPS interactions to maintain strength and integrity. Microbiology (Reading) 2005; 151:2829-2839. [PMID: 16151196 DOI: 10.1099/mic.0.27984-0] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The wrinkly spreader (WS) isolate of Pseudomonas fluorescens SBW25 forms a substantial biofilm at the air-liquid interface. The biofilm is composed of an extracellular partially acetylated cellulose-fibre matrix, and previous mutagenesis of WS with mini-Tn5 had identified both the regulatory and cellulose-biosynthetic operons. One uncharacterized WS mutant, WS-5, still expressed cellulose but produced very weak biofilms. In this work, the mini-Tn5 insertion site in WS-5 has been identified as being immediately upstream of the tol-pal operon. Like Tol-Pal mutants of other Gram-negative bacteria, WS-5 showed a "leaky-membrane" phenotype, including the serendipitous ability to utilize sucrose, increased uptake of the hydrophilic dye propidium iodide, and the loss of lipopolysaccharide (LPS) expression. WS-5 cells were altered in relative hydrophobicity, and showed poorer recruitment and maintenance in the biofilm than WS. The WS-5 biofilm was also less sensitive to chemical interference during development. However, growth rate, cellulose expression and attachment were not significantly different between WS and WS-5. Finally, WS-5 biofilms could be partially complemented with WS-4, a biofilm- and attachment-deficient mutant that expressed LPS, resulting in a mixed biofilm with significantly increased strength. These findings show that a major component of the WS air-liquid biofilm strength results from the interactions between LPS and the cellulose matrix of the biofilm--and that in the WS biofilm, cellulose fibres, attachment factor and LPS are required for biofilm development, strength and integrity.
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Affiliation(s)
- Andrew J Spiers
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
| | - Paul B Rainey
- School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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Gal M, Preston GM, Massey RC, Spiers AJ, Rainey PB. Genes encoding a cellulosic polymer contribute toward the ecological success of Pseudomonas fluorescens SBW25 on plant surfaces. Mol Ecol 2004; 12:3109-21. [PMID: 14629390 DOI: 10.1046/j.1365-294x.2003.01953.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Pseudomonas fluorescens SBW25 is a Gram-negative bacterium that grows in close association with plants. In common with a broad range of functionally similar bacteria it plays an important role in the turnover of organic matter and certain isolates can promote plant growth. Despite its environmental significance, the causes of its ecological success are poorly understood. Here we describe the development and application of a simple promoter trapping strategy (IVET) to identify P. fluorescens SBW25 genes showing elevated levels of expression in the sugar beet rhizosphere. A total of 25 rhizosphere-induced (rhi) fusions are reported with predicted roles in nutrient acquisition, stress responses, biosynthesis of phytohormones and antibiotics. One rhi fusion is to wss, an operon encoding an acetylated cellulose polymer. A mutant carrying a defective wss locus was competitively compromised (relative to the wild type) in the rhizosphere and in the phyllosphere, but not in bulk soil. The rhizosphere-induced wss locus therefore contributes to the ecological performance of SBW25 in the plant environment and supports our conjecture that genes inactive in the laboratory environment, but active in the wild, are likely to be determinants of fitness in natural environments.
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Affiliation(s)
- Micaela Gal
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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Spiers AJ, Bohannon J, Gehrig SM, Rainey PB. Biofilm formation at the air-liquid interface by the Pseudomonas fluorescens SBW25 wrinkly spreader requires an acetylated form of cellulose. Mol Microbiol 2003; 50:15-27. [PMID: 14507360 DOI: 10.1046/j.1365-2958.2003.03670.x] [Citation(s) in RCA: 268] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The wrinkly spreader (WS) genotype of Pseudomonas fluorescens SBW25 colonizes the air-liquid interface of spatially structured microcosms resulting in formation of a thick biofilm. Its ability to colonize this niche is largely due to overproduction of a cellulosic polymer, the product of the wss operon. Chemical analysis of the biofilm matrix shows that the cellulosic polymer is partially acetylated cellulose, which is consistent with predictions of gene function based on in silico analysis of wss. Both polar and non-polar mutations in the sixth gene of the wss operon (wssF ) or adjacent downstream genes (wssGHIJ ) generated mutants that overproduce non-acetylated cellulose, thus implicating WssFGHIJ in acetylation of cellulose. WssGHI are homologues of AlgFIJ from P. aeruginosa, which together are necessary and sufficient to acetylate alginate polymer. WssF belongs to a newly established Pfam family and is predicted to provide acyl groups to WssGHI. The role of WssJ is unclear, but its similarity to MinD-like proteins suggests a role in polar localization of the acetylation complex. Fluorescent microscopy of Calcofluor-stained biofilms revealed a matrix structure composed of networks of cellulose fibres, sheets and clumped material. Quantitative analyses of biofilm structure showed that acetylation of cellulose is important for effective colonization of the air-liquid interface: mutants identical to WS, but defective in enzymes required for acetylation produced biofilms with altered physical properties. In addition, mutants producing non-acetylated cellulose were unable to spread rapidly across solid surfaces. Inclusion in these assays of a WS mutant with a defect in the GGDEF regulator (WspR) confirmed the requirement for this protein in expression of both acetylated cellulose polymer and bacterial attachment. These results suggest a model in which WspR regulation of cellulose expression and attachment plays a role in the co-ordination of surface colonization.
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Affiliation(s)
- Andrew J Spiers
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
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Spiers AJ, Kahn SG, Bohannon J, Travisano M, Rainey PB. Adaptive divergence in experimental populations of Pseudomonas fluorescens. I. Genetic and phenotypic bases of wrinkly spreader fitness. Genetics 2002; 161:33-46. [PMID: 12019221 PMCID: PMC1462107 DOI: 10.1093/genetics/161.1.33] [Citation(s) in RCA: 200] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A central feature of all adaptive radiations is morphological divergence, but the phenotypic innovations that are responsible are rarely known. When selected in a spatially structured environment, populations of the bacterium Pseudomonas fluorescens rapidly diverge. Among the divergent morphs is a mutant type termed "wrinkly spreader" (WS) that colonizes a new niche through the formation of self-supporting biofilms. Loci contributing to the primary phenotypic innovation were sought by screening a WS transposon library for niche-defective (WS(-)) mutants. Detailed analysis of one group of mutants revealed an operon of 10 genes encoding enzymes necessary to produce a cellulose-like polymer (CLP). WS genotypes overproduce CLP and overproduction of the polymer is necessary for the distinctive morphology of WS colonies; it is also required for biofilm formation and to maximize fitness in spatially structured microcosms, but overproduction of CLP alone is not sufficient to cause WS. A working model predicts that modification of cell cycle control of CLP production is an important determinant of the phenotypic innovation. Analysis of >30 kb of DNA encoding traits required for expression of the WS phenotype, including a regulatory locus, has not revealed the mutational causes, indicating a complex genotype-phenotype map.
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Affiliation(s)
- Andrew J Spiers
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, United Kingdom
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Spiers AJ, Field D, Bailey M, Rainey PB. Notes on designing a partial genomic database: The PfSBW25 Encyclopaedia, a sequence database for Pseudomonas fluorescens SBW25. Microbiology (Reading) 2001; 147:247-249. [PMID: 11158339 DOI: 10.1099/00221287-147-2-247] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Affiliation(s)
| | - Dawn Field
- Molecular Infectious Diseases Group, Institute of Molecular Medicine, University of Oxford, , UK2
| | - Mark Bailey
- Molecular Microbial Ecology Group, Institute of Virology and Environmental Microbiology, Oxford, , UK3
| | - Paul B Rainey
- Department of Plant Sciences, University of Oxford, , UK1
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Affiliation(s)
- Andrew J Spiers
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK1
| | - Angus Buckling
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK1
| | - Paul B Rainey
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK1
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Abstract
Studies of the site-specific recombinase Cre suggest a key role for interactions between the C-terminus of the protein and a region located about 30 residues from the C-terminus in linking in a cyclical manner the four recombinase monomers present in a recombination complex, and in controlling the catalytic activity of each monomer. By extrapolating the Cre DNA recombinase structure to the related site-specific recombinases XerC and XerD, it is predicted that the extreme C-termini of XerC and XerD interact with alpha-helix M in XerD and the equivalent region of XerC respectively. Consequently, XerC and XerD recombinases deleted for C-terminal residues, and mutated XerD proteins containing single amino acid substitutions in alphaM or in the C-terminal residues were analysed. Deletion of C-terminal residues of XerD has no measurable effect on co-operative interactions with XerC in DNA-binding assays to the recombination site dif, whereas deletion of 5 or 10 residues of XerC reduces co-operativity with XerD some 20-fold. Co-operative interactions between pairs of truncated proteins during dif DNA binding are reduced 20- to 30-fold. All of the XerD mutants, except one, were catalytically proficient in vitro; nevertheless, many failed to mediate a recombination reaction on supercoiled plasmid in vivo or in vitro, implying that the ability to form a productive recombination complex and/or mediate a controlled recombination reaction is impaired.
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Affiliation(s)
- A J Spiers
- Division of Molecular Genetics, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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44
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Abstract
XerC and XerD are related 298-amino-acid site-specific recombinases, each of which is responsible for the exchange of one pair of strands in Xer recombination. Both recombinases encode functions necessary for sequence-specific DNA-binding, co-operative XerC/D interactions, synapsis and catalysis. These functions were related to the primary amino acid sequence by constructing and analysing internal and C-terminal XerD deletions. An XerD derivative containing residues 1-233 was proficient in specific DNA binding, but did not interact co-operatively with XerC. Deletion of a further five C-terminal amino acids abolished binding to DNA. Proteins deleted for residues 32-88 and for residues 145-159 were deficient in DNA binding. Deletion of residues 244-281, a region containing amino acids necessary for catalysis, gave a protein that bound to DNA. An XerD derivative containing residues 1-268 retained co-operative interactions with XerC; nevertheless, it did not support XerC strand exchange and was defective in XerD catalysis. Residues 1-283 retain a functional catalytic active site, though a protein lacking the five C-terminal amino acids was still unable to mediate normal in vivo recombination, indicating that these residues are needed for a function that is not directly related to DNA binding or catalysis.
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Affiliation(s)
- A J Spiers
- Department of Biochemistry, University of Oxford, UK
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45
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Spiers AJ, Bhana N, Bergquist PL. Regulatory interactions between RepA, an essential replication protein, and the DNA repeats of RepFIB from plasmid P307. J Bacteriol 1993; 175:4016-24. [PMID: 8320218 PMCID: PMC204830 DOI: 10.1128/jb.175.13.4016-4024.1993] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The control of RepFIB replication appears to rely on the interaction between an initiator protein (RepA) and two sets of DNA repeat elements located on either side of the repA gene (BCDD'D" and EFGHIJ). In vivo genetic tests demonstrate that the BCDD'D" repeats form part of the origin of replication, while some of the downstream repeat elements (HIJ) are involved in the sensing and setting of plasmid copy number. RepA DNA binding to these groups of repeats has been investigated in vivo by utilizing the fact that the replicon contains three active promoters (orip, repAp, and EFp), one of which has previously been shown to control the expression of repA (repAp). All three promoters are closely associated with the repeat elements flanking repA, and an investigation using lacZ or cml gene fusions has demonstrated that RepA expressed in trans is able to repress each promoter. However, these assays suggest that the transcriptional responses of orip and repAp to RepA repression are significantly different, despite the fact that both promoters are embedded within the BCDD'D" repeat elements. Extra copies of the BCDD'D" or EFG repeats in trans have no effect on RepA repression of repAp embedded in a second copy of the BCDD'D" repeats, but copies of the HIJ or EFGHIJ repeats are able to derepress repAp, suggesting that there is a fundamental difference between RepA-BCDD'D" or -HIJ complexes and RepA-EFG or -EFGHIJ complexes.
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Affiliation(s)
- A J Spiers
- Centre for Gene Technology, University of Auckland, New Zealand
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46
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Abstract
The distribution of the RepFIB replicon among a total of 20 plasmid incompatibility groups was determined using Southern blot and polymerase chain reaction analysis. The presence of the replicon was confirmed in 25 of 55 plasmids tested. The majority of plasmids carrying RepFIB are from the IncF incompatibility groups, but one plasmid from IncI and one plasmid from IncP also possess the replicon. Seven different examples of RepFIB were sequenced in the minimal replicon region to obtain 1525 bp of sequence information covering the repA gene and flanking repeat regions for comparison. An analysis of these sequences plus three sequences previously reported showed almost perfect conservation of the predicted protein sequence of RepA and of the flanking DNA repeats. DNA sequence data were analyzed using maximum parsimony techniques to describe the possible evolutionary relationships of the 10 examples of RepFIB.
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Affiliation(s)
- M D Gibbs
- Department of Cellular & Molecular Biology, University of Auckland, New Zealand
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47
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Abstract
The control of RepFIB replication appears to rely on the interaction between an initiator protein (RepA) and two sets of DNA repeat elements located on either side of the repA gene. Limited N-terminal sequence information obtained from a RepA:beta-galactosidase fusion protein indicates that although the first residue of RepA is methionine, the initiation of translation of RepA occurs from a CTG codon rather than from the predicted GTG codon located further downstream. Overexpressed RepA in trans is capable of repressing a repA:lacZ fusion plasmid in which the expression of the fusion protein is under the control of the repA promoter. The repA promoter has been located functionally by testing a series of repA:lacZ fusion plasmids. Both in vivo genetic tests and in vitro DNA-binding studies indicate that repA autoregulation can be achieved by RepA binding to one or more repeat elements which overlap the repA promoter sequence.
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Affiliation(s)
- A J Spiers
- Centre for Gene Technology, University of Auckland, New Zealand
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Saul D, Spiers AJ, McAnulty J, Gibbs MG, Bergquist PL, Hill DF. Nucleotide sequence and replication characteristics of RepFIB, a basic replicon of IncF plasmids. J Bacteriol 1989; 171:2697-707. [PMID: 2651415 PMCID: PMC209954 DOI: 10.1128/jb.171.5.2697-2707.1989] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
A second autonomous replicon of P307, RepFIB, has been isolated that has significant homology with other replicons in IncFI group plasmids. Eleven homologous repeats of 21 base pairs are present on the sequence and flank an open reading frame capable of coding for a protein of about Mr = 40,000. This protein was identified by maxicell analysis of cloned RepFIB. A series of deletion mutations of RepFIB were inserted into a DNA polymerase I-dependent vector and examined for their replication proficiency in a polA1 strain. These experiments defined a minimal replication region of 1.6 kilobases which includes the three repeats immediately upstream and downstream of the open reading frame. Deletion of a second set of repeats further downstream doubled the copy number of a chimeric plasmid replicating under RepFIB control. It was concluded that these repeats control the copy number of the replicon. Incompatibility tests showed that all three sets of repeats could express incompatibility with a resident RepFIB plasmid.
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Affiliation(s)
- D Saul
- Department of Cellular and Molecular Biology, University of Auckland, New Zealand
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