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Prieto A, Miró L, Margolles Y, Bernabeu M, Salguero D, Merino S, Tomas J, Corbera JA, Perez-Bosque A, Huttener M, Fernández LÁ, Juarez A. Targeting plasmid-encoded proteins that contain immunoglobulin-like domains to combat antimicrobial resistance. eLife 2024; 13:RP95328. [PMID: 39046772 PMCID: PMC11268884 DOI: 10.7554/elife.95328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2024] Open
Abstract
Antimicrobial resistance (AMR) poses a significant threat to human health. Although vaccines have been developed to combat AMR, it has proven challenging to associate specific vaccine antigens with AMR. Bacterial plasmids play a crucial role in the transmission of AMR. Our recent research has identified a group of bacterial plasmids (specifically, IncHI plasmids) that encode large molecular mass proteins containing bacterial immunoglobulin-like domains. These proteins are found on the external surface of the bacterial cells, such as in the flagella or conjugative pili. In this study, we show that these proteins are antigenic and can protect mice from infection caused by an AMR Salmonella strain harboring one of these plasmids. Furthermore, we successfully generated nanobodies targeting these proteins, that were shown to interfere with the conjugative transfer of IncHI plasmids. Considering that these proteins are also encoded in other groups of plasmids, such as IncA/C and IncP2, targeting them could be a valuable strategy in combating AMR infections caused by bacteria harboring different groups of AMR plasmids. Since the selected antigens are directly linked to AMR itself, the protective effect extends beyond specific microorganisms to include all those carrying the corresponding resistance plasmids.
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Affiliation(s)
- Alejandro Prieto
- Department of Genetics, Microbiology and Statistics, University of BarcelonaBarcelonaSpain
| | - Luïsa Miró
- Department of Biochemistry and Physiology, Universitat de BarcelonaBarcelonaSpain
- Institut de Nutrició i Seguretat Alimentària, Universitat de BarcelonaBarcelonaSpain
| | - Yago Margolles
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CNB-CSIC)MadridSpain
| | - Manuel Bernabeu
- Department of Genetics, Microbiology and Statistics, University of BarcelonaBarcelonaSpain
| | - David Salguero
- Department of Genetics, Microbiology and Statistics, University of BarcelonaBarcelonaSpain
| | - Susana Merino
- Department of Genetics, Microbiology and Statistics, University of BarcelonaBarcelonaSpain
| | - Joan Tomas
- Department of Genetics, Microbiology and Statistics, University of BarcelonaBarcelonaSpain
| | - Juan Alberto Corbera
- Instituto Universitario de Investigaciones Biomédicas y Sanitarias (IUIBS), Facultad de Veterinaria, Universidad de Las Palmas de Gran Canaria (ULPGC), Campus Universitario de ArucasLas PalmasSpain
| | - Anna Perez-Bosque
- Department of Biochemistry and Physiology, Universitat de BarcelonaBarcelonaSpain
- Institut de Nutrició i Seguretat Alimentària, Universitat de BarcelonaBarcelonaSpain
| | - Mario Huttener
- Department of Genetics, Microbiology and Statistics, University of BarcelonaBarcelonaSpain
| | - Luis Ángel Fernández
- Department of Microbial Biotechnology, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas (CNB-CSIC)MadridSpain
| | - Antonio Juarez
- Department of Genetics, Microbiology and Statistics, University of BarcelonaBarcelonaSpain
- Institute for Bioengineering of Catalonia, The Barcelona Institute of Science and TechnologyBarcelonaSpain
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Merkushova AV, Shikov AE, Nizhnikov AA, Antonets KS. For Someone, You Are the Whole World: Host-Specificity of Salmonella enterica. Int J Mol Sci 2023; 24:13670. [PMID: 37761974 PMCID: PMC10530738 DOI: 10.3390/ijms241813670] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 08/27/2023] [Accepted: 09/01/2023] [Indexed: 09/29/2023] Open
Abstract
Salmonella enterica is a bacterial pathogen known to cause gastrointestinal infections in diverse hosts, including humans and animals. Despite extensive knowledge of virulence mechanisms, understanding the factors driving host specificity remains limited. In this study, we performed a comprehensive pangenome-wide analysis of S. enterica to identify potential loci determining preference towards certain hosts. We used a dataset of high-quality genome assemblies grouped into 300 reference clusters with a special focus on four host groups: humans, pigs, cattle, and birds. The reconstructed pangenome was shown to be open and enriched with the accessory component implying high genetic diversity. Notably, phylogenetic inferences did not correspond to the distribution of affected hosts, as large compact phylogenetic groups were absent. By performing a pangenome-wide association study, we identified potential host specificity determinants. These included multiple genes encoding proteins involved in distinct infection stages, e.g., secretion systems, surface structures, transporters, transcription regulators, etc. We also identified antibiotic resistance loci in host-adapted strains. Functional annotation corroborated the results obtained with significant enrichments related to stress response, antibiotic resistance, ion transport, and surface or extracellular localization. We suggested categorizing the revealed specificity factors into three main groups: pathogenesis, resistance to antibiotics, and propagation of mobile genetic elements (MGEs).
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Affiliation(s)
- Anastasiya V. Merkushova
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.V.M.); (A.E.S.); (A.A.N.)
| | - Anton E. Shikov
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.V.M.); (A.E.S.); (A.A.N.)
- Faculty of Biology, St. Petersburg State University (SPbSU), 199034 St. Petersburg, Russia
| | - Anton A. Nizhnikov
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.V.M.); (A.E.S.); (A.A.N.)
- Faculty of Biology, St. Petersburg State University (SPbSU), 199034 St. Petersburg, Russia
| | - Kirill S. Antonets
- Laboratory for Proteomics of Supra-Organismal Systems, All-Russia Research Institute for Agricultural Microbiology (ARRIAM), 196608 St. Petersburg, Russia; (A.V.M.); (A.E.S.); (A.A.N.)
- Faculty of Biology, St. Petersburg State University (SPbSU), 199034 St. Petersburg, Russia
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Differential Expression of Two Copies of the irmA Gene in the Enteroaggregative E. coli Strain 042. Microbiol Spectr 2022; 10:e0045422. [PMID: 35766495 PMCID: PMC9431211 DOI: 10.1128/spectrum.00454-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gene duplications significantly impact the gene repertoires of both eukaryotic and prokaryotic microorganisms. The genomes of pathogenic Escherichia coli strains share a group of duplicated genes whose function is mostly unknown. The irmA gene is one of the duplicates encoded in several pathogenic E. coli strains. The function of its gene product was investigated in the uropathogenic E. coli strain CFT073, which contains a single functional copy. The IrmA protein structure mimics that of human interleukin receptors and likely plays a role during infection. The enteroaggregative E. coli strain 042 contains two functional copies of the irmA gene. In the present work, we investigated their biological roles. The irmA_4509 allele is expressed under several growth conditions. Its expression is modulated by the global regulators OxyR and Hha, with optimal expression at 37°C and under nutritional stress conditions. Expression of the irmA_2244 allele can only be detected when the irmA_4509 allele is knocked out. Differences in the promoter regions of both alleles account for their differential expression. Our results show that under several environmental conditions, the expression of the IrmA protein in strain 042 is dictated by the irmA_4509 allele. The irmA_2244 allele appears to play a backup role to ensure IrmA expression when the irmA_4509 allele loses its function. IMPORTANCE Gene duplications occur in prokaryotic genomes at a detectable frequency. In many instances, the biological function of the duplicates is unknown, and hence, the significance of the presence of multiple copies of these genes remains unclear. In pathogenic E. coli isolates, the irmA gene can be present either as a single copy or in two or more copies. We focused our work on studying why a different pathogenic E. coli strain encodes two functional copies of the irmA gene. We show that under several environmental conditions, one of the alleles dictates IrmA expression, and the second remains silent. The latter allele is only expressed when the former is silenced. The presence of more than one functional copy of the irmA gene in some pathogenic E. coli strains can result in sufficient expression of this virulence factor during the infection process.
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Abstract
Horizontal transfer of bacterial plasmids generates genetic variability and contributes to the dissemination of the genes that enable bacterial cells to develop antimicrobial resistance (AMR). Several aspects of the conjugative process have long been known, namely, those related to the proteins that participate in the establishment of cell-to-cell contact and to the enzymatic processes associated with the processing of plasmid DNA and its transfer to the recipient cell. In this work, we describe the roles of newly identified proteins that influence the conjugation of several plasmids. Genes encoding high-molecular-weight bacterial proteins that contain one or several immunoglobulin-like domains (Big) are located in the transfer regions of several plasmids that usually harbor AMR determinants. These Big proteins are exported to the external medium and target two extracellular organelles: the flagella and conjugative pili. The plasmid gene-encoded Big proteins facilitate conjugation by reducing cell motility and facilitating cell-to-cell contact by binding both to the flagella and to the conjugative pilus. They use the same export machinery as that used by the conjugative pilus components. In the examples characterized in this paper, these proteins influence conjugation at environmental temperatures (i.e., 25°C). This suggests that they may play relevant roles in the dissemination of plasmids in natural environments. Taking into account that they interact with outer surface organelles, they could be targeted to control the dissemination of different bacterial plasmids carrying AMR determinants. IMPORTANCE Transmission of a plasmid from one bacterial cell to another, in several instances, underlies the dissemination of antimicrobial resistance (AMR) genes. The process requires well-characterized enzymatic machinery that facilitates cell-to-cell contact and the transfer of the plasmid. Our paper identifies novel plasmid gene-encoded high-molecular-weight proteins that contain an immunoglobulin-like domain and are required for plasmid transmission. They are encoded by genes on different groups of plasmids. These proteins are exported outside the cell. They bind to extracellular cell appendages such as the flagella and conjugative pili. Expression of these proteins reduces cell motility and increases the ability of the bacterial cells to transfer the plasmid. These proteins could be targeted with specific antibodies to combat infections caused by AMR microorganisms that harbor these plasmids.
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Prieto A, Bernabeu M, Sánchez-Herrero JF, Pérez-Bosque A, Miró L, Bäuerl C, Collado C, Hüttener M, Juárez A. Modulation of AggR levels reveals features of virulence regulation in enteroaggregative E. coli. Commun Biol 2021; 4:1295. [PMID: 34785760 PMCID: PMC8595720 DOI: 10.1038/s42003-021-02820-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Accepted: 10/22/2021] [Indexed: 11/16/2022] Open
Abstract
Enteroaggregative Escherichia coli (EAEC) strains are one of the diarrheagenic pathotypes. EAEC strains harbor a virulence plasmid (pAA2) that encodes, among other virulence determinants, the aggR gene. The expression of the AggR protein leads to the expression of several virulence determinants in both plasmids and chromosomes. In this work, we describe a novel mechanism that influences AggR expression. Because of the absence of a Rho-independent terminator in the 3'UTR, aggR transcripts extend far beyond the aggR ORF. These transcripts are prone to PNPase-mediated degradation. Structural alterations in the 3'UTR result in increased aggR transcript stability, leading to increased AggR levels. We therefore investigated the effect of increased AggR levels on EAEC virulence. Upon finding the previously described AggR-dependent virulence factors, we detected novel AggR-regulated genes that may play relevant roles in EAEC virulence. Mutants exhibiting high AggR levels because of structural alterations in the aggR 3'UTR show increased mobility and increased pAA2 conjugation frequency. Furthermore, among the genes exhibiting increased fold change values, we could identify those of metabolic pathways that promote increased degradation of arginine, fatty acids and gamma-aminobutyric acid (GABA), respectively. In this paper, we discuss how the AggR-dependent increase in specific metabolic pathways activity may contribute to EAEC virulence.
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Affiliation(s)
- Alejandro Prieto
- Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Spain
| | - Manuel Bernabeu
- Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Spain
| | | | - Anna Pérez-Bosque
- Department of Biochemistry and Physiology, Universitat de Barcelona, Barcelona, Spain
- Institut de Nutrició i Seguretat Alimentària, Universitat de Barcelona, Barcelona, Spain
| | - Lluïsa Miró
- Department of Biochemistry and Physiology, Universitat de Barcelona, Barcelona, Spain
- Institut de Nutrició i Seguretat Alimentària, Universitat de Barcelona, Barcelona, Spain
| | - Christine Bäuerl
- Institute of Agrochemistry and Food Technology, National Research Council (IATA-CSIC), Paterna, Valencia, Spain
| | - Carmen Collado
- Institute of Agrochemistry and Food Technology, National Research Council (IATA-CSIC), Paterna, Valencia, Spain
| | - Mário Hüttener
- Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Spain.
| | - Antonio Juárez
- Department of Genetics, Microbiology and Statistics, Universitat de Barcelona, Barcelona, Spain.
- Institute for Bioengineering of Catalonia, The Barcelona Institute of Science and Technology, Barcelona, Spain.
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Hüttener M, Prieto A, Aznar S, Bernabeu M, Glaría E, Valledor AF, Paytubi S, Merino S, Tomás J, Juárez A. Expression of a novel class of bacterial Ig-like proteins is required for IncHI plasmid conjugation. PLoS Genet 2019; 15:e1008399. [PMID: 31527905 PMCID: PMC6764697 DOI: 10.1371/journal.pgen.1008399] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 09/27/2019] [Accepted: 09/04/2019] [Indexed: 01/10/2023] Open
Abstract
Antimicrobial resistance (AMR) is currently one of the most important challenges to the treatment of bacterial infections. A critical issue to combat AMR is to restrict its spread. In several instances, bacterial plasmids are involved in the global spread of AMR. Plasmids belonging to the incompatibility group (Inc)HI are widespread in Enterobacteriaceae and most of them express multiple antibiotic resistance determinants. They play a relevant role in the recent spread of colistin resistance. We present in this report novel findings regarding IncHI plasmid conjugation. Conjugative transfer in liquid medium of an IncHI plasmid requires expression of a plasmid-encoded, large-molecular-mass protein that contains an Ig-like domain. The protein, termed RSP, is encoded by a gene (ORF R0009) that maps in the Tra2 region of the IncHI1 R27 plasmid. The RSP protein is exported outside the cell by using the plasmid-encoded type IV secretion system that is also used for its transmission to new cells. Expression of the protein reduces cell motility and enables plasmid conjugation. Flagella are one of the cellular targets of the RSP protein. The RSP protein is required for a high rate of plasmid transfer in both flagellated and nonflagellated Salmonella cells. This effect suggests that RSP interacts with other cellular structures as well as with flagella. These unidentified interactions must facilitate mating pair formation and, hence, facilitate IncHI plasmid conjugation. Due to its location on the outer surfaces of the bacterial cell, targeting the RSP protein could be a means of controlling IncHI plasmid conjugation in natural environments or of combatting infections caused by AMR enterobacteria that harbor IncHI plasmids. Dissemination of antimicrobial resistance (AMR) among different bacterial populations occurs due to mainly the presence of plasmids that encode AMR determinants. IncHI plasmids are one of the groups of bacterial plasmids that confer AMR to several enterobacteria. Recently, resistance to one of the last-resort antibiotics (colistin) for some multidrug-resistant infections has spread very rapidly. IncHI plasmids represent 20% of all plasmids transmitting colistin resistance worldwide and 40% in Europe. When analyzing the interactions of the IncHI1 plasmid R27 with Salmonella, we identified a large-molecular-mass protein that is encoded by this plasmid and is exported to the external medium. The R27 plasmid gene coding for that protein (R0009) is widespread among IncHI plasmids. In this report, we characterize the protein, termed RSP. The presented data show that RSP plays a relevant role in IncHI plasmid conjugation and suggest that the protein is retained on the outer surface of the bacterial cells and facilitates cell-to-cell contact before plasmid DNA transfer. Considering that IncHI plasmids significantly contribute to AMR dissemination within enterobacteria, the findings reported in this paper suggest that the identified protein can be a target to control both IncHI-mediated AMR dissemination and infections caused by AMR enterobacteria that harbor these plasmids.
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Affiliation(s)
- Mário Hüttener
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - Alejandro Prieto
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - Sonia Aznar
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - Manuel Bernabeu
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - Estibaliz Glaría
- Department of Cell Biology, Physiology and Immunology, University of Barcelona, Barcelona, Spain
| | - Annabel F. Valledor
- Department of Cell Biology, Physiology and Immunology, University of Barcelona, Barcelona, Spain
| | - Sonia Paytubi
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - Susana Merino
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - Joan Tomás
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
| | - Antonio Juárez
- Department of Genetics, Microbiology and Statistics, University of Barcelona, Barcelona, Spain
- Institute for Bioengineering of Catalonia, The Barcelona Institute of Science and Technology, Barcelona, Spain
- * E-mail:
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Hao H, Shi DY, Yang D, Yang ZW, Qiu ZG, Liu WL, Shen ZQ, Yin J, Wang HR, Li JW, Wang H, Jin M. Profiling of intracellular and extracellular antibiotic resistance genes in tap water. JOURNAL OF HAZARDOUS MATERIALS 2019; 365:340-345. [PMID: 30448547 DOI: 10.1016/j.jhazmat.2018.11.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2018] [Revised: 10/26/2018] [Accepted: 11/01/2018] [Indexed: 05/26/2023]
Abstract
Antibiotic resistance genes (ARGs) have gained global attention due to their public health threat. Extracelluar ARGs (eARGs) can result in the dissemination of antibiotic resistance via free-living ARGs in natural environments, where they promote ARB transmission in drinking water distribution systems. However, eARG pollution in tap water has not been well researched. In this study, concentrations of eARGs and intracellular ARGs (iARGs) in tap water, sampled at Tianjin, China, were investigated for one year. Fourteen eARG types were found at the highest concentration of 1.3 × 105 gene copies (GC)/L. TetC was detected in 66.7% of samples, followed by sul1, sul2, and qnrA with the same detection frequency of 41.7%. Fifteen iARGs (including tetA, tetB, tetM, tetQ, tetX, sul1, sul2, sul3, ermB, blaTEM, and qnrA) were continuously detected in all collected tap water samples with sul1 and sul2 the most abundant. Additionally, both eARG and iARG concentrations in tap water presented a seasonal pattern with most abundant prevalence in summer. The concentration of observed intracellular sulfonamide resistance genes showed a significantly positive correlation with total nitrogen concentrations. This study suggested that eARG and iARG pollution of drinking water systems pose a potential risk to human public health.
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Affiliation(s)
- Han Hao
- School of Environment Science and Engineering, Tsinghua University, Beijing, 100084, China
| | - Dan-Yang Shi
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Dong Yang
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Zhong-Wei Yang
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Zhi-Gang Qiu
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Wei-Li Liu
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Zhi-Qiang Shen
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Jing Yin
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Hua-Ran Wang
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Jun-Wen Li
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China
| | - Hui Wang
- School of Environment Science and Engineering, Tsinghua University, Beijing, 100084, China.
| | - Min Jin
- Department of Environment and Health, Tianjin Institute of Environmental & Operational Medicine, Key Laboratory of Risk Assessment and Control for Environment & Food Safety, Tianjin, 300050, China.
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García-Pastor L, Sánchez-Romero MA, Gutiérrez G, Puerta-Fernández E, Casadesús J. Formation of phenotypic lineages in Salmonella enterica by a pleiotropic fimbrial switch. PLoS Genet 2018; 14:e1007677. [PMID: 30252837 PMCID: PMC6173445 DOI: 10.1371/journal.pgen.1007677] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 10/05/2018] [Accepted: 09/05/2018] [Indexed: 11/29/2022] Open
Abstract
The std locus of Salmonella enterica, an operon acquired by horizontal transfer, encodes fimbriae that permit adhesion to epithelial cells in the large intestine. Expression of the std operon is bistable, yielding a major subpopulation of StdOFF cells (99.7%) and a minor subpopulation of StdON cells (0.3%). In addition to fimbrial proteins, the std operon encodes two proteins, StdE and StdF, that have DNA binding capacity and control transcription of loci involved in flagellar synthesis, chemotaxis, virulence, conjugal transfer, biofilm formation, and other cellular functions. As a consequence of StdEF pleiotropic transcriptional control, StdON and StdOFF subpopulations may differ not only in the presence or absence of Std fimbriae but also in additional phenotypic traits. Separation of StdOFF and StdON lineages by cell sorting confirms the occurrence of lineage-specific features. Formation of StdOFF and StdON lineages may thus be viewed as a rudimentary bacterial differentiation program. We show that the std fimbrial operon of Salmonella enterica undergoes bistable expression, a trait far from exceptional among loci that encode components of the bacterial envelope. However, an unsuspected trait of the std operon is the presence of two genes that encode pleiotropic regulators of gene expression. Indeed, StdE and StdF are DNA-binding proteins that control transcription of hundreds of genes. As a consequence, StdEF govern multiple phenotypic traits, and the fimbriated and non-fimbriated Salmonella lineages may differ in motility, virulence, conjugal transfer, biofilm formation, and potentially in other phenotypic features. We hypothesize that pleiotropic control of gene expression by StdEF may contribute to adapt the non-fimbriated lineage to acute infection and the fimbriated lineage to chronic infection.
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Affiliation(s)
- Lucía García-Pastor
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | | | - Gabriel Gutiérrez
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Elena Puerta-Fernández
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
- Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Sevilla, Spain
- * E-mail: (EPF); (JC)
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
- * E-mail: (EPF); (JC)
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