1
|
Bedore AM, Waters CM. Plasmid-free cheater cells commonly evolve during laboratory growth. Appl Environ Microbiol 2024; 90:e0231123. [PMID: 38446071 PMCID: PMC11022567 DOI: 10.1128/aem.02311-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Accepted: 02/06/2024] [Indexed: 03/07/2024] Open
Abstract
It has been nearly a century since the isolation and use of penicillin, heralding the discovery of a wide range of different antibiotics. In addition to clinical applications, such antibiotics have been essential laboratory tools, allowing for selection and maintenance of laboratory plasmids that encode cognate resistance genes. However, antibiotic resistance mechanisms can additionally function as public goods. For example, extracellular beta-lactamases produced by resistant cells that subsequently degrade penicillin and related antibiotics allow neighboring plasmid-free susceptible bacteria to survive antibiotic treatment. How such cooperative mechanisms impact selection of plasmids during experiments in laboratory conditions is poorly understood. Here, we show in multiple bacterial species that the use of plasmid-encoded beta-lactamases leads to significant curing of plasmids in surface-grown bacteria. Furthermore, such curing was also evident for aminoglycoside phosphotransferase and tetracycline antiporter resistance mechanisms. Alternatively, antibiotic selection in liquid growth led to more robust plasmid maintenance, although plasmid loss was still observed. The net outcome of such plasmid loss is the generation of a heterogenous population of plasmid-containing and plasmid-free cells, leading to experimental confounds that are not widely appreciated.IMPORTANCEPlasmids are routinely used in microbiology as readouts of cell biology or tools to manipulate cell function. Central to these studies is the assumption that all cells in an experiment contain the plasmid. Plasmid maintenance in a host cell typically depends on a plasmid-encoded antibiotic resistance marker, which provides a selective advantage when the plasmid-containing cell is grown in the presence of antibiotic. Here, we find that growth of plasmid-containing bacteria on a surface and to a lesser extent in liquid culture in the presence of three distinct antibiotic families leads to the evolution of a significant number of plasmid-free cells, which rely on the resistance mechanisms of the plasmid-containing cells. This process generates a heterogenous population of plasmid-free and plasmid-containing bacteria, an outcome which could confound further experimentation.
Collapse
Affiliation(s)
- Amber M. Bedore
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Christopher M. Waters
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| |
Collapse
|
2
|
Liang Z, Huang L, Liu H, Zheng Y, Feng J, Shi Z, Chen Y, Lv M, Zhou J, Zhang L, Chen S. Characterization of the Arn lipopolysaccharide modification system essential for zeamine resistance unveils its new roles in Dickeya oryzae physiology and virulence. MOLECULAR PLANT PATHOLOGY 2023; 24:1480-1494. [PMID: 37740253 PMCID: PMC10632790 DOI: 10.1111/mpp.13386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 07/14/2023] [Accepted: 08/22/2023] [Indexed: 09/24/2023]
Abstract
The zeamines produced by Dickeya oryzae are potent polyamine antibiotics and phytotoxins that are essential for bacterial virulence. We recently showed that the RND efflux pump DesABC in D. oryzae confers partial resistance to zeamines. To fully elucidate the bacterial self-protection mechanisms, in this study we used transposon mutagenesis to identify the genes encoding proteins involved in zeamine resistance in D. oryzae EC1. This led to the identification of a seven-gene operon, arnEC1 , that encodes enzyme homologues associated with lipopolysaccharide modification. Deletion of the arnEC1 genes in strain EC1 compromised its zeamine resistance 8- to 16-fold. Further deletion of the des gene in the arnEC1 mutant background reduced zeamine resistance to a level similar to that of the zeamine-sensitive Escherichia coli DH5α. Intriguingly, the arnEC1 mutants showed varied bacterial virulence on rice, potato, and Chinese cabbage. Further analyses demonstrated that ArnBCATEC1 are involved in maintenance of the bacterial nonmucoid morphotype by repressing the expression of capsular polysaccharide genes and that ArnBEC1 is a bacterial virulence determinant, influencing transcriptional expression of over 650 genes and playing a key role in modulating bacterial motility and virulence. Taken together, these findings decipher a novel zeamine resistance mechanism in D. oryzae and document new roles of the Arn enzymes in modulation of bacterial physiology and virulence.
Collapse
Affiliation(s)
- Zhibin Liang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- Guangdong Laboratory for Lingnan Modern AgricultureGuangzhouChina
| | - Luhao Huang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
| | - Huidi Liu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- Guangdong Laboratory for Lingnan Modern AgricultureGuangzhouChina
| | - Ying Zheng
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
| | - Jiani Feng
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
| | - Zurong Shi
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- School of Biological EngineeringHuainan Normal UniversityHuainanChina
| | - Yufan Chen
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- Research Center of Chinese Herbal Resource Science and EngineeringGuangzhou University of Chinese MedicineGuangzhouChina
| | - Mingfa Lv
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- College of Plant ProtectionFujian Agriculture and Forestry UniversityFuzhouChina
| | - Jianuan Zhou
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- Guangdong Laboratory for Lingnan Modern AgricultureGuangzhouChina
| | - Lian‐Hui Zhang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- Guangdong Laboratory for Lingnan Modern AgricultureGuangzhouChina
| | - Shaohua Chen
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research CentreSouth China Agricultural UniversityGuangzhouChina
- Guangdong Laboratory for Lingnan Modern AgricultureGuangzhouChina
| |
Collapse
|
3
|
Yang Z, He S, Wei Y, Li X, Shan A, Wang J. Antimicrobial peptides in combination with citronellal efficiently kills multidrug resistance bacteria. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2023; 120:155070. [PMID: 37729771 DOI: 10.1016/j.phymed.2023.155070] [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: 03/19/2023] [Revised: 09/01/2023] [Accepted: 09/04/2023] [Indexed: 09/22/2023]
Abstract
BACKGROUND Antimicrobial peptides (AMPs) are considered as the most potential alternatives to antibiotics, but they have several drawbacks, including high cost, medium antimicrobial efficacy, poor cell selectivity, which limit clinical application. To overcome the above problems, combination therapy of AMPs with adjuvants might maximize the effectiveness of AMPs. We found that citronellal can substantially potentiate the ZY4R peptide efficacy against Escherichia coli ATCC25922. However, it is unclear whether ZY4R/citronellal combination poses synergistic antimicrobial effects against most bacteria, and their synergy mechanism has not been elucidated. PURPOSE To investigate synergistic antimicrobial efficacies, biosafety, and synergy mechanism of ZY4R/citronellal combination. METHOD Checkerboard, time-kill curves, cytotoxicity assays, and in vivo animal models were conducted to assess synergistic antimicrobial effects and biosafety of the ZY4R/citronellal combination. To evaluate their synergy mechanism, a series of cell-based assays and transcriptome analysis were performed. RESULTS ZY4R/citronellal combination exhibited synergistic antimicrobial effects against 20 clinically significant pathogens, with the fractional inhibitory concentration index (FICI) ranging from 0.313 to 0.047. Meanwhile, ZY4R/citronellal combination enhanced antimicrobial efficacies without compromising cell selectivity, contributing to decreasing drug dosage and improving biosafety. Compared with ZY4R (4 mg/kg) and citronellal (25 mg/kg) alone, ZY4R (4 mg/kg)/citronellal (25 mg/kg) combination significantly decreased the bacterial load in peritoneal fluid, liver, and kidney (P < 0.05) and alleviated pathological damage of the organs of mice. Mechanistic studies showed that ZY4R allowed citronellal to pass through the outer membrane rapidly and acted on the inner membrane together with citronellal, causing more potent membrane damage. The membrane damage prompted the continuous accumulation of citronellal in cells, and citronellal further induced energy breakdown and inhibited exopolysaccharide (EPS) production, which aggravated ZY4R-induced outer membrane damage, thereby resulting in bacterial death. CONCLUSIONS ZY4R/citronellal combination exhibited broad-spectrum synergy with a low resistance development and high biosafety. Their synergy mechanism acted on two important cellular targets (energy metabolism and membrane integrity). Combination therapy of ZY4R with citronellal may be a promising mixture to combat bacterial infections facing an antibiotic-resistance crisis.
Collapse
Affiliation(s)
- Zhanyi Yang
- College of animal science and technology, Northeast Agricultural University, Harbin 150030, P. R. China
| | - Shiqi He
- College of animal science and technology, Northeast Agricultural University, Harbin 150030, P. R. China
| | - Yingxin Wei
- College of animal science and technology, Northeast Agricultural University, Harbin 150030, P. R. China
| | - Xuefeng Li
- College of animal science and technology, Northeast Agricultural University, Harbin 150030, P. R. China
| | - Anshan Shan
- College of animal science and technology, Northeast Agricultural University, Harbin 150030, P. R. China.
| | - Jiajun Wang
- College of animal science and technology, Northeast Agricultural University, Harbin 150030, P. R. China.
| |
Collapse
|
4
|
Huang W, Qu L, Gao P, Du G. Bioassay and Whole-Genome Analysis of Bacillus velezensis FIO1408, a Biocontrol Agent Against Pathogenic Bacteria in Aquaculture. Curr Microbiol 2023; 80:354. [PMID: 37740122 DOI: 10.1007/s00284-023-03423-9] [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: 02/16/2022] [Accepted: 03/04/2023] [Indexed: 09/24/2023]
Abstract
Bacterial disease is one of the most critical problems in aquaculture. Probiotics represent a promising biological approach to control bacterial disease because it is effective against pathogens and environmentally friendly. This study assessed the antagonistic activities of a bacterial strain FIO1408 isolated from deep-sea water against many pathogenic bacteria in aquaculture, including Listonella anguillarum, Vibrio parahaemolyticus, Vibrio alginolyticus, Aeromonas hydrophila, Edwardsiella anguillarum, Edwardsiella tarda, and Edwardsiella piscicida. The complete genome of strain FIO1408 consisted of a circular chromosome of 4,137,639 bp and two plasmids of 16,439 bp and 24,472 bp. Phylogenetic analysis showed strain FIO1408 clustered with Bacillus velezensis strains. 12 genes/gene clusters responsible for the synthesis of secondary metabolites were identified in the FIO1408 genome, including three lipopeptides, three polyketides, three bacteriocins, one siderophore, one dipeptide, and one unknown type. Also identified were 273 unique orthologous genes primarily involved in phage resistance, protein hydrolysis, environmental survivability, and genetic stability compared to B. velezensis KACC 13105, B. velezensis FZB42T, and B. velezensis NRRL B-41580. The principal safety of FIO1408 was demonstrated by genetic analyses and feeding trials. These findings will contribute to studies on the biocontrol mechanisms of B. velezensis FIO1408 and facilitate its application as a potent biological control agent against bacterial pathogens in aquaculture.
Collapse
Affiliation(s)
- Wenhao Huang
- Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources (MNR), Qingdao, 266061, China
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, 266237, China
| | - Lingyun Qu
- Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources (MNR), Qingdao, 266061, China.
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, 266237, China.
| | - Ping Gao
- Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources (MNR), Qingdao, 266061, China.
- Laboratory for Marine Fisheries Science and Food Production Processes, Laoshan Laboratory, Qingdao, 266237, China.
| | - Guangxun Du
- Key Laboratory of Marine Eco-Environmental Science and Technology, First Institute of Oceanography, Ministry of Natural Resources (MNR), Qingdao, 266061, China
| |
Collapse
|
5
|
Liu W, Peng J, Zou S, Xu L, Cheng H, Wang Y, Chen Z, Zhou H. Regulation on Pathway Metabolic Fluxes to Enhance Colanic Acid Production in Escherichia coli. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023; 71:13857-13868. [PMID: 37688786 DOI: 10.1021/acs.jafc.3c05046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/11/2023]
Abstract
Colanic acid (CA) is a natural polysaccharide macromolecule with rich and unique biological properties and is a promising candidate for use in food and cosmetics. To date, the efficient biosynthesis of CA and the influence of product accumulation on the strains used have yet to be precisely investigated. Herein, bottlenecks in the CA metabolic pathway were untangled by finely regulating the expression of manA, cpsG, fcl, and rcsA. Engineered strains produced CA at >1 g/L in shake flasks without dependence on cold temperatures, and it was verified in a 1 L bioreactor with a titer up to 18.64 g/L within 24 h. The accumulation of CA caused a decrease in the saturated fatty acid content (represented by C16:0 and C18:0) in the cell membrane. This study demonstrated pathway engineering for efficient CA production in cell factories and provided insights into the barriers and solutions faced in the biosynthesis of natural products.
Collapse
Affiliation(s)
- Wenxian Liu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
| | - Jing Peng
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
| | - Sini Zou
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
| | - Liting Xu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
| | - Haina Cheng
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, Hunan 410083, P. R. China
| | - Yuguang Wang
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, Hunan 410083, P. R. China
| | - Zhu Chen
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, Hunan 410083, P. R. China
| | - Hongbo Zhou
- School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, P. R. China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, Hunan 410083, P. R. China
| |
Collapse
|
6
|
Bedore AM, Waters CM. Plasmid-free cheater cells commonly evolve during laboratory growth. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.19.541508. [PMID: 37292590 PMCID: PMC10245762 DOI: 10.1101/2023.05.19.541508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
It has been nearly a century since the isolation and use of penicillin, heralding the discovery of a wide range of different antibiotics. In addition to clinical applications, such antibiotics have been essential laboratory tools, allowing for selection and maintenance of laboratory plasmids that encode cognate resistance genes. However, antibiotic resistance mechanisms can additionally function as public goods. For example, secretion of beta-lactamase from resistant cells, and subsequent degradation of nearby penicillin and related antibiotics, allows neighboring plasmid-free susceptible bacteria to survive antibiotic treatment. How such cooperative mechanisms impact selection of plasmids during experiments in laboratory conditions is poorly understood. Here, we show that the use of plasmid-encoded beta-lactamases leads to significant curing of plasmids in surface grown bacteria. Furthermore, such curing was also evident for aminoglycoside phosphotransferase and tetracycline antiporter resistance mechanisms. Alternatively, antibiotic selection in liquid growth led to more robust plasmid maintenance, although plasmid loss still occurred. The net outcome of such plasmid loss is the generation of a heterogenous population of plasmid-containing and plasmid-free cells, leading to experimental confounds that are not widely appreciated.
Collapse
Affiliation(s)
| | - Christopher M. Waters
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA, 48824
| |
Collapse
|
7
|
Kurzylewska M, Bomba A, Dworaczek K, Pękala-Safińska A, Turska-Szewczuk A. Structure and gene cluster annotation of the O-antigen of Aeromonas sobria strain K928 isolated from common carp and classified into the new Aeromonas PGO1 serogroup. Carbohydr Res 2023; 528:108809. [PMID: 37086562 DOI: 10.1016/j.carres.2023.108809] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/05/2023] [Accepted: 04/05/2023] [Indexed: 04/24/2023]
Abstract
Aeromonas sobria strain K928 was isolated from a common carp during a Motile Aeromonas Infection/Motile Aeromonas Septicaemia disease outbreak on a Polish fish farm and classified into the new provisional PGO1 serogroup. The lipopolysaccharide of A. sobria K928 was subjected to mild acid hydrolysis, and the O-specific polysaccharide, which was isolated by gel-permeation chromatography, was studied using sugar and methylation analyses and 1H and 13C NMR spectroscopy. The following structure of the branched O-specific polysaccharide repeating unit of A. sobria K928 was established. →2)[α-D-Fucp3NRHb-(1→3)]-α-L-Rhap-(1→3)-β-L-Rhap-(1→4)-α-L-Rhap-(1→3)-β-D-FucpNAc-(1→ The O-antigen gene cluster was identified and characterized in the genome of the A. sobria K928 strain after comparison with sequences in the available databases. The composition of the O-antigen genetic region was found to be consistent with the O-polysaccharide structure, and its organization was proposed.
Collapse
Affiliation(s)
- Maria Kurzylewska
- Department of Genetics and Microbiology, Institute of Biological Sciences, M. Curie-Sklodowska University, Akademicka 19, 20-033, Lublin, Poland
| | - Arkadiusz Bomba
- Department of Omics Analyses, National Veterinary Research Institute, Partyzantow 57, 24-100, Pulawy, Poland
| | - Katarzyna Dworaczek
- Department of Genetics and Microbiology, Institute of Biological Sciences, M. Curie-Sklodowska University, Akademicka 19, 20-033, Lublin, Poland
| | - Agnieszka Pękala-Safińska
- Department of Preclinical Sciences and Infectious Diseases, Faculty of Veterinary Medicine and Animal Science, Poznan University of Life Sciences, Wolynska 35, 60-637, Poznan, Poland
| | - Anna Turska-Szewczuk
- Department of Genetics and Microbiology, Institute of Biological Sciences, M. Curie-Sklodowska University, Akademicka 19, 20-033, Lublin, Poland.
| |
Collapse
|
8
|
Jeje O, Ewunkem AJ, Jeffers-Francis LK, Graves JL. Serving Two Masters: Effect of Escherichia coli Dual Resistance on Antibiotic Susceptibility. Antibiotics (Basel) 2023; 12:antibiotics12030603. [PMID: 36978471 PMCID: PMC10044975 DOI: 10.3390/antibiotics12030603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/10/2023] [Accepted: 03/13/2023] [Indexed: 03/30/2023] Open
Abstract
The prevalence of multidrug-resistant bacteria and their increased pathogenicity has led to a growing interest in metallic antimicrobial materials and bacteriophages as potential alternatives to conventional antibiotics. This study examines how resistance to excess iron (III) influences the evolution of bacteriophage resistance in the bacterium Escherichia coli. We utilized experimental evolution in E. coli to test the effect of the evolution of phage T7 resistance on populations resistant to excess iron (III) and populations without excess iron resistance. Phage resistance evolved rapidly in both groups. Dual-resistant (iron (III)/phage) populations were compared to their controls (excess iron (III)-resistant, phage-resistant, no resistance to either) for their performance against each stressor, excess iron (III) and phage; and correlated resistances to excess iron (II), gallium (III), silver (I) and conventional antibiotics. Excess iron (III)/phage-resistant populations demonstrated superior 24 h growth compared to all other populations when exposed to increasing concentrations of iron (II, III), gallium (III), ampicillin, and tetracycline. No differences in 24 h growth were shown between excess iron (III)/phage-resistant and excess iron (III)-resistant populations in chloramphenicol, sulfonamide, and silver (I). The genomic analysis identified selective sweeps in the iron (III) resistant (rpoB, rpoC, yegB, yeaG), phage-resistant (clpX →/→ lon, uvaB, yeaG, fliR, gatT, ypjF, waaC, rpoC, pgi, and yjbH) and iron (III)/phage resistant populations (rcsA, hldE, rpoB, and waaC). E. coli selected for resistance to both excess iron (III) and T7 phage showed some evidence of a synergistic effect on various components of fitness. Dual selection resulted in correlated resistances to ionic metals {iron (II), gallium (III), and silver (I)} and several conventional antibiotics. There is a likelihood that this sort of combination antimicrobial treatment may result in bacterial variants with multiple resistances.
Collapse
Affiliation(s)
- Olusola Jeje
- Biology Department, North Carolina Agricultural and Technical State University, 1601 E Market Street, Greensboro, NC 27411, USA
| | - Akamu J Ewunkem
- Department of Biological Sciences, Winston Salem State University, 601 S Martin Luther King Jr Drive, Winston Salem, NC 27110, USA
| | - Liesl K Jeffers-Francis
- Biology Department, North Carolina Agricultural and Technical State University, 1601 E Market Street, Greensboro, NC 27411, USA
| | - Joseph L Graves
- Biology Department, North Carolina Agricultural and Technical State University, 1601 E Market Street, Greensboro, NC 27411, USA
| |
Collapse
|
9
|
Saïdi F, Mahanta U, Panda A, Kezzo AA, Jolivet NY, Bitazar R, John G, Martinez M, Mellouk A, Calmettes C, Chang YW, Sharma G, Islam ST. Bacterial Outer Membrane Polysaccharide Export (OPX) Proteins Occupy Three Structural Classes with Selective β-Barrel Porin Requirements for Polymer Secretion. Microbiol Spectr 2022; 10:e0129022. [PMID: 36200915 PMCID: PMC9603273 DOI: 10.1128/spectrum.01290-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 09/08/2022] [Indexed: 12/30/2022] Open
Abstract
Secretion of high-molecular-weight polysaccharides across the bacterial envelope is ubiquitous, as it enhances prokaryotic survival in (a)biotic settings. Such polymers are often assembled by Wzx/Wzy- or ABC transporter-dependent schemes implicating outer membrane (OM) polysaccharide export (OPX) proteins in cell-surface polymer translocation. In the social predatory bacterium Myxococcus xanthus, the exopolysaccharide (EPS) pathway WzaX, major spore coat (MASC) pathway WzaS, and biosurfactant polysaccharide (BPS) pathway WzaB were herein found to be truncated OPX homologues of Escherichia coli Wza lacking OM-spanning α-helices. Comparative genomics across all bacteria (>91,000 OPX proteins identified and analyzed), complemented with cryo-electron tomography cell-envelope analyses, revealed such "truncated" WzaX/S/B architecture to be the most common among three defined OPX-protein structural classes independent of periplasm thickness. Fold recognition and deep learning revealed the conserved M. xanthus proteins MXAN_7418/3226/1916 (encoded beside wzaX/S/B, respectively) to be integral OM β-barrels, with structural homology to the poly-N-acetyl-d-glucosamine synthase-dependent pathway porin PgaA. Such bacterial porins were identified near numerous genes for all three OPX protein classes. Interior MXAN_7418/3226/1916 β-barrel electrostatics were found to match properties of their associated polymers. With MXAN_3226 essential for MASC export, and MXAN_7418 herein shown to mediate EPS translocation, we have designated this new secretion machinery component "Wzp" (i.e., Wz porin), with the final step of M. xanthus EPS/MASC/BPS secretion across the OM now proposed to be mediated by WzpX/S/B (i.e., MXAN_7418/3226/1916). Importantly, these data support a novel and widespread secretion paradigm for polysaccharide biosynthesis pathways in which those containing OPX components that cannot span the OM instead utilize β-barrel porins to mediate polysaccharide transport across the OM. IMPORTANCE Diverse bacteria assemble and secrete polysaccharides that alter their physiologies through modulation of motility, biofilm formation, and host immune system evasion. Most such pathways require outer membrane (OM) polysaccharide export (OPX) proteins for sugar-polymer transport to the cell surface. In the prototypic Escherichia coli Group-1-capsule biosynthesis system, eight copies of this canonical OPX protein cross the OM with an α-helix, forming a polysaccharide-export pore. Herein, we instead reveal that most OPX proteins across all bacteria lack this α-helix, raising questions as to the manner by which most secreted polysaccharides actually exit cells. In the model developmental bacterium Myxococcus xanthus, we show this process to depend on OPX-coupled OM-spanning β-barrel porins, with similar porins encoded near numerous OPX genes in diverse bacteria. Knowledge of the terminal polysaccharide secretion step will enable development of antimicrobial compounds targeted to blocking polymer export from outside the cell, thus bypassing any requirements for antimicrobial compound uptake by the cell.
Collapse
Affiliation(s)
- Fares Saïdi
- Institut National de la Recherche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Université du Québec, Institut Pasteur International Network, Laval, Quebec, Canada
- PROTEO, the Quebec Network for Research on Protein Function, Engineering, and Applications, Université Laval, Québec, Quebec, Canada
| | - Utkarsha Mahanta
- Institute of Bioinformatics and Applied Biotechnology (IBAB), Bengaluru, Karnataka, India
| | - Adyasha Panda
- Institute of Bioinformatics and Applied Biotechnology (IBAB), Bengaluru, Karnataka, India
| | - Ahmad A. Kezzo
- Institut National de la Recherche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Université du Québec, Institut Pasteur International Network, Laval, Quebec, Canada
- PROTEO, the Quebec Network for Research on Protein Function, Engineering, and Applications, Université Laval, Québec, Quebec, Canada
| | - Nicolas Y. Jolivet
- Institut National de la Recherche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Université du Québec, Institut Pasteur International Network, Laval, Quebec, Canada
- PROTEO, the Quebec Network for Research on Protein Function, Engineering, and Applications, Université Laval, Québec, Quebec, Canada
| | - Razieh Bitazar
- Institut National de la Recherche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Université du Québec, Institut Pasteur International Network, Laval, Quebec, Canada
- PROTEO, the Quebec Network for Research on Protein Function, Engineering, and Applications, Université Laval, Québec, Quebec, Canada
| | - Gavin John
- Department of Pediatrics, Division of Infectious Diseases, Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
| | - Matthew Martinez
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Abdelkader Mellouk
- Institut National de la Recherche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Université du Québec, Institut Pasteur International Network, Laval, Quebec, Canada
- PROTEO, the Quebec Network for Research on Protein Function, Engineering, and Applications, Université Laval, Québec, Quebec, Canada
| | - Charles Calmettes
- Institut National de la Recherche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Université du Québec, Institut Pasteur International Network, Laval, Quebec, Canada
- PROTEO, the Quebec Network for Research on Protein Function, Engineering, and Applications, Université Laval, Québec, Quebec, Canada
| | - Yi-Wei Chang
- Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Gaurav Sharma
- Institute of Bioinformatics and Applied Biotechnology (IBAB), Bengaluru, Karnataka, India
| | - Salim T. Islam
- Institut National de la Recherche Scientifique (INRS), Centre Armand-Frappier Santé Biotechnologie, Université du Québec, Institut Pasteur International Network, Laval, Quebec, Canada
- PROTEO, the Quebec Network for Research on Protein Function, Engineering, and Applications, Université Laval, Québec, Quebec, Canada
| |
Collapse
|
10
|
Larson MR, Biddle K, Gorman A, Boutom S, Rosenshine I, Saper MA. Escherichia coli O127 group 4 capsule proteins assemble at the outer membrane. PLoS One 2021; 16:e0259900. [PMID: 34780538 PMCID: PMC8592465 DOI: 10.1371/journal.pone.0259900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 10/28/2021] [Indexed: 12/26/2022] Open
Abstract
Enteropathogenic Escherichia coli O127 is encapsulated by a protective layer of polysaccharide made of the same strain specific O-antigen as the serotype lipopolysaccharide. Seven genes encoding capsule export functions comprise the group 4 capsule (gfc) operon. Genes gfcE, etk and etp encode homologs of the group 1 capsule secretion system but the upstream gfcABCD genes encode unknown functions specific to group 4 capsule export. We have developed an expression system for the large-scale production of the outer membrane protein GfcD. Contrary to annotations, we find that GfcD is a non-acylated integral membrane protein. Circular dichroism spectroscopy, light-scattering data, and the HHomp server suggested that GfcD is a monomeric β-barrel with 26 β-strands and an internal globular domain. We identified a set of novel protein-protein interactions between GfcB, GfcC, and GfcD, both in vivo and in vitro, and quantified the binding properties with isothermal calorimetry and biolayer interferometry. GfcC and GfcB form a high-affinity heterodimer with a KD near 100 nM. This heterodimer binds to GfcD (KD = 28 μM) significantly better than either GfcB or GfcC alone. These gfc proteins may form a complex at the outer membrane for group 4 capsule secretion or for a yet unknown function.
Collapse
Affiliation(s)
- Matthew R. Larson
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Kassia Biddle
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Adam Gorman
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Sarah Boutom
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Ilan Rosenshine
- Dept of Microbiology and Molecular Genetics, Hebrew University Faculty of Medicine, Ein Kerem, Jerusalem, Israel
| | - Mark A. Saper
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan, United States of America
- Program in Biophysics, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail:
| |
Collapse
|
11
|
Predatory Bacteria Select for Sustained Prey Diversity. Microorganisms 2021; 9:microorganisms9102079. [PMID: 34683400 PMCID: PMC8540638 DOI: 10.3390/microorganisms9102079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Revised: 09/22/2021] [Accepted: 09/23/2021] [Indexed: 11/17/2022] Open
Abstract
Predator impacts on prey diversity are often studied among higher organisms over short periods, but microbial predator-prey systems allow examination of prey-diversity dynamics over evolutionary timescales. We previously showed that Escherichia coli commonly evolved minority mucoid phenotypes in response to predation by the bacterial predator Myxococcus xanthus by one time point of a coevolution experiment now named MyxoEE-6. Here we examine mucoid frequencies across several MyxoEE-6 timepoints to discriminate between the hypotheses that mucoids were increasing to fixation, stabilizing around equilibrium frequencies, or heading to loss toward the end of MyxoEE-6. In four focal coevolved prey populations, mucoids rose rapidly early in the experiment and then fluctuated within detectable minority frequency ranges through the end of MyxoEE-6, generating frequency dynamics suggestive of negative frequency-dependent selection. However, a competition experiment between mucoid and non-mucoid clones found a predation-specific advantage of the mucoid clone that was insensitive to frequency over the examined range, leaving the mechanism that maintains minority mucoidy unresolved. The advantage of mucoidy under predation was found to be associated with reduced population size after growth (productivity) in the absence of predators, suggesting a tradeoff between productivity and resistance to predation that we hypothesize may reverse mucoid vs non-mucoid fitness ranks within each MyxoEE-6 cycle. We also found that mucoidy was associated with diverse colony phenotypes and diverse candidate mutations primarily localized in the exopolysaccharide operon yjbEFGH. Collectively, our results show that selection from predatory bacteria can generate apparently stable sympatric phenotypic polymorphisms within coevolving prey populations and also allopatric diversity across populations by selecting for diverse mutations and colony phenotypes associated with mucoidy. More broadly, our results suggest that myxobacterial predation increases long-term diversity within natural microbial communities.
Collapse
|
12
|
Matanza XM, López-Suárez L, do Vale A, Osorio CR. The two-component system RstAB regulates production of a polysaccharide capsule with a role in virulence in the marine pathogen Photobacterium damselae subsp. damselae. Environ Microbiol 2021; 23:4859-4880. [PMID: 34423883 DOI: 10.1111/1462-2920.15731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 06/23/2021] [Accepted: 07/21/2021] [Indexed: 12/29/2022]
Abstract
The marine bacterium Photobacterium damselae subsp. damselae (Pdd) causes disease in marine animals and humans. Previous studies demonstrated that mutation of the two-component system RstAB strongly impacts virulence of this pathogen, but the RstAB regulon has not been thoroughly elucidated. We here compared the transcriptomes of Pdd RM-71 and ΔrstA and ΔrstB derivatives using RNA-seq. In accordance with previous studies, RstAB positively regulated cytotoxins Dly, PhlyP and PhlyC. This analysis also demonstrated a positive regulation of outer membrane proteins, resistance against antimicrobials and potential virulence factors by this system. Remarkably, RstAB positively regulated two hitherto uncharacterised gene clusters involved in the synthesis of a polysaccharide capsule. Presence of a capsular layer in wild-type cells was confirmed by transmission electron microscopy, whereas rstA and rstB mutants were non-capsulated. Mutants for capsule synthesis genes, wza and wzc exhibited acapsular phenotypes, were impaired in resistance against the bactericidal action of fish serum and mucus, and were strongly impaired in virulence for fish, indicating a major role of capsule in virulence. Collectively, this study demonstrates that RstAB is a major positive regulator of key virulence factors including a polysaccharide capsule essential for full virulence in a pathogenic Photobacterium.
Collapse
Affiliation(s)
- Xosé M Matanza
- Departamento de Microbioloxía e Parasitoloxía, Instituto de Acuicultura, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Laura López-Suárez
- Departamento de Microbioloxía e Parasitoloxía, Instituto de Acuicultura, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Ana do Vale
- Fish Immunology and Vaccinology Group, IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.,i3S-Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal
| | - Carlos R Osorio
- Departamento de Microbioloxía e Parasitoloxía, Instituto de Acuicultura, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| |
Collapse
|
13
|
Abstract
All currently known architectures of outer-membrane beta barrels (OMBBs) have only one barrel. While the vast majority function as oligomers, with barrels from different chains packing against each other in the membrane, it was assumed that these multiple chains are needed to form multibarrel structures. And yet, here we show that multibarrel chains exist. Using state-of-the-art sequence and structure analysis tools, we report the discovery of more than 30 multibarrel architectures from gram-negative bacteria. The discovery of these architectures reveals another interesting chapter in OMBB evolution and has implications for protein engineering. The evolutionary advantages of multibarrels are yet to be discovered. Outer-membrane beta barrels (OMBBs) are found in the outer membrane of gram-negative bacteria and eukaryotic organelles. OMBBs fold as antiparallel β-sheets that close onto themselves, forming pores that traverse the membrane. Currently known structures include only one barrel, of 8 to 36 strands, per chain. The lack of multi-OMBB chains is surprising, as most OMBBs form oligomers, and some function only in this state. Using a combination of sensitive sequence comparison methods and coevolutionary analysis tools, we identify many proteins combining multiple beta barrels within a single chain; combinations that include eight-stranded barrels prevail. These multibarrels seem to be the result of independent, lineage-specific fusion and amplification events. The absence of multibarrels that are universally conserved in bacteria with an outer membrane, coupled with their frequent de novo genesis, suggests that their functions are not essential but rather beneficial in specific environments. Adjacent barrels of complementary function within the same chain may allow for functions beyond those of the individual barrels.
Collapse
|
14
|
Wahlig TA, Stanton E, Godfrey JJ, Stasic AJ, Wong ACL, Kaspar CW. A Single Nucleotide Polymorphism in lptG Increases Tolerance to Bile Salts, Acid, and Staining of Calcofluor-Binding Polysaccharides in Salmonella enterica Serovar Typhimurium E40. Front Microbiol 2021; 12:671453. [PMID: 34149657 PMCID: PMC8208086 DOI: 10.3389/fmicb.2021.671453] [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] [Received: 02/25/2021] [Accepted: 04/12/2021] [Indexed: 11/13/2022] Open
Abstract
The outer membrane of Salmonella enterica plays an important role in combating stress encountered in the environment and hosts. The transport and insertion of lipopolysaccharides (LPS) into the outer membrane involves lipopolysaccharide transport proteins (LptA-F) and mutations in the genes encoding for these proteins are often lethal or result in the transport of atypical LPS that can alter stress tolerance in bacteria. During studies of heterogeneity in bile salts tolerance, S. enterica serovar Typhimurium E40 was segregated into bile salts tolerant and sensitive cells by screening for growth in TSB with 10% bile salts. An isolate (E40V) with a bile salts MIC >20% was selected for further characterization. Whole-genome sequencing of E40 and E40V using Illumina and PacBio SMRT technologies revealed a non-synonymous single nucleotide polymorphism (SNP) in lptG. Leucine at residue 26 in E40 was substituted with proline in E40V. In addition to growth in the presence of 10% bile salts, E40V was susceptible to novobiocin while E40 was not. Transcriptional analysis of E40 and E40V, in the absence of bile salts, revealed significantly greater (p < 0.05) levels of transcript in three genes in E40V; yjbE (encoding for an extracellular polymeric substance production protein), yciE (encoding for a putative stress response protein), and an uncharacterized gene annotated as an acid shock protein precursor (ASPP). No transcripts of genes were present at a greater level in E40 compared to E40V. Corresponding with the greater level of these transcripts, E40V had greater survival at pH 3.35 and staining of Calcofluor-binding polysaccharide (CBPS). To confirm the SNP in lptG was associated with these phenotypes, strain E40E was engineered from E40 to encode for the variant form of LptG (L26P). E40E exhibited the same differences in gene transcripts and phenotypes as E40V, including susceptibility to novobiocin, confirming the SNP was responsible for these differences.
Collapse
Affiliation(s)
- Taylor A Wahlig
- Department of Bacteriology, University of Wisconsin, Madison, WI, United States
| | - Eliot Stanton
- Department of Bacteriology, University of Wisconsin, Madison, WI, United States
| | - Jared J Godfrey
- Department of Bacteriology, University of Wisconsin, Madison, WI, United States
| | - Andrew J Stasic
- U. S. Food and Drug Administration, Center for Biologics Evaluation and Research, Washington, DC, United States
| | - Amy C L Wong
- Department of Bacteriology, University of Wisconsin, Madison, WI, United States
| | - Charles W Kaspar
- Department of Bacteriology, University of Wisconsin, Madison, WI, United States
| |
Collapse
|
15
|
Abstract
By evolving strains of E. coli that hyper-resist sedimentation, we discovered an uncharacterized mechanism that bacteria can use to remain in suspension indefinitely without expending energy. This unusual phenotype was traced to the anchoring of long colanic acid polymers (CAP) that project from the cell surface. Although each characterized mutant activated this same mechanism, the genes responsible and the strengths of the phenotypes varied. Mutations in rcsC, lpp, igaA, or the yjbEFGH operon were sufficient to stimulate sedimentation resistance, while mutations altering the cps promoter, cdgI, or yjbF provided phenotypic enhancements. The sedimentation resistances changed in response to temperature, growth phase, and carbon source and each mutant exhibited significantly reduced biofilm formation. We discovered that the degree of colony mucoidy exhibited by these mutants was not related to the degree of Rcs pathways activation or to the amount of CAP that was produced; rather, it was related to the fraction of CAP that was shed as a true exopolysaccharide. Therefore, these and other mutations that activate this phenotype are likely to be absent from genetic screens that relied on centrifugation to harvest bacteria. We also found that this anchored CAP form is not linked to LPS cores and may not be attached to the outer membrane.IMPORTANCEBacteria can partition in aqueous environments between surface-dwelling, planktonic, sedimentary, and biofilm forms. Residence in each location provides an advantage depending on nutritional and environmental stresses and a community of a single species is often observed to be distributed throughout two or more of these niches. Another adaptive strategy is to produce an extracellular capsule, which provides an environmental shield for the microbe and can allow escape from predators and immune systems. We discovered that bacteria can either shed or stably anchor capsules to dramatically alter their propensity to sediment. The degree to which the bacteria anchor their capsule is controlled by a stress sensing system, suggesting that anchoring may be used as an adaptive response to severe environmental challenges.
Collapse
|
16
|
Huesa J, Giner-Lamia J, Pucciarelli MG, Paredes-Martínez F, García-del Portillo F, Marina A, Casino P. Structure-based analyses of Salmonella RcsB variants unravel new features of the Rcs regulon. Nucleic Acids Res 2021; 49:2357-2374. [PMID: 33638994 PMCID: PMC7913699 DOI: 10.1093/nar/gkab060] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/13/2021] [Accepted: 01/26/2021] [Indexed: 12/13/2022] Open
Abstract
RcsB is a transcriptional regulator that controls expression of numerous genes in enteric bacteria. RcsB accomplishes this role alone or in combination with auxiliary transcriptional factors independently or dependently of phosphorylation. To understand the mechanisms by which RcsB regulates such large number of genes, we performed structural studies as well as in vitro and in vivo functional studies with different RcsB variants. Our structural data reveal that RcsB binds promoters of target genes such as rprA and flhDC in a dimeric active conformation. In this state, the RcsB homodimer docks the DNA-binding domains into the major groove of the DNA, facilitating an initial weak read-out of the target sequence. Interestingly, comparative structural analyses also show that DNA binding may stabilize an active conformation in unphosphorylated RcsB. Furthermore, RNAseq performed in strains expressing wild-type or several RcsB variants provided new insights into the contribution of phosphorylation to gene regulation and assign a potential role of RcsB in controlling iron metabolism. Finally, we delimited the RcsB box for homodimeric active binding to DNA as the sequence TN(G/A)GAN4TC(T/C)NA. This RcsB box was found in promoter, intergenic and intragenic regions, facilitating both increased or decreased gene transcription.
Collapse
Affiliation(s)
- Juanjo Huesa
- Departamento de Bioquímica y Biología Molecular, Universitat de València. Dr Moliner 50, 46100 Burjassot, Spain.,Instituto universitario de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València. Dr Moliner 50, 46100 Burjassot, Spain
| | - Joaquín Giner-Lamia
- Laboratorio de Patógenos Bacterianos Intracelulares. Centro Nacional de Biotecnología (CNB)-CSIC. Darwin 3, 28049 Madrid. Spain.,Centro de Biotecnología y Genómica de Plantas (CBGP, UPM-INIA), Campus Montegancedo, E-28223 Pozuelo de Alarcón, Madrid, Spain.,Departamento de Biotecnología y Biología Vegetal, ETSI Agronómica, Alimentaria y de Biosistemas, Universidad Politócnica de Madrid, 28040 Madrid, Spain
| | - M Graciela Pucciarelli
- Laboratorio de Patógenos Bacterianos Intracelulares. Centro Nacional de Biotecnología (CNB)-CSIC. Darwin 3, 28049 Madrid. Spain.,Centro de Biología Molecular 'Severo Ochoa' (CBMSO)-CSIC. Departamento de Biología Molecular. Universidad Autónoma de Madrid, Madrid, Spain
| | - Francisco Paredes-Martínez
- Departamento de Bioquímica y Biología Molecular, Universitat de València. Dr Moliner 50, 46100 Burjassot, Spain.,Instituto universitario de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València. Dr Moliner 50, 46100 Burjassot, Spain
| | - Francisco García-del Portillo
- Laboratorio de Patógenos Bacterianos Intracelulares. Centro Nacional de Biotecnología (CNB)-CSIC. Darwin 3, 28049 Madrid. Spain
| | - Alberto Marina
- Department of Genomic and Proteomic, Instituto de Biomedicina de Valencia (IBV-CSIC), Jaume Roig 11, 46010 Valencia, Spain.,Group 739 of the Centro de Investigación Biomédica en Red sobre Enfermedades Raras (CIBERER) del Instituto de Salud Carlos III, Spain
| | - Patricia Casino
- Departamento de Bioquímica y Biología Molecular, Universitat de València. Dr Moliner 50, 46100 Burjassot, Spain.,Instituto universitario de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València. Dr Moliner 50, 46100 Burjassot, Spain.,Group 739 of the Centro de Investigación Biomédica en Red sobre Enfermedades Raras (CIBERER) del Instituto de Salud Carlos III, Spain
| |
Collapse
|
17
|
Ranjan M, Khokhani D, Nayaka S, Srivastava S, Keyser ZP, Ranjan A. Genomic diversity and organization of complex polysaccharide biosynthesis clusters in the genus Dickeya. PLoS One 2021; 16:e0245727. [PMID: 33571209 PMCID: PMC7877592 DOI: 10.1371/journal.pone.0245727] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 01/07/2021] [Indexed: 11/18/2022] Open
Abstract
The pectinolytic genus Dickeya (formerly Erwinia chrysanthemi) comprises numerous pathogenic species which cause diseases in various crops and ornamental plants across the globe. Their pathogenicity is governed by complex multi-factorial processes of adaptive virulence gene regulation. Extracellular polysaccharides and lipopolysaccharides present on bacterial envelope surface play a significant role in the virulence of phytopathogenic bacteria. However, very little is known about the genomic location, diversity, and organization of the polysaccharide and lipopolysaccharide biosynthetic gene clusters in Dickeya. In the present study, we report the diversity and structural organization of the group 4 capsule (G4C)/O-antigen capsule, putative O-antigen lipopolysaccharide, enterobacterial common antigen, and core lipopolysaccharide biosynthesis clusters from 54 Dickeya strains. The presence of these clusters suggests that Dickeya has both capsule and lipopolysaccharide carrying O-antigen to their external surface. These gene clusters are key regulatory components in the composition and structure of the outer surface of Dickeya. The O-antigen capsule/group 4 capsule (G4C) coding region shows a variation in gene content and organization. Based on nucleotide sequence homology in these Dickeya strains, two distinct groups, G4C group I and G4C group II, exist. However, comparatively less variation is observed in the putative O-antigen lipopolysaccharide cluster in Dickeya spp. except for in Dickeya zeae. Also, enterobacterial common antigen and core lipopolysaccharide biosynthesis clusters are present mostly as conserved genomic regions. The variation in the O-antigen capsule and putative O-antigen lipopolysaccharide coding region in relation to their phylogeny suggests a role of multiple horizontal gene transfer (HGT) events. These multiple HGT processes might have been manifested into the current heterogeneity of O-antigen capsules and O-antigen lipopolysaccharides in Dickeya strains during its evolution.
Collapse
Affiliation(s)
- Manish Ranjan
- CSIR-National Botanical Research Institute (CSIR-NBRI), Lucknow, Uttar Pradesh, India
| | - Devanshi Khokhani
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Plant Pathology, University of Minnesota—Twin Cities, St. Paul, Minnesota, United States of America
| | - Sanjeeva Nayaka
- CSIR-National Botanical Research Institute (CSIR-NBRI), Lucknow, Uttar Pradesh, India
| | - Suchi Srivastava
- CSIR-National Botanical Research Institute (CSIR-NBRI), Lucknow, Uttar Pradesh, India
| | - Zachary P. Keyser
- Department of Agronomy, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Ashish Ranjan
- Department of Plant Pathology, University of Minnesota—Twin Cities, St. Paul, Minnesota, United States of America
- Department of Plant Sciences (SLS), University of Hyderabad, Hyderabad, India
| |
Collapse
|
18
|
Envelope Stress and Regulation of the Salmonella Pathogenicity Island 1 Type III Secretion System. J Bacteriol 2020; 202:JB.00272-20. [PMID: 32571967 DOI: 10.1128/jb.00272-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Accepted: 06/15/2020] [Indexed: 01/19/2023] Open
Abstract
Salmonella enterica serovar Typhimurium uses a type three secretion system (T3SS) encoded on the Salmonella pathogenicity island 1 (SPI1) to invade intestinal epithelial cells and induce inflammatory diarrhea. The SPI1 T3SS is regulated by numerous environmental and physiological signals, integrated to either activate or repress invasion. Transcription of hilA, encoding the transcriptional activator of the SPI1 structural genes, is activated by three AraC-like regulators, HilD, HilC, and RtsA, that act in a complex feed-forward loop. Deletion of bamB, encoding a component of the β-barrel assembly machinery, causes a dramatic repression of SPI1, but the mechanism was unknown. Here, we show that partially defective β-barrel assembly activates the RcsCDB regulon, leading to decreased hilA transcription. This regulation is independent of RpoE activation. Though Rcs has been previously shown to repress SPI1 when disulfide bond formation is impaired, we show that activation of Rcs in a bamB background is dependent on the sensor protein RcsF, whereas disulfide bond status is sensed independently. Rcs decreases transcription of the flagellar regulon, including fliZ, the product of which indirectly activates HilD protein activity. Rcs also represses hilD, hilC, and rtsA promoters by an unknown mechanism. Both dsbA and bamB mutants have motility defects, though this is simply regulatory in a bamB background; motility is restored in the absence of Rcs. Effector secretion assays show that repression of SPI1 in a bamB background is also regulatory; if expressed, the SPI1 T3SS is functional in a bamB background. This emphasizes the sensitivity of SPI1 regulation to overall envelope homeostasis.IMPORTANCE Salmonella causes worldwide foodborne illness, leading to massive disease burden and an estimated 600,000 deaths per year. Salmonella infects orally and invades intestinal epithelial cells using a type 3 secretion system that directly injects effector proteins into host cells. This first step in invasion is tightly regulated by a variety of inputs. In this work, we demonstrate that Salmonella senses the functionality of outer membrane assembly in determining regulation of invasion machinery, and we show that Salmonella uses distinct mechanisms to detect specific perturbations in envelope assembly.
Collapse
|
19
|
Kortright KE, Chan BK, Turner PE. High-throughput discovery of phage receptors using transposon insertion sequencing of bacteria. Proc Natl Acad Sci U S A 2020; 117:18670-18679. [PMID: 32675236 PMCID: PMC7414163 DOI: 10.1073/pnas.2001888117] [Citation(s) in RCA: 68] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
As the most abundant microbes on Earth, novel bacteriophages (phages; bacteria-specific viruses) are readily isolated from environmental samples. However, it remains challenging to characterize phage-bacteria interactions, such as the host receptor(s) phages bind to initiate infection. Here, we tested whether transposon insertion sequencing (INSeq) could be used to identify bacterial genes involved in phage binding. As proof of concept, results showed that INSeq screens successfully identified genes encoding known receptors for previously characterized viruses of Escherichia coli (phages T6, T2, T4, and T7). INSeq screens were then used to identify genes involved during infection of six newly isolated coliphages. Results showed that candidate receptors could be successfully identified for the majority (five of six) of the phages; furthermore, genes encoding the phage receptor(s) were the top hit(s) in the analyses of the successful screens. INSeq screens provide a generally useful method for high-throughput discovery of phage receptors. We discuss limitations of our approach when examining uncharacterized phages, as well as usefulness of the method for exploring the evolution of broad versus narrow use of cellular receptors among phages in the biosphere.
Collapse
Affiliation(s)
| | - Benjamin K Chan
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520
| | - Paul E Turner
- Program in Microbiology, Yale School of Medicine, New Haven, CT 06520;
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520
| |
Collapse
|
20
|
Abstract
The distribution of fitness effects of mutation plays a central role in constraining protein evolution. The underlying mechanisms by which mutations lead to fitness effects are typically attributed to changes in protein specific activity or abundance. Here, we reveal the importance of a mutation's collateral fitness effects, which we define as effects that do not derive from changes in the protein's ability to perform its physiological function. We comprehensively measured the collateral fitness effects of missense mutations in the Escherichia coli TEM-1 β-lactamase antibiotic resistance gene using growth competition experiments in the absence of antibiotic. At least 42% of missense mutations in TEM-1 were deleterious, indicating that for some proteins collateral fitness effects occur as frequently as effects on protein activity and abundance. Deleterious mutations caused improper posttranslational processing, incorrect disulfide-bond formation, protein aggregation, changes in gene expression, and pleiotropic effects on cell phenotype. Deleterious collateral fitness effects occurred more frequently in TEM-1 than deleterious effects on antibiotic resistance in environments with low concentrations of the antibiotic. The surprising prevalence of deleterious collateral fitness effects suggests they may play a role in constraining protein evolution, particularly for highly expressed proteins, for proteins under intermittent selection for their physiological function, and for proteins whose contribution to fitness is buffered against deleterious effects on protein activity and protein abundance.
Collapse
|
21
|
Cho SH, Lee KM, Kim CH, Kim SS. Construction of a Lectin-Glycan Interaction Network from Enterohemorrhagic Escherichia coli Strains by Multi-omics Analysis. Int J Mol Sci 2020; 21:ijms21082681. [PMID: 32290560 PMCID: PMC7215717 DOI: 10.3390/ijms21082681] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/04/2020] [Accepted: 04/07/2020] [Indexed: 11/17/2022] Open
Abstract
Enterohemorrhagic Escherichia coli (EHEC) causes hemorrhagic colitis and hemolytic uremic syndrome. EHEC infection begins with bacterial adherence to the host intestine via lectin-like adhesins that bind to the intestinal wall. However, EHEC-related lectin–glycan interactions (LGIs) remain unknown. Here, we conducted a genome-wide investigation of putative adhesins to construct an LGI network. We performed microarray-based transcriptomic and proteomic analyses with E. coli EDL933. Using PSORTb-based analysis, potential outer-membrane-embedded adhesins were predicted from the annotated genes of 318 strains. Predicted proteins were classified using TMHMM v2.0, SignalP v5.0, and LipoP v1.0. Functional and protein–protein interaction analyses were performed using InterProScan and String databases, respectively. Structural information of lectin candidate proteins was predicted using Iterative Threading ASSEmbly Refinement (I-TASSER) and Spatial Epitope Prediction of Protein Antigens (SEPPA) tools based on 3D structure and B-cell epitopes. Pathway analysis returned 42,227 Gene Ontology terms; we then selected 2585 lectin candidate proteins by multi-omics analysis and performed homology modeling and B-cell epitope analysis. We predicted a total of 24,400 outer-membrane-embedded proteins from the genome of 318 strains and integrated multi-omics information into the genomic information of the proteins. Our integrated multi-omics data will provide a useful resource for the construction of LGI networks of E. coli.
Collapse
Affiliation(s)
- Seung-Hak Cho
- Division of Bacterial Disease Research, Center for Infectious Disease Research, Korea National Institute of Health, Cheongju, Chungchungbuk-do 28160, Korea; (S.-H.C.); (K.M.L.)
| | - Kang Mo Lee
- Division of Bacterial Disease Research, Center for Infectious Disease Research, Korea National Institute of Health, Cheongju, Chungchungbuk-do 28160, Korea; (S.-H.C.); (K.M.L.)
| | - Cheorl-Ho Kim
- Glycobiology Unit, Department of Biological Science, Sungkyunkwan University and Samsung Advanced Institute for Health Science and Technology (SAIHST), Suwon, Gyeonggi-do 16419, Korea
- Correspondence: (C.-H.K.); (S.S.K.); Tel.: +82-031-290-7002 (C.-H.K.); +82-043-719-8400 (S.S.K.); Fax: +82-043-719-8402 (S.S.K.)
| | - Sung Soon Kim
- Division of Bacterial Disease Research, Center for Infectious Disease Research, Korea National Institute of Health, Cheongju, Chungchungbuk-do 28160, Korea; (S.-H.C.); (K.M.L.)
- Correspondence: (C.-H.K.); (S.S.K.); Tel.: +82-031-290-7002 (C.-H.K.); +82-043-719-8400 (S.S.K.); Fax: +82-043-719-8402 (S.S.K.)
| |
Collapse
|
22
|
Abstract
The Gram-negative envelope is a complex structure that consists of the inner membrane, the periplasm, peptidoglycan and the outer membrane, and protects the bacterial cell from the environment. Changing environmental conditions can cause damage, which triggers the envelope stress responses to maintain cellular homeostasis. In this Review, we explore the causes, both environmental and intrinsic, of envelope stress, as well as the cellular stress response pathways that counter these stresses. Furthermore, we discuss the damage to the cell that occurs when these pathways are aberrantly activated either in the absence of stress or to an excessive degree. Finally, we review the mechanisms whereby the σE response constantly acts to prevent cell death caused by highly toxic unfolded outer membrane proteins. Together, the recent work that we discuss has provided insights that emphasize the necessity for proper levels of stress response activation and the detrimental consequences that can occur in the absence of proper regulation.
Collapse
|
23
|
Huang WC, Lin CY, Hashimoto M, Wu JJ, Wang MC, Lin WH, Chen CS, Teng CH. The role of the bacterial protease Prc in the uropathogenesis of extraintestinal pathogenic Escherichia coli. J Biomed Sci 2020; 27:14. [PMID: 31900139 PMCID: PMC6941253 DOI: 10.1186/s12929-019-0605-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 12/19/2019] [Indexed: 02/07/2023] Open
Abstract
Background Extraintestinal pathogenic E. coli (ExPEC) remains one of the most prevalent bacterial pathogens that cause extraintestinal infections, including neonatal meningitis, septicemia, and urinary tract (UT) infections (UTIs). Antibiotic therapy has been the conventional treatment for such infections, but its efficacy has decreased due to the emergence of antibiotic-resistant bacteria. Identification and characterization of bacterial factors that contribute to the severity of infection would facilitate the development of novel therapeutic strategies. The ExPEC periplasmic protease Prc contributes to the pathogen’s ability to evade complement-mediated killing in the serum. Here, we further investigated the role of the Prc protease in ExPEC-induced UTIs and the underlying mechanism. Methods The uropathogenic role of Prc was determined in a mouse model of UTIs. Using global quantitative proteomic analyses, we revealed that the expression of FliC and other outer membrane-associated proteins was altered by Prc deficiency. Comparative transcriptome analyses identified that Prc deficiency affected expression of the flagellar regulon and genes that are regulated by five extracytoplasmic signaling systems. Results A mutant ExPEC with a prc deletion was attenuated in bladder and kidney colonization. Global quantitative proteomic analyses of the prc mutant and wild-type ExPEC strains revealed significantly reduced flagellum expression in the absence of Prc, consequently impairing bacterial motility. The prc deletion triggered downregulation of the flhDC operon encoding the master transcriptional regulator of flagellum biogenesis. Overexpressing flhDC restored the prc mutant’s motility and ability to colonize the UT, suggesting that the impaired motility is responsible for attenuated UT colonization of the mutant. Further comparative transcriptome analyses revealed that Prc deficiency activated the σE and RcsCDB signaling pathways. These pathways were responsible for the diminished flhDC expression. Finally, the activation of the RcsCDB system was attributed to the intracellular accumulation of a known Prc substrate Spr in the prc mutant. Spr is a peptidoglycan hydrolase and its accumulation destabilizes the bacterial envelope. Conclusions We demonstrated for the first time that Prc is essential for full ExPEC virulence in UTIs. Our results collectively support the idea that Prc is essential for bacterial envelope integrity, thus explaining how Prc deficiency results in an attenuated ExPEC.
Collapse
Affiliation(s)
- Wen-Chun Huang
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chung-Yen Lin
- Institute of Information Science, Academia Sinica, Taipei, Taiwan
| | - Masayuki Hashimoto
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan
| | - Jiunn-Jong Wu
- Department of Biotechnology and Laboratory Science in Medicine, School of Biomedical Science and Engineering, National Yang Ming University, Taipei, Taiwan
| | - Ming-Cheng Wang
- Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Wei-Hung Lin
- Department of Internal Medicine, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Chang-Shi Chen
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan.,Department of Biochemistry and Molecular Biology, College of Medicine, National Cheng Kung University, Tainan, Taiwan
| | - Ching-Hao Teng
- Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan. .,Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan. .,Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan, Taiwan.
| |
Collapse
|
24
|
Under Elevated c-di-GMP in Escherichia coli, YcgR Alters Flagellar Motor Bias and Speed Sequentially, with Additional Negative Control of the Flagellar Regulon via the Adaptor Protein RssB. J Bacteriol 2019; 202:JB.00578-19. [PMID: 31611290 DOI: 10.1128/jb.00578-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 10/11/2019] [Indexed: 12/19/2022] Open
Abstract
In Escherichia coli and Salmonella, the c-di-GMP effector YcgR inhibits flagellar motility by interacting directly with the motor to alter both its bias and speed. Here, we demonstrate that in both of these bacteria, YcgR acts sequentially, altering motor bias first and then decreasing motor speed. We show that when c-di-GMP levels are high, deletion of ycgR restores wild-type motor behavior in E. coli, indicating that YcgR is the only motor effector in this bacterium. Yet, motility and chemotaxis in soft agar do not return to normal, suggesting that there is a second mechanism that inhibits motility under these conditions. In Salmonella, c-di-GMP-induced synthesis of extracellular cellulose has been reported to entrap flagella and to be responsible for the YcgR-independent motility defect. We found that this is not the case in E. coli Instead, we found through reversion analysis that deletion of rssB, which codes for a response regulator/adaptor protein that normally directs ClpXP protease to target σS for degradation, restored wild-type motility in the ycgR mutant. Our data suggest that high c-di-GMP levels may promote altered interactions between these proteins to downregulate flagellar gene expression.IMPORTANCE Flagellum-driven motility has been studied in E. coli and Salmonella for nearly half a century. Over 60 genes control flagellar assembly and function. The expression of these genes is regulated at multiple levels in response to a variety of environmental signals. Cues that elevate c-di-GMP levels, however, inhibit motility by direct binding of the effector YcgR to the flagellar motor. In this study conducted mainly in E. coli, we show that YcgR is the only effector of motor control and tease out the order of YcgR-mediated events. In addition, we find that the σS regulator protein RssB contributes to negative regulation of flagellar gene expression when c-di-GMP levels are elevated.
Collapse
|
25
|
Pang Y, Guo X, Tian X, Liu F, Wang L, Wu J, Zhang S, Li S, Liu B. Developing a novel molecular serotyping system based on capsular polysaccharide synthesis gene clusters of Vibrio parahaemolyticus. Int J Food Microbiol 2019; 309:108332. [DOI: 10.1016/j.ijfoodmicro.2019.108332] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 08/26/2019] [Accepted: 08/31/2019] [Indexed: 12/12/2022]
|
26
|
Wu H, Chen S, Ji M, Chen Q, Shi J, Sun J. Activation of colanic acid biosynthesis linked to heterologous expression of the polyhydroxybutyrate pathway in Escherichia coli. Int J Biol Macromol 2019; 128:752-760. [DOI: 10.1016/j.ijbiomac.2019.02.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 02/01/2019] [Accepted: 02/02/2019] [Indexed: 01/31/2023]
|
27
|
Ma J, An C, Jiang F, Yao H, Logue C, Nolan LK, Li G. Extraintestinal pathogenic Escherichia coli increase extracytoplasmic polysaccharide biosynthesis for serum resistance in response to bloodstream signals. Mol Microbiol 2018; 110:689-706. [PMID: 29802751 DOI: 10.1111/mmi.13987] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Revised: 05/14/2018] [Accepted: 05/14/2018] [Indexed: 01/08/2023]
Abstract
Extraintestinal pathogenic Escherichia coli (ExPEC) is one of the leading causes of bloodstream infections. Characteristically, these organisms exhibit strong resistance to the bactericidal action of host serum. Although numerous serum resistance factors in ExPEC have been identified, their regulatory mechanisms during in vivo infection remain largely unknown. Here, RNA sequencing analyses together with quantitative reverse-transcription PCR revealed that ExPEC genes involved in the biosynthesis of extracytoplasmic polysaccharides (ECPs) including K-capsule, lipopolysaccharide (LPS), colanic acid, peptidoglycan and Yjb exopolysaccharides were significantly upregulated in response to serum under low oxygen conditions and during bloodstream infection. The oxygen sensor FNR directly activated the expression of K-capsule and colanic acid and also indirectly modulated the expression of colanic acid, Yjb exopolysaccharides and peptidoglycan via the known Rcs regulatory system. The global regulator Fur directly or indirectly repressed the expression ofECP biosynthesis genes in iron replete media, whereas the low iron conditions in the bloodstream could relieve Fur repression. Using in vitro and animal models, FNR, Fur and the Rcs system were confirmed as contributing to ExPEC ECP production, serum resistance and virulence. Altogether, these findings indicated that the global regulators FNR andFur and the signaling transduction system Rcs coordinately regulated the expression of ECP biosynthesis genes leading to increased ExPEC serum resistance in response to low oxygen and low iron levels in the bloodstream.
Collapse
Affiliation(s)
- Jiale Ma
- Department of Veterinary Preventive Medicine College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.,Department of Veterinary Diagnostic and Production Animal Medicine College of Veterinary Medicine, Iowa State University, Ames, IA, 50011, USA
| | - Chunxia An
- Department of Veterinary Preventive Medicine College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Fengwei Jiang
- Department of Veterinary Preventive Medicine College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China.,Department of Veterinary Diagnostic and Production Animal Medicine College of Veterinary Medicine, Iowa State University, Ames, IA, 50011, USA
| | - Huochun Yao
- Department of Veterinary Preventive Medicine College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, 210095, China
| | - Catherine Logue
- Department of Veterinary Microbiology and Preventive Medicine College of Veterinary Medicine, Iowa State University, Ames, IA, 50011, USA
| | - Lisa K Nolan
- Department of Veterinary Microbiology and Preventive Medicine College of Veterinary Medicine, Iowa State University, Ames, IA, 50011, USA
| | - Ganwu Li
- Department of Veterinary Diagnostic and Production Animal Medicine College of Veterinary Medicine, Iowa State University, Ames, IA, 50011, USA.,State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute Chinese Academy of Agricultural Sciences, 678 Haping Street, Harbin, 150069, China
| |
Collapse
|
28
|
More than Rotating Flagella: Lipopolysaccharide as a Secondary Receptor for Flagellotropic Phage 7-7-1. J Bacteriol 2018; 200:JB.00363-18. [PMID: 30012730 DOI: 10.1128/jb.00363-18] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 07/10/2018] [Indexed: 12/13/2022] Open
Abstract
Bacteriophage 7-7-1, a member of the family Myoviridae, infects the soil bacterium Agrobacterium sp. strain H13-3. Infection requires attachment to actively rotating bacterial flagellar filaments, with flagellar number, length, and rotation speed being important determinants for infection efficiency. To identify the secondary receptor(s) on the cell surface, we isolated motile, phage-resistant Agrobacterium sp. H13-3 transposon mutants. Transposon insertion sites were pinpointed using arbitrary primed PCR and bioinformatics analyses. Three genes were recognized, whose corresponding proteins had the following computationally predicted functions: AGROH133_07337, a glycosyltransferase; AGROH133_13050, a UDP-glucose 4-epimerase; and AGROH133_08824, an integral cytoplasmic membrane protein. The first two gene products are part of the lipopolysaccharide (LPS) synthesis pathway, while the last is predicted to be a relatively small (13.4-kDa) cytosolic membrane protein with up to four transmembrane helices. The phenotypes of the transposon mutants were verified by complementation and site-directed mutagenesis. Additional characterization of motile, phage-resistant mutants is also described. Given these findings, we propose a model for Agrobacterium sp. H13-3 infection by bacteriophage 7-7-1 where the phage initially attaches to the flagellar filament and is propelled down toward the cell surface by clockwise flagellar rotation. The phage then attaches to and degrades the LPS to reach the outer membrane and ejects its DNA into the host using its syringe-like contractile tail. We hypothesize that the integral membrane protein plays an important role in events following viral DNA ejection or in LPS processing and/or deployment. The proposed two-step attachment mechanism may be conserved among other flagellotropic phages infecting Gram-negative bacteria.IMPORTANCE Flagellotropic bacteriophages belong to the tailed-phage order Caudovirales, the most abundant phages in the virome. While it is known that these viruses adhere to the bacterial flagellum and use flagellar rotation to reach the cell surface, their infection mechanisms are poorly understood. Characterizing flagellotropic-phage-host interactions is crucial to understanding how microbial communities are shaped. Using a transposon mutagenesis approach combined with a screen for motile, phage-resistant mutants, we identified lipopolysaccharides as the secondary cell surface receptor for phage 7-7-1. This is the first cell surface receptor identified for flagellotropic phages. One hypothetical membrane protein was also recognized as essential for infection. These new findings, together with previous results, culminated in an infection model for phage 7-7-1.
Collapse
|
29
|
Cao H, Wang M, Wang Q, Xu T, Du Y, Li H, Qian C, Yin Z, Wang L, Wei Y, Wu P, Guo X, Yang B, Liu B. Identifying genetic diversity of O antigens in Aeromonas hydrophila for molecular serotype detection. PLoS One 2018; 13:e0203445. [PMID: 30183757 PMCID: PMC6124807 DOI: 10.1371/journal.pone.0203445] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 08/21/2018] [Indexed: 01/08/2023] Open
Abstract
Aeromonas hydrophila is a globally occurring, potentially virulent, gram-negative opportunistic pathogen that is known to cause water and food-borne diseases around the world. In this study, we use whole genome sequencing and in silico analyses to identify 14 putative O antigen gene clusters (OGCs) located downstream of the housekeeping genes acrB and/or oprM. We have also identified 7 novel OGCs by analyzing 15 publicly available genomes of different A. hydrophila strains. From the 14 OGCs identified initially, we have deduced that O antigen processing genes involved in the wzx/wzy pathway and the ABC transporter (wzm/wzt) pathway exhibit high molecular diversity among different A. hydrophila strains. Using these genes, we have developed a multiplexed Luminex-based array system that can identify up to 14 A. hydrophila strains. By combining our other results and including the sequences of processing genes from 13 other OGCs (7 OGCs identified from publicly available genome sequences and 6 OGCs that were previously published), we also have the data to create an array system that can identify 25 different A. hydrophila serotypes. Although clinical detection, epidemiological surveillance, and tracing of pathogenic bacteria are typically done using serotyping methods that rely on identifying bacterial surface O antigens through agglutination reactions with antisera, molecular methods such as the one we have developed may be quicker and more cost effective. Our assay shows high specificity, reproducibility, and sensitivity, being able to classify A. hydrophila strains using just 0.1 ng of genomic DNA. In conclusion, our findings indicate that a molecular serotyping system for A. hydrophila could be developed based on specific genes, providing an important molecular tool for the identification of A. hydrophila serotypes.
Collapse
Affiliation(s)
- Hengchun Cao
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Min Wang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Qian Wang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Tingting Xu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Yuhui Du
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Huiying Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Chengqian Qian
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Zhiqiu Yin
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Lu Wang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Yi Wei
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Pan Wu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Xi Guo
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
| | - Bin Yang
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
- * E-mail: (BY); (BL)
| | - Bin Liu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin Economic-Technological Development Area, Tianjin, China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin Economic-Technological Development Area, Tianjin, China
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin Economic-Technological Development Area, Tianjin, China
- * E-mail: (BY); (BL)
| |
Collapse
|
30
|
Chen S, Zhou Q, Tan X, Li Y, Ren G, Wang X. The Global Response of Cronobacter sakazakii Cells to Amino Acid Deficiency. Front Microbiol 2018; 9:1875. [PMID: 30154778 PMCID: PMC6102319 DOI: 10.3389/fmicb.2018.01875] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Accepted: 07/25/2018] [Indexed: 12/29/2022] Open
Abstract
Cronobacter species can cause necrotizing enterocolitis and meningitis in neonates and infants, their infection is closely relevant to their responses to extreme growth conditions. In this study, the response of Cronobacter species to amino acid deficiency has been investigated. Four Cronobacter species formed smooth colonies when grown on the solid LB medium, but formed mucoid colonies when grown on the amino acid deficient M9 medium. When the mucoid colonies were stained with tannin mordant, exopolysaccharide around the cells could be discerned. The exopolysaccharide was isolated, analyzed, and identified as colanic acid. When genes wcaD and wcaE relevant to colanic acid biosynthesis were deleted in Cronobacter sakazakii BAA-894, no exopolysaccharide could be produced, confirming the exopolysaccharide formed in C. sakazakii grown in M9 is colanic acid. On the other hand, when genes rcsA, rcsB, rcsC, rcsD, or rcsF relevant to Rcs phosphorelay system was deleted in C. sakazakii BAA-894, colanic acid could not be produced, suggesting that the production of colanic acid in C. sakazakii is regulated by Rcs phosphorelay system. Furthermore, C. sakazakii BAA-894 grown in M9 supplemented with amino acids could not produce exopolysaccharide. Transcriptomes of C. sakazakii BAA-894 grown in M9 or LB were analyzed. A total of 3956 genes were differentially expressed in M9, of which 2339 were up-regulated and 1617 were down-regulated. When C. sakazakii BAA-894 was grown in M9, the genes relevant to the biosynthesis of exopolysaccharide were significantly up-regulated; on the other hand, the genes relevant to the flagellum formation and chemotaxis were significantly down-regulated; in addition, most genes relevant to various amino acid biosynthesis were also significantly regulated. The results demonstrate that amino acid deficiency has a global impact on C. sakazakii cells.
Collapse
Affiliation(s)
- Si Chen
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Qing Zhou
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Xin Tan
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
| | - Ye Li
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Ge Ren
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
| | - Xiaoyuan Wang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, China
| |
Collapse
|
31
|
Abstract
RcsB, a response regulator of the FixJ/NarL family, is at the center of a complex network of regulatory inputs and outputs. Cell surface stress is sensed by an outer membrane lipoprotein, RcsF, which regulates interactions of the inner membrane protein IgaA, lifting negative regulation of a phosphorelay. In vivo evidence supports a pathway in which histidine kinase RcsC transfers phosphate to phosphotransfer protein RcsD, resulting in phosphorylation of RcsB. RcsB acts either alone or in combination with RcsA to positively regulate capsule synthesis and synthesis of small RNA (sRNA) RprA as well as other genes, and to negatively regulate motility. RcsB in combination with other FixJ/NarL auxiliary proteins regulates yet other functions, independent of RcsB phosphorylation. Proper expression of Rcs and its targets is critical for success of Escherichia coli commensal strains, for proper development of biofilm, and for virulence in some pathogens. New understanding of how the Rcs phosphorelay works provides insight into the flexibility of the two-component system paradigm.
Collapse
Affiliation(s)
- Erin Wall
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
| | - Nadim Majdalani
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
| | - Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
| |
Collapse
|
32
|
Cole BK, Scott E, Ilikj M, Bard D, Akins DR, Dyer DW, Chavez-Bueno S. Route of infection alters virulence of neonatal septicemia Escherichia coli clinical isolates. PLoS One 2017; 12:e0189032. [PMID: 29236742 PMCID: PMC5728477 DOI: 10.1371/journal.pone.0189032] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 09/05/2017] [Indexed: 12/03/2022] Open
Abstract
Escherichia coli is the leading cause of Gram-negative neonatal septicemia in the United States. Invasion and passage across the neonatal gut after ingestion of maternal E. coli strains produce bacteremia. In this study, we compared the virulence properties of the neonatal E. coli bacteremia clinical isolate SCB34 with the archetypal neonatal E. coli meningitis strain RS218. Whole-genome sequencing data was used to compare the protein coding sequences among these clinical isolates and 33 other representative E. coli strains. Oral inoculation of newborn animals with either strain produced septicemia, whereas intraperitoneal injection caused septicemia only in pups infected with RS218 but not in those injected with SCB34. In addition to being virulent only through the oral route, SCB34 demonstrated significantly greater invasion and transcytosis of polarized intestinal epithelial cells in vitro as compared to RS218. Protein coding sequences comparisons highlighted the presence of known virulence factors that are shared among several of these isolates, and revealed the existence of proteins exclusively encoded in SCB34, many of which remain uncharacterized. Our study demonstrates that oral acquisition is crucial for the virulence properties of the neonatal bacteremia clinical isolate SCB34. This characteristic, along with its enhanced ability to invade and transcytose intestinal epithelium are likely determined by the specific virulence factors that predominate in this strain.
Collapse
Affiliation(s)
- Bryan K. Cole
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Edgar Scott
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Marko Ilikj
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - David Bard
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Darrin R. Akins
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - David W. Dyer
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Susana Chavez-Bueno
- Department of Pediatrics, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America
- * E-mail:
| |
Collapse
|
33
|
Guo XP, Sun YC. New Insights into the Non-orthodox Two Component Rcs Phosphorelay System. Front Microbiol 2017; 8:2014. [PMID: 29089936 PMCID: PMC5651002 DOI: 10.3389/fmicb.2017.02014] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/29/2017] [Indexed: 01/18/2023] Open
Abstract
The Rcs phosphorelay system, a non-orthodox two-component regulatory system, integrates environmental signals, regulates gene expression, and alters the physiological behavior of members of the Enterobacteriaceae family of Gram-negative bacteria. Recent studies of Rcs system focused on protein interactions, functions, and the evolution of Rcs system components and its auxiliary regulatory proteins. Herein we review the latest advances on the Rcs system proteins, and discuss the roles that the Rcs system plays in the environmental adaptation of various Enterobacteriaceae species.
Collapse
Affiliation(s)
- Xiao-Peng Guo
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yi-Cheng Sun
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| |
Collapse
|
34
|
The Rcs-Regulated Colanic Acid Capsule Maintains Membrane Potential in Salmonella enterica serovar Typhimurium. mBio 2017; 8:mBio.00808-17. [PMID: 28588134 PMCID: PMC5461412 DOI: 10.1128/mbio.00808-17] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The Rcs phosphorelay and Psp (phage shock protein) systems are envelope stress responses that are highly conserved in gammaproteobacteria. The Rcs regulon was found to be strongly induced during metal deprivation of Salmonella enterica serovar Typhimurium lacking the Psp response. Nineteen genes activated by the RcsA-RcsB response regulator make up an operon responsible for the production of colanic acid capsular polysaccharide, which promotes biofilm development. Despite more than half a century of research, the physiological function of colanic acid has remained elusive. Here we show that Rcs-dependent colanic acid production maintains the transmembrane electrical potential and proton motive force in cooperation with the Psp response. Production of negatively charged exopolysaccharide covalently bound to the outer membrane may enhance the surface potential by increasing the local proton concentration. This provides a unifying mechanism to account for diverse Rcs/colanic acid-related phenotypes, including susceptibility to membrane-damaging agents and biofilm formation. Colanic acid is a negatively charged polysaccharide capsule produced by Escherichia coli, Salmonella, and other gammaproteobacteria. Research conducted over the 50 years since the discovery of colanic acid suggests that this exopolysaccharide plays an important role for bacteria living in biofilms. However, a precise physiological role for colanic acid has not been defined. In this study, we provide evidence that colanic acid maintains the transmembrane potential and proton motive force during envelope stress. This work provides a new and fundamental insight into bacterial physiology.
Collapse
|
35
|
Transcriptional Responses of Escherichia coli to a Small-Molecule Inhibitor of LolCDE, an Essential Component of the Lipoprotein Transport Pathway. J Bacteriol 2016; 198:3162-3175. [PMID: 27645386 PMCID: PMC5105897 DOI: 10.1128/jb.00502-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 08/20/2016] [Indexed: 11/20/2022] Open
Abstract
In Gram-negative bacteria, a dedicated machinery consisting of LolABCDE components targets lipoproteins to the outer membrane. We used a previously identified small-molecule inhibitor of the LolCDE complex of Escherichia coli to assess the global transcriptional consequences of interference with lipoprotein transport. Exposure of E. coli to the LolCDE inhibitor at concentrations leading to minimal and significant growth inhibition, followed by transcriptome sequencing, identified a small group of genes whose transcript levels were decreased and a larger group whose mRNA levels increased 10- to 100-fold compared to those of untreated cells. The majority of the genes whose mRNA concentrations were reduced were part of the flagellar assembly pathway, which contains an essential lipoprotein component. Most of the genes whose transcript levels were elevated encode proteins involved in selected cell stress pathways. Many of these genes are involved with envelope stress responses induced by the mislocalization of outer membrane lipoproteins. Although several of the genes whose RNAs were induced have previously been shown to be associated with the general perturbation of the cell envelope by antibiotics, a small subset was affected only by LolCDE inhibition. Findings from this work suggest that the efficiency of the Lol system function may be coupled to a specific monitoring system, which could be exploited in the development of reporter constructs suitable for use for screening for additional inhibitors of lipoprotein trafficking. IMPORTANCE Inhibition of the lipoprotein transport pathway leads to E. coli death and subsequent lysis. Early significant changes in the levels of RNA for a subset of genes identified to be associated with some periplasmic and envelope stress responses were observed. Together these findings suggest that disruption of this key pathway can have a severe impact on balanced outer membrane synthesis sufficient to affect viability.
Collapse
|
36
|
Miller NT, Fuller D, Couger MB, Bagazinski M, Boyne P, Devor RC, Hanafy RA, Budd C, French DP, Hoff WD, Youssef N. Draft genome sequence of Pseudomonas moraviensis strain Devor implicates metabolic versatility and bioremediation potential. GENOMICS DATA 2016; 9:154-9. [PMID: 27583206 PMCID: PMC4993851 DOI: 10.1016/j.gdata.2016.08.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 08/02/2016] [Indexed: 11/26/2022]
Abstract
Pseudomonas moraviensis is a predominant member of soil environments. We here report on the genomic analysis of Pseudomonas moraviensis strain Devor that was isolated from a gate at Oklahoma State University, Stillwater, OK, USA. The partial genome of Pseudomonas moraviensis strain Devor consists of 6016489 bp of DNA with 5290 protein-coding genes and 66 RNA genes. This is the first detailed analysis of a P. moraviensis genome. Genomic analysis revealed metabolic versatility with genes involved in the metabolism and transport of fructose, xylose, mannose and all amino acids with the exception of tryptophan and valine, implying that the organism is a versatile heterotroph. The genome of P. moraviensis strain Devor was rich in transporters and, based on COG analysis, did not cluster closely with P. moraviensis R28-S genome, the only previous report of a P. moraviensis genome with a native mercury resistance plasmid.
Collapse
Affiliation(s)
- Neil T Miller
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Danny Fuller
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - M B Couger
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Mark Bagazinski
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Philip Boyne
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Robert C Devor
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Radwa A Hanafy
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Connie Budd
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Donald P French
- Department of Integrative Biology, Oklahoma State University, Stillwater, OK, United States
| | - Wouter D Hoff
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| | - Noha Youssef
- Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, United States
| |
Collapse
|
37
|
Effects of Lipopolysaccharide Core Sugar Deficiency on Colanic Acid Biosynthesis in Escherichia coli. J Bacteriol 2016; 198:1576-1584. [PMID: 27002133 DOI: 10.1128/jb.00094-16] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/12/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED When 10 Escherichia coli mutant strains with defects in lipopolysaccharide (LPS) core biosynthesis were grown on agar medium at 30°C, four of them, the ΔwaaF, ΔwaaG, ΔwaaP, and ΔwaaB strains, formed mucoid colonies, while the other six, the ΔwaaU, ΔwaaR, ΔwaaO, ΔwaaC, ΔwaaQ, and ΔwaaY strains, did not. Using light microscopy with tannin mordant staining, the presence of exopolysaccharide around the cells of the mutants that formed mucoid colonies could be discerned. The ΔwaaF mutant produced the largest amounts of exopolysaccharide, regardless of whether it was grown on agar or in liquid medium. The exopolysaccharide was isolated from the liquid growth medium of ΔwaaF cells, hydrolyzed, and analyzed by high-performance liquid chromatography with an ion-exchange column, and the results indicated that the exopolysaccharide was consistent with colanic acid. When the key genes related to the biosynthesis of colanic acid, i.e., wza, wzb, wzc, and wcaA, were deleted in the ΔwaaF background, the exopolysaccharide could not be produced any more, further confirming that it was colanic acid. Colanic acid could not be produced in strains in which rcsA, rcsB, rcsD, or rcsF was deleted in the ΔwaaF background, but a reduced level of colanic acid production was detected when the rcsC gene was deleted, suggesting that a change of lipopolysaccharide structure in ΔwaaF cells might be sensed by the RcsCDB phosphorelay system, leading to the production of colanic acid. The results demonstrate that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural deficiency of lipopolysaccharide. IMPORTANCE Lipopolysaccharide and colanic acid are important forms of exopolysaccharide for Escherichia coli cells. Their metabolism and biological significance have been investigated, but their interrelation with the cell stress response process is not understood. This study demonstrates, for the first time, that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural change of lipopolysaccharide, suggesting that bacterial cells can monitor the outer membrane integrity, which is essential for cell survival and damage repair.
Collapse
|
38
|
Pannen D, Fabisch M, Gausling L, Schnetz K. Interaction of the RcsB Response Regulator with Auxiliary Transcription Regulators in Escherichia coli. J Biol Chem 2015; 291:2357-70. [PMID: 26635367 DOI: 10.1074/jbc.m115.696815] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Indexed: 11/06/2022] Open
Abstract
The Rcs phosphorelay is a two-component signal transduction system that is induced by cell envelope stress. RcsB, the response regulator of this signaling system, is a pleiotropic transcription regulator, which is involved in the control of various stress responses, cell division, motility, and biofilm formation. RcsB regulates transcription either as a homodimer or together with auxiliary regulators, such as RcsA, BglJ, and GadE in Escherichia coli. In this study, we show that RcsB in addition forms heterodimers with MatA (also known as EcpR) and with DctR. Our data suggest that the MatA-dependent transcription regulation is mediated by the MatA-RcsB heterodimer and is independent of RcsB phosphorylation. Furthermore, we analyzed the relevance of amino acid residues of the active quintet of conserved residues, and of surface-exposed residues for activity of RcsB. The data suggest that the activity of the phosphorylation-dependent dimers, such as RcsA-RcsB and RcsB-RcsB, is affected by mutation of residues in the vicinity of the phosphorylation site, suggesting that a phosphorylation-induced structural change modulates their activity. In contrast, the phosphorylation-independent heterodimers BglJ-RcsB and MatA-RcsB are affected by only very few mutations. Heterodimerization of RcsB with various auxiliary regulators and their differential dependence on phosphorylation add an additional level of control to the Rcs system that is operating at the output level.
Collapse
Affiliation(s)
- Derk Pannen
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
| | - Maria Fabisch
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
| | - Lisa Gausling
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
| | - Karin Schnetz
- From the Institute for Genetics, University of Cologne, Zülpicher Strasse 47a, 50674 Cologne, Germany
| |
Collapse
|
39
|
Transcriptional responses to sucrose mimic the plant-associated life style of the plant growth promoting endophyte Enterobacter sp. 638. PLoS One 2015; 10:e0115455. [PMID: 25607953 PMCID: PMC4301647 DOI: 10.1371/journal.pone.0115455] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Accepted: 11/24/2014] [Indexed: 11/19/2022] Open
Abstract
Growth in sucrose medium was previously found to trigger the expression of functions involved in the plant associated life style of the endophytic bacterium Enterobacter sp. 638. Therefore, comparative transcriptome analysis between cultures grown in sucrose or lactate medium was used to gain insights in the expression levels of bacterial functions involved in the endophytic life style of strain 638. Growth on sucrose as a carbon source resulted in major changes in cell physiology, including a shift from a planktonic life style to the formation of bacterial aggregates. This shift was accompanied by a decrease in transcription of genes involved in motility (e.g. flagella biosynthesis) and an increase in the transcription of genes involved in colonization, adhesion and biofilm formation. The transcription levels of functions previously suggested as being involved in endophytic behavior and functions responsible for plant growth promoting properties, including the synthesis of indole-acetic acid, acetoin and 2,3-butanediol, also increased significantly for cultures grown in sucrose medium. Interestingly, despite an abundance of essential nutrients transcription levels of functions related to uptake and processing of nitrogen and iron became increased for cultures grown on sucrose as sole carbon source. Transcriptome data were also used to analyze putative regulatory relationships. In addition to the small RNA csrABCD regulon, which seems to play a role in the physiological adaptation and possibly the shift between free-living and plant-associated endophytic life style of Enterobacter sp. 638, our results also pointed to the involvement of rcsAB in controlling responses by Enterobacter sp. 638 to a plant-associated life style. Targeted mutagenesis was used to confirm this role and showed that compared to wild-type Enterobacter sp. 638 a ΔrcsB mutant was affected in its plant growth promoting ability.
Collapse
|
40
|
Transcriptome-based analysis of the Pantoea stewartii quorum-sensing regulon and identification of EsaR direct targets. Appl Environ Microbiol 2014; 80:5790-800. [PMID: 25015891 DOI: 10.1128/aem.01489-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pantoea stewartii subsp. stewartii is a proteobacterium that causes Stewart's wilt disease in corn plants. The bacteria form a biofilm in the xylem of infected plants and produce capsule that blocks water transport, eventually causing wilt. At low cell densities, the quorum-sensing (QS) regulatory protein EsaR is known to directly repress expression of esaR itself as well as the genes for the capsular synthesis operon transcription regulator, rcsA, and a 2,5-diketogluconate reductase, dkgA. It simultaneously directly activates expression of genes for a putative small RNA, esaS, the glycerol utilization operon, glpFKX, and another transcriptional regulator, lrhA. At high bacterial cell densities, all of this regulation is relieved when EsaR binds an acylated homoserine lactone signal, which is synthesized constitutively over growth. QS-dependent gene expression is critical for the establishment of disease in the plant. However, the identity of the full set of genes controlled by EsaR/QS is unknown. A proteomic approach previously identified around 30 proteins in the QS regulon. In this study, a whole-transcriptome, next-generation sequencing analysis of rRNA-depleted RNA from QS-proficient and -deficient P. stewartii strains was performed to identify additional targets of EsaR. EsaR-dependent transcriptional regulation of a subset of differentially expressed genes was confirmed by quantitative reverse transcription-PCR (qRT-PCR). Electrophoretic mobility shift assays demonstrated that EsaR directly bound 10 newly identified target promoters. Overall, the QS regulon of P. stewartii orchestrates three major physiological responses: capsule and cell envelope biosynthesis, surface motility and adhesion, and stress response.
Collapse
|
41
|
Thomassin JL, Lee MJ, Brannon JR, Sheppard DC, Gruenheid S, Le Moual H. Both group 4 capsule and lipopolysaccharide O-antigen contribute to enteropathogenic Escherichia coli resistance to human α-defensin 5. PLoS One 2013; 8:e82475. [PMID: 24324796 PMCID: PMC3853201 DOI: 10.1371/journal.pone.0082475] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 11/02/2013] [Indexed: 12/18/2022] Open
Abstract
Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are food-borne pathogens that colonize the small intestine and colon, respectively. To cause disease, these pathogens must overcome the action of different host antimicrobial peptides (AMPs) secreted into these distinct niches. We have shown previously that EHEC expresses high levels of the OmpT protease to inactivate the human cathelicidin LL-37, an AMP present in the colon. In this study, we investigate the mechanisms used by EPEC to resist human α-defensin 5 (HD-5), the most abundant AMP in the small intestine. Quantitative PCR was used to measure transcript levels of various EPEC surface structures. High transcript levels of gfcA, a gene required for group 4 capsule (G4C) production, were observed in EPEC, but not in EHEC. The unencapsulated EPEC ∆gfcA and EHEC wild-type strains were more susceptible to HD-5 than EPEC wild-type. Since the G4C is composed of the same sugar repeats as the lipopolysaccharide O-antigen, an -antigen ligase (waaL) deletion mutant was generated in EPEC to assess its role in HD-5 resistance. The ∆waaL EPEC strain was more susceptible to HD-5 than both the wild-type and ∆gfcA strains. The ∆gfcA∆waaL EPEC strain was not significantly more susceptible to HD-5 than the ∆waaL strain, suggesting that the absence of -antigen influences G4C formation. To determine whether the G4C and -antigen interact with HD-5, total polysaccharide was purified from wild-type EPEC and added to the ∆gfcA∆waaL strain in the presence of HD-5. The addition of exogenous polysaccharide protected the susceptible strain against HD-5 killing in a dose-dependent manner, suggesting that HD-5 binds to the polysaccharides present on the surface of EPEC. Altogether, these findings indicate that EPEC relies on both the G4C and the -antigen to resist the bactericidal activity of HD-5.
Collapse
Affiliation(s)
- Jenny-Lee Thomassin
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
| | - Mark J. Lee
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
| | - John R. Brannon
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
| | - Donald C. Sheppard
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
- Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec, Canada
| | - Samantha Gruenheid
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
- Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec, Canada
| | - Hervé Le Moual
- Department of Microbiology and Immunology, McGill University, Montreal, Quebec, Canada
- Microbiome and Disease Tolerance Centre, McGill University, Montreal, Quebec, Canada
- Faculty of Dentistry, McGill University, Montreal, Quebec, Canada
- * E-mail:
| |
Collapse
|
42
|
Response of extraintestinal pathogenic Escherichia coli to human serum reveals a protective role for Rcs-regulated exopolysaccharide colanic acid. Infect Immun 2013; 82:298-305. [PMID: 24166954 DOI: 10.1128/iai.00800-13] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Extraintestinal Escherichia coli (ExPEC) organisms are the leading cause of Gram-negative bacterial bloodstream infections. These bacteria adapt to survival in the bloodstream through expression of factors involved in scavenging of nutrients and resisting the killing activity of serum. In this study, the transcriptional response of a prototypic ExPEC strain (CFT073) to human serum was investigated. Resistance of CFT073 to the bactericidal properties of serum involved increased expression of envelope stress regulators, including CpxR, σE, and RcsB. Many of the upregulated genes induced by active serum were regulated by the Rcs two-component system. This system is triggered by envelope stress such as changes to cell wall integrity. RcsB-mediated serum resistance was conferred through induction of the exopolysaccharide colanic acid. Production of this exopolysaccharide may be protective while cell wall damage caused by serum components is repaired.
Collapse
|
43
|
Kamenšek S, Žgur-Bertok D. Global transcriptional responses to the bacteriocin colicin M in Escherichia coli. BMC Microbiol 2013; 13:42. [PMID: 23421615 PMCID: PMC3599342 DOI: 10.1186/1471-2180-13-42] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 02/18/2013] [Indexed: 01/17/2023] Open
Abstract
Background Bacteriocins are protein antimicrobial agents that are produced by all prokaryotic lineages. Escherichia coli strains frequently produce the bacteriocins known as colicins. One of the most prevalent colicins, colicin M, can kill susceptible cells by hydrolyzing the peptidoglycan lipid II intermediate, which arrests peptidoglycan polymerization steps and provokes cell lysis. Due to the alarming rise in antibiotic resistance and the lack of novel antimicrobial agents, colicin M has recently received renewed attention as a promising antimicrobial candidate. Here the effects of subinhibitory concentrations of colicin M on whole genome transcription in E. coli were investigated, to gain insight into its ecological role and for purposes related to antimicrobial therapy. Results Transcriptome analysis revealed that exposure to subinhibitory concentrations of colicin M altered expression of genes involved in envelope, osmotic and other stresses, including genes of the CreBC two-component system, exopolysaccharide production and cell motility. Nonetheless, there was no induction of biofilm formation or genes involved in mutagenesis. Conclusion At subinhibitory concentrations colicin M induces an adaptive response primarily to protect the bacterial cells against envelope stress provoked by peptidoglycan damage. Among the first induced were genes of the CreBC two-component system known to promote increased resistance against colicins M and E2, providing novel insight into the ecology of colicin M production in natural environments. While an adaptive response was induced nevertheless, colicin M application did not increase biofilm formation, nor induce SOS genes, adverse effects that can be provoked by a number of traditional antibiotics, providing support for colicin M as a promising antimicrobial agent.
Collapse
Affiliation(s)
- Simona Kamenšek
- Department of Biology, Biotechnical Faculty, University of Ljubljana, 1000, Ljubljana, Slovenia
| | | |
Collapse
|
44
|
Genome sequence and comparative pathogenomics analysis of a Salmonella enterica Serovar Typhi strain associated with a typhoid carrier in Malaysia. J Bacteriol 2013; 194:5970-1. [PMID: 23045488 DOI: 10.1128/jb.01416-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Salmonella enterica serovar Typhi is a human pathogen that causes typhoid fever predominantly in developing countries. In this article, we describe the whole genome sequence of the S. Typhi strain CR0044 isolated from a typhoid fever carrier in Kelantan, Malaysia. These data will further enhance the understanding of its host persistence and adaptive mechanism.
Collapse
|
45
|
Aslam SN, Cresswell-Maynard T, Thomas DN, Underwood GJC. Production and Characterization of the Intra- and Extracellular Carbohydrates and Polymeric Substances (EPS) of Three Sea-Ice Diatom Species, and Evidence for a Cryoprotective Role for EPS. JOURNAL OF PHYCOLOGY 2012; 48:1494-509. [PMID: 27009999 DOI: 10.1111/jpy.12004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 05/09/2012] [Indexed: 05/15/2023]
Abstract
Diatoms and their associated extracellular polymeric substances (EPS) are major constituents of the microalgal assemblages present within sea ice. Yields and chemical composition of soluble and cell-associated polysaccharides produced by three sea-ice diatoms, Synedropsis sp., Fragilariopsis curta, and F. cylindrus, were compared. Colloidal carbohydrates (CC) contained heteropolysaccharides rich in mannose, xylose, galactose, and glucose. Synedropsis sp. CC consisted mainly of carbohydrates <8 kDa size, with relatively soluble EPS, compared to high proportions of less-soluble EPS produced by both Fragilariopsis spp. F. curta colloidal EPS contained high concentrations of amino sugars (AS). Both Fragilariopsis species had high yields of hot bicarbonate (HB) soluble EPS, rich in xylose, mannose, galactose, and fucose (and AS in F. cylindrus). All species had frustule-associated EPS rich in glucose-mannose. Nutrient limitation resulted in declines in EPS yields and in glucose content of all EPS fractions. Significant similarities between EPS fractions from cultures and different components of natural EPS from Antarctic sea ice were found. Increased salinity (52) reduced growth, but increased yields of EPS in Fragilariopsis cylindrus. Ice formation was inhibited byF. cylindrus, EPS, and by enhanced EPS content (additional xanthan gum) down to -12°C, with growth rate reduced in the presence of xanthan. Differences in the production and composition of EPS between Synedropsis sp. and Fragilariopsis spp., and the association between EPS, freezing and cell survival, supports the hypothesis that EPS production is a strategy to assist polar ice diatoms to survive the cold and saline conditions present in sea ice.
Collapse
Affiliation(s)
- Shazia N Aslam
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| | | | - David N Thomas
- Ocean Sciences, College of Natural Science, Bangor University, Menai Bridge, Anglesey, LL59 5AB, UK
- Finnish Environment Institute (SYKE), Marine Research Centre, P.O. Box 140, Helsinki, FI-00251, Finland
| | - Graham J C Underwood
- School of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, CO4 3SQ, UK
| |
Collapse
|
46
|
Large mutational target size for rapid emergence of bacterial persistence. Proc Natl Acad Sci U S A 2012; 109:12740-5. [PMID: 22802628 DOI: 10.1073/pnas.1205124109] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phenotypic heterogeneity displayed by a clonal bacterial population permits a small fraction of cells to survive prolonged exposure to antibiotics. Although first described over 60 y ago, the molecular mechanisms underlying this behavior, termed persistence, remain largely unknown. To systematically explore the genetic basis of persistence, we selected a library of transposon-mutagenized Escherichia coli cells for survival to multiple rounds of lethal ampicillin exposure. Application of microarray-based genetic footprinting revealed a large number of loci that drastically elevate persistence frequency through null mutations and domain disruptions. In one case, the C-terminal disruption of methionyl-tRNA synthetase (MetG) results in a 10,000-fold higher persistence frequency than wild type. We discovered a mechanism by which null mutations in transketolase A (tktA) and glycerol-3-phosphate (G3P) dehydrogenase (glpD) increase persistence through metabolic flux alterations that increase intracellular levels of the growth-inhibitory metabolite methylglyoxal. Systematic double-mutant analyses revealed the genetic network context in which such persistent mutants function. Our findings reveal a large mutational target size for increasing persistence frequency, which has fundamental implications for the emergence of antibiotic tolerance in the clinical setting.
Collapse
|
47
|
Effects of subinhibitory concentrations of menthol on adaptation, morphological, and gene expression changes in enterohemorrhagic Escherichia coli. Appl Environ Microbiol 2012; 78:5361-7. [PMID: 22635999 DOI: 10.1128/aem.00894-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Menthol (C(10)H(20)O) possesses antibacterial activity; nevertheless, bacterial adaptation to this compound has never been studied. Here we report that precultivation of enterohemorrhagic Escherichia coli (EHEC) strains in increasing subinhibitory (SI) concentrations of menthol significantly elevates (4- to 16-fold) their resistance to menthol. Concomitant morphological alterations included the appearance of mucoid colonies and reduced biofilm production. Scanning electron microscopy (SEM) examination revealed suppressed curli formation in menthol-adapted cells. Expression of the gene cpsB10 (encoding one of the enzymes responsible for colanic acid production) was elevated in response to SI concentrations of menthol in a laboratory E. coli strain, whereas expression in an rcsC null mutant was reduced, implicating a partial role for the Rcs phosphorelay system in mediating the menthol signal. Adaptation to menthol also reduced expression of the locus of enterocyte effacement-encoded regulator (Ler). This reduction, together with reduced curli and biofilm formation and elevated mucoidity, suggests a general reduction in bacterial virulence following adaptation to menthol. Our results thus suggest menthol as a potential lead in the recently emerging alternative strategy of targeting bacterial virulence factors to develop new types of anti-infective agents.
Collapse
|
48
|
Ionescu M, Elgrably-Weiss M, Elad T, Rasouly A, Yagur-Kroll S, Belkin S. Negative regulation of σ70-driven promoters by σ70. Res Microbiol 2011; 162:461-9. [DOI: 10.1016/j.resmic.2011.03.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2010] [Accepted: 02/14/2011] [Indexed: 11/26/2022]
|
49
|
Sathiyamoorthy K, Mills E, Franzmann TM, Rosenshine I, Saper MA. The crystal structure of Escherichia coli group 4 capsule protein GfcC reveals a domain organization resembling that of Wza. Biochemistry 2011; 50:5465-76. [PMID: 21449614 DOI: 10.1021/bi101869h] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report the 1.9 Å resolution crystal structure of enteropathogenic Escherichia coli GfcC, a periplasmic protein encoded by the gfc operon, which is essential for assembly of group 4 polysaccharide capsule (O-antigen capsule). Presumed gene orthologs of gfcC are present in capsule-encoding regions of at least 29 genera of Gram-negative bacteria. GfcC, a member of the DUF1017 family, is comprised of tandem β-grasp (ubiquitin-like) domains (D2 and D3) and a carboxyl-terminal amphipathic helix, a domain arrangement reminiscent of that of Wza that forms an exit pore for group 1 capsule export. Unlike the membrane-spanning C-terminal helix from Wza, the GfcC C-terminal helix packs against D3. Previously unobserved in a β-grasp domain structure is a 48-residue helical hairpin insert in D2 that binds to D3, constraining its position and sequestering the carboxyl-terminal amphipathic helix. A centrally located and invariant Arg115 not only is essential for proper localization but also forms one of two mostly conserved pockets. Finally, we draw analogies between a GfcC protein fused to an outer membrane β-barrel pore in some species and fusion proteins necessary for secreting biofilm-forming exopolysaccharides.
Collapse
|
50
|
BglJ-RcsB heterodimers relieve repression of the Escherichia coli bgl operon by H-NS. J Bacteriol 2010; 192:6456-64. [PMID: 20952573 DOI: 10.1128/jb.00807-10] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
RcsB is the response regulator of the complex Rcs two-component system, which senses perturbations in the outer membrane and peptidoglycan layer. BglJ is a transcriptional regulator whose constitutive expression causes activation of the H-NS- and StpA-repressed bgl (aryl-β,D-glucoside) operon in Escherichia coli. RcsB and BglJ both belong to the LuxR-type family of transcriptional regulators with a characteristic C-terminal DNA-binding domain. Here, we show that BglJ and RcsB interact and form heterodimers that presumably bind upstream of the bgl promoter, as suggested by mutation of a sequence motif related to the consensus sequence for RcsA-RcsB heterodimers. Heterodimerization of BglJ-RcsB and relief of H-NS-mediated repression of bgl by BglJ-RcsB are apparently independent of RcsB phosphorylation. In addition, we show that LeuO, a pleiotropic LysR-type transcriptional regulator, likewise binds to the bgl upstream regulatory region and relieves repression of bgl independently of BglJ-RcsB. Thus, LeuO can affect bgl directly, as shown here, and indirectly by activating the H-NS-repressed yjjQ-bglJ operon, as shown previously. Taken together, heterodimer formation of RcsB and BglJ expands the role of the Rcs two-component system and the network of regulators affecting the bgl promoter.
Collapse
|