51
|
Luby E, Ibekwe AM, Zilles J, Pruden A. Molecular Methods for Assessment of Antibiotic Resistance in Agricultural Ecosystems: Prospects and Challenges. JOURNAL OF ENVIRONMENTAL QUALITY 2016; 45:441-453. [PMID: 27065390 DOI: 10.2134/jeq2015.07.0367] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Agricultural ecosystems are of special interest for monitoring the potential for antibiotic resistance to spread through the environment and contribute to human exposure. Molecular methods, which target DNA, RNA, and other molecular components of bacterial cells, present certain advantages for characterizing and quantifying markers of antibiotic resistance and their horizontal gene transfer. These include rapid, unambiguous detection of targets; consistent results; and avoidance of culture bias. However, molecular methods are also subject to limitations that are not always clearly addressed or taken into consideration in the interpretation of scientific data. In particular, DNA-based methods do not directly assess viability or presence within an intact bacterial host, but such information may be inferred based on appropriate experimental design or in concert with complementary methods. The purpose of this review is to provide an overview of existing molecular methods for tracking antibiotic resistance in agricultural ecosystems, to define their strengths and weaknesses, and to recommend a path forward for future applications of molecular methods and standardized reporting in the literature. This will guide research along the farm-to-fork continuum and support comparability of the growing number of studies in the literature in a manner that informs management decisions and policy development.
Collapse
|
52
|
Not so simple, not so subtle: the interspecies competition between Bacillus simplex and Bacillus subtilis and its impact on the evolution of biofilms. NPJ Biofilms Microbiomes 2016; 2:15027. [PMID: 28721238 PMCID: PMC5515258 DOI: 10.1038/npjbiofilms.2015.27] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2015] [Revised: 10/11/2015] [Accepted: 10/16/2015] [Indexed: 01/17/2023] Open
Abstract
Bacillus subtilis biofilms have a fundamental role in shaping the soil ecosystem. During this process, they unavoidably interact with neighbour bacterial species. We studied the interspecies interactions between biofilms of the soil-residing bacteria B. subtilis and related Bacillus species. We found that proximity between the biofilms triggered recruitment of motile B. subtilis cells, which engulfed the competing Bacillus simplex colony. Upon interaction, B. subtilis secreted surfactin and cannibalism toxins, at concentrations that were inert to B. subtilis itself, which eliminated the B. simplex colony, as well as colonies of Bacillus toyonensis. Surfactin toxicity was correlated with the presence of short carbon-tail length isomers, and synergistic with the cannibalism toxins. Importantly, during biofilm development and interspecies interactions a subpopulation in B. subtilis biofilm lost its native plasmid, leading to increased virulence against the competing Bacillus species. Overall, these findings indicate that genetic programs and traits that have little effect on biofilm development when each species is grown in isolation have a dramatic impact when different bacterial species interact.
Collapse
|
53
|
Ambroset C, Coluzzi C, Guédon G, Devignes MD, Loux V, Lacroix T, Payot S, Leblond-Bourget N. New Insights into the Classification and Integration Specificity of Streptococcus Integrative Conjugative Elements through Extensive Genome Exploration. Front Microbiol 2016; 6:1483. [PMID: 26779141 PMCID: PMC4701971 DOI: 10.3389/fmicb.2015.01483] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 12/08/2015] [Indexed: 12/30/2022] Open
Abstract
Recent genome analyses suggest that integrative and conjugative elements (ICEs) are widespread in bacterial genomes and therefore play an essential role in horizontal transfer. However, only a few of these elements are precisely characterized and correctly delineated within sequenced bacterial genomes. Even though previous analysis showed the presence of ICEs in some species of Streptococci, the global prevalence and diversity of ICEs was not analyzed in this genus. In this study, we searched for ICEs in the completely sequenced genomes of 124 strains belonging to 27 streptococcal species. These exhaustive analyses revealed 105 putative ICEs and 26 slightly decayed elements whose limits were assessed and whose insertion site was identified. These ICEs were grouped in seven distinct unrelated or distantly related families, according to their conjugation modules. Integration of these streptococcal ICEs is catalyzed either by a site-specific tyrosine integrase, a low-specificity tyrosine integrase, a site-specific single serine integrase, a triplet of site-specific serine integrases or a DDE transposase. Analysis of their integration site led to the detection of 18 target-genes for streptococcal ICE insertion including eight that had not been identified previously (ftsK, guaA, lysS, mutT, rpmG, rpsI, traG, and ebfC). It also suggests that all specificities have evolved to minimize the impact of the insertion on the host. This overall analysis of streptococcal ICEs emphasizes their prevalence and diversity and demonstrates that exchanges or acquisitions of conjugation and recombination modules are frequent.
Collapse
Affiliation(s)
- Chloé Ambroset
- DynAMic, Faculté des Sciences et Technologies, Université de Lorraine, UMR 1128Vandœuvre-lès-Nancy, France; DynAMic, Institut National de la Recherche Agronomique, UMR 1128Vandœuvre-lès-Nancy, France
| | - Charles Coluzzi
- DynAMic, Faculté des Sciences et Technologies, Université de Lorraine, UMR 1128Vandœuvre-lès-Nancy, France; DynAMic, Institut National de la Recherche Agronomique, UMR 1128Vandœuvre-lès-Nancy, France
| | - Gérard Guédon
- DynAMic, Faculté des Sciences et Technologies, Université de Lorraine, UMR 1128Vandœuvre-lès-Nancy, France; DynAMic, Institut National de la Recherche Agronomique, UMR 1128Vandœuvre-lès-Nancy, France
| | - Marie-Dominique Devignes
- Laboratoire Lorrain de Recherche en Informatique et ses Applications, Faculté des Sciences et Technologies, Université de Lorraine, UMR 7503Vandœuvre-lès-Nancy, France; CNRS, Laboratoire Lorrain de Recherche en Informatique et ses Applications, UMR 7503Vandśuvre-lès-Nancy, France
| | - Valentin Loux
- UR 1404 Mathématiques et Informatique Appliquées du Génome à l'Environnement, Institut National de la Recherche Agronomique Jouy-en-Josas, France
| | - Thomas Lacroix
- UR 1404 Mathématiques et Informatique Appliquées du Génome à l'Environnement, Institut National de la Recherche Agronomique Jouy-en-Josas, France
| | - Sophie Payot
- DynAMic, Faculté des Sciences et Technologies, Université de Lorraine, UMR 1128Vandœuvre-lès-Nancy, France; DynAMic, Institut National de la Recherche Agronomique, UMR 1128Vandœuvre-lès-Nancy, France
| | - Nathalie Leblond-Bourget
- DynAMic, Faculté des Sciences et Technologies, Université de Lorraine, UMR 1128Vandœuvre-lès-Nancy, France; DynAMic, Institut National de la Recherche Agronomique, UMR 1128Vandœuvre-lès-Nancy, France
| |
Collapse
|
54
|
Wisniewski JA, Traore DA, Bannam TL, Lyras D, Whisstock JC, Rood JI. TcpM: a novel relaxase that mediates transfer of large conjugative plasmids from Clostridium perfringens. Mol Microbiol 2015; 99:884-96. [PMID: 26560080 DOI: 10.1111/mmi.13270] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/09/2015] [Indexed: 11/30/2022]
Abstract
Conjugative transfer of toxin and antibiotic resistance plasmids in Clostridium perfringens is mediated by the tcp conjugation locus. Surprisingly, neither a relaxase gene nor an origin of transfer (oriT) has been identified on these plasmids, which are typified by the 47 kb tetracycline resistance plasmid pCW3. The tcpM gene (previously called intP) encodes a potential tyrosine recombinase that was postulated to be an atypical relaxase. Mutagenesis and complementation studies showed that TcpM was required for wild-type transfer of pCW3 and that a tyrosine residue, Y259, was essential for TcpM activity, which was consistent with the need for a relaxase-mediated hydrophilic attack at the oriT site. Other catalytic residues conserved in tyrosine recombinases were not required for TcpM activity, suggesting that TcpM was not a site-specific recombinase. Mobilization studies led to the identification of the oriT site, which was located in the 391 bp intergenic region upstream of tcpM. The oriT site was localized to a 150 bp region, and gel mobility shift studies showed that TcpM could bind to this region. Based on these studies we postulate that conjugative transfer of pCW3 involves the atypical relaxase TcpM binding to and processing the oriT site to initiate plasmid transfer.
Collapse
Affiliation(s)
- Jessica A Wisniewski
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia.,Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Daouda A Traore
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, 3800, Australia
| | - Trudi L Bannam
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia.,Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| | - Dena Lyras
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia.,Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| | - James C Whisstock
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia.,Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, 3800, Australia
| | - Julian I Rood
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, and Infection and Immunity Program, Biomedicine Discovery Institute, Monash University, Clayton, Victoria, 3800, Australia.,Department of Microbiology, Monash University, Clayton, Victoria, 3800, Australia
| |
Collapse
|
55
|
O'Callaghan A, Bottacini F, O'Connell Motherway M, van Sinderen D. Pangenome analysis of Bifidobacterium longum and site-directed mutagenesis through by-pass of restriction-modification systems. BMC Genomics 2015; 16:832. [PMID: 26489930 PMCID: PMC4618763 DOI: 10.1186/s12864-015-1968-4] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 09/30/2015] [Indexed: 12/16/2022] Open
Abstract
Background Bifidobacterial genome analysis has provided insights as to how these gut commensals adapt to and persist in the human GIT, while also revealing genetic diversity among members of a given bifidobacterial (sub)species. Bifidobacteria are notoriously recalcitrant to genetic modification, which prevents exploration of their genomic functions, including those that convey (human) health benefits. Methods PacBio SMRT sequencing was used to determine the whole genome seqeunces of two B. longum subsp. longum strains. The B. longum pan-genome was computed using PGAP v1.2 and the core B. longum phylogenetic tree was constructed using a maximum-likelihood based approach in PhyML v3.0. M.blmNCII was cloned in E. coli and an internal fragment if arfBarfB was cloned into pORI19 for insertion mutagenesis. Results In this study we present the complete genome sequences of two Bifidobacterium longum subsp. longum strains. Comparative analysis with thirty one publicly available B. longum genomes allowed the definition of the B. longum core and dispensable genomes. This analysis also highlighted differences in particular metabolic abilities between members of the B. longum subspecies infantis, longum and suis. Furthermore, phylogenetic analysis of the B. longum core genome indicated the existence of a novel subspecies. Methylome data, coupled to the analysis of restriction-modification systems, allowed us to substantially increase the genetic accessibility of B. longum subsp. longum NCIMB 8809 to a level that was shown to permit site-directed mutagenesis. Conclusions Comparative genomic analysis of thirty three B. longum representatives revealed a closed pan-genome for this bifidobacterial species. Phylogenetic analysis of the B. longum core genome also provides evidence for a novel fifth B. longum subspecies. Finally, we improved genetic accessibility for the strain B. longum subsp. longum NCIMB 8809, which allowed the generation of a mutant of this strain. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1968-4) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- A O'Callaghan
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
| | - F Bottacini
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
| | - M O'Connell Motherway
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
| | - D van Sinderen
- APC Microbiome Institute & School of Microbiology, University College Cork, Western Road, Cork, Ireland.
| |
Collapse
|
56
|
Abstract
Horizontal gene transfer plays a major role in microbial evolution, allowing microbes to acquire new genes and phenotypes. Integrative and conjugative elements (ICEs, a.k.a. conjugative transposons) are modular mobile genetic elements integrated into a host genome and are passively propagated during chromosomal replication and cell division. Induction of ICE gene expression leads to excision, production of the conserved conjugation machinery (a type IV secretion system), and the potential to transfer DNA to appropriate recipients. ICEs typically contain cargo genes that are not usually related to the ICE life cycle and that confer phenotypes to host cells. We summarize the life cycle and discovery of ICEs, some of the regulatory mechanisms, and how the types of cargo have influenced our view of ICEs. We discuss how ICEs can acquire new cargo genes and describe challenges to the field and various perspectives on ICE biology.
Collapse
Affiliation(s)
- Christopher M Johnson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; ,
| | | |
Collapse
|
57
|
Giaouris E, Heir E, Desvaux M, Hébraud M, Møretrø T, Langsrud S, Doulgeraki A, Nychas GJ, Kačániová M, Czaczyk K, Ölmez H, Simões M. Intra- and inter-species interactions within biofilms of important foodborne bacterial pathogens. Front Microbiol 2015; 6:841. [PMID: 26347727 PMCID: PMC4542319 DOI: 10.3389/fmicb.2015.00841] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Accepted: 07/31/2015] [Indexed: 12/15/2022] Open
Abstract
A community-based sessile life style is the normal mode of growth and survival for many bacterial species. Under such conditions, cell-to-cell interactions are inevitable and ultimately lead to the establishment of dense, complex and highly structured biofilm populations encapsulated in a self-produced extracellular matrix and capable of coordinated and collective behavior. Remarkably, in food processing environments, a variety of different bacteria may attach to surfaces, survive, grow, and form biofilms. Salmonella enterica, Listeria monocytogenes, Escherichia coli, and Staphylococcus aureus are important bacterial pathogens commonly implicated in outbreaks of foodborne diseases, while all are known to be able to create biofilms on both abiotic and biotic surfaces. Particularly challenging is the attempt to understand the complexity of inter-bacterial interactions that can be encountered in such unwanted consortia, such as competitive and cooperative ones, together with their impact on the final outcome of these communities (e.g., maturation, physiology, antimicrobial resistance, virulence, dispersal). In this review, up-to-date data on both the intra- and inter-species interactions encountered in biofilms of these pathogens are presented. A better understanding of these interactions, both at molecular and biophysical levels, could lead to novel intervention strategies for controlling pathogenic biofilm formation in food processing environments and thus improve food safety.
Collapse
Affiliation(s)
- Efstathios Giaouris
- Department of Food Science and Nutrition, Faculty of the Environment, University of the Aegean, Myrina, Lemnos Island, Greece
| | - Even Heir
- Nofima, Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås, Norway
| | - Mickaël Desvaux
- INRA, UR454 Microbiologie, Centre Auvergne-Rhône-Alpes, Saint-Genès-Champanelle, France
| | - Michel Hébraud
- INRA, UR454 Microbiologie, Centre Auvergne-Rhône-Alpes, Saint-Genès-Champanelle, France
| | - Trond Møretrø
- Nofima, Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås, Norway
| | - Solveig Langsrud
- Nofima, Norwegian Institute of Food, Fisheries and Aquaculture Research, Ås, Norway
| | - Agapi Doulgeraki
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, Faculty of Foods, Biotechnology and Development, Agricultural University of Athens, Athens, Greece
| | - George-John Nychas
- Laboratory of Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, Faculty of Foods, Biotechnology and Development, Agricultural University of Athens, Athens, Greece
| | - Miroslava Kačániová
- Department of Microbiology, Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture in Nitra, Nitra, Slovakia
| | - Katarzyna Czaczyk
- Department of Biotechnology and Food Microbiology, Poznan University of Life Sciences, Poznań, Poland
| | - Hülya Ölmez
- TÜBİTAK Marmara Research Center, Food Institute, Gebze, Kocaeli, Turkey
| | - Manuel Simões
- Laboratory for Process Engineering, Environment, Biotechnology and Energy, Department of Chemical Engineering, Faculty of Engineering, University of Porto, Porto, Portugal
| |
Collapse
|
58
|
O'Brien FG, Yui Eto K, Murphy RJT, Fairhurst HM, Coombs GW, Grubb WB, Ramsay JP. Origin-of-transfer sequences facilitate mobilisation of non-conjugative antimicrobial-resistance plasmids in Staphylococcus aureus. Nucleic Acids Res 2015; 43:7971-83. [PMID: 26243776 PMCID: PMC4652767 DOI: 10.1093/nar/gkv755] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Accepted: 07/14/2015] [Indexed: 11/17/2022] Open
Abstract
Staphylococcus aureus is a common cause of hospital, community and livestock-associated infections and is increasingly resistant to multiple antimicrobials. A significant proportion of antimicrobial-resistance genes are plasmid-borne, but only a minority of S. aureus plasmids encode proteins required for conjugative transfer or Mob relaxase proteins required for mobilisation. The pWBG749 family of S. aureus conjugative plasmids can facilitate the horizontal transfer of diverse antimicrobial-resistance plasmids that lack Mob genes. Here we reveal that these mobilisable plasmids carry copies of the pWBG749 origin-of-transfer (oriT) sequence and that these oriT sequences facilitate mobilisation by pWBG749. Sequences resembling the pWBG749 oriT were identified on half of all sequenced S. aureus plasmids, including the most prevalent large antimicrobial-resistance/virulence-gene plasmids, pIB485, pMW2 and pUSA300HOUMR. oriT sequences formed five subfamilies with distinct inverted-repeat-2 (IR2) sequences. pWBG749-family plasmids encoding each IR2 were identified and pWBG749 mobilisation was found to be specific for plasmids carrying matching IR2 sequences. Specificity of mobilisation was conferred by a putative ribbon-helix-helix-protein gene smpO. Several plasmids carried 2–3 oriT variants and pWBG749-mediated recombination occurred between distinct oriT sites during mobilisation. These observations suggest this relaxase-in trans mechanism of mobilisation by pWBG749-family plasmids is a common mechanism of plasmid dissemination in S. aureus.
Collapse
Affiliation(s)
- Frances G O'Brien
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia
| | - Karina Yui Eto
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia
| | - Riley J T Murphy
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia
| | - Heather M Fairhurst
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia
| | - Geoffrey W Coombs
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia PathWest Laboratory Medicine, Fiona Stanley Hospital, Perth, Western Australia, Australia
| | - Warren B Grubb
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia
| | - Joshua P Ramsay
- CHIRI Biosciences Precinct, School of Biomedical Sciences, Faculty of Health Sciences, Curtin University, Bentley WA 6102, Australia Australian Collaborating Centre for Enterococcus and Staphylococcus Species (ACCESS) Typing and Research, School of Veterinary Sciences and Life Sciences, Murdoch University and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia
| |
Collapse
|
59
|
Critical Components of the Conjugation Machinery of the Integrative and Conjugative Element ICEBs1 of Bacillus subtilis. J Bacteriol 2015; 197:2558-67. [PMID: 26013486 DOI: 10.1128/jb.00142-15] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Accepted: 05/14/2015] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Conjugation, or mating, plays a profound role in bacterial evolution by spreading genes that allow bacteria to adapt to and colonize new niches. ICEBs1, an integrative and conjugative element of Bacillus subtilis, can transfer itself and mobilize resident plasmids. DNA transfer is mediated by a type IV secretion system (T4SS). Characterized components of the ICEBs1 T4SS include the conserved VirB4-like ATPase ConE, the bifunctional cell wall hydrolase CwlT, and the presumed VirD4-like coupling protein ConQ. A fusion of ConE to green fluorescent protein (GFP) localizes to the membrane preferentially at the cell poles. One or more ICEBs1 proteins are required for ConE's localization at the membrane, as ConE lacks predicted transmembrane segments and ConE-GFP is found dispersed throughout the cytoplasm in cells lacking ICEBs1. Here, we analyzed five ICEBs1 genes to determine if they are required for DNA transfer and/or ConE-GFP localization. We found that conB, conC, conD, and conG, but not yddF, are required for both ICEBs1 transfer and plasmid mobilization. All four required genes encode predicted integral membrane proteins. conB and, to some extent, conD were required for localization of ConE-GFP to the membrane. Using an adenylate cyclase-based bacterial two-hybrid system, we found that ConE interacts with ConB. We propose a model in which the ICEBs1 conjugation machinery is composed of ConB, ConC, ConD, ConE, ConG, CwlT, ConQ, and possibly other ICEBs1 proteins, and that ConB interacts with ConE, helping to recruit and/or maintain ConE at the membrane. IMPORTANCE Conjugation is a major form of horizontal gene transfer and has played a profound role in bacterial evolution by moving genes, including those involved in antibiotic resistance, metabolism, symbiosis, and infectious disease. During conjugation, DNA is transferred from cell to cell through the conjugation machinery, a type of secretion system. Relatively little is known about the conjugation machinery of Gram-positive bacteria. Here, we analyzed five genes of the integrative and conjugative element ICEBs1 of Bacillus subtilis. Our research identifies four new components of the ICEBs1 conjugation machinery (ConB, ConC, ConD, and ConG) and shows an interaction between ConB and ConE that is required for ConE to associate with the cell membrane.
Collapse
|
60
|
The All-Alpha Domains of Coupling Proteins from the Agrobacterium tumefaciens VirB/VirD4 and Enterococcus faecalis pCF10-Encoded Type IV Secretion Systems Confer Specificity to Binding of Cognate DNA Substrates. J Bacteriol 2015; 197:2335-49. [PMID: 25939830 DOI: 10.1128/jb.00189-15] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 04/23/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Bacterial type IV coupling proteins (T4CPs) bind and mediate the delivery of DNA substrates through associated type IV secretion systems (T4SSs). T4CPs consist of a transmembrane domain, a conserved nucleotide-binding domain (NBD), and a sequence-variable helical bundle called the all-alpha domain (AAD). In the T4CP structural prototype, plasmid R388-encoded TrwB, the NBD assembles as a homohexamer resembling RecA and DNA ring helicases, and the AAD, which sits at the channel entrance of the homohexamer, is structurally similar to N-terminal domain 1 of recombinase XerD. Here, we defined the contributions of AADs from the Agrobacterium tumefaciens VirD4 and Enterococcus faecalis PcfC T4CPs to DNA substrate binding. AAD deletions abolished DNA transfer, whereas production of the AAD in otherwise wild-type donor strains diminished the transfer of cognate but not heterologous substrates. Reciprocal swaps of AADs between PcfC and VirD4 abolished the transfer of cognate DNA substrates, although strikingly, the VirD4-AADPcfC chimera (VirD4 with the PcfC AAD) supported the transfer of a mobilizable plasmid. Purified AADs from both T4CPs bound DNA substrates without sequence preference but specifically bound cognate processing proteins required for cleavage at origin-of-transfer sequences. The soluble domains of VirD4 and PcfC lacking their AADs neither exerted negative dominance in vivo nor specifically bound cognate processing proteins in vitro. Our findings support a model in which the T4CP AADs contribute to DNA substrate selection through binding of associated processing proteins. Furthermore, MOBQ plasmids have evolved a docking mechanism that bypasses the AAD substrate discrimination checkpoint, which might account for their capacity to promiscuously transfer through many different T4SSs. IMPORTANCE For conjugative transfer of mobile DNA elements, members of the VirD4/TraG/TrwB receptor superfamily bind cognate DNA substrates through mechanisms that are largely undefined. Here, we supply genetic and biochemical evidence that a helical bundle, designated the all-alpha domain (AAD), of T4SS receptors functions as a substrate specificity determinant. We show that AADs from two substrate receptors, Agrobacterium tumefaciens VirD4 and Enterococcus faecalis PcfC, bind DNA without sequence or strand preference but specifically bind the cognate relaxases responsible for nicking and piloting the transferred strand through the T4SS. We propose that interactions of receptor AADs with DNA-processing factors constitute a basis for selective coupling of mobile DNA elements with type IV secretion channels.
Collapse
|
61
|
Puymège A, Bertin S, Guédon G, Payot S. Analysis of Streptococcus agalactiae pan-genome for prevalence, diversity and functionality of integrative and conjugative or mobilizable elements integrated in the tRNA(Lys CTT) gene. Mol Genet Genomics 2015; 290:1727-40. [PMID: 25832353 DOI: 10.1007/s00438-015-1031-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 03/17/2015] [Indexed: 11/27/2022]
Abstract
Streptococcus agalactiae is the first cause of invasive infections in human neonates and is also a major bovine and fish pathogen. High genomic diversity was observed in this species that hosts numerous mobile genetic elements, in particular elements transferable by conjugation. This works aims to evaluate the contribution of these elements to GBS genome diversity. Focusing on genomic islands integrated in the tRNA(Lys) (CTT) gene, a known hotspot of recombination, an extensive in silico search was performed on the sequenced genome of 303 strains of S. agalactiae isolated from different hosts. In all the isolates (except 9), whatever their origin (human, bovine, camel, dog, gray seal, dolphin, fish species or bullfrog), this locus carries highly diverse genomic islands transferable by conjugation such as integrative and conjugative elements (ICEs), integrative and mobilizable elements (IMEs), CIs-mobilizable elements (CIMEs) or composite elements. Transfer of an ICE from an ST67 bovine strain to a phylogenetically distant ST23 human isolate was obtained experimentally indicating that there was no barrier to ICE transfer between strains from different hosts. Interestingly, a novel family of putative IMEs that site-specifically integrate in the nic site of oriT of ICEs belonging to Tn916/ICESt3 superfamily was detected in silico. These elements carry an antibiotic resistance gene (lsa(C)) already described to confer cross-resistance to lincosamides, streptogramins A and pleuromutilins. Further work is needed to evaluate the impact of these IMEs on the transfer of targeted ICEs and the mobility and the dissemination of these IMEs.
Collapse
Affiliation(s)
- Aurore Puymège
- Faculté des Sciences et Technologies, INRA, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France.,Faculté des Sciences et Technologies, Université de Lorraine, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France
| | - Stéphane Bertin
- Faculté des Sciences et Technologies, INRA, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France.,Faculté des Sciences et Technologies, Université de Lorraine, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France
| | - Gérard Guédon
- Faculté des Sciences et Technologies, INRA, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France.,Faculté des Sciences et Technologies, Université de Lorraine, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France
| | - Sophie Payot
- Faculté des Sciences et Technologies, INRA, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France. .,Faculté des Sciences et Technologies, Université de Lorraine, UMR1128 DynAMic, Bd des Aiguillettes, BP70239, 54506, Vandœuvre-lès-Nancy, France.
| |
Collapse
|
62
|
Shintani M, Sanchez ZK, Kimbara K. Genomics of microbial plasmids: classification and identification based on replication and transfer systems and host taxonomy. Front Microbiol 2015; 6:242. [PMID: 25873913 PMCID: PMC4379921 DOI: 10.3389/fmicb.2015.00242] [Citation(s) in RCA: 213] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 03/12/2015] [Indexed: 12/21/2022] Open
Abstract
Plasmids are important "vehicles" for the communication of genetic information between bacteria. The exchange of plasmids transmits pathogenically and environmentally relevant traits to the host bacteria, promoting their rapid evolution and adaptation to various environments. Over the past six decades, a large number of plasmids have been identified and isolated from different microbes. With the revolution of sequencing technology, more than 4600 complete sequences of plasmids found in bacteria, archaea, and eukaryotes have been determined. The classification of a wide variety of plasmids is not only important to understand their features, host ranges, and microbial evolution but is also necessary to effectively use them as genetic tools for microbial engineering. This review summarizes the current situation of the classification of fully sequenced plasmids based on their host taxonomy and their features of replication and conjugative transfer. The majority of the fully sequenced plasmids are found in bacteria in the Proteobacteria, Firmicutes, Spirochaetes, Actinobacteria, Cyanobacteria and Euryarcheota phyla, and key features of each phylum are included. Recent advances in the identification of novel types of plasmids and plasmid transfer by culture-independent methods using samples from natural environments are also discussed.
Collapse
Affiliation(s)
- Masaki Shintani
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Shizuoka, Japan ; Department of Bioscience, Graduate School of Science and Technology, Shizuoka University Shizuoka, Japan
| | - Zoe K Sanchez
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Shizuoka, Japan
| | - Kazuhide Kimbara
- Department of Applied Chemistry and Biochemical Engineering, Graduate School of Engineering, Shizuoka University Shizuoka, Japan
| |
Collapse
|
63
|
Makart L, Gillis A, Mahillon J. pXO16 from Bacillus thuringiensis serovar israelensis: Almost 350 kb of terra incognita. Plasmid 2015; 80:8-15. [PMID: 25770691 DOI: 10.1016/j.plasmid.2015.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 02/21/2015] [Accepted: 03/03/2015] [Indexed: 11/20/2022]
Abstract
Bacillus thuringiensis strains usually harbor large sets of plasmids, some of which carrying the entomopathogenic δ-endotoxins. B. thuringiensis serovar israelensis, active on Dipteran larvae, carries the very large conjugative plasmid pXO16 (350 kb). pXO16 displays a macroscopic aggregation phenotype when liquid cultures of conjugative partners are mixed. Its conjugative apparatus is able of transferring itself and other non-conjugative and non-mobilizable plasmids in a fast and very efficient manner. Even though its conjugative kinetics and capabilities have been extensively studied, the genetic bases for this unique transfer system remain largely unknown. In this work, the sequence of pXO16 has been identified in the existing sequenced genome of B. thuringiensis sv. israelensis HD-789 as corresponding to the p01 plasmid. Despite pXO16 sequence being highly coding, few CDS possess homologs in the databases. However, potential regions responsible for the aggregation phenotype and the plasmid replication have been highlighted. The common orientation of all CDS and the presence of a high number of potential paralogs suggested a phage-like nature. Concerning conjugative functions, no significant type IV secretion system homologs have been found, indicating that pXO16 encodes an unforeseen conjugative system.
Collapse
Affiliation(s)
- Lionel Makart
- Laboratory of Food and Environmental Microbiology, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Annika Gillis
- Laboratory of Food and Environmental Microbiology, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Jacques Mahillon
- Laboratory of Food and Environmental Microbiology, Université Catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium.
| |
Collapse
|
64
|
Two novel membrane proteins, TcpD and TcpE, are essential for conjugative transfer of pCW3 in Clostridium perfringens. J Bacteriol 2014; 197:774-81. [PMID: 25488300 DOI: 10.1128/jb.02466-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The anaerobic pathogen Clostridium perfringens encodes either toxin genes or antibiotic resistance determinants on a unique family of conjugative plasmids that have a novel conjugation region, the tcp locus. Studies of the paradigm conjugative plasmid from C. perfringens, the 47-kb tetracycline resistance plasmid pCW3, have identified several tcp-encoded proteins that are involved in conjugative transfer and form part of the transfer apparatus. In this study, the role of the conserved hypothetical proteins TcpD, TcpE, and TcpJ was examined. Mutation and complementation analyses showed that TcpD and TcpE were essential for the conjugative transfer of pCW3, whereas TcpJ was not required. To analyze the TcpD and TcpE proteins in C. perfringens, functional hemagglutinin (HA)-tagged derivatives were constructed. Western blots showed that TcpD and TcpE localized to the cell envelope fraction independently of the presence of other pCW3-encoded proteins. Finally, examination of the subcellular localization of TcpD and TcpE by immunofluorescence showed that these proteins were concentrated at both poles of C. perfringens donor cells, where they are postulated to form essential components of the multiprotein complex that comprises the transfer apparatus.
Collapse
|
65
|
Abstract
Plasmid-encoded virulence factors are important in the pathogenesis of diseases caused by spore-forming bacteria. Unlike many other bacteria, the most common virulence factors encoded by plasmids in Clostridium and Bacillus species are protein toxins. Clostridium perfringens causes several histotoxic and enterotoxin diseases in both humans and animals and produces a broad range of toxins, including many pore-forming toxins such as C. perfringens enterotoxin, epsilon-toxin, beta-toxin, and NetB. Genetic studies have led to the determination of the role of these toxins in disease pathogenesis. The genes for these toxins are generally carried on large conjugative plasmids that have common core replication, maintenance, and conjugation regions. There is considerable functional information available about the unique tcp conjugation locus carried by these plasmids, but less is known about plasmid maintenance. The latter is intriguing because many C. perfringens isolates stably maintain up to four different, but closely related, toxin plasmids. Toxin genes may also be plasmid-encoded in the neurotoxic clostridia. The tetanus toxin gene is located on a plasmid in Clostridium tetani, but the botulinum toxin genes may be chromosomal, plasmid-determined, or located on bacteriophages in Clostridium botulinum. In Bacillus anthracis it is well established that virulence is plasmid determined, with anthrax toxin genes located on pXO1 and capsule genes on a separate plasmid, pXO2. Orthologs of these plasmids are also found in other members of the Bacillus cereus group such as B. cereus and Bacillus thuringiensis. In B. thuringiensis these plasmids may carry genes encoding one or more insecticidal toxins.
Collapse
|
66
|
Freedman JC, Theoret JR, Wisniewski JA, Uzal FA, Rood JI, McClane BA. Clostridium perfringens type A-E toxin plasmids. Res Microbiol 2014; 166:264-79. [PMID: 25283728 DOI: 10.1016/j.resmic.2014.09.004] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Revised: 09/04/2014] [Accepted: 09/09/2014] [Indexed: 12/26/2022]
Abstract
Clostridium perfringens relies upon plasmid-encoded toxin genes to cause intestinal infections. These toxin genes are associated with insertion sequences that may facilitate their mobilization and transfer, giving rise to new toxin plasmids with common backbones. Most toxin plasmids carry a transfer of clostridial plasmids locus mediating conjugation, which likely explains the presence of similar toxin plasmids in otherwise unrelated C. perfringens strains. The association of many toxin genes with insertion sequences and conjugative plasmids provides virulence flexibility when causing intestinal infections. However, incompatibility issues apparently limit the number of toxin plasmids maintained by a single cell.
Collapse
Affiliation(s)
- John C Freedman
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - James R Theoret
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | | | - Francisco A Uzal
- California Animal Health and Food Safety Laboratory, San Bernadino Branch, School of Veterinary Medicine, University of California-Davis, San Bernadino, CA, USA
| | - Julian I Rood
- Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Bruce A McClane
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
| |
Collapse
|
67
|
Identification of a novel conjugative plasmid in mycobacteria that requires both type IV and type VII secretion. mBio 2014; 5:e01744-14. [PMID: 25249284 PMCID: PMC4173767 DOI: 10.1128/mbio.01744-14] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Conjugative plasmids have been identified in a wide variety of different bacteria, ranging from proteobacteria to firmicutes, and conjugation is one of the most efficient routes for horizontal gene transfer. The most widespread mechanism of plasmid conjugation relies on different variants of the type IV secretion pathway. Here, we describe the identification of a novel type of conjugative plasmid that seems to be unique for mycobacteria. Interestingly, while this plasmid is efficiently exchanged between different species of slow-growing mycobacteria, including Mycobacterium tuberculosis, it could not be transferred to any of the fast-growing mycobacteria tested. Genetic analysis of the conjugative plasmid showed the presence of a locus containing homologues of three type IV secretion system components and a relaxase. In addition, a new type VII secretion locus was present. Using transposon insertion mutagenesis, we show that in fact both these secretion systems are essential for conjugation, indicating that this plasmid represents a new class of conjugative plasmids requiring two secretion machineries. This plasmid could form a useful new tool to exchange or introduce DNA in slow-growing mycobacteria. Conjugative plasmids play an important role in horizontal gene transfer between different bacteria and, as such, in their adaptation and evolution. This effect is most obvious in the spread of antibiotic resistance genes. Thus far, conjugation of natural plasmids has been described only rarely for mycobacterial species. In fact, it is generally accepted that M. tuberculosis does not show any recent sign of horizontal gene transfer. In this study, we describe the identification of a new widespread conjugative plasmid that can also be efficiently transferred to M. tuberculosis. This plasmid therefore poses both a threat and an opportunity. The threat is that, through the acquisition of antibiotic resistance markers, this plasmid could start a rapid spread of antibiotic resistance genes between pathogenic mycobacteria. The opportunity is that we could use this plasmid to generate new tools for the efficient introduction of foreign DNA in slow-growing mycobacteria.
Collapse
|
68
|
Goessweiner-Mohr N, Eder M, Hofer G, Fercher C, Arends K, Birner-Gruenberger R, Grohmann E, Keller W. Structure of the double-stranded DNA-binding type IV secretion protein TraN from Enterococcus. ACTA ACUST UNITED AC 2014; 70:2376-89. [PMID: 25195751 DOI: 10.1107/s1399004714014187] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 06/17/2014] [Indexed: 11/10/2022]
Abstract
Conjugative transfer through type IV secretion multiprotein complexes is the most important means of spreading antimicrobial resistance. Plasmid pIP501, frequently found in clinical Enterococcus faecalis and Enterococcus faecium isolates, is the first Gram-positive (G+) conjugative plasmid for which self-transfer to Gram-negative (G-) bacteria has been demonstrated. The pIP501-encoded type IV secretion system (T4SS) protein TraN localizes to the cytoplasm and shows specific DNA binding. The specific DNA-binding site upstream of the pIP501 origin of transfer (oriT) was identified by a novel footprinting technique based on exonuclease digestion and sequencing, suggesting TraN to be an accessory protein of the pIP501 relaxase TraA. The structure of TraN was determined to 1.35 Å resolution. It revealed an internal dimer fold with antiparallel β-sheets in the centre and a helix-turn-helix (HTH) motif at both ends. Surprisingly, structurally related proteins (excisionases from T4SSs of G+ conjugative transposons and transcriptional regulators of the MerR family) resembling only one half of TraN were found. Thus, TraN may be involved in the early steps of pIP501 transfer, possibly triggering pIP501 TraA relaxase activity by recruiting the relaxosome to the assembled mating pore.
Collapse
Affiliation(s)
| | - Markus Eder
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| | - Gerhard Hofer
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| | - Christian Fercher
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| | - Karsten Arends
- Robert Koch Institute Berlin, Nordufer 20, 13353 Berlin, Germany
| | - Ruth Birner-Gruenberger
- Institute for Pathology and Omics Center Graz, Medical University Graz, Stiftingtalstrasse 24, 8010 Graz, Austria
| | - Elisabeth Grohmann
- Division of Infectious Diseases, University Medical Center Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany
| | - Walter Keller
- Institute of Molecular Biosciences, University of Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| |
Collapse
|
69
|
Johnson CM, Grossman AD. Identification of host genes that affect acquisition of an integrative and conjugative element in Bacillus subtilis. Mol Microbiol 2014; 93:1284-301. [PMID: 25069588 DOI: 10.1111/mmi.12736] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/26/2014] [Indexed: 01/28/2023]
Abstract
Conjugation, a major type of horizontal gene transfer in bacteria, involves transfer of DNA from a donor to a recipient using donor-encoded conjugation machinery. Using a high-throughput screen (Tn-seq), we identified genes in recipients that contribute to acquisition of the integrative and conjugative element ICEBs1 by Bacillus subtilis. We found that null mutations in some genes caused an increase, and others a decrease in conjugation efficiency. Some mutations affected conjugation only when present in recipients. Other mutations affected conjugation when present in donors or recipients. Most of the genes identified are known or predicted to affect the cell envelope. Several encode enzymes involved in phospholipid biosynthesis and one encodes a homologue of penicillin-binding proteins. Two of the genes identified also affected conjugation of Tn916, indicating that their roles in conjugation may be general. We did not identify any genes in recipients that were essential for ICEBs1 conjugation, indicating that if there are such genes, then these are either essential for cell growth or redundant. Our results indicate that acquisition of ICEBs1, and perhaps other conjugative elements, is robust and not easily avoided by mutation and that several membrane-related functions affect the efficiency of conjugation.
Collapse
Affiliation(s)
- Christopher M Johnson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | | |
Collapse
|
70
|
Lorenzo-Díaz F, Fernández-López C, Garcillán-Barcia MP, Espinosa M. Bringing them together: plasmid pMV158 rolling circle replication and conjugation under an evolutionary perspective. Plasmid 2014; 74:15-31. [PMID: 24942190 PMCID: PMC7103276 DOI: 10.1016/j.plasmid.2014.05.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 05/21/2014] [Accepted: 05/22/2014] [Indexed: 11/29/2022]
Abstract
Rolling circle-replicating plasmids constitute a vast family that is particularly abundant in, but not exclusive of, Gram-positive bacteria. These plasmids are constructed as cassettes that harbor genes involved in replication and its control, mobilization, resistance determinants and one or two origins of lagging strand synthesis. Any given plasmid may contain all, some, or just only the replication cassette. We discuss here the family of the promiscuous streptococcal plasmid pMV158, with emphasis on its mobilization functions: the product of the mobM gene, prototype of the MOBV relaxase family, and its cognate origin of transfer, oriT. Amongst the subfamily of MOBV1 plasmids, three groups of oriT sequences, represented by plasmids pMV158, pT181, and p1414 were identified. In the same subfamily, we found four types of single-strand origins, namely ssoA, ssoU, ssoW, and ssoT. We found that plasmids of the rolling-circle Rep_2 family (to which pMV158 belongs) are more frequently found in Lactobacillales than in any other bacterial order, whereas Rep_1 initiators seemed to prefer hosts included in the Bacillales order. In parallel, MOBV1 relaxases associated with Rep_2 initiators tended to cluster separately from those linked to Rep_1 plasmids. The updated inventory of MOBV1 plasmids still contains exclusively mobilizable elements, since no genes associated with conjugative transfer (other than the relaxase) were detected. These plasmids proved to have a great plasticity at using a wide variety of conjugative apparatuses. The promiscuous recognition of non-cognate oriT sequences and the role of replication origins for lagging-strand origin in the host range of these plasmids are also discussed.
Collapse
Affiliation(s)
- Fabián Lorenzo-Díaz
- Unidad de Investigación, Hospital Universitario Nuestra Señora de Candelaria and Instituto Universitario de Enfermedades Tropicales y Salud Pública de Canarias, Centro de Investigaciones Biomédicas de Canarias, Universidad de La Laguna, Santa Cruz de Tenerife, Spain.
| | - Cris Fernández-López
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu, 9, E-28040 Madrid, Spain.
| | - M Pilar Garcillán-Barcia
- Instituto de Biomedicina y Biotecnología de Cantabria (IBBTEC), Universidad de Cantabria - CSIC-SODERCAN, Santander, Cantabria, Spain.
| | - Manuel Espinosa
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu, 9, E-28040 Madrid, Spain.
| |
Collapse
|
71
|
TgaA, a VirB1-like component belonging to a putative type IV secretion system of Bifidobacterium bifidum MIMBb75. Appl Environ Microbiol 2014; 80:5161-9. [PMID: 24951779 DOI: 10.1128/aem.01413-14] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Bifidobacterium bifidum MIMBb75 is a human intestinal isolate demonstrated to be interactive with the host and efficacious as a probiotic. However, the molecular biology of this microorganism is yet largely unknown. For this reason, we undertook whole-genome sequencing of B. bifidum MIMBb75 to identify potential genetic factors that would explain the metabolic and probiotic attributes of this bacterium. Comparative genomic analysis revealed a 45-kb chromosomal region that comprises 19 putative genes coding for a potential type IV secretion system (T4SS). Thus, we undertook the initial characterization of this genetic region by studying the putative virB1-like gene, named tgaA. Gene tgaA encodes a peptidoglycan lytic enzyme containing two active domains: lytic murein transglycosylase (LT, cd00254.3) and cysteine- and histidine-dependent amidohydrolase/peptidase (CHAP, pfam05257.4). By means of several in vitro assays, we experimentally confirmed that protein TgaA, consistent with its computationally assigned role, has peptidoglycan lytic activity, which is principally associated to the LT domain. Furthermore, immunofluorescence and immunogold labeling showed that the protein TgaA is abundantly expressed on the cell surface of B. bifidum MIMBb75. According to the literature, the T4SSs, which have not been characterized before in bifidobacteria, can have important implications for bacterial cell-to-cell communication as well as cross talk with host cells, justifying the interest for further studies aimed at the investigation of this genetic region.
Collapse
|
72
|
Koraimann G, Wagner MA. Social behavior and decision making in bacterial conjugation. Front Cell Infect Microbiol 2014; 4:54. [PMID: 24809026 PMCID: PMC4010749 DOI: 10.3389/fcimb.2014.00054] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 04/09/2014] [Indexed: 01/05/2023] Open
Abstract
Bacteria frequently acquire novel genes by horizontal gene transfer (HGT). HGT through the process of bacterial conjugation is highly efficient and depends on the presence of conjugative plasmids (CPs) or integrated conjugative elements (ICEs) that provide the necessary genes for DNA transmission. This review focuses on recent advancements in our understanding of ssDNA transfer systems and regulatory networks ensuring timely and spatially controlled DNA transfer (tra) gene expression. As will become obvious by comparing different systems, by default, tra genes are shut off in cells in which conjugative elements are present. Only when conditions are optimal, donor cells—through epigenetic alleviation of negatively acting roadblocks and direct stimulation of DNA transfer genes—become transfer competent. These transfer competent cells have developmentally transformed into specialized cells capable of secreting ssDNA via a T4S (type IV secretion) complex directly into recipient cells. Intriguingly, even under optimal conditions, only a fraction of the population undergoes this transition, a finding that indicates specialization and cooperative, social behavior. Thereby, at the population level, the metabolic burden and other negative consequences of tra gene expression are greatly reduced without compromising the ability to horizontally transfer genes to novel bacterial hosts. This undoubtedly intelligent strategy may explain why conjugative elements—CPs and ICEs—have been successfully kept in and evolved with bacteria to constitute a major driving force of bacterial evolution.
Collapse
Affiliation(s)
- Günther Koraimann
- Institute of Molecular Biosciences, University of Graz Graz, Austria
| | - Maria A Wagner
- Max von Pettenkofer-Institut, Ludwig-Maximilians-Universität München Munich, Germany
| |
Collapse
|
73
|
Fernandez-Gonzalez E, Backert S. DNA transfer in the gastric pathogen Helicobacter pylori. J Gastroenterol 2014; 49:594-604. [PMID: 24515309 DOI: 10.1007/s00535-014-0938-y] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 01/16/2014] [Indexed: 02/08/2023]
Abstract
The gastric pathogen Helicobacter pylori is one of the most genetically diverse bacteria. Recombination and DNA transfer contribute to its genetic variability and enhance host adaptation. Among the strategies described to increase genetic diversity in bacteria, DNA transfer by conjugation is one of the best characterized. Using this mechanism, a fragment of DNA from a donor cell can be transferred to a recipient, always mediated by a conjugative nucleoprotein complex, which is evolutionarily related to type IV secretion systems (T4SSs). Interestingly, the H. pylori chromosomes can encode up to four T4SSs, including the cagPAI, comB, tfs3, and tfs4 genes, some of which are known to promote chronic H. pylori infection. The T4SS encoded by the cagPAI mediates the injection of the effector protein CagA and proinflammatory signaling, and the comB system is involved in DNA uptake from the environment. However, the role of tfs3 and tfs4 is not yet clear. The presence of a functional XerD tyrosine recombinase and 5'AAAGAATG-3' border sequences as well as two putative conjugative relaxases (Rlx1 and Rlx2), a coupling protein (TraG), and a chromosomal region carrying a putative origin of transfer (oriT) suggest the existence of a DNA transfer apparatus in tfs4. Moreover, a conjugation-like DNA transfer mechanism in H. pylori has already been described in vitro, but whether this occurs in vivo is still unknown. Some extrachromosomal plasmids and phages are also present in various H. pylori strains. Genetic exchange among plasmids and chromosomes, and involved DNA mobilization events, could explain part of H. pylori's genetic diversity. Here, we review our knowledge about the possible DNA transfer mechanisms in H. pylori and its implications in bacterial adaptation to the host environment.
Collapse
Affiliation(s)
- Esther Fernandez-Gonzalez
- Division of Microbiology, Department of Biology, Friedrich Alexander University Erlangen/Nuremberg, Staudtstr. 5, 91058, Erlangen, Germany
| | | |
Collapse
|
74
|
Goessweiner-Mohr N, Fercher C, Arends K, Birner-Gruenberger R, Laverde-Gomez D, Huebner J, Grohmann E, Keller W. The type IV secretion protein TraK from the Enterococcus conjugative plasmid pIP501 exhibits a novel fold. ACTA ACUST UNITED AC 2014; 70:1124-35. [PMID: 24699656 DOI: 10.1107/s1399004714001606] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 01/22/2014] [Indexed: 11/11/2022]
Abstract
Conjugative plasmid transfer presents a serious threat to human health as the most important means of spreading antibiotic resistance and virulence genes among bacteria. The required direct cell-cell contact is established by a multi-protein complex, the conjugative type IV secretion system (T4SS). The conjugative core complex spans the cellular envelope and serves as a channel for macromolecular secretion. T4SSs of Gram-negative (G-) origin have been studied in great detail. In contrast, T4SSs of Gram-positive (G+) bacteria have only received little attention thus far, despite the medical relevance of numerous G+ pathogens (e.g. enterococci, staphylococci and streptococci). This study provides structural information on the type IV secretion (T4S) protein TraK of the G+ broad host range Enterococcus conjugative plasmid pIP501. The crystal structure of the N-terminally truncated construct TraKΔ was determined to 3.0 Å resolution and exhibits a novel fold. Immunolocalization demonstrated that the protein localizes to the cell wall facing towards the cell exterior, but does not exhibit surface accessibility. Circular dichroism, dynamic light scattering and size-exclusion chromatography confirmed the protein to be a monomer. With the exception of proteins from closely related T4SSs, no significant sequence or structural relatives were found. This observation marks the protein as a very exclusive, specialized member of the pIP501 T4SS.
Collapse
Affiliation(s)
- Nikolaus Goessweiner-Mohr
- Institute for Molecular Biosciences, Karl-Franzens-University Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| | - Christian Fercher
- Institute for Molecular Biosciences, Karl-Franzens-University Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| | | | - Ruth Birner-Gruenberger
- Institute for Pathology and Center of Medical Research, Medical University Graz, Stiftingtalstrasse 24, 8010 Graz, Austria
| | - Diana Laverde-Gomez
- Division of Infectious Diseases, University Medical Center Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany
| | - Johannes Huebner
- Division of Infectious Diseases, University Medical Center Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany
| | - Elisabeth Grohmann
- Division of Infectious Diseases, University Medical Center Freiburg, Hugstetter Strasse 55, 79106 Freiburg, Germany
| | - Walter Keller
- Institute for Molecular Biosciences, Karl-Franzens-University Graz, Humboldtstrasse 50/III, 8010 Graz, Austria
| |
Collapse
|
75
|
Christie PJ, Whitaker N, González-Rivera C. Mechanism and structure of the bacterial type IV secretion systems. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:1578-91. [PMID: 24389247 DOI: 10.1016/j.bbamcr.2013.12.019] [Citation(s) in RCA: 194] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 12/20/2013] [Accepted: 12/23/2013] [Indexed: 01/25/2023]
Abstract
The bacterial type IV secretion systems (T4SSs) translocate DNA and protein substrates to bacterial or eukaryotic target cells generally by a mechanism dependent on direct cell-to-cell contact. The T4SSs encompass two large subfamilies, the conjugation systems and the effector translocators. The conjugation systems mediate interbacterial DNA transfer and are responsible for the rapid dissemination of antibiotic resistance genes and virulence determinants in clinical settings. The effector translocators are used by many Gram-negative bacterial pathogens for delivery of potentially hundreds of virulence proteins to eukaryotic cells for modulation of different physiological processes during infection. Recently, there has been considerable progress in defining the structures of T4SS machine subunits and large machine subassemblies. Additionally, the nature of substrate translocation sequences and the contributions of accessory proteins to substrate docking with the translocation channel have been elucidated. A DNA translocation route through the Agrobacterium tumefaciens VirB/VirD4 system was defined, and both intracellular (DNA ligand, ATP energy) and extracellular (phage binding) signals were shown to activate type IV-dependent translocation. Finally, phylogenetic studies have shed light on the evolution and distribution of T4SSs, and complementary structure-function studies of diverse systems have identified adaptations tailored for novel functions in pathogenic settings. This review summarizes the recent progress in our understanding of the architecture and mechanism of action of these fascinating machines, with emphasis on the 'archetypal' A. tumefaciens VirB/VirD4 T4SS and related conjugation systems. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.
Collapse
Affiliation(s)
- Peter J Christie
- Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA.
| | - Neal Whitaker
- Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA
| | - Christian González-Rivera
- Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA
| |
Collapse
|