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Characterisation of Dichelobacter nodosus on Misshapen and Damaged Ovine Feet: A Longitudinal Study of Four UK Sheep Flocks. Animals (Basel) 2021; 11:ani11051312. [PMID: 34063612 PMCID: PMC8147629 DOI: 10.3390/ani11051312] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2021] [Revised: 04/27/2021] [Accepted: 04/30/2021] [Indexed: 12/15/2022] Open
Abstract
Simple Summary The bacterium Dichelobacter nodosus is the cause of footrot in sheep: a painful, contagious foot disease. Some sheep may be more susceptible to carrying D. nodosus on their feet, despite showing no signs of disease, and pose a risk to flock health and welfare. This study investigated whether misshapen or damaged feet (poor hoof conformation) were more likely to have D. nodosus present and in greater quantities than feet in good condition. Eighty-five ewes from four flocks were examined three times, on average, across a 12-month period. Poor hoof conformation traits were observed in over 92% of foot observations. Feet with poor sole and heel conformation were more likely to have higher quantities of D. nodosus than those in good conformation. Furthermore, on feet positive for D. nodosus, wall overgrowth contributed towards higher D. nodosus load. We highlight feet with aspects of poor conformation traits to covertly harbour D. nodosus. These feet could transmit D. nodosus to other feet of sheep. Increasing our understanding of D. nodosus infection is crucial in helping farmers improve management practices to reduce footrot. Abstract Dichelobacter nodosus is the causal agent of ovine footrot, a contagious disease of welfare and economic concern worldwide. Damaged feet may be subclinical carriers of D. nodosus and covertly spread infection. Accordingly, we evaluated the risk of misshapen and damaged feet on D. nodosus presence and load in four commercial UK sheep flocks. Foot-level observations and swabs (n = 972) were collected from ewes (n = 85) over 12 months. On average, ewes were sampled three times. Feet were inspected for disease and scored (good/poor) for three hoof conformation traits (sole and heel, wall, and wall overgrowth). Swabs were analysed for presence and load of D. nodosus, and mixed models were constructed. Poor hoof conformation traits were present in 92.5% of foot-level observations. Feet with poor sole and heel conformation were more likely to have higher D. nodosus loads (β = 0.19, 95% CI: 0.04–0.35) than those with good conformation. Furthermore, on feet positive for D. nodosus, wall overgrowth was associated with higher D. nodosus loads (β = 0.27, 95% CI: 0.01–0.52). Feet with aspects of poor conformation covertly harbour D. nodosus and are a source of infection. Flock management should be guided by hoof conformation to reduce disease challenge.
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Low LY, Harrison PF, Gould J, Powell DR, Choo JM, Forster SC, Chapman R, Gearing LJ, Cheung JK, Hertzog P, Rood JI. Concurrent Host-Pathogen Transcriptional Responses in a Clostridium perfringens Murine Myonecrosis Infection. mBio 2018; 9:e00473-18. [PMID: 29588405 PMCID: PMC5874911 DOI: 10.1128/mbio.00473-18] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 03/01/2018] [Indexed: 11/20/2022] Open
Abstract
To obtain an insight into host-pathogen interactions in clostridial myonecrosis, we carried out comparative transcriptome analysis of both the bacterium and the host in a murine Clostridium perfringens infection model, which is the first time that such an investigation has been conducted. Analysis of the host transcriptome from infected muscle tissues indicated that many genes were upregulated compared to the results seen with mock-infected mice. These genes were enriched for host defense pathways, including Toll-like receptor (TLR) and Nod-like receptor (NLR) signaling components. Real-time PCR confirmed that host TLR2 and NLRP3 inflammasome genes were induced in response to C. perfringens infection. Comparison of the transcriptome of C. perfringens cells from the infected tissues with that from broth cultures showed that host selective pressure induced a global change in C. perfringens gene expression. A total of 33% (923) of C. perfringens genes were differentially regulated, including 10 potential virulence genes that were upregulated relative to their expression in vitro These genes encoded putative proteins that may be involved in the synthesis of cell wall-associated macromolecules, in adhesion to host cells, or in protection from host cationic antimicrobial peptides. This report presents the first successful expression profiling of coregulated transcriptomes of bacterial and host genes during a clostridial myonecrosis infection and provides new insights into disease pathogenesis and host-pathogen interactions.IMPORTANCEClostridium perfringens is the causative agent of traumatic clostridial myonecrosis, or gas gangrene. In this study, we carried out transcriptional analysis of both the host and the bacterial pathogen in a mouse myonecrosis infection. The results showed that in comparison to mock-infected control tissues, muscle tissues from C. perfringens-infected mice had a significantly altered gene expression profile. In particular, the expression of many genes involved in the innate immune system was upregulated. Comparison of the expression profiles of C. perfringens cells isolated from the infected tissues with those from equivalent broth cultures identified many potential virulence genes that were significantly upregulated in vivo These studies have provided a new understanding of the range of factors involved in host-pathogen interactions in a myonecrosis infection.
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Affiliation(s)
- Lee-Yean Low
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Australia
| | - Paul F Harrison
- Monash Bioinformatics Platform, Monash University, Clayton, Australia
| | - Jodee Gould
- Department of Molecular and Translational Science, Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, School of Clinical Science, Monash University, Clayton, Australia
| | - David R Powell
- Monash Bioinformatics Platform, Monash University, Clayton, Australia
| | - Jocelyn M Choo
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Australia
| | - Samuel C Forster
- Department of Molecular and Translational Science, Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, School of Clinical Science, Monash University, Clayton, Australia
| | - Ross Chapman
- Department of Molecular and Translational Science, Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, School of Clinical Science, Monash University, Clayton, Australia
| | - Linden J Gearing
- Department of Molecular and Translational Science, Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, School of Clinical Science, Monash University, Clayton, Australia
| | - Jackie K Cheung
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Australia
| | - Paul Hertzog
- Department of Molecular and Translational Science, Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, School of Clinical Science, Monash University, Clayton, Australia
| | - Julian I Rood
- Infection and Immunity Program, Monash Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Australia
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Detection and Serogrouping of Dichelobacter nodosus Infection by Use of Direct PCR from Lesion Swabs To Support Outbreak-Specific Vaccination for Virulent Footrot in Sheep. J Clin Microbiol 2018; 56:JCM.01730-17. [PMID: 29436426 DOI: 10.1128/jcm.01730-17] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 02/02/2018] [Indexed: 11/20/2022] Open
Abstract
Virulent footrot is an economically significant disease in most sheep-rearing countries. The disease can be controlled with vaccine targeting the fimbriae of virulent strains of the essential causative agent, Dichelobacter nodosus However, the bacterium is immunologically heterogeneous, and 10 distinct fimbrial serogroups have been identified. Ideally, in each outbreak the infecting strains would be cultured and serogrouped so that the appropriate serogroup-specific mono- or bivalent vaccine could be administered, because multivalent vaccines lack efficacy due to antigenic competition. If clinical disease expression is suspected to be incomplete, culture-based virulence tests are required to confirm the diagnosis, because control of benign footrot is economically unjustifiable. Both diagnosis and vaccination are conducted at the flock level. The aims of this study were to develop a PCR-based procedure for detecting and serogrouping D. nodosus directly from foot swabs and to determine whether this could be done accurately from the same cultured swab. A total of 269 swabs from the active margins of foot lesions of 261 sheep in 12 Merino sheep flocks in southeastern Australia were evaluated. DNA extracts taken from putative pure cultures of D. nodosus and directly from the swabs were evaluated in PCR assays for the 16S rRNA and fimA genes of D. nodosus Pure cultures were tested also by the slide agglutination test. Direct PCR using extracts from swabs was more sensitive than culture for detecting and serogrouping D. nodosus strains. Using the most sensitive sample collection method of the use of swabs in lysis buffer, D. nodosus was more likely to be detected by PCR in active than in inactive lesions, and in lesions with low levels of fecal contamination, but lesion score was not a significant factor. PCR conducted on extracts from swabs in modified Stuart's transport medium that had already been used to inoculate culture plates had lower sensitivity. Therefore, if culture is required to enable virulence tests to be conducted, it is recommended that duplicate swabs be collected from each foot lesion, one in transport medium for culture and the other in lysis buffer for PCR.
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Frosth S, Slettemeås JS, Jørgensen HJ, Angen Ø, Aspán A. Development and comparison of a real-time PCR assay for detection of Dichelobacter nodosus with culturing and conventional PCR: harmonisation between three laboratories. Acta Vet Scand 2012; 54:6. [PMID: 22293440 PMCID: PMC3292931 DOI: 10.1186/1751-0147-54-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 01/31/2012] [Indexed: 11/15/2022] Open
Abstract
Background Ovine footrot is a contagious disease with worldwide occurrence in sheep. The main causative agent is the fastidious bacterium Dichelobacter nodosus. In Scandinavia, footrot was first diagnosed in Sweden in 2004 and later also in Norway and Denmark. Clinical examination of sheep feet is fundamental to diagnosis of footrot, but D. nodosus should also be detected to confirm the diagnosis. PCR-based detection using conventional PCR has been used at our institutes, but the method was laborious and there was a need for a faster, easier-to-interpret method. The aim of this study was to develop a TaqMan-based real-time PCR assay for detection of D. nodosus and to compare its performance with culturing and conventional PCR. Methods A D. nodosus-specific TaqMan based real-time PCR assay targeting the 16S rRNA gene was designed. The inclusivity and exclusivity (specificity) of the assay was tested using 55 bacterial and two fungal strains. To evaluate the sensitivity and harmonisation of results between different laboratories, aliquots of a single DNA preparation were analysed at three Scandinavian laboratories. The developed real-time PCR assay was compared to culturing by analysing 126 samples, and to a conventional PCR method by analysing 224 samples. A selection of PCR-products was cloned and sequenced in order to verify that they had been identified correctly. Results The developed assay had a detection limit of 3.9 fg of D. nodosus genomic DNA. This result was obtained at all three laboratories and corresponds to approximately three copies of the D. nodosus genome per reaction. The assay showed 100% inclusivity and 100% exclusivity for the strains tested. The real-time PCR assay found 54.8% more positive samples than by culturing and 8% more than conventional PCR. Conclusions The developed real-time PCR assay has good specificity and sensitivity for detection of D. nodosus, and the results are easy to interpret. The method is less time-consuming than either culturing or conventional PCR.
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Han X, Kennan RM, Parker D, Davies JK, Rood JI. Type IV fimbrial biogenesis is required for protease secretion and natural transformation in Dichelobacter nodosus. J Bacteriol 2007; 189:5022-33. [PMID: 17513472 PMCID: PMC1951885 DOI: 10.1128/jb.00138-07] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The objective of this study was to develop an understanding of the molecular mechanisms by which type IV fimbrial biogenesis, natural transformation, and protease secretion are linked in the ovine foot rot pathogen, Dichelobacter nodosus. We have shown that like the D. nodosus fimbrial subunit FimA, the pilin-like protein PilE and the FimN, FimO, and FimP proteins, which are homologs of PilB, PilC, and PilD from Pseudomonas aeruginosa, are essential for fimbrial biogenesis and natural transformation, indicating that transformation requires an intact type IV fimbrial apparatus. The results also showed that extracellular protease secretion in the fimN, fimO, fimP, and pilE mutants was significantly reduced, which represents the first time that PilB, PilC, and PilE homologs have been shown to be required for the secretion of unrelated extracellular proteins in a type IV fimbriate bacterium. Quantitative real-time PCR analysis of the three extracellular protease genes aprV2, aprV5, and bprV showed that the effects on protease secretion were not mediated at the transcriptional level. Bioinformatic analysis did not identify a classical type II secretion system, and the putative fimbrial biogenesis gene pilQ was the only outer membrane secretin gene identified. Based on these results, it is postulated that in D. nodosus, protease secretion occurs by a type II secretion-related process that directly involves components of the type IV fimbrial biogenesis machinery, which represents the only type II secretion system encoded by the small genome of this highly evolved pathogen.
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MESH Headings
- Amino Acid Sequence
- Animals
- Dichelobacter nodosus/genetics
- Dichelobacter nodosus/metabolism
- Dichelobacter nodosus/ultrastructure
- Electrophoresis, Gel, Two-Dimensional
- Electrophoresis, Polyacrylamide Gel
- Fimbriae Proteins/analysis
- Fimbriae Proteins/genetics
- Fimbriae Proteins/metabolism
- Fimbriae, Bacterial/genetics
- Fimbriae, Bacterial/metabolism
- Fimbriae, Bacterial/ultrastructure
- Gene Order
- Genes, Bacterial
- Immunoblotting
- Microscopy, Electron, Transmission
- Molecular Sequence Data
- Multigene Family
- Mutation
- Peptide Hydrolases/metabolism
- Sequence Homology, Amino Acid
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Affiliation(s)
- Xiaoyan Han
- Australian Research Council Centre of Excellence in Structural and Functional Microbial Genomics, Department of Microbiology, Monash University, Victoria 3800, Australia
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Arnvig KB, Gopal B, Papavinasasundaram KG, Cox RA, Colston MJ. The mechanism of upstream activation in the rrnB operon of Mycobacterium smegmatis is different from the Escherichia coli paradigm. MICROBIOLOGY-SGM 2005; 151:467-473. [PMID: 15699196 DOI: 10.1099/mic.0.27597-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Mycobacteria are slow-growing bacteria with a generation time of from 2-3 h up to several weeks. Consistent with the low growth rate, mycobacterial species have a maximum of two rRNA operons, rrnA and rrnB. The rrnA operon is present in all mycobacteria and has between two and five promoters, depending on species, whereas the rrnB operon, with a single promoter, is only found in some of the faster-growing species. The promoter region of the rrnB operon of a typical fast grower, Mycobacterium smegmatis, was investigated. By using lacZ reporter gene fusions it was demonstrated that the rrnB operon contains a highly activating region upstream of the core promoter, comparable to other bacterial rrn operons. However, the results suggest that, unlike the situation in, for example, Escherichia coli, the activating mechanism is solely factor dependent, and that no UP element is involved.
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Affiliation(s)
- Kristine B Arnvig
- Division of Mycobacterial Research, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - B Gopal
- Division of Protein Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - K G Papavinasasundaram
- Division of Mycobacterial Research, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - Robert A Cox
- Division of Mycobacterial Research, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
| | - M Joseph Colston
- Division of Mycobacterial Research, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
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Parker D, Kennan RM, Myers GS, Paulsen IT, Rood JI. Identification of a Dichelobacter nodosus ferric uptake regulator and determination of its regulatory targets. J Bacteriol 2005; 187:366-75. [PMID: 15601721 PMCID: PMC538842 DOI: 10.1128/jb.187.1.366-375.2005] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The expression of iron regulated genes in bacteria is typically controlled by the ferric uptake regulator (Fur) protein, a global transcriptional repressor that regulates functions as diverse as iron acquisition, oxidative stress, and virulence. We have identified a fur homologue in Dichelobacter nodosus, the causative agent of ovine footrot, and shown that it complements an Escherichia coli fur mutant. Homology modeling of the D. nodosus Fur protein with the recently solved crystal structure of Fur from Pseudomonas aeruginosa indicated extensive structural conservation. As Southern hybridization analysis of different clinical isolates of D. nodosus indicated that the fur gene was present in all of these strains, the fur gene was insertionally inactivated to determine its functional role. Analysis of these mutants by various techniques did not indicate any significant differences in the expression of known virulence genes or in iron-dependent growth. However, we determined several Fur regulatory targets by two-dimensional gel electrophoresis coupled with mass spectrometry. Analysis of proteins from cytoplasmic, membrane, and extracellular fractions revealed numerous differentially expressed proteins. The transcriptional basis of these differences was analyzed by using quantitative reverse transcriptase PCR. Proteins with increased expression in the fur mutant were homologues of the periplasmic iron binding protein YfeA and a cobalt chelatase, CbiK. Down-regulated proteins included a putative manganese superoxide dismutase and ornithine decarboxylase. Based on these data, it is suggested that in D. nodosus the Fur protein functions as a regulator of iron and oxidative metabolism.
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Affiliation(s)
- Dane Parker
- ARC Centre for Structural and Functional Microbial Genomics and Victorian Bioinformatics Consortium, Department of Microbiology, Monash University, Victoria, Australia
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Chen I, Gotschlich EC. ComE, a competence protein from Neisseria gonorrhoeae with DNA-binding activity. J Bacteriol 2001; 183:3160-8. [PMID: 11325945 PMCID: PMC95217 DOI: 10.1128/jb.183.10.3160-3168.2001] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Neisseria gonorrhoeae is naturally able to take up exogenous DNA and undergo genetic transformation. This ability correlates with the presence of functional type IV pili, and uptake of DNA is dependent on the presence of a specific 10-bp sequence. Among the known competence factors in N. gonorrhoeae, none has been shown to interact with the incoming DNA. Here we describe ComE, a DNA-binding protein involved in neisserial competence. The gene comE was identified through similarity searches in the gonococcal genome sequence, using as the query ComEA, the DNA receptor in competent Bacillus subtilis. The gene comE is present in four identical copies in the genomes of both N. gonorrhoeae and Neisseria meningitidis, located downstream of each of the rRNA operons. Single-copy deletion of comE in N. gonorrhoeae did not have a measurable effect on competence, whereas serial deletions led to gradual decrease in transformation frequencies, reaching a 4 x 10(4)-fold reduction when all copies were deleted. Transformation deficiency correlated with impaired ability to take up exogenous DNA; however, the mutants presented normal piliation and twitching motility phenotype. The product of comE has 99 amino acids, with a predicted signal peptide; by immunodetection, a 8-kDa protein corresponding to processed ComE was observed in different strains of N. gonorrhoeae and N. meningitidis. Recombinant His-tagged ComE showed DNA binding activity, without any detectable sequence specificity. Thus, we identified a novel gonococcal DNA-binding competence factor which is necessary for DNA uptake and does not affect pilus biogenesis or function.
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Affiliation(s)
- I Chen
- Laboratory of Bacterial Pathogenesis and Immunology, The Rockefeller University, New York, New York 10021.
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Cheung JK, Rood JI. Glutamate residues in the putative transmembrane region are required for the function of the VirS sensor histidine kinase from Clostridium perfringens. MICROBIOLOGY (READING, ENGLAND) 2000; 146 ( Pt 2):517-525. [PMID: 10708390 DOI: 10.1099/00221287-146-2-517] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The causative agent of gas gangrene, Clostridium perfringens, is a Gram-positive anaerobe which produces a number of extracellular toxins and enzymes. The production of several of these toxins is regulated by the VirS/VirR two-component signal transduction system. The sensor histidine kinase, VirS, contains motifs that are conserved amongst sensor histidine kinases, although not in the same relative positions. In this study, the conserved histidine residue (H255), the GXGL and DXGXG motifs, and two glutamate residues located in putative transmembrane domains were altered by site-directed mutagenesis to examine their significance for VirS function. Introduction of the mutated virS genes into the virS::Tn916 mutant, JIR4000, showed that the altered virS genes were not able to complement the host mutation. These results demonstrate that the conserved motifs, including the cytoplasmic DXGXG motif which is located between the putative transmembrane domains 4 and 5, are functional. Furthermore, it is concluded that charged residues located within two of these transmembrane domains are also required for the structural or functional integrity of the VirS sensor kinase.
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Affiliation(s)
- Jackie K Cheung
- Bacterial Pathogenesis Research Group, Department of Microbiology, Monash University, 3800 Clayton, Australia1
| | - Julian I Rood
- Bacterial Pathogenesis Research Group, Department of Microbiology, Monash University, 3800 Clayton, Australia1
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Chun J, Huq A, Colwell RR. Analysis of 16S-23S rRNA intergenic spacer regions of Vibrio cholerae and Vibrio mimicus. Appl Environ Microbiol 1999; 65:2202-8. [PMID: 10224020 PMCID: PMC91317 DOI: 10.1128/aem.65.5.2202-2208.1999] [Citation(s) in RCA: 205] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vibrio cholerae identification based on molecular sequence data has been hampered by a lack of sequence variation from the closely related Vibrio mimicus. The two species share many genes coding for proteins, such as ctxAB, and show almost identical 16S DNA coding for rRNA (rDNA) sequences. Primers targeting conserved sequences flanking the 3' end of the 16S and the 5' end of the 23S rDNAs were used to amplify the 16S-23S rRNA intergenic spacer regions of V. cholerae and V. mimicus. Two major (ca. 580 and 500 bp) and one minor (ca. 750 bp) amplicons were consistently generated for both species, and their sequences were determined. The largest fragment contains three tRNA genes (tDNAs) coding for tRNAGlu, tRNALys, and tRNAVal, which has not previously been found in bacteria examined to date. The 580-bp amplicon contained tDNAIle and tDNAAla, whereas the 500-bp fragment had single tDNA coding either tRNAGlu or tRNAAla. Little variation, i.e., 0 to 0.4%, was found among V. cholerae O1 classical, O1 El Tor, and O139 epidemic strains. Slightly more variation was found against the non-O1/non-O139 serotypes (ca. 1% difference) and V. mimicus (2 to 3% difference). A pair of oligonucleotide primers were designed, based on the region differentiating all of V. cholerae strains from V. mimicus. The PCR system developed was subsequently evaluated by using representatives of V. cholerae from environmental and clinical sources, and of other taxa, including V. mimicus. This study provides the first molecular tool for identifying the species V. cholerae.
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Affiliation(s)
- J Chun
- Center of Marine Biotechnology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21202, USA
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Kennan RM, Billington SJ, Rood JI. Electroporation-mediated transformation of the ovine footrot pathogen Dichelobacter nodosus. FEMS Microbiol Lett 1998; 169:383-9. [PMID: 9868785 DOI: 10.1111/j.1574-6968.1998.tb13344.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Studies on the potential virulence genes of the ovine footrot pathogen Dichelobacter nodosus have been hindered by the lack of a genetic system for this organism. In an attempt to accomplish the transformation of D. nodosus cells, we constructed a plasmid that contained part of a native D. nodosus plasmid and carried a tetracycline resistance gene that was located between the D. nodosus rrnA promoter and terminator. This plasmid was used to transform several D. nodosus strains to tetracycline resistance. Analysis of two independent transformants from each parental strain showed that in nearly all of these derivatives, the plasmid was not replicating independently, but that the tetracycline resistance gene had inserted by homologous recombination into one of the three rrn operons located on the chromosome. In most of the transformants, double reciprocal crossover events had occurred. These results are highly significant for genetic studies in D. nodosus and for footrot pathogenesis studies, since by using reverse genetics it will now be possible to examine the role of putative D. nodosus-encoded virulence genes in the disease process.
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Affiliation(s)
- R M Kennan
- Department of Microbiology, Monash University, Clayton, Vic., Australia.
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von Wintzingerode F, Göbel UB, Stackebrandt E. Determination of microbial diversity in environmental samples: pitfalls of PCR-based rRNA analysis. FEMS Microbiol Rev 1997; 21:213-29. [PMID: 9451814 DOI: 10.1111/j.1574-6976.1997.tb00351.x] [Citation(s) in RCA: 1054] [Impact Index Per Article: 39.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
After nearly 10 years of PCR-based analysis of prokaryotic small-subunit ribosomal RNAs for ecological studies it seems necessary to summarize reported pitfalls of this approach which will most likely lead to an erroneous description on the microbial diversity of a given habitat. The following article will cover specific aspects of sample collection, cell lysis, nucleic acid extraction, PCR amplification, separation of amplified DNA, application of nucleic probes and data analysis.
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MESH Headings
- Artifacts
- Bacteria/classification
- Bacteria/genetics
- Bacteria/isolation & purification
- DNA, Bacterial/analysis
- DNA, Bacterial/genetics
- DNA, Bacterial/isolation & purification
- DNA, Ribosomal/analysis
- DNA, Ribosomal/genetics
- DNA, Ribosomal/isolation & purification
- Environmental Microbiology
- Equipment Contamination
- False Negative Reactions
- False Positive Reactions
- Mutagenesis
- Polymerase Chain Reaction/instrumentation
- Polymerase Chain Reaction/methods
- RNA, Bacterial/genetics
- RNA, Bacterial/isolation & purification
- RNA, Ribosomal/genetics
- RNA, Ribosomal/isolation & purification
- RNA, Ribosomal, 16S/genetics
- RNA, Ribosomal, 16S/isolation & purification
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Affiliation(s)
- F von Wintzingerode
- Institut für Mikrobiologie und Hygiene, Universitätsklinikum Charité, Berlin, Germany
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Abstract
A physical map of the chromosome of Dichelobacter nodosus strain A198 was constructed using the restriction endonucleases EagI and StuI. Mapping data indicated the presence of a single, circular chromosome of 1.54 Mb. The three rRNA operons and the virulence related locus (vrl) were precisely positioned at the junctions of EagI and StuI fragments, and their transcriptional orientations were also determined. Other D. nodosus genes were assigned to specific EagI and StuI fragments. Analysis of the resultant map revealed that the putative virulence genes were not clustered on the chromosome which suggests that the D. nodosus virulence determinants have been acquired gradually and that virulence in D. nodosus is an evolving trait.
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Affiliation(s)
- S La Fontaine
- Department of Microbiology, Monash University, Clayton, Vic, Australia
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