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Pagan E, Merino N, Berdejo D, Campillo R, Gayan E, García-Gonzalo D, Pagan R. Adaptive evolution of Salmonella Typhimurium LT2 exposed to carvacrol lacks a uniform pattern. Appl Microbiol Biotechnol 2024; 108:38. [PMID: 38175235 PMCID: PMC10766787 DOI: 10.1007/s00253-023-12840-6] [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: 04/10/2023] [Revised: 10/05/2023] [Accepted: 10/17/2023] [Indexed: 01/05/2024]
Abstract
Emergence of genetic variants with increased resistance/tolerance to natural antimicrobials, such as essential oils, has been previously evidenced; however, it is unknown whether mutagenesis follows a general or a specific pattern. For this purpose, we carried out four adaptive laboratory evolutions (ALE) in parallel of Salmonella enterica Typhimurium with carvacrol. After 10 evolution steps, we selected and characterized one colony from each lineage (SeCarA, SeCarB, SeCarC, and SeCarD). Phenotypic characterization of the four evolved strains revealed enhanced survival to lethal treatments; two of them (SeCarA and SeCarB) showed an increase of minimum inhibitory concentration of carvacrol and a better growth fitness in the presence of carvacrol compared to wild-type strain. Whole genome sequencing revealed 10 mutations, of which four (rrsH, sseG, wbaV, and flhA) were present in more than one strain, whereas six (nirC, fliH, lon, rob, upstream yfhP, and upstream argR) were unique to individual strains. Single-mutation genetic constructs in SeWT confirmed lon and rob as responsible for the increased resistance to carvacrol as well as to antibiotics (ampicillin, ciprofloxacin, chloramphenicol, nalidixic acid, rifampicin, tetracycline, and trimethoprim). wbaV played an important role in increased tolerance against carvacrol and chloramphenicol, and flhA in cross-tolerance to heat treatments. As a conclusion, no common phenotypical or genotypical pattern was observed in the isolated resistant variants of Salmonella Typhimurium emerged under carvacrol stress. Furthermore, the demonstration of cross-resistance against heat and antibiotics exhibited by resistant variants raises concerns regarding food safety. KEY POINTS: • Stable resistant variants of Salmonella Typhimurium emerged under carvacrol stress • No common pattern of mutagenesis after cyclic exposures to carvacrol was observed • Resistant variants to carvacrol showed cross-resistance to heat and to antibiotics.
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Affiliation(s)
- Elisa Pagan
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza-CITA, Zaragoza, Spain
| | - Natalia Merino
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza-CITA, Zaragoza, Spain
| | - Daniel Berdejo
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza-CITA, Zaragoza, Spain
| | - Raul Campillo
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza-CITA, Zaragoza, Spain
| | - Elisa Gayan
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza-CITA, Zaragoza, Spain
| | - Diego García-Gonzalo
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza-CITA, Zaragoza, Spain
| | - Rafael Pagan
- Departamento de Producción Animal y Ciencia de los Alimentos, Facultad de Veterinaria, Instituto Agroalimentario de Aragón-IA2, Universidad de Zaragoza-CITA, Zaragoza, Spain.
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Gil-Gil T, Berryhill BA, Manuel JA, Smith AP, McCall IC, Baquero F, Levin BR. The evolution of heteroresistance via small colony variants in Escherichia coli following long term exposure to bacteriostatic antibiotics. Nat Commun 2024; 15:7936. [PMID: 39261449 PMCID: PMC11391013 DOI: 10.1038/s41467-024-52166-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Accepted: 08/27/2024] [Indexed: 09/13/2024] Open
Abstract
Traditionally, bacteriostatic antibiotics are agents able to arrest bacterial growth. Despite being traditionally viewed as unable to kill bacterial cells, when they are used clinically the outcome of these drugs is frequently as effective as when a bactericidal drug is used. We explore the dynamics of Escherichia coli after exposure to two ribosome-targeting bacteriostatic antibiotics, chloramphenicol and azithromycin, for thirty days. The results of our experiments provide evidence that bacteria exposed to these drugs replicate, evolve, and generate a sub-population of small colony variants (SCVs) which are resistant to multiple drugs. These SCVs contribute to the evolution of heteroresistance and rapidly revert to a susceptible state once the antibiotic is removed. Stated another way, exposure to bacteriostatic drugs selects for the evolution of heteroresistance in populations previously lacking this trait. More generally, our results question the definition of bacteriostasis as populations exposed to bacteriostatic drugs are replicating despite the lack of net growth.
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Affiliation(s)
- Teresa Gil-Gil
- Department of Biology, Emory University, Atlanta, GA, 30322, USA
| | - Brandon A Berryhill
- Department of Biology, Emory University, Atlanta, GA, 30322, USA
- Program in Microbiology and Molecular Genetics, Graduate Division of Biological and Biomedical Sciences, Laney Graduate School, Emory University, Atlanta, GA, 30322, USA
| | - Joshua A Manuel
- Department of Biology, Emory University, Atlanta, GA, 30322, USA
| | - Andrew P Smith
- Department of Biology, Emory University, Atlanta, GA, 30322, USA
| | - Ingrid C McCall
- Department of Biology, Emory University, Atlanta, GA, 30322, USA
| | - Fernando Baquero
- Hospital Universitario Ramón y Cajal, Instituto Ramón y Cajal de Investigación Sanitaria, and Centro de Investigación Médica en Red, Epidemiología y Salud Pública (CIBERESP), Madrid, Spain
| | - Bruce R Levin
- Department of Biology, Emory University, Atlanta, GA, 30322, USA.
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Verma T, Nandini SS, Singh V, Raghavan A, Annappa H, Bhaskarla C, Dubey AK, Nandi D. Divergent Roles of Escherichia Coli Encoded Lon Protease in Imparting Resistance to Uncouplers of Oxidative Phosphorylation: Roles of marA, rob, soxS and acrB. Curr Microbiol 2024; 81:98. [PMID: 38372817 DOI: 10.1007/s00284-024-03632-w] [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: 09/19/2023] [Accepted: 02/01/2024] [Indexed: 02/20/2024]
Abstract
Uncouplers of oxidative phosphorylation dissipate the proton gradient, causing lower ATP production. Bacteria encounter several non-classical uncouplers in the environment, leading to stress-induced adaptations. Here, we addressed the molecular mechanisms responsible for the effects of uncouplers in Escherichia coli. The expression and functions of genes involved in phenotypic antibiotic resistance were studied using three compounds: two strong uncouplers, i.e., Carbonyl cyanide m-chlorophenyl hydrazone (CCCP) and 2,4-Dinitrophenol (DNP), and one moderate uncoupler, i.e., Sodium salicylate (NaSal). Quantitative expression studies demonstrated induction of transcripts encoding marA, soxS and acrB with NaSal and DNP, but not CCCP. Since MarA and SoxS are degraded by the Lon protease, we investigated the roles of Lon using a lon-deficient strain (Δlon). Compared to the wild-type strain, Δlon shows compromised growth upon exposure to NaSal or 2, 4-DNP. This sensitivity is dependent on marA but not rob and soxS. On the other hand, the Δlon strain shows enhanced growth in the presence of CCCP, which is dependent on acrB. Interestingly, NaSal and 2,4-DNP, but not CCCP, induce resistance to antibiotics, such as ciprofloxacin and tetracycline. This study addresses the effects of uncouplers and the roles of genes involved during bacterial growth and phenotypic antibiotic resistance. Strong uncouplers are often used to treat wastewater, and these results shed light on the possible mechanisms by which bacteria respond to uncouplers. Also, the rampant usage of some uncouplers to treat wastewater may lead to the development of antibiotic resistance.
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Affiliation(s)
- Taru Verma
- Department of Bioengineering, Indian Institute of Science, Bengaluru, 560012, India
| | - Santhi Sanil Nandini
- Department of Biochemistry, Indian Institute of Science, Bengaluru, 560012, India
| | - Varsha Singh
- Department of Biochemistry, Indian Institute of Science, Bengaluru, 560012, India
| | - Abinaya Raghavan
- Department of Biochemistry, Indian Institute of Science, Bengaluru, 560012, India
| | - Harshita Annappa
- Department of Biochemistry, Indian Institute of Science, Bengaluru, 560012, India
| | - Chetana Bhaskarla
- Department of Biochemistry, Indian Institute of Science, Bengaluru, 560012, India
| | - Ashim Kumar Dubey
- Undergraduate program, Indian Institute of Science, Bengaluru, 560012, India
| | - Dipankar Nandi
- Department of Biochemistry, Indian Institute of Science, Bengaluru, 560012, India.
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Abstract
Understanding the factors that shape viral evolution is critical for developing effective antiviral strategies, accurately predicting viral evolution, and preventing pandemics. One fundamental determinant of viral evolution is the interplay between viral protein biophysics and the host machineries that regulate protein folding and quality control. Most adaptive mutations in viruses are biophysically deleterious, resulting in a viral protein product with folding defects. In cells, protein folding is assisted by a dynamic system of chaperones and quality control processes known as the proteostasis network. Host proteostasis networks can determine the fates of viral proteins with biophysical defects, either by assisting with folding or by targeting them for degradation. In this review, we discuss and analyze new discoveries revealing that host proteostasis factors can profoundly shape the sequence space accessible to evolving viral proteins. We also discuss the many opportunities for research progress proffered by the proteostasis perspective on viral evolution and adaptation.
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Affiliation(s)
- Jimin Yoon
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA;
| | - Jessica E Patrick
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA;
| | - C Brandon Ogbunugafor
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA;
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, USA
- Santa Fe Institute, Santa Fe, New Mexico, USA
| | - Matthew D Shoulders
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA;
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Structure, Substrate Specificity and Role of Lon Protease in Bacterial Pathogenesis and Survival. Int J Mol Sci 2023; 24:ijms24043422. [PMID: 36834832 PMCID: PMC9961632 DOI: 10.3390/ijms24043422] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 01/29/2023] [Accepted: 02/01/2023] [Indexed: 02/11/2023] Open
Abstract
Proteases are the group of enzymes that carry out proteolysis in all forms of life and play an essential role in cell survival. By acting on specific functional proteins, proteases affect the transcriptional and post-translational pathways in a cell. Lon, FtsH, HslVU and the Clp family are among the ATP-dependent proteases responsible for intracellular proteolysis in bacteria. In bacteria, Lon protease acts as a global regulator, governs an array of important functions such as DNA replication and repair, virulence factors, stress response and biofilm formation, among others. Moreover, Lon is involved in the regulation of bacterial metabolism and toxin-antitoxin systems. Hence, understanding the contribution and mechanisms of Lon as a global regulator in bacterial pathogenesis is crucial. In this review, we discuss the structure and substrate specificity of the bacterial Lon protease, as well as its ability to regulate bacterial pathogenesis.
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Cisneros-Mayoral S, Graña-Miraglia L, Pérez-Morales D, Peña-Miller R, Fuentes-Hernáandez A. Evolutionary history and strength of selection determine the rate of antibiotic resistance adaptation. Mol Biol Evol 2022; 39:6692293. [PMID: 36062982 PMCID: PMC9512152 DOI: 10.1093/molbev/msac185] [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: 11/29/2022] Open
Abstract
Bacterial adaptation to stressful environments often produces evolutionary constraints whereby increases in resistance are associated with reduced fitness in a different environment. The exploitation of this resistance-cost trade-off has been proposed as the basis of rational antimicrobial treatment strategies designed to limit the evolution of drug resistance in bacterial pathogens. Recent theoretical, laboratory, and clinical studies have shown that fluctuating selection can maintain drug efficacy and even restore drug susceptibility, but can also increase the rate of adaptation and promote cross-resistance to other antibiotics. In this paper, we combine mathematical modeling, experimental evolution, and whole-genome sequencing to follow evolutionary trajectories towards β-lactam resistance under fluctuating selective conditions. Our experimental model system consists of eight populations of Escherichia coli K12 evolving in parallel to a serial dilution protocol designed to dynamically control the strength of selection for resistance. We implemented adaptive ramps with mild and strong selection, resulting in evolved populations with similar levels of resistance, but with different evolutionary dynamics and diverging genotypic profiles. We found that mutations that emerged under strong selection are unstable in the absence of selection, in contrast to resistance mutations previously selected in the mild selection regime that were stably maintained in drug-free environments and positively selected for when antibiotics were reintroduced. Altogether, our population dynamics model and the phenotypic and genomic analysis of the evolved populations show that the rate of resistance adaptation is contingent upon the strength of selection, but also on evolutionary constraints imposed by prior drug exposures.
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Affiliation(s)
- Sandra Cisneros-Mayoral
- Programa de Biología Sintética, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Mexico
| | - Lucía Graña-Miraglia
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Deyanira Pérez-Morales
- Programa de Biología de Sistemas, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de Méexico, 62210, Cuernavaca, Mexico
| | - Rafael Peña-Miller
- Programa de Biología de Sistemas, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, 62210, Cuernavaca, Mexico
| | - Ayari Fuentes-Hernáandez
- Programa de Biología Sintética, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de Méexico, 62210, Cuernavaca, Mexico
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Abstract
Bacterial persisters are nongrowing cells highly tolerant to bactericidal antibiotics. However, this tolerance is reversible and not mediated by heritable genetic changes. Lon, an ATP-dependent protease, has repeatedly been shown to play a critical role in fluoroquinolone persistence in Escherichia coli. Although lon deletion (Δlon) is thought to eliminate persister cells via accumulation of the cell division inhibitor protein SulA, the exact mechanism underlying this phenomenon is not yet elucidated. Here, we show that Lon is an important regulatory protein for the resuscitation of the fluoroquinolone persisters in E. coli, and lon deletion impairs the ability of persister cells to form colonies during recovery through a sulA- and ftsZ-dependent mechanism. Notably, this observed "viable but nonculturable" state of antibiotic-tolerant Δlon cells is transient, as environmental conditions, such as starvation, can restore their culturability. Our data further indicate that starvation-induced SulA degradation or expression of Lon during recovery facilitates Z-ring formation in Δlon persisters, and Z-ring architecture is important for persister resuscitation in both wild-type and Δlon strains. Our in-depth image analysis clearly shows that the ratio of cell length to number of FtsZ rings for each intact ofloxacin-treated cell predicts the probability of resuscitation and, hence, can be used as a potential biomarker for persisters. IMPORTANCE The ATP-dependent Lon protease is one of the most studied bacterial proteases. Although deletion of lon has been frequently shown to reduce fluoroquinolone persistence, the proposed mechanisms underlying this phenomenon are highly controversial. Here, we have shown that lon deletion in Escherichia coli impairs the ability of persister cells to form colonies during recovery and that this reduction of persister levels in lon-deficient cells can be transient. We also found that altered Z-ring architecture is a key biomarker in both wild-type and lon-deficient persister cells transitioning to a normal cell state. Collectively, our findings highlight the importance of differentiating persister formation mechanisms from resuscitation mechanisms and underscore the critical role of the nonculturable cell state in antibiotic tolerance.
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Coscia F, Löwe J. Cryo-EM structure of the full-length Lon protease from Thermus thermophilus. FEBS Lett 2021; 595:2691-2700. [PMID: 34591981 PMCID: PMC8835725 DOI: 10.1002/1873-3468.14199] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 09/24/2021] [Accepted: 09/24/2021] [Indexed: 11/30/2022]
Abstract
In bacteria, Lon is a large hexameric ATP-dependent protease that targets misfolded and also folded substrates, some of which are involved in cell division and survival of cellular stress. The N-terminal domain of Lon facilitates substrate recognition, but how the domains confer such activity has remained unclear. Here, we report the full-length structure of Lon protease from Thermus thermophilus at 3.9 Å resolution in a substrate-engaged state. The six N-terminal domains are arranged in three pairs, stabilized by coiled-coil segments and forming an additional channel for substrate sensing and entry into the AAA+ ring. Sequence conservation analysis and proteolysis assays confirm that this architecture is required for the degradation of both folded and unfolded substrates in bacteria.
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Affiliation(s)
- Francesca Coscia
- MRC Laboratory of Molecular BiologyCambridge Biomedical CampusCambridgeUK
| | - Jan Löwe
- MRC Laboratory of Molecular BiologyCambridge Biomedical CampusCambridgeUK
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Patel V, Matange N. Adaptation and compensation in a bacterial gene regulatory network evolving under antibiotic selection. eLife 2021; 10:70931. [PMID: 34591012 PMCID: PMC8483737 DOI: 10.7554/elife.70931] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 09/22/2021] [Indexed: 12/28/2022] Open
Abstract
Gene regulatory networks allow organisms to generate coordinated responses to environmental challenges. In bacteria, regulatory networks are re-wired and re-purposed during evolution, though the relationship between selection pressures and evolutionary change is poorly understood. In this study, we discover that the early evolutionary response of Escherichia coli to the antibiotic trimethoprim involves derepression of PhoPQ signaling, an Mg2+-sensitive two-component system, by inactivation of the MgrB feedback-regulatory protein. We report that derepression of PhoPQ confers trimethoprim-tolerance to E. coli by hitherto unrecognized transcriptional upregulation of dihydrofolate reductase (DHFR), target of trimethoprim. As a result, mutations in mgrB precede and facilitate the evolution of drug resistance. Using laboratory evolution, genome sequencing, and mutation re-construction, we show that populations of E. coli challenged with trimethoprim are faced with the evolutionary ‘choice’ of transitioning from tolerant to resistant by mutations in DHFR, or compensating for the fitness costs of PhoPQ derepression by inactivating the RpoS sigma factor, itself a PhoPQ-target. Outcomes at this evolutionary branch-point are determined by the strength of antibiotic selection, such that high pressures favor resistance, while low pressures favor cost compensation. Our results relate evolutionary changes in bacterial gene regulatory networks to strength of selection and provide mechanistic evidence to substantiate this link.
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Affiliation(s)
- Vishwa Patel
- Dr. Vikram Sarabhai Institute of Cell and Molecular Biology, The Maharaja Sayajirao University of Baroda, Vadodara, India.,Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India
| | - Nishad Matange
- Indian Institute of Science Education and Research (IISER), Pune, India
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Low Cytoplasmic Magnesium Increases the Specificity of the Lon and ClpAP Proteases. J Bacteriol 2021; 203:e0014321. [PMID: 33941609 DOI: 10.1128/jb.00143-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Proteolysis is a fundamental property of all living cells. In the bacterium Salmonella enterica serovar Typhimurium, the HspQ protein controls the specificities of the Lon and ClpAP proteases. Upon acetylation, HspQ stops being a Lon substrate and no longer enhances proteolysis of the Lon substrate Hha. The accumulated HspQ protein binds to the protease adaptor ClpS, hindering proteolysis of ClpS-dependent substrates of ClpAP, such as Oat, a promoter of antibiotic persistence. HspQ is acetylated by the protein acetyltransferase Pat from acetyl coenzyme A (acetyl-CoA) bound to the acetyl-CoA binding protein Qad. We now report that low cytoplasmic Mg2+ promotes qad expression, which protects substrates of Lon and ClpSAP by increasing HspQ amounts. The qad promoter is activated by PhoP, a regulatory protein highly activated in low cytoplasmic Mg2+ that also represses clpS transcription. Both the qad gene and PhoP repression of the clpS promoter are necessary for antibiotic persistence. PhoP also promotes qad transcription in Escherichia coli, which shares a similar PhoP box in the qad promoter region with S. Typhimurium, Salmonella bongori, and Enterobacter cloacae. Our findings identify cytoplasmic Mg2+ and the PhoP protein as critical regulators of protease specificity in multiple enteric bacteria. IMPORTANCE The bacterium Salmonella enterica serovar Typhimurium narrows down the spectrum of substrates degraded by the proteases Lon and ClpAP in response to low cytoplasmic Mg2+, a condition that decreases protein synthesis. This control is exerted by PhoP, a transcriptional regulator activated in low cytoplasmic Mg2+ that governs proteostasis and is conserved in enteric bacteria. The uncovered mechanism enables bacteria to control the abundance of preexisting proteins.
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Ferrand A, Vergalli J, Pagès JM, Davin-Regli A. An Intertwined Network of Regulation Controls Membrane Permeability Including Drug Influx and Efflux in Enterobacteriaceae. Microorganisms 2020; 8:E833. [PMID: 32492979 PMCID: PMC7355843 DOI: 10.3390/microorganisms8060833] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 05/29/2020] [Accepted: 05/31/2020] [Indexed: 12/19/2022] Open
Abstract
The transport of small molecules across membranes is a pivotal step for controlling the drug concentration into the bacterial cell and it efficiently contributes to the antibiotic susceptibility in Enterobacteriaceae. Two types of membrane transports, passive and active, usually represented by porins and efflux pumps, are involved in this process. Importantly, the expression of these transporters and channels are modulated by an armamentarium of tangled regulatory systems. Among them, Helix-turn-Helix (HTH) family regulators (including the AraC/XylS family) and the two-component systems (TCS) play a key role in bacterial adaptation to environmental stresses and can manage a decrease of porin expression associated with an increase of efflux transporters expression. In the present review, we highlight some recent genetic and functional studies that have substantially contributed to our better understanding of the sophisticated mechanisms controlling the transport of small solutes (antibiotics) across the membrane of Enterobacteriaceae. This information is discussed, taking into account the worrying context of clinical antibiotic resistance and fitness of bacterial pathogens. The localization and relevance of mutations identified in the respective regulation cascades in clinical resistant strains are discussed. The possible way to bypass the membrane/transport barriers is described in the perspective of developing new therapeutic targets to combat bacterial resistance.
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Affiliation(s)
| | | | | | - Anne Davin-Regli
- UMR_MD1, U-1261, Aix-Marseille University, INSERM, SSA, IRBA, MCT, Faculté de Pharmacie, 27 Bd Jean Moulin, 13385 Marseille CEDEX 05, France; (A.F.); (J.V.); (J.-M.P.)
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