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Zappa S, Berne C, Morton Iii RI, Whitfield GB, De Stercke J, Brun YV. The HmrABCX pathway regulates the transition between motile and sessile lifestyles in Caulobacter crescentus by a mechanism independent of hfiA transcription. mBio 2024:e0100224. [PMID: 39230277 DOI: 10.1128/mbio.01002-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Accepted: 06/03/2024] [Indexed: 09/05/2024] Open
Abstract
During its cell cycle, the bacterium Caulobacter crescentus switches from a motile, free-living state, to a sessile surface-attached cell. During this coordinated process, cells undergo irreversible morphological changes, such as shedding of their polar flagellum and synthesis of an adhesive holdfast at the same pole. In this work, we used genetic screens to identify genes involved in the regulation of the transition from the motile to the sessile lifestyle. We identified a predicted hybrid histidine kinase that inhibits biofilm formation and promotes the motile lifestyle: HmrA (holdfast and motility regulator A). Genetic screens and genomic localization led to the identification of additional genes that form a putative phosphorelay pathway with HmrA. We postulate that the Hmr pathway acts as a rheostat to control the proportion of cells harboring a flagellum or a holdfast in the population. Further genetic analysis suggests that the Hmr pathway impacts c-di-GMP synthesis through the diguanylate cyclase DgcB pathway. Our results also indicate that the Hmr pathway is involved in the regulation of motile to sessile lifestyle transition as a function of various environmental factors: biofilm formation is repressed when excess copper is present and derepressed under non-optimal temperatures. Finally, we provide evidence that the Hmr pathway regulates motility and adhesion without modulating the transcription of the holdfast synthesis regulator HfiA. IMPORTANCE Complex communities attached to a surface, or biofilms, represent the major lifestyle of bacteria in the environment. Such a sessile state enables the inhabitants to be more resistant to adverse environmental conditions. Thus, having a deeper understanding of the underlying mechanisms that regulate the transition between the motile and the sessile states could help design strategies to improve biofilms when they are beneficial or impede them when they are detrimental. For Caulobacter crescentus motile cells, the transition to the sessile lifestyle is irreversible, and this decision is regulated at several levels. In this work, we describe a putative phosphorelay that promotes the motile lifestyle and inhibits biofilm formation, providing new insights into the control of adhesin production that leads to the formation of biofilms.
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Affiliation(s)
- Sébastien Zappa
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Quebec, Canada
| | - Cécile Berne
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Quebec, Canada
| | | | - Gregory B Whitfield
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Quebec, Canada
| | - Jonathan De Stercke
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Quebec, Canada
| | - Yves V Brun
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Quebec, Canada
- Department of Biology, Indiana University, Bloomington, Indiana, USA
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2
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Zappa S, Berne C, Morton RI, De Stercke J, Brun YV. The HmrABCX pathway regulates the transition between motile and sessile lifestyles in Caulobacter crescentus by a HfiA-independent mechanism. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.13.571505. [PMID: 38168291 PMCID: PMC10760086 DOI: 10.1101/2023.12.13.571505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Through its cell cycle, the bacterium Caulobacter crescentus switches from a motile, free-living state, to a sessile surface-attached cell. During this coordinated process, cells undergo irreversible morphological changes, such as shedding of their polar flagellum and synthesis of an adhesive holdfast at the same pole. In this work, we used genetic screens to identify genes involved in the regulation of the motile to sessile lifestyle transition. We identified a predicted hybrid histidine kinase that inhibits biofilm formation and activates the motile lifestyle: HmrA (Holdfast and motility regulator A). Genetic screens and genomic localization led to the identification of additional genes that regulate the proportion of cells harboring an active flagellum or a holdfast and that form a putative phosphorelay pathway with HmrA. Further genetic analysis indicates that the Hmr pathway is independent of the holdfast synthesis regulator HfiA and may impact c-di-GMP synthesis through the diguanylate cyclase DgcB pathway. Finally, we provide evidence that the Hmr pathway is involved in the regulation of sessile-to-motile lifestyle as a function of environmental stresses, namely excess copper and non-optimal temperatures.
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Affiliation(s)
- Sébastien Zappa
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Québec, CANADA
| | - Cecile Berne
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Québec, CANADA
| | - Robert I. Morton
- Department of Biology, Indiana University, Bloomington, IN, USA
- Present address: Boston Scientific, Yokneam, Northern, ISRAEL
| | - Jonathan De Stercke
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Québec, CANADA
- Present address: Unité de Recherche en Biologie des Micro-organismes, Université de Namur, 61 rue de Bruxelles, B-5000 Namur, BELGIUM
| | - Yves V. Brun
- Département de microbiologie, infectiologie et immunologie, Université de Montréal, Montréal, Québec, CANADA
- Department of Biology, Indiana University, Bloomington, IN, USA
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3
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Mijnendonckx K, Rogiers T, Giménez Del Rey FJ, Merroun ML, Williamson A, Ali MM, Charlier D, Leys N, Boon N, Van Houdt R. PrsQ 2, a small periplasmic protein involved in increased uranium resistance in the bacterium Cupriavidus metallidurans. JOURNAL OF HAZARDOUS MATERIALS 2023; 444:130410. [PMID: 36413896 DOI: 10.1016/j.jhazmat.2022.130410] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 11/10/2022] [Accepted: 11/14/2022] [Indexed: 06/16/2023]
Abstract
Uranium contamination is a widespread problem caused by natural and anthropogenic activities. Although microorganisms thrive in uranium-contaminated environments, little is known about the actual molecular mechanisms mediating uranium resistance. Here, we investigated the resistance mechanisms driving the adaptation of Cupriavidus metallidurans NA4 to toxic uranium concentrations. We selected a spontaneous mutant able to grow in the presence of 1 mM uranyl nitrate compared to 250 µM for the parental strain. The increased uranium resistance was acquired via the formation of periplasmic uranium-phosphate precipitates facilitated by the increased expression of a genus-specific small periplasmic protein, PrsQ2, regulated as non-cognate target of the CzcS2-CzcR2 two-component system. This study shows that bacteria can adapt to toxic uranium concentrations and explicates the complete genetic circuit behind the adaptation.
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Affiliation(s)
- Kristel Mijnendonckx
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Tom Rogiers
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Francisco J Giménez Del Rey
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium; Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium.
| | - Mohamed L Merroun
- Campus Fuentenueva, Department of Microbiology, University of Granada, Granada, Spain.
| | - Adam Williamson
- Center for Microbial Ecology and Technology, UGent, Ghent, Belgium.
| | - Md Muntasir Ali
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Daniel Charlier
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Brussels, Belgium.
| | - Natalie Leys
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
| | - Nico Boon
- Center for Microbial Ecology and Technology, UGent, Ghent, Belgium.
| | - Rob Van Houdt
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium.
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4
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Regulatory cross-talk supports resistance to Zn intoxication in Streptococcus. PLoS Pathog 2022; 18:e1010607. [PMID: 35862444 PMCID: PMC9345489 DOI: 10.1371/journal.ppat.1010607] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 08/02/2022] [Accepted: 05/19/2022] [Indexed: 01/07/2023] Open
Abstract
Metals such as copper (Cu) and zinc (Zn) are important trace elements that can affect bacterial cell physiology but can also intoxicate bacteria at high concentrations. Discrete genetic systems for management of Cu and Zn efflux have been described in several bacterial pathogens, including streptococci. However, insight into molecular cross-talk between systems for Cu and Zn management in bacteria that drive metal detoxification, is limited. Here, we describe a biologically consequential cross-system effect of metal management in group B Streptococcus (GBS) governed by the Cu-responsive copY regulator in response to Zn. RNAseq analysis of wild-type (WT) and copY-deficient GBS subjected to metal stress revealed unique transcriptional links between the systems for Cu and Zn detoxification. We show that the Cu-sensing role of CopY extends beyond Cu and enables CopY to regulate Cu and Zn stress responses that effect changes in gene function for central cellular processes, including riboflavin synthesis. CopY also supported GBS intracellular survival in human macrophages and virulence during disseminated infection in mice. In addition, we show a novel role for CovR in modulating GBS resistance to Zn intoxication. Identification of the Zn resistome of GBS using TraDIS revealed a suite of genes essential for GBS growth in metal stress. Several of the genes identified are novel to systems that support bacterial survival in metal stress and represent a diverse set of mechanisms that underpin microbial metal homeostasis during cell stress. Overall, this study reveals a new and important mechanism of cross-system complexity driven by CopY in bacteria to regulate cellular management of metal stress and survival. Metals, such as Cu and Zn, can be used by the mammalian immune system to target bacterial pathogens for destruction, and consequently, bacteria have evolved discrete genetic systems to enable subversion of this host antimicrobial response. Systems for Cu and Zn homeostasis are well characterized, including transcriptional control elements that sense and respond to metal stress. Here, we discover novel features of metal response systems in Streptococcus, which have broad implications for bacterial pathogenesis and virulence. We show that Streptococcus resists Zn intoxication by utilizing a bona fide Cu regulator, CopY, to manage cellular metal homeostasis, and enable the bacteria to survive stressful conditions. We identify several new genes that confer resistance to Zn intoxication in Streptococcus, including some that have hitherto not been linked to metal ion homeostasis in any bacterial pathogen. Identification of a novel cross-system metal management mechanism exploited by Streptococcus to co-ordinate and achieve metal resistance enhances our understanding of metal ion homeostasis in bacteria and its effect on pathogenesis.
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Liu C, Yu H, Zhang B, Liu S, Liu CG, Li F, Song H. Engineering whole-cell microbial biosensors: Design principles and applications in monitoring and treatment of heavy metals and organic pollutants. Biotechnol Adv 2022; 60:108019. [PMID: 35853551 DOI: 10.1016/j.biotechadv.2022.108019] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 07/13/2022] [Accepted: 07/13/2022] [Indexed: 01/18/2023]
Abstract
Biosensors have been widely used as cost-effective, rapid, in situ, and real-time analytical tools for monitoring environments. The development of synthetic biology has enabled emergence of genetically engineered whole-cell microbial biosensors. This review updates the design and optimization principles for a diverse array of whole-cell biosensors based on transcription factors (TF) including activators or repressors derived from heavy metal resistance systems, alkanes, and aromatics metabolic pathways of bacteria. By designing genetic circuits, the whole-cell biosensors could be engineered to intelligently sense heavy metals (Hg2+, Zn2+, Pb2+, Au3+, Cd2+, As3+, Ni2+, Cu2+, and UO22+) or organic compounds (alcohols, alkanes, phenols, and benzenes) through one-component or two-component system-based TFs, transduce signals through genetic amplifiers, and response as various outputs such as cell fluorescence and bioelectricity for monitoring heavy metals and organic pollutants in real conditions, synthetic curli and surface metal-binding peptides for in situ bio-sorption of heavy metals. We further review strategies that have been implemented to optimize the selectivity and correlation between ligand concentration and output signal of the TF-based biosensors, so as to meet requirements of practical applications. The optimization strategies include protein engineering to change specificities, promoter engineering to improve sensitivities, and genetic circuit-based amplification to enhance dynamic ranges via designing transcriptional amplifiers, logic gates, and feedback loops. At last, we outlook future trends in developing novel forms of biosensors.
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Affiliation(s)
- Changjiang Liu
- Frontiers Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Huan Yu
- Frontiers Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Baocai Zhang
- Frontiers Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Shilin Liu
- Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Chen-Guang Liu
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences of Ministry of Education, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Feng Li
- Frontiers Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
| | - Hao Song
- Frontiers Science Center for Synthetic Biology (Ministry of Education), Key Laboratory of Systems Bioengineering, Tianjin University, Tianjin 300072, China; Collaborative Innovation Center of Chemical Science and Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.
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Rogiers T, Van Houdt R, Williamson A, Leys N, Boon N, Mijnendonckx K. Molecular Mechanisms Underlying Bacterial Uranium Resistance. Front Microbiol 2022; 13:822197. [PMID: 35359714 PMCID: PMC8963506 DOI: 10.3389/fmicb.2022.822197] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 01/27/2022] [Indexed: 11/16/2022] Open
Abstract
Environmental uranium pollution due to industries producing naturally occurring radioactive material or nuclear accidents and releases is a global concern. Uranium is hazardous for ecosystems as well as for humans when accumulated through the food chain, through contaminated groundwater and potable water sources, or through inhalation. In particular, uranium pollution pressures microbial communities, which are essential for healthy ecosystems. In turn, microorganisms can influence the mobility and toxicity of uranium through processes like biosorption, bioreduction, biomineralization, and bioaccumulation. These processes were characterized by studying the interaction of different bacteria with uranium. However, most studies unraveling the underlying molecular mechanisms originate from the last decade. Molecular mechanisms help to understand how bacteria interact with radionuclides in the environment. Furthermore, knowledge on these underlying mechanisms could be exploited to improve bioremediation technologies. Here, we review the current knowledge on bacterial uranium resistance and how this could be used for bioremediation applications.
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Affiliation(s)
- Tom Rogiers
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
- Center for Microbial Ecology and Technology, Ghent University, Ghent, Belgium
| | - Rob Van Houdt
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
| | - Adam Williamson
- Centre Etudes Nucléaires de Bordeaux Gradignan (CENBG), Bordeaux, France
| | - Natalie Leys
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
| | - Nico Boon
- Center for Microbial Ecology and Technology, Ghent University, Ghent, Belgium
| | - Kristel Mijnendonckx
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
- *Correspondence: Kristel Mijnendonckx,
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7
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Maertens L, Cherry P, Tilquin F, Van Houdt R, Matroule JY. Environmental Conditions Modulate the Transcriptomic Response of Both Caulobacter crescentus Morphotypes to Cu Stress. Microorganisms 2021; 9:1116. [PMID: 34064119 PMCID: PMC8224329 DOI: 10.3390/microorganisms9061116] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/18/2021] [Accepted: 05/19/2021] [Indexed: 12/13/2022] Open
Abstract
Bacteria encounter elevated copper (Cu) concentrations in multiple environments, varying from mining wastes to antimicrobial applications of copper. As the role of the environment in the bacterial response to Cu ion exposure remains elusive, we used a tagRNA-seq approach to elucidate the disparate responses of two morphotypes of Caulobacter crescentus NA1000 to moderate Cu stress in a complex rich (PYE) medium and a defined poor (M2G) medium. The transcriptome was more responsive in M2G, where we observed an extensive oxidative stress response and reconfiguration of the proteome, as well as the induction of metal resistance clusters. In PYE, little evidence was found for an oxidative stress response, but several transport systems were differentially expressed, and an increased need for histidine was apparent. These results show that the Cu stress response is strongly dependent on the cellular environment. In addition, induction of the extracytoplasmic function sigma factor SigF and its regulon was shared by the Cu stress responses in both media, and its central role was confirmed by the phenotypic screening of a sigF::Tn5 mutant. In both media, stalked cells were more responsive to Cu stress than swarmer cells, and a stronger basal expression of several cell protection systems was noted, indicating that the swarmer cell is inherently more Cu resistant. Our approach also allowed for detecting several new transcription start sites, putatively indicating small regulatory RNAs, and additional levels of Cu-responsive regulation.
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Affiliation(s)
- Laurens Maertens
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre (SCK CEN), 2400 Mol, Belgium; (L.M.); (R.V.H.)
- Research Unit in Microorganisms Biology (URBM), Narilis Institute, University of Namur, 5000 Namur, Belgium; (P.C.); (F.T.)
| | - Pauline Cherry
- Research Unit in Microorganisms Biology (URBM), Narilis Institute, University of Namur, 5000 Namur, Belgium; (P.C.); (F.T.)
| | - Françoise Tilquin
- Research Unit in Microorganisms Biology (URBM), Narilis Institute, University of Namur, 5000 Namur, Belgium; (P.C.); (F.T.)
| | - Rob Van Houdt
- Microbiology Unit, Interdisciplinary Biosciences, Belgian Nuclear Research Centre (SCK CEN), 2400 Mol, Belgium; (L.M.); (R.V.H.)
| | - Jean-Yves Matroule
- Research Unit in Microorganisms Biology (URBM), Narilis Institute, University of Namur, 5000 Namur, Belgium; (P.C.); (F.T.)
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Park DM, Taffet MJ. Combinatorial Sensor Design in Caulobacter crescentus for Selective Environmental Uranium Detection. ACS Synth Biol 2019; 8:807-817. [PMID: 30897331 DOI: 10.1021/acssynbio.8b00484] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ability to detect uranium (U) through environmental monitoring is of critical importance for informing water resource protection and nonproliferation efforts. While technologies exist for environmental U detection, wide-area environmental monitoring, i.e. sampling coverage over large areas not known to possess U contamination, remains a challenging prospect that necessitates the development of novel detection approaches. Herein, we describe the development of a whole-cell U sensor by integrating two functionally independent, native U-responsive two-component signaling systems (TCS), UzcRS and UrpRS, within an AND gate circuit in the bacterium Caulobacter crescentus. Through leverage of the distinct but imperfect selectivity profiles of both TCS, this combinatorial approach enabled greater selectivity relative to a prior biosensor developed with UzcRS alone; no cross-reactivity was observed with most common environmental metals (e.g, Fe, As, Cu, Ca, Mg, Cd, Cr, Al) or the U decay-chain product Th, and the selectivity against Zn and Pb was significantly improved. In addition, integration of the UzcRS signal amplifier protein UzcY within the AND gate circuit further enhanced overall sensitivity and selectivity for U. The functionality of the sensor in an environmental context was confirmed by detection of U concentrations as low as 1 μM in groundwater samples. The results highlight the value of a combinatorial approach for constructing whole-cell sensors for the selective detection of analytes for which there are no known evolved regulators.
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Affiliation(s)
- Dan M. Park
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Michael J. Taffet
- Environmental Restoration Department (ERD), Operations and Business Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
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9
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García-Bayona L, Gozzi K, Laub MT. Mechanisms of Resistance to the Contact-Dependent Bacteriocin CdzC/D in Caulobacter crescentus. J Bacteriol 2019; 201:e00538-18. [PMID: 30692171 PMCID: PMC6436349 DOI: 10.1128/jb.00538-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 01/22/2019] [Indexed: 01/02/2023] Open
Abstract
The Cdz bacteriocin system allows the aquatic oligotrophic bacterium Caulobacter crescentus to kill closely related species in a contact-dependent manner. The toxin, which aggregates on the surfaces of producer cells, is composed of two small hydrophobic proteins, CdzC and CdzD, each bearing an extended glycine-zipper motif, that together induce inner membrane depolarization and kill target cells. To further characterize the mechanism of Cdz delivery and toxicity, we screened for mutations that render a target strain resistant to Cdz-mediated killing. These mutations mapped to four loci, including a TonB-dependent receptor, a three-gene operon (named zerRAB for zipper envelope resistance), and perA (for pentapeptide envelope resistance). Mutations in the zerRAB locus led to its overproduction and to potential changes in cell envelope composition, which may diminish the susceptibility of cells to Cdz toxins. The perA gene is also required to maintain a normal cell envelope, but our screen identified mutations that confer resistance to Cdz toxins without substantially affecting the cell envelope functions of PerA. We demonstrate that PerA, which encodes a pentapeptide repeat protein predicted to form a quadrilateral β-helix, localizes primarily to the outer membrane of cells, where it may serve as a receptor for the Cdz toxins. Collectively, these results provide new insights into the function and mechanisms of an atypical, contact-dependent bacteriocin system.IMPORTANCE Bacteriocins are commonly used by bacteria to kill neighboring cells that compete for resources. Although most bacteriocins are secreted, the aquatic, oligotrophic bacterium Caulobacter crescentus produces a two-peptide bacteriocin, CdzC/D, that remains attached to the outer membranes of cells, enabling contact-dependent killing of cells lacking the immunity protein CdzI. The receptor for CdzC/D has not previously been reported. Here, we describe a genetic screen for mutations that confer resistance to CdzC/D. One locus identified, perA, encodes a pentapeptide repeat protein that resides in the outer membrane of target cells, where it may act as the direct receptor for CdzC/D. Collectively, our results provide new insight into bacteriocin function and diversity.
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Affiliation(s)
- Leonor García-Bayona
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Howard Hughes Medical Institute, Cambridge, Massachusetts, USA
- Graduate Program in Microbiology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Kevin Gozzi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Howard Hughes Medical Institute, Cambridge, Massachusetts, USA
- Graduate Program in Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Howard Hughes Medical Institute, Cambridge, Massachusetts, USA
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Park DM, Overton KW, Jiao Y. The UzcRS two‐component system in
Caulobacter crescentus
integrates regulatory input from diverse auxiliary regulators. Mol Microbiol 2019; 111:678-699. [DOI: 10.1111/mmi.14180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2018] [Indexed: 11/28/2022]
Affiliation(s)
- Dan M. Park
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate Lawrence Livermore National Laboratory Livermore CA USA
| | - K. Wesley Overton
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate Lawrence Livermore National Laboratory Livermore CA USA
| | - Yongqin Jiao
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate Lawrence Livermore National Laboratory Livermore CA USA
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