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Cervantes PW, Segelke BW, Lau EY, Robinson BV, Abisoye-Ogunniyan A, Pal S, de la Maza LM, Coleman MA, D’haeseleer P. Sequence, structure prediction, and epitope analysis of the polymorphic membrane protein family in Chlamydia trachomatis. PLoS One 2024; 19:e0304525. [PMID: 38861498 PMCID: PMC11166332 DOI: 10.1371/journal.pone.0304525] [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: 11/01/2023] [Accepted: 05/13/2024] [Indexed: 06/13/2024] Open
Abstract
The polymorphic membrane proteins (Pmps) are a family of autotransporters that play an important role in infection, adhesion and immunity in Chlamydia trachomatis. Here we show that the characteristic GGA(I,L,V) and FxxN tetrapeptide repeats fit into a larger repeat sequence, which correspond to the coils of a large beta-helical domain in high quality structure predictions. Analysis of the protein using structure prediction algorithms provided novel insight to the chlamydial Pmp family of proteins. While the tetrapeptide motifs themselves are predicted to play a structural role in folding and close stacking of the beta-helical backbone of the passenger domain, we found many of the interesting features of Pmps are localized to the side loops jutting out from the beta helix including protease cleavage, host cell adhesion, and B-cell epitopes; while T-cell epitopes are predominantly found in the beta-helix itself. This analysis more accurately defines the Pmp family of Chlamydia and may better inform rational vaccine design and functional studies.
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Affiliation(s)
- Patrick W. Cervantes
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California, United States of America
| | - Brent W. Segelke
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California, United States of America
| | - Edmond Y. Lau
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California, United States of America
| | - Beverly V. Robinson
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California, United States of America
| | - Abisola Abisoye-Ogunniyan
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California, United States of America
| | - Sukumar Pal
- Department of Pathology and Laboratory Medicine, University of California Irvine, Irvine, California, United States of America
| | - Luis M. de la Maza
- Department of Pathology and Laboratory Medicine, University of California Irvine, Irvine, California, United States of America
| | - Matthew A. Coleman
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California, United States of America
| | - Patrik D’haeseleer
- Biosciences and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California, United States of America
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2
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Lin Q, Jiang Z, Zhong B, Chen JQ, Lv ZB, Nie ZM. Unveiling the impact of cryptic plasmids curing on Escherichia coli Nissle 1917: massive increase in Ag43c expression. AMB Express 2024; 14:48. [PMID: 38678482 PMCID: PMC11056357 DOI: 10.1186/s13568-024-01681-9] [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: 02/07/2024] [Accepted: 02/16/2024] [Indexed: 05/01/2024] Open
Abstract
Escherichia coli Nissle 1917 (EcN) is an important chassis strain widely used for the development of live biotherapeutic products (LBPs). EcN strain naturally harbors two cryptic plasmids with unknown function. During the development of LBPs using EcN strain, the cryptic plasmids were cured usually to avoid plasmid incompatibility or alleviate metabolic burdens associated with these cryptic plasmids. While the cryptic plasmids curing in EcN may appear to be a routine procedure, the comprehensive impact of cryptic plasmids curing on the EcN strain remains incompletely understood. In the present study, the effects of cryptic plasmids curing on EcN were investigated using transcriptome sequencing. The results revealed that only a small number of genes showed significant changes in mRNA levels after cryptic plasmid curing (4 upregulated and 6 downregulated genes), primarily involved in amino acid metabolism. Furthermore, the flu gene showed the most significant different expression, encoding Antigen 43 (Ag43) protein, a Cah family adhesin. Mass spectrometry analysis further confirmed the significant increase in Ag43 expression. Ag43 is commonly present in Escherichia coli and mediates the bacterial autoaggregation. However, despite the upregulation of Ag43 expression, no Ag43-mediated cell self-sedimentation was observed in the cured EcN strain. These findings contribute to making informed decisions regarding the curing of the cryptic plasmids when Escherichia coli Nissle 1917 is used as the chassis strain.
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Affiliation(s)
- Qi Lin
- College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, 310018, China
- Center for Bioreactor and Protein Drug Research, Shaoxing Biomedical Research Institute of Zhejiang Sci-Tech University Co., Ltd, Shaoxing, 312075, China
| | - Zhuo Jiang
- College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, 310018, China
| | - Bo Zhong
- College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, 310018, China
| | - Jian-Qing Chen
- College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, 310018, China
- Center for Bioreactor and Protein Drug Research, Shaoxing Biomedical Research Institute of Zhejiang Sci-Tech University Co., Ltd, Shaoxing, 312075, China
| | - Zheng-Bing Lv
- College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, 310018, China
- Center for Bioreactor and Protein Drug Research, Shaoxing Biomedical Research Institute of Zhejiang Sci-Tech University Co., Ltd, Shaoxing, 312075, China
| | - Zuo-Ming Nie
- College of Life Sciences and Medicine, Zhejiang Sci-Tech University, Hangzhou, 310018, China.
- Center for Bioreactor and Protein Drug Research, Shaoxing Biomedical Research Institute of Zhejiang Sci-Tech University Co., Ltd, Shaoxing, 312075, China.
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3
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Mousavi SM, Archangi B, Zamani I. Antibacterial Properties of Bacteriocin Purified from Serratia marcescens and Computerized Assessment of its Interaction with Antigen 43 in Escherichia coli. ARCHIVES OF RAZI INSTITUTE 2023; 78:1738-1745. [PMID: 38828162 PMCID: PMC11139391 DOI: 10.32592/ari.2023.78.6.2694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Accepted: 06/06/2023] [Indexed: 06/05/2024]
Abstract
Bacteriocins are a kind of antimicrobial peptides that kill or inhibit the growth of bacterial strains. The purpose of this study was to investigate the antibacterial effect of Serratia marcescens on several pathogenic bacterial strains. Bacteriocin produced by S. marcescens was purified by chromatography with Sephadex G-75 column, and its antibacterial effect on gram-negative bacteria, including Escherichia coli ATCC 700928, Pseudomonas aeruginosa PTCC 1707, S. marcescens PTCC 1621, Vibrio fischeri PTCC 1693, and Vibrio harveyi PTCC 1755, were evaluated by the disk diffusion method. The structure of bacteriocin was determined by nuclear magnetic resonance spectroscopy. The interaction of bacteriocin with the antigen 43 (Ag43) of E. coli was evaluated by the molecular docking method. Bacteriocin extracted from bacterial isolates had antibacterial activity on E. coli strains but not on other studied strains. Bioinformatics analysis also showed bacteriocin docking with Ag43 with an energy of -159.968 kJ/mol. Natural compounds, such as bacteriocin, can be an alternative to common chemical compounds and antibiotics. To reach a definite conclusion in this regard, there is a need for further research and understanding of their mechanism of action.
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Affiliation(s)
- S M Mousavi
- Department of Marine Biotechnology, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran
| | - B Archangi
- Department of Marine Biotechnology, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran
| | - I Zamani
- Department of Marine Biotechnology, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran
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Nejad MK, Hasani A, Soofiyani SR, Nahandi MZ, Hasani A. Aptitude of Uropathogenic Escherichia coli in Renal Transplant Recipients: A Comprehensive Review on Characteristic Features, and Production of Extended Spectrum β-Lactamase. Curr Microbiol 2023; 80:382. [PMID: 37864769 DOI: 10.1007/s00284-023-03476-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Accepted: 09/05/2023] [Indexed: 10/23/2023]
Abstract
Urinary tract infection is the most common infection in almost half of the renal transplant patients. The development of UTI in these patients may progress to bacteremia, acute T cell-mediated rejection, impaired allograft function, or allograft loss, along with the increased risk of hospitalization and death. Among various pathogens implicated, Uropathogenic E. coli (UPEC), especially sequence type 131 (ST131), is the most virulent and multidrug-resistant pathogen. High antimicrobial resistance to most β-lactam antibiotics, mediated by extended spectrum β-lactamases (ESBLs) produced by UPEC, is a challenge in the clinical management of UTIs in kidney transplant recipients. Indeed, multidrug resistance to β-lactam antibiotics is a direct consequence of ESBL production. Resistance to other antibiotics such as aminoglycosides, fluoroquinolones, and trimethoprim-sulphamethoxazole has also been reported in ESBLs-producing UPEC, which reduces the therapeutic options, rising healthcare-associated costs and subsequently leads to renal failure or even graft loss. In this review, we aimed to discuss the post-transplant risk factors of UTI, UPEC virulence factors (VF), and the related factors including quorum sensing, and stress resistance genes. Furthermore, we searched for the current treatment strategies and some of the alternate approaches proposed as therapeutic options that may affirm the treatment of ESBL-producing UPEC.
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Affiliation(s)
- Masoomeh Kashef Nejad
- Clinical Research Development Unit, Sina Educational, Research and Treatment Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Alka Hasani
- Clinical Research Development Unit, Sina Educational, Research and Treatment Center, Tabriz University of Medical Sciences, Tabriz, Iran.
- Department of Bacteriology and Virology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
| | - Saiedeh Razi Soofiyani
- Clinical Research Development Unit, Sina Educational, Research and Treatment Center, Tabriz University of Medical Sciences, Tabriz, Iran
- Department of Molecular Medicine, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Maryam Zaare Nahandi
- Clinical Research Development Unit, Sina Educational, Research and Treatment Center, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Akbar Hasani
- Department of Clinical Biochemistry and Laboratory Sciences, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
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Ntui CM, Fleckenstein JM, Schubert WD. Structural and biophysical characterization of the secreted, β-helical adhesin EtpA of Enterotoxigenic Escherichia coli. PLoS One 2023; 18:e0287100. [PMID: 37343026 PMCID: PMC10284417 DOI: 10.1371/journal.pone.0287100] [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: 03/07/2023] [Accepted: 05/30/2023] [Indexed: 06/23/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a diarrhoeal pathogen associated with high morbidity and mortality especially among young children in developing countries. At present, there is no vaccine for ETEC. One candidate vaccine antigen, EtpA, is a conserved secreted adhesin that binds to the tips of flagellae to bridge ETEC to host intestinal glycans. EtpA is exported through a Gram-negative, two-partner secretion system (TPSS, type Vb) comprised of the secreted EtpA passenger (TpsA) protein and EtpB (TpsB) transporter that is integrated into the outer bacterial membrane. TpsA proteins share a conserved, N-terminal TPS domain followed by an extensive C-terminal domain with divergent sequence repeats. Two soluble, N-terminal constructs of EtpA were prepared and analysed respectively including residues 67 to 447 (EtpA67-447) and 1 to 606 (EtpA1-606). The crystal structure of EtpA67-447 solved at 1.76 Å resolution revealed a right-handed parallel β-helix with two extra-helical hairpins and an N-terminal β-strand cap. Analyses by circular dichroism spectroscopy confirmed the β-helical fold and indicated high resistance to chemical and thermal denaturation as well as rapid refolding. A theoretical AlphaFold model of full-length EtpA largely concurs with the crystal structure adding an extended β-helical C-terminal domain after an interdomain kink. We propose that robust folding of the TPS domain upon secretion provides a template to extend the N-terminal β-helix into the C-terminal domains of TpsA proteins.
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Affiliation(s)
- Clifford Manyo Ntui
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa
| | - James M. Fleckenstein
- Department of Medicine, Division of Infectious Diseases Washington University in Saint Louis, School of Medicine, Saint Louis, Missouri, United States of Ameirca
- Infectious Disease Service Saint Louis VA Health Care System, Saint Louis, Missouri, United States of Ameirca
| | - Wolf-Dieter Schubert
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, South Africa
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6
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Reichhardt C. The Pseudomonas aeruginosa Biofilm Matrix Protein CdrA Has Similarities to Other Fibrillar Adhesin Proteins. J Bacteriol 2023; 205:e0001923. [PMID: 37098957 PMCID: PMC10210978 DOI: 10.1128/jb.00019-23] [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] [Indexed: 04/27/2023] Open
Abstract
The ability of bacteria to adhere to each other and both biotic and abiotic surfaces is key to biofilm formation, and one way that bacteria adhere is using fibrillar adhesins. Fibrillar adhesins share several key characteristics, including (i) they are extracellular, surface-associated proteins, (ii) they contain an adhesive domain as well as a repetitive stalk domain, and (iii) they are either a monomer or homotrimer (i.e., identical, coiled-coil) of a high molecular weight protein. Pseudomonas aeruginosa uses the fibrillar adhesin called CdrA to promote bacterial aggregation and biofilm formation. Here, the current literature on CdrA is reviewed, including its transcriptional and posttranslational regulation by the second messenger c-di-GMP as well as what is known about its structure and ability to interact with other molecules. I highlight its similarities to other fibrillar adhesins and discuss open questions that remain to be answered toward a better understanding of CdrA.
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Affiliation(s)
- Courtney Reichhardt
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
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7
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Lindberg SK, Willsey GG, Mantis NJ. Flagellar-based motility accelerates IgA-mediated agglutination of Salmonella Typhimurium at high bacterial cell densities. Front Immunol 2023; 14:1193855. [PMID: 37275888 PMCID: PMC10232770 DOI: 10.3389/fimmu.2023.1193855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2023] [Accepted: 05/03/2023] [Indexed: 06/07/2023] Open
Abstract
Introduction Secretory IgA (SIgA) protects the intestinal epithelium from enteric pathogens such as Salmonella enterica serovar Typhimurium (STm) through a process known as immune exclusion, where invading bacteria are aggregated via antibody cross-linking, encased in mucus, and then cleared from the intestinal tract via peristalsis. At high cell densities, the STm aggregates form a tightly packed network that is reminiscent of early bacterial biofilms. However, the underlying mechanism of how SIgA mediates this transition from a motile and invasive state to an avirulent sessile state in STm is currently unknown. Methods In this report, we developed and validated a methodology known as the "snow globe" assay to enable real-time imaging and quantification of STm agglutination by the mouse monoclonal IgA Sal4. Results We observed that agglutination in the snow globe assay was dose-dependent, antigen-specific, and influenced by antibody isotype. We determined that flagellar-based motility was a prerequisite for rapid onset of agglutination, even at high cell densities where cell-cell contacts are expected to be frequent. We also investigated the roles of individual cyclic-di-GMP metabolizing enzymes previously implicated in motility and biofilm formation in Sal4 IgA-mediated agglutination. Discussion Taken together, our results demonstrate that IgA-mediated agglutination is a dynamic process influenced by bacterial motility and cell-cell collisions. We conclude that the snow globe assay is a viable platform to further decipher the molecular and genetic determinants that drive this interaction.
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Affiliation(s)
- Samantha K. Lindberg
- Department of Biomedical Sciences, University at Albany School of Public Health, Albany, NY, United States
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, United States
| | - Graham G. Willsey
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, United States
| | - Nicholas J. Mantis
- Department of Biomedical Sciences, University at Albany School of Public Health, Albany, NY, United States
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, United States
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8
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Smoak RA, Snyder LF, Fassler JS, He BZ. Parallel expansion and divergence of an adhesin family in pathogenic yeasts. Genetics 2023; 223:iyad024. [PMID: 36794645 PMCID: PMC10319987 DOI: 10.1093/genetics/iyad024] [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: 12/07/2022] [Revised: 02/08/2023] [Accepted: 02/09/2023] [Indexed: 02/17/2023] Open
Abstract
Opportunistic yeast pathogens arose multiple times in the Saccharomycetes class, including the recently emerged, multidrug-resistant (MDR) Candida auris. We show that homologs of a known yeast adhesin family in Candida albicans, the Hyr/Iff-like (Hil) family, are enriched in distinct clades of Candida species as a result of multiple, independent expansions. Following gene duplication, the tandem repeat-rich region in these proteins diverged extremely rapidly and generated large variations in length and β-aggregation potential, both of which are known to directly affect adhesion. The conserved N-terminal effector domain was predicted to adopt a β-helical fold followed by an α-crystallin domain, making it structurally similar to a group of unrelated bacterial adhesins. Evolutionary analyses of the effector domain in C. auris revealed relaxed selective constraint combined with signatures of positive selection, suggesting functional diversification after gene duplication. Lastly, we found the Hil family genes to be enriched at chromosomal ends, which likely contributed to their expansion via ectopic recombination and break-induced replication. Combined, these results suggest that the expansion and diversification of adhesin families generate variation in adhesion and virulence within and between species and are a key step toward the emergence of fungal pathogens.
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Affiliation(s)
- Rachel A Smoak
- Civil and Environmental Engineering, The University of Iowa, Iowa City, IA 52242, USA
| | - Lindsey F Snyder
- Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA
| | - Jan S Fassler
- Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
| | - Bin Z He
- Interdisciplinary Graduate Program in Genetics, The University of Iowa, Iowa City, IA 52242, USA
- Department of Biology, The University of Iowa, Iowa City, IA 52242, USA
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9
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Ageorges V, Wawrzyniak I, Ruiz P, Bicep C, Zorgani MA, Paxman JJ, Heras B, Henderson IR, Leroy S, Bailly X, Sapountzis P, Peyretaillade E, Desvaux M. Genome-Wide Analysis of Antigen 43 (Ag43) Variants: New Insights in Their Diversity, Distribution and Prevalence in Bacteria. Int J Mol Sci 2023; 24:5500. [PMID: 36982580 PMCID: PMC10058404 DOI: 10.3390/ijms24065500] [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: 01/26/2023] [Revised: 03/05/2023] [Accepted: 03/08/2023] [Indexed: 03/17/2023] Open
Abstract
Antigen 43 (Ag43) expression induces aggregation and biofilm formation that has consequences for bacterial colonisation and infection. Ag43 is secreted through the Type 5 subtype "a" secretion system (T5aSS) and is a prototypical member of the family of self-associating autotransporters (SAATs). As a T5aSS protein, Ag43 has a modular architecture comprised of (i) a signal peptide, (ii) a passenger domain that can be subdivided into three subdomains (SL, EJ, and BL), (iii) an autochaperone (AC) domain, and (iv) an outer membrane translocator. The cell-surface SL subdomain is directly involved in the "Velcro-handshake" mechanism resulting in bacterial autoaggregation. Ag43 is considered to have a ubiquitous distribution in E. coli genomes and many strains harbour multiple agn43 genes. However, recent phylogenetic analyses indicated the existence of four distinct Ag43 classes exhibiting different propensities for autoaggregation and interactions. Given the knowledge of the diversity and distribution of Ag43 in E. coli genomes is incomplete, we have performed a thorough in silico investigation across bacterial genomes. Our comprehensive analyses indicate that Ag43 passenger domains cluster in six phylogenetic classes associated with different SL subdomains. The diversity of Ag43 passenger domains is a result of the association of the SL subtypes with two different EJ-BL-AC modules. We reveal that agn43 is almost exclusively present among bacterial species of the Enterobacteriaceae family and essentially in the Escherichia genus (99.6%) but that it is not ubiquitous in E. coli. The gene is typically present as a single copy but up to five copies of agn43 with different combinations of classes can be observed. The presence of agn43 as well as its different classes appeared to differ between Escherichia phylogroups. Strikingly, agn43 is present in 90% of E. coli from E phylogroup. Our results shed light on Ag43 diversity and provide a rational framework for investigating its role in E. coli ecophysiology and physiopathology.
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Affiliation(s)
| | | | - Philippe Ruiz
- INRAE, UCA, UMR0454 MEDIS, 63000 Clermont-Ferrand, France
| | - Cédric Bicep
- UCA, CNRS, UMR6023 LMGE, 63000 Clermont-Ferrand, France
| | | | - Jason J. Paxman
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC 3086, Australia
| | - Begoña Heras
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, VIC 3086, Australia
| | - Ian R. Henderson
- Institute for Molecular Biosciences, University of Queensland, St. Lucia, QLD 4067, Australia
| | - Sabine Leroy
- INRAE, UCA, UMR0454 MEDIS, 63000 Clermont-Ferrand, France
| | - Xavier Bailly
- INRAE, UCA, VetAgro Sup, UMR0346 EPIA, 63122 Saint Genes Champanelle, France
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10
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Öztürk FY, Darcan C, Kariptaş E. The Determination, Monitoring, Molecular Mechanisms and Formation of Biofilm in E. coli. Braz J Microbiol 2023; 54:259-277. [PMID: 36577889 PMCID: PMC9943865 DOI: 10.1007/s42770-022-00895-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 12/16/2022] [Indexed: 12/30/2022] Open
Abstract
Biofilms are cell assemblies embedded in an exopolysaccharide matrix formed by microorganisms of a single or many different species. This matrix in which they are embedded protects the bacteria from external influences and antimicrobial effects. The biofilm structure that microorganisms form to protect themselves from harsh environmental conditions and survive is found in nature in many different environments. These environments where biofilm formation occurs have in common that they are in contact with fluids. The gene expression of bacteria in complex biofilm differs from that of bacteria in the planktonic state. The differences in biofilm cell expression are one of the effects of community life. Means of quorum sensing, bacteria can act in coordination with each other. At the same time, while biofilm formation provides many benefits to bacteria, it has positive and negative effects in many different areas. Depending on where they occur, biofilms can cause serious health problems, contamination risks, corrosion, and heat and efficiency losses. However, they can also be used in water treatment plants, bioremediation, and energy production with microbial fuel cells. In this review, the basic steps of biofilm formation and biofilm regulation in the model organism Escherichia coli were discussed. Finally, the methods by which biofilm formation can be detected and monitored were briefly discussed.
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Affiliation(s)
- Fırat Yavuz Öztürk
- Department of Molecular Biology and Genetic, Faculty of Arts and Science, Bilecik Seyh Edebali University, Bilecik, Turkey.
| | - Cihan Darcan
- Department of Molecular Biology and Genetic, Faculty of Arts and Science, Bilecik Seyh Edebali University, Bilecik, Turkey
| | - Ergin Kariptaş
- Department of Medical Microbiology, Faculty of Medicine, Samsun University, Samsun, Turkey
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11
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Hor L, Pilapitiya A, McKenna JA, Panjikar S, Anderson MA, Desvaux M, Paxman JJ, Heras B. Crystal structure of a subtilisin-like autotransporter passenger domain reveals insights into its cytotoxic function. Nat Commun 2023; 14:1163. [PMID: 36859523 PMCID: PMC9977779 DOI: 10.1038/s41467-023-36719-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 02/14/2023] [Indexed: 03/03/2023] Open
Abstract
Autotransporters (ATs) are a large family of bacterial secreted and outer membrane proteins that encompass a wide range of enzymatic activities frequently associated with pathogenic phenotypes. We present the structural and functional characterisation of a subtilase autotransporter, Ssp, from the opportunistic pathogen Serratia marcescens. Although the structures of subtilases have been well documented, this subtilisin-like protein is associated with a 248 residue β-helix and itself includes three finger-like protrusions around its active site involved in substrate interactions. We further reveal that the activity of the subtilase AT is required for entry into epithelial cells as well as causing cellular toxicity. The Ssp structure not only provides details about the subtilase ATs, but also reveals a common framework and function to more distantly related ATs. As such these findings also represent a significant step forward toward understanding the molecular mechanisms underlying the functional divergence in the large AT superfamily.
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Affiliation(s)
- Lilian Hor
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, VIC, 3086, Australia
| | - Akila Pilapitiya
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, VIC, 3086, Australia
| | - James A McKenna
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, VIC, 3086, Australia
| | - Santosh Panjikar
- Australian Synchrotron, ANSTO, Clayton, VIC, 3168, Australia
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC, 3800, Australia
| | - Marilyn A Anderson
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, VIC, 3086, Australia
| | - Mickaël Desvaux
- INRAE, Université Clermont Auvergne, UMR454 MEDiS, 63000, Clermont-Ferrand, France
| | - Jason J Paxman
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, VIC, 3086, Australia.
| | - Begoña Heras
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Kingsbury Drive, Bundoora, VIC, 3086, Australia.
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12
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Puri D, Fang X, Allison KR. Evidence of a possible multicellular life cycle in Escherichia coli. iScience 2022; 26:105795. [PMID: 36594031 PMCID: PMC9804144 DOI: 10.1016/j.isci.2022.105795] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 10/07/2022] [Accepted: 12/08/2022] [Indexed: 12/14/2022] Open
Abstract
Biofilms are surface-attached multicellular microbial communities. Their genetics have been extensively studied, but the cell-scale morphogenetic events of their formation are largely unknown. Here, we recorded the entirety of morphogenesis in Escherichia coli, and discovered a previously unknown multicellular self-assembly process. Unattached, single-cells formed 4-cell rosettes which grew into constant-width chains. After ∼10 cell generations, these multicellular chains attached to surfaces and stopped growing. Chains remained clonal throughout morphogenesis. We showed that this process generates biofilms, which we found are composed of attached clonal chains, aligned in parallel. We investigated genetics of chain morphogenesis: Ag43 facilitates rosette formation and clonality; type-1 fimbriae and curli promote stability and configuration; and extracellular polysaccharide production facilitates attachment. Our study establishes that E. coli, a unicellular organism, can follow a multistage, clonal, genetically-regulated, rosette-initiated multicellular life cycle. These findings have implications for synthetic biology, multicellular development, and the treatment and prevention of bacterial diseases.
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Affiliation(s)
- Devina Puri
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Xin Fang
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA
| | - Kyle R. Allison
- Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, GA, USA,Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA,Corresponding author
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13
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Agglutination of Borreliella burgdorferi by Transmission-Blocking OspA Monoclonal Antibodies and Monovalent Fab Fragments. Infect Immun 2022; 90:e0030622. [PMID: 36000876 PMCID: PMC9476992 DOI: 10.1128/iai.00306-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Lyme disease vaccines based on recombinant Outer surface protein A (OspA) elicit protective antibodies that interfere with tick-to-host transmission of the disease-causing spirochete Borreliella burgdorferi. Another hallmark of OspA antisera and certain OspA monoclonal antibodies (MAbs) is their capacity to induce B. burgdorferi agglutination in vitro, a phenomenon first reported more than 30 years ago but never studied in molecular detail. In this report, we demonstrate that transmission-blocking OspA MAbs, individually and in combination, promote dose-dependent and epitope-specific agglutination of B. burgdorferi. Agglutination occurred within minutes and persisted for hours. Spirochetes in the core of the aggregates exhibited evidence of outer membrane (OM) stress, revealed by propidium iodide uptake. The most potent agglutinator was the mouse MAb LA-2, which targets the OspA C terminus (β-strands 18 to 20). Human MAb 319-44, which also targets the OspA C terminus (β-strand 20), and 857-2, which targets the OspA central β-sheet (strands 8 to 10), were less potent agglutinators, while MAb 221-7, which targets β-strands 10 to 11, had little to no measurable agglutinating activity, even though its affinity for OspA exceeded that of LA-2. Remarkably, monovalent Fab fragments derived from LA-2, and to a lesser degree 319-44, retained the capacity to induce B. burgdorferi aggregation and OM stress, a particularly intriguing observation considering that "LA-2-like" Fabs have been shown to experimentally entrap B. burgdorferi within infected ticks and prevent transmission during feeding to a mammalian host. It is therefore tempting to speculate that B. burgdorferi aggregation triggered by OspA-specific antibodies in vitro may in fact reflect an important biological activity in vivo.
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14
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Pierrat X, Pham A, Wong JPH, Al-Mayyah Z, Persat A. Engineering Agrobacterium tumefaciens Adhesion to Target Cells. ACS Synth Biol 2022; 11:2662-2671. [PMID: 35881049 DOI: 10.1021/acssynbio.2c00069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Agrobacterium tumefaciens is a plant pathogen commonly repurposed for genetic modification of crops. Despite its versatility, it remains inefficient at transferring DNA to many hosts, including to animal cells. Like many pathogens, physical contact between A. tumefaciens and host cells promotes infection efficacy. Thus, improving the strength and specificity of A. tumefaciens to target cells has the potential for enhancing DNA transfer for biotechnological and therapeutic purposes. Here, we demonstrate a methodology for engineering genetically encoded exogeneous adhesins at the surface of A. tumefaciens. We identified an autotransporter gene we named Aat that is predicted to show canonical β-barrel and passenger domains. We engineered the β-barrel scaffold and linker (Aatβ) to display synthetic adhesins susceptible to rewire A. tumefaciens to alternative host targets. As a proof of concept, we leveraged the versatility of a VHH domain to rewire A. tumefaciens adhesion to yeast and mammalian hosts displaying a GFP target receptor. Finally, to demonstrate how synthetic A. tumefaciens adhesion can improve transfer to host cells, we showed improved protein translocation into HeLa cells using a sensitive split luciferase reporter system. Engineering A. tumefaciens adhesion has therefore a strong potential in generating complex heterogeneous cellular assemblies and in improving DNA transfer efficiency against non-natural hosts.
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Affiliation(s)
- Xavier Pierrat
- School of Life Sciences, Institute of Bioengineering and Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Alix Pham
- School of Life Sciences, Institute of Bioengineering and Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Jeremy P H Wong
- School of Life Sciences, Institute of Bioengineering and Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Zainebe Al-Mayyah
- School of Life Sciences, Institute of Bioengineering and Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Alexandre Persat
- School of Life Sciences, Institute of Bioengineering and Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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15
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Clarke KR, Hor L, Pilapitiya A, Luirink J, Paxman JJ, Heras B. Phylogenetic Classification and Functional Review of Autotransporters. Front Immunol 2022; 13:921272. [PMID: 35860281 PMCID: PMC9289746 DOI: 10.3389/fimmu.2022.921272] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Accepted: 06/06/2022] [Indexed: 11/30/2022] Open
Abstract
Autotransporters are the core component of a molecular nano-machine that delivers cargo proteins across the outer membrane of Gram-negative bacteria. Part of the type V secretion system, this large family of proteins play a central role in controlling bacterial interactions with their environment by promoting adhesion to surfaces, biofilm formation, host colonization and invasion as well as cytotoxicity and immunomodulation. As such, autotransporters are key facilitators of fitness and pathogenesis and enable co-operation or competition with other bacteria. Recent years have witnessed a dramatic increase in the number of autotransporter sequences reported and a steady rise in functional studies, which further link these proteins to multiple virulence phenotypes. In this review we provide an overview of our current knowledge on classical autotransporter proteins, the archetype of this protein superfamily. We also carry out a phylogenetic analysis of their functional domains and present a new classification system for this exquisitely diverse group of bacterial proteins. The sixteen phylogenetic divisions identified establish sensible relationships between well characterized autotransporters and inform structural and functional predictions of uncharacterized proteins, which may guide future research aimed at addressing multiple unanswered aspects in this group of therapeutically important bacterial factors.
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Affiliation(s)
- Kaitlin R. Clarke
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
| | - Lilian Hor
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
| | - Akila Pilapitiya
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
| | - Joen Luirink
- Department of Molecular Microbiology, Amsterdam Institute of Molecular and Life Sciences (AIMMS), Vrije Universiteit, Amsterdam, Netherlands
| | - Jason J. Paxman
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
- *Correspondence: Begoña Heras, ; Jason J. Paxman,
| | - Begoña Heras
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, Australia
- *Correspondence: Begoña Heras, ; Jason J. Paxman,
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16
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Zhao F, Chavez MS, Naughton KL, Niman CM, Atkinson JT, Gralnick JA, El-Naggar MY, Boedicker JQ. Light-Induced Patterning of Electroactive Bacterial Biofilms. ACS Synth Biol 2022; 11:2327-2338. [PMID: 35731987 DOI: 10.1021/acssynbio.2c00024] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Electroactive bacterial biofilms can function as living biomaterials that merge the functionality of living cells with electronic components. However, the development of such advanced living electronics has been challenged by the inability to control the geometry of electroactive biofilms relative to solid-state electrodes. Here, we developed a lithographic strategy to pattern conductive biofilms of Shewanella oneidensis by controlling aggregation protein CdrAB expression with a blue light-induced genetic circuit. This controlled deposition enabled S. oneidensis biofilm patterning on transparent electrode surfaces, and electrochemical measurements allowed us to both demonstrate tunable conduction dependent on pattern size and quantify the intrinsic conductivity of the living biofilms. The intrinsic biofilm conductivity measurements enabled us to experimentally confirm predictions based on simulations of a recently proposed collision-exchange electron transport mechanism. Overall, we developed a facile technique for controlling electroactive biofilm formation on electrodes, with implications for both studying and harnessing bioelectronics.
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Affiliation(s)
- Fengjie Zhao
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Marko S Chavez
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Kyle L Naughton
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Christina M Niman
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Joshua T Atkinson
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States
| | - Jeffrey A Gralnick
- BioTechnology Institute and Department of Plant and Microbial Biology, University of Minnesota-Twin Cities, St. Paul, Minnesota 55108, United States
| | - Mohamed Y El-Naggar
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States.,Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, United States.,Department of Chemistry, University of Southern California, Los Angeles, California 90089, United States
| | - James Q Boedicker
- Department of Physics and Astronomy, University of Southern California, Los Angeles, California 90089, United States.,Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, United States
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17
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Lin L, Capozzoli R, Ferrand A, Plum M, Vettiger A, Basler M. Subcellular localization of Type VI secretion system assembly in response to cell–cell contact. EMBO J 2022; 41:e108595. [PMID: 35634969 PMCID: PMC9251886 DOI: 10.15252/embj.2021108595] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 04/18/2022] [Accepted: 04/29/2022] [Indexed: 11/13/2022] Open
Abstract
Bacteria require a number of systems, including the type VI secretion system (T6SS), for interbacterial competition and pathogenesis. The T6SS is a large nanomachine that can deliver toxins directly across membranes of proximal target cells. Since major reassembly of T6SS is necessary after each secretion event, accurate timing and localization of T6SS assembly can lower the cost of protein translocation. Although critically important, mechanisms underlying spatiotemporal regulation of T6SS assembly remain poorly understood. Here, we used super‐resolution live‐cell imaging to show that while Acinetobacter and Burkholderia thailandensis can assemble T6SS at any site, a significant subset of T6SS assemblies localizes precisely to the site of contact between neighboring bacteria. We identified a class of diverse, previously uncharacterized, periplasmic proteins required for this dynamic localization of T6SS to cell–cell contact (TslA). This precise localization is also dependent on the outer membrane porin OmpA. Our analysis links transmembrane communication to accurate timing and localization of T6SS assembly as well as uncovers a pathway allowing bacterial cells to respond to cell–cell contact during interbacterial competition.
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Affiliation(s)
- Lin Lin
- Biozentrum University of Basel Basel Switzerland
| | | | - Alexia Ferrand
- Biozentrum Imaging Core Facility University of Basel Basel Switzerland
| | - Miro Plum
- Biozentrum University of Basel Basel Switzerland
| | | | - Marek Basler
- Biozentrum University of Basel Basel Switzerland
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18
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Vo JL, Ortiz GCM, Totsika M, Lo AW, Hancock SJ, Whitten AE, Hor L, Peters KM, Ageorges V, Caccia N, Desvaux M, Schembri MA, Paxman JJ, Heras B. Variation of Antigen 43 self-association modulates bacterial compacting within aggregates and biofilms. NPJ Biofilms Microbiomes 2022; 8:20. [PMID: 35396507 PMCID: PMC8993888 DOI: 10.1038/s41522-022-00284-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 03/03/2022] [Indexed: 12/13/2022] Open
Abstract
The formation of aggregates and biofilms enhances bacterial colonisation and infection progression by affording protection from antibiotics and host immune factors. Despite these advantages there is a trade-off, whereby bacterial dissemination is reduced. As such, biofilm development needs to be controlled to suit adaptation to different environments. Here we investigate members from one of largest groups of bacterial adhesins, the autotransporters, for their critical role in the assembly of bacterial aggregates and biofilms. We describe the structural and functional characterisation of autotransporter Ag43 variants from different Escherichia coli pathotypes. We show that specific interactions between amino acids on the contacting interfaces of adjacent Ag43 proteins drives a common mode of trans-association that leads to cell clumping. Furthermore, subtle variation of these interactions alters aggregation kinetics and the degree of compacting within cell clusters. Together, our structure–function investigation reveals an underlying molecular basis for variations in the density of bacterial communities.
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Affiliation(s)
- Julieanne L Vo
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia
| | - Gabriela C Martínez Ortiz
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia
| | - Makrina Totsika
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Herston, QLD, 4006, Australia
| | - Alvin W Lo
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Steven J Hancock
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Andrew E Whitten
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, 2234, Australia
| | - Lilian Hor
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia
| | - Kate M Peters
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia
| | - Valentin Ageorges
- Université Clermont Auvergne, INRAE, UMR454 MEDiS, 63000, Clermont-Ferrand, France
| | - Nelly Caccia
- Université Clermont Auvergne, INRAE, UMR454 MEDiS, 63000, Clermont-Ferrand, France
| | - Mickaël Desvaux
- Université Clermont Auvergne, INRAE, UMR454 MEDiS, 63000, Clermont-Ferrand, France
| | - Mark A Schembri
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD, 4072, Australia.
| | - Jason J Paxman
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia.
| | - Begoña Heras
- Department of Biochemistry and Chemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, VIC, 3086, Australia.
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19
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Interaction of childhood abuse and depressive symptoms on cortical thickness: a general population study. Eur Arch Psychiatry Clin Neurosci 2022; 272:1523-1534. [PMID: 35217912 PMCID: PMC9653317 DOI: 10.1007/s00406-022-01387-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Accepted: 02/01/2022] [Indexed: 11/29/2022]
Abstract
Childhood abuse was inconsistently related to whole-brain cortical thickness in former studies. However, both childhood abuse and cortical thickness have been associated with depressive symptoms. We hypothesised that childhood abuse moderates the association between depressive symptoms and cortical thickness. In 1551 individuals of the general population, associations between whole-brain cortical thickness and the interaction of childhood abuse (emotional, physical, and sexual) and depressive symptoms were analysed using an ANCOVA. Linear regression analyses were used to estimate the same effect on the cortical thickness of 34 separate regions (Desikan-Killiany-atlas). A significant interaction effect of childhood abuse and depressive symptoms was observed for whole-brain cortical thickness (F(2, 1534) = 5.28, p = 0.007). A thinner cortex was associated with depressive symptoms in abused (t value = 2.78, p = 0.025) but not in non-abused participants (t value = - 1.50, p = 0.224). Focussing on non-depressed participants, a thicker whole-brain cortex was found in abused compared to non-abused participants (t value = - 2.79, p = 0.025). Similar interaction effects were observed in 12 out of 34 cortical regions. Our results suggest that childhood abuse is associated with reduced cortical thickness in subjects with depressive symptoms. In abused subjects without depressive symptoms, larger cortical thickness might act compensatory and thus reflect resilience against depressive symptoms.
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20
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Xue Z, Pang Y, Quan S. Revisiting the functions of periplasmic chaperones in the quality control of the autotransporter Ag43 using a phenotypically homogeneous Escherichia coli strain. Biochem Biophys Res Commun 2021; 591:37-43. [PMID: 34995984 DOI: 10.1016/j.bbrc.2021.12.110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 12/28/2021] [Indexed: 11/02/2022]
Abstract
Antigen 43 is a surface-displayed autotransporter protein that mediates bacterial self-association and pathogenicity. The quality control factors that facilitate Ag43 crossing the periplasm and inserting into the outer membrane remain enigmatic, mostly because Ag43 is phase variable and associated with heterologous phenotypes, which obscures the mutational effects of potential quality control factors. Here, we describe a screening method that allowed us to isolate a subpopulation of Escherichia coli that consistently displays an Ag43-mediated autoaggregation phenotype. Based on this subpopulation, we analyzed how disruptions of known periplasmic chaperones affect Ag43 biogenesis. We found that only the disruption of surA reduced Ag43 levels and abolished the autoaggregation phenotype of cells, but surA disruption did not affect the phase-variable expression of agn43. Using purified proteins, we showed that SurA effectively protected the β-barrel domain of Ag43 from aggregation. In contrast, the previously reported Ag43 biogenesis factor OsmY showed weak chaperoning effects on Ag43 only in the absence of SurA. Our results shed light on the roles of different periplasmic chaperones in Ag43 biogenesis and provide a methodology applicable to the study of other phase-variable proteins.
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Affiliation(s)
- Zixiao Xue
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai, 200237, China
| | - Yonghao Pang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai, 200237, China
| | - Shu Quan
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai, 200237, China; Shanghai Frontiers Science Center of Optogenetic Techniques for Cell Metabolism, Shanghai, 200237, China.
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21
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Yasmeen N, Etienne M, Sharma PS, El-Kirat-Chatel S, Helú MB, Kutner W. Molecularly imprinted polymer as a synthetic receptor mimic for capacitive impedimetric selective recognition of Escherichia coli K-12. Anal Chim Acta 2021; 1188:339177. [PMID: 34794582 DOI: 10.1016/j.aca.2021.339177] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 10/02/2021] [Accepted: 10/13/2021] [Indexed: 11/28/2022]
Abstract
We fabricated an electrochemical molecularly imprinted polymer (MIP) chemosensor for rapid identification and quantification of E. coli strain using 2-aminophenyl boronic acid as the functional monomer. This strain is a modified Gram-negative strain of Escherichia coli bacterium, an ordinary human gut component. The E. coli strongly interacts with a boronic acid because of porous and flexible polymers of the cell wall. The SEM imaging showed that the bacteria template was partially entrapped within the polymeric matrix in a single step. Moreover, this imaging confirmed E. coli K-12 cell template extraction effectiveness. The prepared MIP determined the E. coli K-12 strain up to 2.9 × 104 cells mL-1. The interference study performed in the presence of E. coli variants expressing different surface appendages (type 1 fimbriae or Antigen 43 protein) or Shewanella oneidensis MR1, another Gram-negative bacteria, demonstrated that the bacterial surface composition notably impacts sensing properties of the bacteria imprinted polymer.
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Affiliation(s)
- Nabila Yasmeen
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland
| | - Mathieu Etienne
- Université de Lorraine, CNRS, LCPME, F-54000, Nancy, France.
| | - Piyush Sindhu Sharma
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland.
| | | | | | - Wlodzimierz Kutner
- Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224, Warsaw, Poland; Faculty of Mathematics and Natural Sciences, School of Sciences, Institute of Chemical Sciences, Cardinal Stefan Wyszynski University in Warsaw, Wóycickiego 1/3, 01-815, Warsaw, Poland
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22
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Ritzmann N, Manioglu S, Hiller S, Müller DJ. Monitoring the antibiotic darobactin modulating the β-barrel assembly factor BamA. Structure 2021; 30:350-359.e3. [PMID: 34875215 DOI: 10.1016/j.str.2021.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Revised: 10/30/2021] [Accepted: 11/11/2021] [Indexed: 12/15/2022]
Abstract
The β-barrel assembly machinery (BAM) complex is an essential component of Escherichia coli that inserts and folds outer membrane proteins (OMPs). The natural antibiotic compound darobactin inhibits BamA, the central unit of BAM. Here, we employ dynamic single-molecule force spectroscopy (SMFS) to better understand the structure-function relationship of BamA and its inhibition by darobactin. The five N-terminal polypeptide transport (POTRA) domains show low mechanical, kinetic, and energetic stabilities. In contrast, the structural region linking the POTRA domains to the transmembrane β-barrel exposes the highest mechanical stiffness and lowest kinetic stability within BamA, thus indicating a mechano-functional role. Within the β-barrel, the four N-terminal β-hairpins H1-H4 expose the highest mechanical stabilities and stiffnesses, while the four C-terminal β-hairpins H5-H6 show lower stabilities and higher flexibilities. This asymmetry within the β-barrel suggests that substrates funneling into the lateral gate formed by β-hairpins H1 and H8 can force the flexible C-terminal β-hairpins to change conformations.
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Affiliation(s)
- Noah Ritzmann
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Selen Manioglu
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Mattenstrasse 26, 4058 Basel, Switzerland
| | - Sebastian Hiller
- Biozentrum, University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Daniel J Müller
- Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH) Zürich, Mattenstrasse 26, 4058 Basel, Switzerland.
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23
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Dose fractionation as a promising strategy to improve UV disinfection. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2021. [DOI: 10.1016/j.jpap.2021.100034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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24
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Architecture of cell-cell junctions in situ reveals a mechanism for bacterial biofilm inhibition. Proc Natl Acad Sci U S A 2021; 118:2109940118. [PMID: 34321357 PMCID: PMC8346871 DOI: 10.1073/pnas.2109940118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Many bacteria, including the major human pathogen Pseudomonas aeruginosa, are naturally found in multicellular, antibiotic-tolerant biofilm communities, in which cells are embedded in an extracellular matrix of polymeric molecules. Cell-cell interactions within P. aeruginosa biofilms are mediated by CdrA, a large, membrane-associated adhesin present in the extracellular matrix of biofilms, regulated by the cytoplasmic concentration of cyclic diguanylate. Here, using electron cryotomography of focused ion beam-milled specimens, we report the architecture of CdrA molecules in the extracellular matrix of P. aeruginosa biofilms at intact cell-cell junctions. Combining our in situ observations at cell-cell junctions with biochemistry, native mass spectrometry, and cellular imaging, we demonstrate that CdrA forms an extended structure that projects from the outer membrane to tether cells together via polysaccharide binding partners. We go on to show the functional importance of CdrA using custom single-domain antibody (nanobody) binders. Nanobodies targeting the tip of functional cell-surface CdrA molecules could be used to inhibit bacterial biofilm formation or disrupt preexisting biofilms in conjunction with bactericidal antibiotics. These results reveal a functional mechanism for cell-cell interactions within bacterial biofilms and highlight the promise of using inhibitors targeting biofilm cell-cell junctions to prevent or treat problematic, chronic bacterial infections.
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25
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Nwoko ESQA, Okeke IN. Bacteria autoaggregation: how and why bacteria stick together. Biochem Soc Trans 2021; 49:1147-1157. [PMID: 34110370 PMCID: PMC8286834 DOI: 10.1042/bst20200718] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/02/2021] [Accepted: 05/12/2021] [Indexed: 12/16/2022]
Abstract
Autoaggregation, adherence between identical bacterial cells, is important for colonization, kin and kind recognition, and survival of bacteria. It is directly mediated by specific interactions between proteins or organelles on the surfaces of interacting cells or indirectly by the presence of secreted macromolecules such as eDNA and exopolysaccharides. Some autoaggregation effectors are self-associating and present interesting paradigms for protein interaction. Autoaggregation can be beneficial or deleterious at specific times and niches. It is, therefore, typically regulated through transcriptional or post-transcriptional mechanisms or epigenetically by phase variation. Autoaggregation can contribute to bacterial adherence, biofilm formation or other higher-level functions. However, autoaggregation is only required for these phenotypes in some bacteria. Thus, autoaggregation should be detected, studied and measured independently using both qualitative and quantitative in vitro and ex vivo methods. If better understood, autoaggregation holds the potential for the discovery of new therapeutic targets that could be cost-effectively exploited.
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Affiliation(s)
- El-shama Q. A. Nwoko
- Department of Pharmaceutical Microbiology, Faculty of Pharmacy, University of Ibadan, Ibadan, Oyo State, Nigeria
| | - Iruka N. Okeke
- Department of Pharmaceutical Microbiology, Faculty of Pharmacy, University of Ibadan, Ibadan, Oyo State, Nigeria
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van Gestel J, Wagner A. Cryptic surface-associated multicellularity emerges through cell adhesion and its regulation. PLoS Biol 2021; 19:e3001250. [PMID: 33983920 PMCID: PMC8148357 DOI: 10.1371/journal.pbio.3001250] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Revised: 05/25/2021] [Accepted: 04/28/2021] [Indexed: 12/20/2022] Open
Abstract
The repeated evolution of multicellularity led to a wide diversity of organisms, many of which are sessile, including land plants, many fungi, and colonial animals. Sessile organisms adhere to a surface for most of their lives, where they grow and compete for space. Despite the prevalence of surface-associated multicellularity, little is known about its evolutionary origin. Here, we introduce a novel theoretical approach, based on spatial lineage tracking of cells, to study this origin. We show that multicellularity can rapidly evolve from two widespread cellular properties: cell adhesion and the regulatory control of adhesion. By evolving adhesion, cells attach to a surface, where they spontaneously give rise to primitive cell collectives that differ in size, life span, and mode of propagation. Selection in favor of large collectives increases the fraction of adhesive cells until a surface becomes fully occupied. Through kin recognition, collectives then evolve a central-peripheral polarity in cell adhesion that supports a division of labor between cells and profoundly impacts growth. Despite this spatial organization, nascent collectives remain cryptic, lack well-defined boundaries, and would require experimental lineage tracking technologies for their identification. Our results suggest that cryptic multicellularity could readily evolve and originate well before multicellular individuals become morphologically evident.
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Affiliation(s)
- Jordi van Gestel
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, Zürich, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Andreas Wagner
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, Zürich, Switzerland
- Swiss Institute of Bioinformatics, Lausanne, Switzerland
- The Santa Fe Institute, Santa Fe, New Mexico, United States of America
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Determination of the Role of Fusobacterium Nucleatum in the Pathogenesis in and Out the Mouth. ACTA ACUST UNITED AC 2021; 41:87-99. [PMID: 32573481 DOI: 10.2478/prilozi-2020-0026] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
INTRODUCTION One of the most important types of microorganisms in the oral cavity in both healthy and non-healthy individuals is Fusobacterium nucleatum. Although present as a normal resident in the oral cavity, this Gram-negative pathogen is dominant in periodontal disease and it is involved in many invasive infections in the population, acute and chronic inflammatory conditions, as well as many adverse events with a fatal outcome. AIM To determine the role of F. nucleatum in the development of polymicrobial biofilms thus pathogenic changes in and out of the oral media. MATERIAL AND METHOD A systematic review of the literature concerning the determination and role of F. nucleatum through available clinical trials, literature reviews, original research and articles published electronically at Pub Med and Google Scholar. CONCLUSION The presence of Fusobacterium nucleatum is commonly associated with the health status of individuals. These anaerobic bacteria plays a key role in oral pathological conditions and has been detected in many systemic disorders causing complex pathogenethic changes probably due to binding ability to various cells thus several virulence mechanisms. Most common diseases and conditions in the oral cavity associated with F.nucleatum are gingivitis (G), chronic periodontitis (CH), aggressive periodontitis (AgP), endo-periodental infections (E-P), chronic apical periodontitis (PCHA). The bacterium has been identified and detected in many systemic disorders such as coronary heart disease (CVD) pathological pregnancy (P); polycystic ovary syndrome (PCOS), high-risk pregnancy (HRP), colorectal cancer (CRC); pre-eclampsia (PE); rheumatoid arthritis (RA); osteoarthritis (OA).
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28
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Liu C, Zhang R. Identification of novel adhesive proteins in pearl oyster by proteomic and bioinformatic analysis. BIOFOULING 2021; 37:299-308. [PMID: 33761798 DOI: 10.1080/08927014.2021.1901890] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 03/06/2021] [Accepted: 03/07/2021] [Indexed: 06/12/2023]
Abstract
Byssuses, which are proteinaceous fibers secreted by mollusks, are remarkable underwater adhesives. Although mussel adhesives are well known, much less is known about the byssal proteins of pearl oysters especially in the adhesive regions. In this study, adhesive proteins from the pearl oyster Pinctada fucata were studied in depth by transcriptomics and proteomics approaches. In total, 16 novel proteins were identified including a von Willebrand factor type A domain-containing protein, a thrombospondin-1-like protein, tyrosinase, mucin-like proteins, protease inhibitors, and Pinctada unannotated foot protein 3 (PUF3) to PUF6. Interestingly, PUF3-6 are enriched with glycine, serine, and PXG (X = F/Y/W/K/L) motifs and are highly expressed in the foot. The identification of byssal proteins of the pearl oyster is a key step for understanding byssus formation and may inspire the synthesis of novel adhesives for underwater use and the development of anti-biofouling strategies.
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Affiliation(s)
- Chuang Liu
- Ministry of Education Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing, China
- College of Oceanography, Hohai University, Nanjing, China
| | - Rongqing Zhang
- Ministry of Education Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing, China
- Zhejiang Provincial Key Laboratory of Applied Enzymology, Yangtze Delta Region Institute of Tsinghua University, Jiaxing, China
- College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, China
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29
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Ageorges V, Monteiro R, Leroy S, Burgess CM, Pizza M, Chaucheyras-Durand F, Desvaux M. Molecular determinants of surface colonisation in diarrhoeagenic Escherichia coli (DEC): from bacterial adhesion to biofilm formation. FEMS Microbiol Rev 2021; 44:314-350. [PMID: 32239203 DOI: 10.1093/femsre/fuaa008] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 03/31/2020] [Indexed: 12/11/2022] Open
Abstract
Escherichia coli is primarily known as a commensal colonising the gastrointestinal tract of infants very early in life but some strains being responsible for diarrhoea, which can be especially severe in young children. Intestinal pathogenic E. coli include six pathotypes of diarrhoeagenic E. coli (DEC), namely, the (i) enterotoxigenic E. coli, (ii) enteroaggregative E. coli, (iii) enteropathogenic E. coli, (iv) enterohemorragic E. coli, (v) enteroinvasive E. coli and (vi) diffusely adherent E. coli. Prior to human infection, DEC can be found in natural environments, animal reservoirs, food processing environments and contaminated food matrices. From an ecophysiological point of view, DEC thus deal with very different biotopes and biocoenoses all along the food chain. In this context, this review focuses on the wide range of surface molecular determinants acting as surface colonisation factors (SCFs) in DEC. In the first instance, SCFs can be broadly discriminated into (i) extracellular polysaccharides, (ii) extracellular DNA and (iii) surface proteins. Surface proteins constitute the most diverse group of SCFs broadly discriminated into (i) monomeric SCFs, such as autotransporter (AT) adhesins, inverted ATs, heat-resistant agglutinins or some moonlighting proteins, (ii) oligomeric SCFs, namely, the trimeric ATs and (iii) supramolecular SCFs, including flagella and numerous pili, e.g. the injectisome, type 4 pili, curli chaperone-usher pili or conjugative pili. This review also details the gene regulatory network of these numerous SCFs at the various stages as it occurs from pre-transcriptional to post-translocational levels, which remains to be fully elucidated in many cases.
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Affiliation(s)
- Valentin Ageorges
- Université Clermont Auvergne, INRAE, MEDiS, F-63000 Clermont-Ferrand, France
| | - Ricardo Monteiro
- Université Clermont Auvergne, INRAE, MEDiS, F-63000 Clermont-Ferrand, France.,GSK, Via Fiorentina 1, 53100 Siena, Italy
| | - Sabine Leroy
- Université Clermont Auvergne, INRAE, MEDiS, F-63000 Clermont-Ferrand, France
| | - Catherine M Burgess
- Food Safety Department, Teagasc Food Research Centre, Ashtown, Dublin 15, Ireland
| | | | - Frédérique Chaucheyras-Durand
- Université Clermont Auvergne, INRAE, MEDiS, F-63000 Clermont-Ferrand, France.,Lallemand Animal Nutrition SAS, F-31702 Blagnac Cedex, France
| | - Mickaël Desvaux
- Université Clermont Auvergne, INRAE, MEDiS, F-63000 Clermont-Ferrand, France
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Chen X, Ding Y, Bamert RS, Le Brun AP, Duff AP, Wu CM, Hsu HY, Shiota T, Lithgow T, Shen HH. Substrate-dependent arrangements of the subunits of the BAM complex determined by neutron reflectometry. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183587. [PMID: 33639106 DOI: 10.1016/j.bbamem.2021.183587] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 02/09/2021] [Accepted: 02/17/2021] [Indexed: 12/22/2022]
Abstract
In Gram-negative bacteria, the β-barrel assembly machinery (BAM) complex catalyses the assembly of β-barrel proteins into the outer membrane, and is composed of five subunits: BamA, BamB, BamC, BamD and BamE. Once assembled, - β-barrel proteins can be involved in various functions including uptake of nutrients, export of toxins and mediating host-pathogen interactions, but the precise mechanism by which these ubiquitous and often essential β-barrel proteins are assembled is yet to be established. In order to determine the relative positions of BAM subunits in the membrane environment we reconstituted each subunit into a biomimetic membrane, characterizing their interaction and structural changes by Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) and neutron reflectometry. Our results suggested that the binding of BamE, or a BamDE dimer, to BamA induced conformational changes in the polypeptide transported-associated (POTRA) domains of BamA, but that BamB or BamD alone did not promote any such changes. As monitored by neutron reflectometry, addition of an unfolded substrate protein extended the length of POTRA domains further away from the membrane interface as part of the mechanism whereby the substrate protein was folded into the membrane.
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Affiliation(s)
- Xiaoyu Chen
- Department of Materials Science & Engineering, Monash University, Clayton, VIC 3800, Australia
| | - Yue Ding
- Department of Materials Science & Engineering, Monash University, Clayton, VIC 3800, Australia; Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC 3800, Australia
| | - Rebecca S Bamert
- Infection & Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia
| | - Anton P Le Brun
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234, Australia
| | - Anthony P Duff
- National Deuteration Facility, Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234, Australia
| | - Chun-Ming Wu
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234, Australia; National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Hsien-Yi Hsu
- School of Energy and Environment & Department of Materials Science and Engineering, City University of Hong Kong, Kowloon Tong, Hong Kong, PR China; Shenzhen Research Institute of City University of Hong Kong, Shenzhen 518057, PR China
| | - Takuya Shiota
- Institute for Tenure Track Promotion, Organization for Promotion of Career Management, University of Miyazaki, Miyazaki, Japan
| | - Trevor Lithgow
- Infection & Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, VIC 3800, Australia.
| | - Hsin-Hui Shen
- Department of Materials Science & Engineering, Monash University, Clayton, VIC 3800, Australia; Biomedicine Discovery Institute and Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC 3800, Australia.
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Liu J, Wu P, Wang F, Niu W, Ahmed Z, Chen M, Lu G, Dang Z. Differential regulation and the underlying mechanisms of clay minerals to Escherichia coli under the stress of polymyxin B: Comparing halloysite with kaolinite. CHEMOSPHERE 2021; 265:129095. [PMID: 33302200 DOI: 10.1016/j.chemosphere.2020.129095] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 11/21/2020] [Accepted: 11/23/2020] [Indexed: 06/12/2023]
Abstract
The reuse of polymyxin B (PMB) has attracted extensive attention. Although the resistance mechanism to PMB is clear, there are few reports on the regulation mechanisms and effects of clay minerals on bacteria induced by PMB. The focus of this study is to investigate the multidrug resistance, cell morphology and physiological modification of Escherichia coli (E. coli) exposed to PMB in the presence and absence of clay minerals. To be specific, E. coli was cultured serially for 15 days in the increasing concentration of PMB, with or without halloysite or kaolinite. The potential influence mechanisms of halloysite and kaolinite on E. coli was analyzed by proteomics, antibiotic resistance testing, confocal laser scanning microscopy, scanning electron microscopy and Fourier transform infrared. The results showed that kaolinite could obviously promote the growth of bacteria. Moreover, compared with halloysite, kaolinite could stimulate the overexpression of PMB resistance-related proteins ArnA, ArnB and EptA in E. coli exposed to PMB, and promote the synthesis of peptidoglycan and activate glycolysis pathway to produce energy. In contrast, halloysite was able to regulate the production of low molecular weight thiols by E. coli to prevent bacteria from producing excessive reactive oxygen species, activate the oxidative phosphorylation pathway to supply energy for bacterial life activities, and reduce multidrug resistance of E. coli in a variety of ways. These findings are essential for exploring the impacts of clay minerals on the emergence and spread of multi-drug resistant strains in the environment.
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Affiliation(s)
- Juan Liu
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China
| | - Pingxiao Wu
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou, 510006, PR China; Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, Guangzhou, 510006, PR China; Guangdong Engineering and Technology Research Center for Environmental Nanomaterials, Guangzhou, 510006, PR China; Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal, Guangzhou, 510006, PR China.
| | - Fang Wang
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China
| | - Wenchao Niu
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China
| | - Zubair Ahmed
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China
| | - Meiqing Chen
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China
| | - Guining Lu
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China
| | - Zhi Dang
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, PR China
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32
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Martínez-García E, Fraile S, Rodríguez Espeso D, Vecchietti D, Bertoni G, de Lorenzo V. Naked Bacterium: Emerging Properties of a Surfome-Streamlined Pseudomonas putida Strain. ACS Synth Biol 2020; 9:2477-2492. [PMID: 32786355 DOI: 10.1021/acssynbio.0c00272] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Environmental bacteria are most often endowed with native surface-attachment programs that frequently conflict with efforts to engineer biofilms and synthetic communities with given tridimensional architectures. In this work, we report the editing of the genome of Pseudomonas putida KT2440 for stripping the cells of most outer-facing structures of the bacterial envelope that mediate motion, binding to surfaces, and biofilm formation. To this end, 23 segments of the P. putida chromosome encoding a suite of such functions were deleted, resulting in the surface-naked strain EM371, the physical properties of which changed dramatically in respect to the wild type counterpart. As a consequence, surface-edited P. putida cells were unable to form biofilms on solid supports and, because of the swimming deficiency and other alterations, showed a much faster sedimentation in liquid media. Surface-naked bacteria were then used as carriers of interacting partners (e.g., Jun-Fos domains) ectopically expressed by means of an autotransporter display system on the now easily accessible cell envelope. Abstraction of individual bacteria as adhesin-coated spherocylinders enabled rigorous quantitative description of the multicell interplay brought about by thereby engineered physical interactions. The model was then applied to parametrize the data extracted from automated analysis of confocal microscopy images of the experimentally assembled bacterial flocks for analyzing their structure and distribution. The resulting data not only corroborated the value of P. putida EM371 over the parental strain as a platform for display artificial adhesins but also provided a strategy for rational engineering of catalytic communities.
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Affiliation(s)
- Esteban Martínez-García
- Systems Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Sofía Fraile
- Systems Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
| | - David Rodríguez Espeso
- Systems Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
| | - Davide Vecchietti
- Department of Biosciences, Università degli Studi di Milano, 20133 Milan, Italy
| | - Giovanni Bertoni
- Department of Biosciences, Università degli Studi di Milano, 20133 Milan, Italy
| | - Víctor de Lorenzo
- Systems Biology Program, Centro Nacional de Biotecnología (CNB-CSIC), Campus de Cantoblanco, 28049 Madrid, Spain
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Muhammad MH, Idris AL, Fan X, Guo Y, Yu Y, Jin X, Qiu J, Guan X, Huang T. Beyond Risk: Bacterial Biofilms and Their Regulating Approaches. Front Microbiol 2020; 11:928. [PMID: 32508772 PMCID: PMC7253578 DOI: 10.3389/fmicb.2020.00928] [Citation(s) in RCA: 270] [Impact Index Per Article: 67.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 04/20/2020] [Indexed: 12/24/2022] Open
Abstract
Bacterial biofilms are complex surface attached communities of bacteria held together by self-produced polymer matrixs mainly composed of polysaccharides, secreted proteins, and extracellular DNAs. Bacterial biofilm formation is a complex process and can be described in five main phases: (i) reversible attachment phase, where bacteria non-specifically attach to surfaces; (ii) irreversible attachment phase, which involves interaction between bacterial cells and a surface using bacterial adhesins such as fimbriae and lipopolysaccharide (LPS); (iii) production of extracellular polymeric substances (EPS) by the resident bacterial cells; (iv) biofilm maturation phase, in which bacterial cells synthesize and release signaling molecules to sense the presence of each other, conducing to the formation of microcolony and maturation of biofilms; and (v) dispersal/detachment phase, where the bacterial cells depart biofilms and comeback to independent planktonic lifestyle. Biofilm formation is detrimental in healthcare, drinking water distribution systems, food, and marine industries, etc. As a result, current studies have been focused toward control and prevention of biofilms. In an effort to get rid of harmful biofilms, various techniques and approaches have been employed that interfere with bacterial attachment, bacterial communication systems (quorum sensing, QS), and biofilm matrixs. Biofilms, however, also offer beneficial roles in a variety of fields including applications in plant protection, bioremediation, wastewater treatment, and corrosion inhibition amongst others. Development of beneficial biofilms can be promoted through manipulation of adhesion surfaces, QS and environmental conditions. This review describes the events involved in bacterial biofilm formation, lists the negative and positive aspects associated with bacterial biofilms, elaborates the main strategies currently used to regulate establishment of harmful bacterial biofilms as well as certain strategies employed to encourage formation of beneficial bacterial biofilms, and highlights the future perspectives of bacterial biofilms.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Tianpei Huang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops & Key Laboratory of Biopesticide and Chemical Biology of Ministry of Education, College of Life Sciences & College of Plant Protection & International College, Fujian Agriculture and Forestry University, Fuzhou, China
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34
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Montero DA, Del Canto F, Salazar JC, Céspedes S, Cádiz L, Arenas-Salinas M, Reyes J, Oñate Á, Vidal RM. Immunization of mice with chimeric antigens displaying selected epitopes confers protection against intestinal colonization and renal damage caused by Shiga toxin-producing Escherichia coli. NPJ Vaccines 2020; 5:20. [PMID: 32194997 PMCID: PMC7067774 DOI: 10.1038/s41541-020-0168-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 02/14/2020] [Indexed: 12/14/2022] Open
Abstract
Shiga toxin-producing Escherichia coli (STEC) cause diarrhea and dysentery, which may progress to hemolytic uremic syndrome (HUS). Vaccination has been proposed as a preventive approach against STEC infection; however, there is no vaccine for humans and those used in animals reduce but do not eliminate the intestinal colonization of STEC. The OmpT, Cah and Hes proteins are widely distributed among clinical STEC strains and are recognized by serum IgG and IgA in patients with HUS. Here, we develop a vaccine formulation based on two chimeric antigens containing epitopes of OmpT, Cah and Hes proteins against STEC strains. Intramuscular and intranasal immunization of mice with these chimeric antigens elicited systemic and local long-lasting humoral responses. However, the class of antibodies generated was dependent on the adjuvant and the route of administration. Moreover, while intramuscular immunization with the combination of the chimeric antigens conferred protection against colonization by STEC O157:H7, the intranasal conferred protection against renal damage caused by STEC O91:H21. This preclinical study supports the potential use of this formulation based on recombinant chimeric proteins as a preventive strategy against STEC infections.
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Affiliation(s)
- David A Montero
- 1Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,2Programa Disciplinario de Inmunología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Felipe Del Canto
- 1Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Juan C Salazar
- 1Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Sandra Céspedes
- 1Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Leandro Cádiz
- 1Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Mauricio Arenas-Salinas
- 3Centro de Bioinformática y Simulación Molecular, Facultad de Ingeniería, Universidad de Talca, Talca, Chile
| | - José Reyes
- 4Departamento de Microbiología, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Ángel Oñate
- 4Departamento de Microbiología, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Roberto M Vidal
- 1Programa de Microbiología y Micología, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.,5Instituto Milenio de Inmunología e Inmunoterapia, Facultad de Medicina, Universidad de Chile, Santiago, Chile
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Abstract
Urinary tract infections (UTIs) cause a substantial health care burden. UTIs (i) are most often caused by uropathogenic Escherichia coli (UPEC), (ii) primarily affect otherwise healthy females (50% of women will have a UTI), (iii) are associated with significant morbidity and economic impact, (iv) can become chronic, and (v) are highly recurrent. A history of UTI is a significant risk factor for a recurrent UTI (rUTI). In otherwise healthy women, an acute UTI leads to a 25 to 50% chance of rUTI within months of the initial infection. Interestingly, rUTIs are commonly caused by the same strain of E. coli that led to the initial infection, arguing that there exist host-associated reservoirs, like the gastrointestinal tract and underlying bladder tissue, that can seed rUTIs. Additionally, catheter-associated UTIs (CAUTI), caused by Enterococcus and Staphylococcus as well as UPEC, represent a major health care concern. The host's response of depositing fibrinogen at the site of infection has been found to be critical to establishing CAUTI. The Drug Resistance Index, an evaluation of antibiotic resistance, indicates that UTIs have become increasingly difficult to treat since the mid-2000s. Thus, UTIs are a "canary in the coal mine," warning of the possibility of a return to the preantibiotic era, where some common infections are untreatable with available antibiotics. Numerous alternative strategies for both the prevention and treatment of UTIs are being pursued, with a focus on the development of vaccines and small-molecule inhibitors targeting virulence factors, in the hopes of reducing the burden of urogenital tract infections in an antibiotic-sparing manner.
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The virulence domain of Shigella IcsA contains a subregion with specific host cell adhesion function. PLoS One 2020; 15:e0227425. [PMID: 31910229 PMCID: PMC6946128 DOI: 10.1371/journal.pone.0227425] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 12/18/2019] [Indexed: 02/08/2023] Open
Abstract
Shigella species cause bacillary dysentery, especially among young individuals. Shigellae target the human colon for invasion; however, the initial adhesion mechanism is poorly understood. The Shigella surface protein IcsA, in addition to its role in actin-based motility, acts as a host cell adhesin through unknown mechanism(s). Here we confirmed the role of IcsA in cell adhesion and defined the region required for IcsA adhesin activity. Purified IcsA passenger domain was able block S. flexneri adherence and was also used as a molecular probe that recognised multiple components from host cells. The region within IcsA's functional passenger domain (aa 138-148) was identified by mutagenesis. Upon the deletion of this region, the purified IcsAΔ138-148 was found to no longer block S. flexneri adherence and had reduced ability to interact with host molecules. Furthermore, S. flexneri expressing IcsAΔ138-148 was found to be significantly defective in both cell adherence and invasion. Taken together, our data identify an adherence region within the IcsA functional domain and provides useful information for designing therapeutics for Shigella infection.
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Unusual Metabolism and Hypervariation in the Genome of a Gracilibacterium (BD1-5) from an Oil-Degrading Community. mBio 2019; 10:mBio.02128-19. [PMID: 31719174 PMCID: PMC6851277 DOI: 10.1128/mbio.02128-19] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
CPR bacteria are generally predicted to be symbionts due to their extensive biosynthetic deficits. Although monophyletic, they are not monolithic in terms of their lifestyles. The organism described here appears to have evolved an unusual metabolic platform not reliant on glucose or pentose sugars. Its biology appears to be centered around bacterial host-derived compounds and/or cell detritus. Amino acids likely provide building blocks for nucleic acids, peptidoglycan, and protein synthesis. We resolved an unusual repeat region that would be invisible without genome curation. The nucleotide sequence is apparently under strong diversifying selection, but the amino acid sequence is under stabilizing selection. The amino acid repeat also occurs in a surface protein of a coexisting bacterium, suggesting colocation and possibly interdependence. The candidate phyla radiation (CPR) comprises a large monophyletic group of bacterial lineages known almost exclusively based on genomes obtained using cultivation-independent methods. Within the CPR, Gracilibacteria (BD1-5) are particularly poorly understood due to undersampling and the inherent fragmented nature of available genomes. Here, we report the first closed, curated genome of a gracilibacterium from an enrichment experiment inoculated from the Gulf of Mexico and designed to investigate hydrocarbon degradation. The gracilibacterium rose in abundance after the community switched to dominance by Colwellia. Notably, we predict that this gracilibacterium completely lacks glycolysis, the pentose phosphate and Entner-Doudoroff pathways. It appears to acquire pyruvate, acetyl coenzyme A (acetyl-CoA), and oxaloacetate via degradation of externally derived citrate, malate, and amino acids and may use compound interconversion and oxidoreductases to generate and recycle reductive power. The initial genome assembly was fragmented in an unusual gene that is hypervariable within a repeat region. Such extreme local variation is rare but characteristic of genes that confer traits under pressure to diversify within a population. Notably, the four major repeated 9-mer nucleotide sequences all generate a proline-threonine-aspartic acid (PTD) repeat. The genome of an abundant Colwellia psychrerythraea population has a large extracellular protein that also contains the repeated PTD motif. Although we do not know the host for the BD1-5 cell, the high relative abundance of the C. psychrerythraea population and the shared surface protein repeat may indicate an association between these bacteria.
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Ma X, Wang Q, Li Y, Tan P, Wu H, Wang P, Dong X, Hong L, Meng G. How BamA recruits OMP substrates via poly-POTRAs domain. FASEB J 2019; 33:14690-14702. [PMID: 31702961 DOI: 10.1096/fj.201900681rr] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Almost all the outer membrane proteins (OMPs) fold into an invariant β-barrel fold via the polypeptide-transport-associated (POTRA) motif and β-barrel assembly machinery (BAM). However, whether and how poly-POTRAs interact with OMPs remain largely unknown. Here, we have characterized the structures of Haemophilus influenzae poly-POTRAs via X-ray crystallography, small angle X-ray scattering, and molecular dynamics simulation. Unexpectedly, crystal packing reveals a putative OMP travel pathway spiraled by the conserved α2-β2 edges in poly-POTRAs. Supportively, the structure-based mutations targeting the OMP binding sites significantly disrupt OMP biogenesis, resulting in severe cell growth defects. Another notable feature in H. influenzae POTRA structures is flexibility. As characterized by ELISA assays, poly-POTRAs could recruit OMP substrates in a step-wise manner. More importantly, the restriction of POTRA-POTRA linkage and flexibility significantly impairs the BamA function and causes cell growth defect. Altogether, these results suggest that the β-strand augmentations and intrinsic flexibility are important factors for BamA-OMP recruitment.-Ma, X., Wang, Q., Li, Y., Tan, P., Wu, H., Wang, P., Dong, X., Hong, L., Meng, G. How BamA recruits OMP substrates via poly-POTRAs domain.
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Affiliation(s)
- Xiaodan Ma
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Qianqian Wang
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yuwen Li
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Pan Tan
- School of Physics and Astronomy, Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai, China
| | - Haiyan Wu
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Pengran Wang
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China.,Institute of Translational Medicine, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Xue Dong
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Liang Hong
- School of Physics and Astronomy, Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai, China
| | - Guoyu Meng
- State Key Laboratory of Medical Genomics, Shanghai Institute of Hematology, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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Sequential Translocation of Polypeptides across the Bacterial Outer Membrane through the Trimeric Autotransporter Pathway. mBio 2019; 10:mBio.01973-19. [PMID: 31641085 PMCID: PMC6805991 DOI: 10.1128/mbio.01973-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Trimeric autotransporter adhesins (TAAs) are a family of bacterial outer membrane (OM) proteins that are comprised of three identical subunits. Each subunit contains an N-terminal extracellular ("passenger") domain and a short C-terminal segment that contributes four β strands to a single 12-stranded β barrel. The mechanism by which the passenger domains are translocated across the OM and the energetics of the translocation reaction are poorly understood. To address these issues, we examined the secretion of modified versions of the passenger domain of UpaG, a TAA produced by Escherichia coli CFT073. Using the SpyTag-SpyCatcher system to probe passenger domain localization, we found that both intrinsically disordered polypeptides fused to the UpaG passenger domain and artificially disulfide-bonded polypeptides were secreted effectively but relatively slowly. Surprisingly, we also found that in some cases, the three nonnative passenger domain segments associated with a single trimer were secreted sequentially. Photo-cross-linking experiments indicated that incompletely assembled UpaG derivatives remained bound to the barrel assembly machinery (Bam) complex until all three passenger domains were fully secreted. Taken together, our results strongly suggest that the secretion of polypeptides through the TAA pathway is coordinated with the assembly of the β barrel domain and that the folding of passenger domains in the extracellular space maximizes the rate of secretion. Furthermore, our work provides evidence for an unprecedented sequential mode of protein translocation, at least under specific experimental conditions.IMPORTANCE Trimeric autotransporter adhesins (TAAs) are specialized bacterial outer membrane proteins consisting of three identical subunits. TAAs contain large extracellular domains that trimerize and promote virulence, but the mechanism by which they are secreted is poorly understood. We found that the extracellular domains of a native TAA were secreted rapidly but that disordered and artificially folded polypeptides fused to native passenger domains were secreted in a slow, sequential fashion. Our results strongly suggest that the efficient secretion of native extracellular domains is driven by their trimerization following export but that alternative energy sources can be harnessed to secrete nonnative polypeptides. Furthermore, we obtained evidence that TAA extracellular domains are secreted before the assembly of the linked membrane spanning domain is completed.
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Yan Z, Hussain S, Wang X, Bernstein HD, Bardwell JCA. Chaperone OsmY facilitates the biogenesis of a major family of autotransporters. Mol Microbiol 2019; 112:1373-1387. [PMID: 31369167 DOI: 10.1111/mmi.14358] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/22/2019] [Indexed: 12/26/2022]
Abstract
OsmY is a widely conserved but poorly understood 20 kDa periplasmic protein. Using a folding biosensor, we previously obtained evidence that OsmY has molecular chaperone activity. To discover natural OsmY substrates, we screened for proteins that are destabilized and thus present at lower steady-state levels in an osmY-null strain. The abundance of an outer membrane protein called antigen 43 was substantially decreased and its β-barrel domain was undetectable in the outer membrane of an osmY-null strain. Antigen 43 is a member of the diffuse adherence family of autotransporters. Like strains that are defective in antigen 43 production, osmY-null mutants failed to undergo cellular autoaggregation. In vitro, OsmY assisted in the refolding of the antigen 43 β-barrel domain and protected it from added protease. Finally, an osmY-null strain that expressed two members of the diffuse adherence family of autotransporters that are distantly related to antigen 43, EhaA and TibA, contained reduced levels of the proteins and failed to undergo cellular autoaggregation. Taken together, our results indicate that OsmY is involved in the biogenesis of a major subset of autotransporters, a group of proteins that play key roles in bacterial pathogenesis.
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Affiliation(s)
- Zhen Yan
- Howard Hughes Medical Institute and Department of Molecular, Cellular & Development Biology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Sunyia Hussain
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Xu Wang
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Harris D Bernstein
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, 20892, USA
| | - James C A Bardwell
- Howard Hughes Medical Institute and Department of Molecular, Cellular & Development Biology, University of Michigan, Ann Arbor, MI, 48109, USA
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Miryala S, Makala H, Yadavali SP, Venkatasubramanian U, Subbaiah N, Srinandan CS. Disperse red 15 (DR15) impedes biofilm formation of uropathogenic Escherichia coli. Microb Pathog 2019; 138:103772. [PMID: 31589910 DOI: 10.1016/j.micpath.2019.103772] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 09/27/2019] [Accepted: 09/30/2019] [Indexed: 12/18/2022]
Abstract
Catheter associated urinary tract infection (CAUTI) is a highly prevalent hospital-acquired infection that is predominantly caused by uropathogenic Escherichia coli (UPEC). It adheres on catheter surface using type I pili as the initial step of pathogenesis that progresses to form biofilm. In this study, potential inhibitors against FimH adhesin of type I pili were screened computationally that yielded ten compounds. These were further validated in vitro against adhesion and biofilm formation. The compounds, 1-Amino-4-hydroxyanthraquinone (Disperse Red 15 or DR15) and 4-(4'-chloro-4-biphenylylsulfonylamino) benzoic acid (CB1) impaired adhesion and biofilm formation without inhibiting the planktonic growth. Also, both compounds inhibited cell assemblages like autoaggregation and swarming motility by unknown mechanisms. DR15 was further derivatised into N-(4-hydroxy-9,10-dioxo-9,10-dihydroanthracen-1-yl) undec-10-enamide that self-assembled with linseed oil, which was used as the coating material on urinary Foley catheters. The thin-film coating on the catheter did not leach when incubated in artificial urine and effectively restricted biofilm formation of UPEC. Altogether, the thin-film coating of urinary catheter with DR15 inhibited biofilm formation of UPEC and this application could potentially help to reduce CAUTI incidents in healthcare facilities.
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Affiliation(s)
- Sandeep Miryala
- Biofilm Biology Lab, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | - Himesh Makala
- Molecular Motors Lab, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | - Siva Prasad Yadavali
- Organic Synthesis Lab, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India
| | | | - Nagarajan Subbaiah
- Department of Chemistry, National Institute of Technology, Warangal, Telangana, India
| | - C S Srinandan
- Biofilm Biology Lab, School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, Tamil Nadu, India; Centre for Research in Infectious Diseases, SASTRA Deemed University, Thanjavur, Tamil Nadu, India.
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Abstract
Escherichia coli is one of the most prevalent facultative anaerobes of the human gut. E. coli normally exists as a harmless commensal but can also cause disease following the acquisition of genes that enhance its pathogenicity. Adhesion is an important first step in colonization of the host and is mediated by an array of cell surface components. In E. coli, these include a family of adhesins secreted by the type V secretion system. Here, we identified and characterized new proteins from an emerging subclass of the type V secretion system known as the inverse autotransporters (IATs). We found that IAT-encoding genes are present in a wide range of strains and showed that three novel IATs were localized on the E. coli cell surface and mediated biofilm formation. Overall, this study provides new insight into the prevalence, function, and regulation of IATs in E. coli. Proteins secreted by the type V secretion system possess multiple functions, including the capacity to mediate adhesion, aggregation, and biolfilm formation. The type V secretion system can be divided into five subclasses, one of which is the type Ve system. Proteins of the type Ve secretion system are also referred to as inverse autotransporters (IATs). In this study, we performed an in silico analysis of 126 completely sequenced Escherichia coli genomes available in the NCBI database and identified several distinct IAT-encoding gene families whose distribution varied throughout the E. coli phylogeny. The genes included three characterized IATs (intimin, fdeC, and yeeJ) and four uncharacterized IATs (here named iatA, iatB, iatC, and iatD). The four iat genes were cloned from the completely sequenced environmental E. coli strain SMS-3-5 and characterized. Three of these IAT proteins (IatB, IatC, and IatD) were expressed at the cell surface and possessed the capacity to mediate biofilm formation in a recombinant E. coli K-12 strain. Further analysis of the iatB gene, which showed a unique association with extraintestinal E. coli strains, suggested that its regulation is controlled by the LeuO global regulator. Overall, this study provides new data describing the prevalence, sequence variation, domain structure, function, and regulation of IATs found in E. coli. IMPORTANCEEscherichia coli is one of the most prevalent facultative anaerobes of the human gut. E. coli normally exists as a harmless commensal but can also cause disease following the acquisition of genes that enhance its pathogenicity. Adhesion is an important first step in colonization of the host and is mediated by an array of cell surface components. In E. coli, these include a family of adhesins secreted by the type V secretion system. Here, we identified and characterized new proteins from an emerging subclass of the type V secretion system known as the inverse autotransporters (IATs). We found that IAT-encoding genes are present in a wide range of strains and showed that three novel IATs were localized on the E. coli cell surface and mediated biofilm formation. Overall, this study provides new insight into the prevalence, function, and regulation of IATs in E. coli.
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Evolutionary Perspectives on the Moonlighting Functions of Bacterial Factors That Support Actin-Based Motility. mBio 2019; 10:mBio.01520-19. [PMID: 31455648 PMCID: PMC6712393 DOI: 10.1128/mbio.01520-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Various bacterial pathogens display an intracellular lifestyle and spread from cell to cell through actin-based motility (ABM). ABM requires actin polymerization at the bacterial pole and is mediated by the expression of bacterial factors that hijack the host cell actin nucleation machinery or exhibit intrinsic actin nucleation properties. Various bacterial pathogens display an intracellular lifestyle and spread from cell to cell through actin-based motility (ABM). ABM requires actin polymerization at the bacterial pole and is mediated by the expression of bacterial factors that hijack the host cell actin nucleation machinery or exhibit intrinsic actin nucleation properties. It is increasingly recognized that bacterial ABM factors, in addition to having a crucial task during the intracellular phase of infection, display “moonlighting” adhesin functions, such as bacterial aggregation, biofilm formation, and host cell adhesion/invasion. Here, we review our current knowledge of ABM factors and their additional functions, and we propose that intracellular ABM functions have evolved from ancestral, extracellular adhesin functions.
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Differential homotypic and heterotypic interactions of antigen 43 (Ag43) variants in autotransporter-mediated bacterial autoaggregation. Sci Rep 2019; 9:11100. [PMID: 31367003 PMCID: PMC6668479 DOI: 10.1038/s41598-019-47608-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 06/18/2019] [Indexed: 12/18/2022] Open
Abstract
Antigen 43 (Ag43) is a cell-surface exposed protein of Escherichia coli secreted by the Type V, subtype a, secretion system (T5aSS) and belonging to the family of self-associating autotransporters (SAATs). These modular proteins, comprising a cleavable N-terminal signal peptide, a surface-exposed central passenger and an outer membrane C-terminal translocator, self-recognise in a Velcro-like handshake mechanism. A phylogenetic network analysis focusing on the passenger revealed for the first time that they actually distribute into four distinct classes, namely C1, C2, C3 and C4. Structural alignment and modelling analyses demonstrated these classes arose from shuffling of two different subdomains within the Ag43 passengers. Functional analyses revealed that homotypic interactions occur for all Ag43 classes but significant differences in the sedimentation kinetics and aggregation state were present when Ag43C3 was expressed. In contrast, heterotypic interaction occurred in a very limited number of cases. Single cell-force spectroscopy demonstrated the importance of specific as well as nonspecific interactions in mediating Ag43-Ag43 recognition. We propose that structural differences in the subdomains of the Ag43 classes account for different autoaggregation dynamics and propensities to co-interact.
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45
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Bacterial outer membrane proteins assemble via asymmetric interactions with the BamA β-barrel. Nat Commun 2019; 10:3358. [PMID: 31350400 PMCID: PMC6659671 DOI: 10.1038/s41467-019-11230-9] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 06/28/2019] [Indexed: 11/09/2022] Open
Abstract
The integration of β-barrel proteins into the bacterial outer membrane (OM) is catalysed by the β-barrel assembly machinery (BAM). The central BAM subunit (BamA) itself contains a β-barrel domain that is essential for OM protein biogenesis, but its mechanism of action is unknown. To elucidate its function, here we develop a method to trap a native Escherichia coli β-barrel protein bound stably to BamA at a late stage of assembly in vivo. Using disulfide-bond crosslinking, we find that the first β-strand of a laterally ‘open’ form of the BamA β-barrel forms a rigid interface with the C-terminal β-strand of the substrate. In contrast, the lipid-facing surface of the last two BamA β-strands forms weaker, conformationally heterogeneous interactions with the first β-strand of the substrate that likely represent intermediate assembly states. Based on our results, we propose that BamA promotes the membrane integration of partially folded β-barrels by a ‘swing’ mechanism. The integration of β-barrel proteins into the bacterial outer membrane (OM) is catalysed by the β-barrel assembly machinery (BAM). Here authors develop a method to trap an E. coli β-barrel protein bound stably to BamA at a late stage of assembly in vivo which provides insights BamA mediated membrane integration.
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Paxman JJ, Lo AW, Sullivan MJ, Panjikar S, Kuiper M, Whitten AE, Wang G, Luan CH, Moriel DG, Tan L, Peters KM, Phan MD, Gee CL, Ulett GC, Schembri MA, Heras B. Unique structural features of a bacterial autotransporter adhesin suggest mechanisms for interaction with host macromolecules. Nat Commun 2019; 10:1967. [PMID: 31036849 PMCID: PMC6488583 DOI: 10.1038/s41467-019-09814-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 03/28/2019] [Indexed: 12/31/2022] Open
Abstract
Autotransporters are the largest family of outer membrane and secreted proteins in Gram-negative bacteria. Most autotransporters are localised to the bacterial surface where they promote colonisation of host epithelial surfaces. Here we present the crystal structure of UpaB, an autotransporter that is known to contribute to uropathogenic E. coli (UPEC) colonisation of the urinary tract. We provide evidence that UpaB can interact with glycosaminoglycans and host fibronectin. Unique modifications to its core β-helical structure create a groove on one side of the protein for interaction with glycosaminoglycans, while the opposite face can bind fibronectin. Our findings reveal far greater diversity in the autotransporter β-helix than previously thought, and suggest that this domain can interact with host macromolecules. The relevance of these interactions during infection remains unclear.
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Affiliation(s)
- Jason J Paxman
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, 3086, VIC, Australia
| | - Alvin W Lo
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, 4072, QLD, Australia
| | - Matthew J Sullivan
- School of Medical Science, and Menzies Health Institute Queensland, Griffith University, Gold Coast, 4222, QLD, Australia
| | - Santosh Panjikar
- Macromolecular Crystallography, Australian Synchrotron, Clayton, 3168, VIC, Australia
- Department of Molecular Biology and Biochemistry, Monash University, Melbourne, 3800, VIC, Australia
| | - Michael Kuiper
- Molecular & Materials Modelling group Data61, CSIRO, Docklands, Melbourne, 8012, VIC, Australia
| | - Andrew E Whitten
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, 2234, NSW, Australia
| | - Geqing Wang
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, 3086, VIC, Australia
| | - Chi-Hao Luan
- High Throughput Analysis Laboratory and Department of Molecular Biosciences, Northwestern University, Chicago, 60208, IL, USA
| | - Danilo G Moriel
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, 4072, QLD, Australia
| | - Lendl Tan
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, 4072, QLD, Australia
| | - Kate M Peters
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, 4072, QLD, Australia
| | - Minh-Duy Phan
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, 4072, QLD, Australia
| | - Christine L Gee
- Macromolecular Crystallography, Australian Synchrotron, Clayton, 3168, VIC, Australia
| | - Glen C Ulett
- School of Medical Science, and Menzies Health Institute Queensland, Griffith University, Gold Coast, 4222, QLD, Australia
| | - Mark A Schembri
- School of Chemistry and Molecular Biosciences, and Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, 4072, QLD, Australia.
| | - Begoña Heras
- Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, 3086, VIC, Australia.
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García-Bayona L, Gozzi K, Laub MT. Mechanisms of Resistance to the Contact-Dependent Bacteriocin CdzC/D in Caulobacter crescentus. J Bacteriol 2019; 201:e00538-18. [PMID: 30692171 PMCID: PMC6436349 DOI: 10.1128/jb.00538-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 01/22/2019] [Indexed: 01/02/2023] Open
Abstract
The Cdz bacteriocin system allows the aquatic oligotrophic bacterium Caulobacter crescentus to kill closely related species in a contact-dependent manner. The toxin, which aggregates on the surfaces of producer cells, is composed of two small hydrophobic proteins, CdzC and CdzD, each bearing an extended glycine-zipper motif, that together induce inner membrane depolarization and kill target cells. To further characterize the mechanism of Cdz delivery and toxicity, we screened for mutations that render a target strain resistant to Cdz-mediated killing. These mutations mapped to four loci, including a TonB-dependent receptor, a three-gene operon (named zerRAB for zipper envelope resistance), and perA (for pentapeptide envelope resistance). Mutations in the zerRAB locus led to its overproduction and to potential changes in cell envelope composition, which may diminish the susceptibility of cells to Cdz toxins. The perA gene is also required to maintain a normal cell envelope, but our screen identified mutations that confer resistance to Cdz toxins without substantially affecting the cell envelope functions of PerA. We demonstrate that PerA, which encodes a pentapeptide repeat protein predicted to form a quadrilateral β-helix, localizes primarily to the outer membrane of cells, where it may serve as a receptor for the Cdz toxins. Collectively, these results provide new insights into the function and mechanisms of an atypical, contact-dependent bacteriocin system.IMPORTANCE Bacteriocins are commonly used by bacteria to kill neighboring cells that compete for resources. Although most bacteriocins are secreted, the aquatic, oligotrophic bacterium Caulobacter crescentus produces a two-peptide bacteriocin, CdzC/D, that remains attached to the outer membranes of cells, enabling contact-dependent killing of cells lacking the immunity protein CdzI. The receptor for CdzC/D has not previously been reported. Here, we describe a genetic screen for mutations that confer resistance to CdzC/D. One locus identified, perA, encodes a pentapeptide repeat protein that resides in the outer membrane of target cells, where it may act as the direct receptor for CdzC/D. Collectively, our results provide new insight into bacteriocin function and diversity.
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Affiliation(s)
- Leonor García-Bayona
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Howard Hughes Medical Institute, Cambridge, Massachusetts, USA
- Graduate Program in Microbiology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Kevin Gozzi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Howard Hughes Medical Institute, Cambridge, Massachusetts, USA
- Graduate Program in Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Michael T Laub
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Howard Hughes Medical Institute, Cambridge, Massachusetts, USA
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Yadegari Z, Nikbakht Brujeni G, Ghorbanpour R, Moosakhani F, Lotfollahzadeh S. Molecular characterization of enterotoxigenic Escherichia coli isolated from neonatal calves diarrhea. VETERINARY RESEARCH FORUM : AN INTERNATIONAL QUARTERLY JOURNAL 2019; 10:73-78. [PMID: 31183019 PMCID: PMC6522186 DOI: 10.30466/vrf.2019.34313] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 07/30/2018] [Indexed: 11/29/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) produces different virulence factors allowing the bacterium to colonize and develop watery diarrhea. Proteomics studies have also introduced new protein belonging to the secretion pathways, antigen 43 (Ag43), which plays important role in E. coli pathogenesis. The objective of this study was to investigate O-types and virulence factors of E. coli isolates from neonatal calves diarrhea. Total of 120 isolates from diarrheic calves were genotyped for their O groups and the presence of virulence genes K99, F41 and STa as well as Ag43. The predominant O-type was O101 (51.00%) and the prevalence of K99, F41 and STa was 7 (5.80%). The Ag43 was detected in all samples with three different allelic patterns. Our results indicated that K99 positive isolates certainly have one of each 2200 bp or 1800 bp or both copies of Ag43 passenger domain, while negative K99 isolates lack the Ag43. The results reported here provide informative data regarding the prevalence of E. coli O-types and their virulence factors in enteric colibacillosis. The Ag43 that was more found in K99 positive isolates might be associated with diarrhea-causing E. coli strains in neonatal calves.
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Affiliation(s)
- Zahra Yadegari
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran;
| | - Gholamreza Nikbakht Brujeni
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran;
| | - Reyhaneh Ghorbanpour
- Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran;
| | - Farhad Moosakhani
- Department of Microbiology, Faculty of Veterinary Medicine, Branch of Karaj, Islamic Azad University, Karaj, Iran;
| | - Samad Lotfollahzadeh
- Department of Internal Medicine, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran.
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Fuqua C, Filloux A, Ghigo JM, Visick KL. Biofilms 2018: A diversity of microbes and mechanisms. J Bacteriol 2019; 201:JB.00118-19. [PMID: 30782638 PMCID: PMC6707918 DOI: 10.1128/jb.00118-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The 8th ASM Conference on Biofilms was held in Washington D.C. on October 7-11, 2018. This very highly subscribed meeting represented a wide breadth of current research in biofilms, and included over 500 attendees, 12 sessions with 64 oral presentations, and four poster sessions with about 400 posters.
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Affiliation(s)
- Clay Fuqua
- Department of Biology, Indiana University, Bloomington, Indiana, USA
| | - Alain Filloux
- Department of Life Sciences, MRC Centre for Molecular Bacteriology and Infection, Imperial College, London, United Kingdom
| | - Jean-Marc Ghigo
- Institut Pasteur, Unité de Génétique des Biofilms, Département de Microbiologie, Paris, France
| | - Karen L. Visick
- Department of Microbiology and Immunology, Loyola University Chicago, Maywood, Illinois, USA
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Abstract
Type V, or "autotransporter," secretion is a term used to refer to several simple protein export pathways that are found in a wide range of Gram-negative bacteria. Autotransporters are generally single polypeptides that consist of an extracellular ("passenger") domain and a β barrel domain that anchors the protein to the outer membrane (OM). Although it was originally proposed that the passenger domain is secreted through a channel formed solely by the covalently linked β barrel domain, experiments performed primarily on the type Va, or "classical," autotransporter pathway have challenged this hypothesis. Several lines of evidence strongly suggest that both the secretion of the passenger domain and the membrane integration of the β barrel domain are catalyzed by the barrel assembly machinery (Bam) complex, a conserved hetero-oligomer that plays an essential role in the assembly of most integral OM proteins. The secretion reaction appears to be driven at least in part by the folding of the passenger domain in the extracellular space. Although many aspects of autotransporter biogenesis remain to be elucidated, it will be especially interesting to determine whether the different classes of proteins that fall under the type V rubric-most of which have not been examined in detail-are assembled by the same basic mechanism as classical autotransporters.
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