A novel type of conserved DNA-binding domain in the transcriptional regulators of the AlgR/AgrA/LytR family.
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Sequence analysis of bacterial genomes revealed a novel DNA-binding domain. This domain is found in several response regulators of the two-component signal transduction system, such as Pseudomonas aeruginosa AlgR, involved in the regulation of alginate biosynthesis and in the pathogenesis of cystic fibrosis; Clostridium perfringens VirR, a regulator of virulence factors, and in several regulators of bacteriocin biosynthesis, previously unified in the AgrA/ComE family. Most of the transcriptional regulators that contain this DNA-binding domain are involved in biosynthesis of extracellular polysaccharides, fimbriation, expression of exoproteins, including toxins, and quorum sensing. We refer to it as the LytTR ('litter') domain, after Bacillus subtilis LytT and Staphylococcus aureus LytR response regulators, involved in regulation of cell autolysis. In addition to response regulators, the LytTR domain is found in combination with MHYT, PAS and other sensor domains. (+info)
Breath hydrogen concentrations of cats given commercial canned and extruded diets indicate gastrointestinal microbial activity vary with diet type.
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Breath hydrogen (H(2)) concentration, an indicator of intestinal microbial abundance, was determined in cats given purified and commercial canned and dry-type diets. Before measurements, the cats were fed diets for more than 2 wk and habituated to a daily feeding interval of 4 hr. Breath H(2) concentrations were determined before a meal (approximately 25% daily MER) and then every 20 min for 8 hr or hourly for 10 hr. A clear rise above baseline breath H(2) concentrations, 1-2 ppm, was not observed in 6 males given a casein-based purified diet. A mean (+/- SEM) peak breath H(2) concentration of 22 +/- 4 ppm was observed in 6 other males, 6.3 hr after ingestion of a canned diet with protein, fat, and carbohydrate proportions similar to those of the purified diet. Area-under-the-curve (AUC) breath H(2) responses to the canned diet were substantially greater (p < 0.05) than responses observed in 5 males given a dry-type diet, but similar to responses observed in 12 males given an uncooked form of the canned diet. Gamma irradiation to inactivate microbes in the uncooked diet did not affect the breath H(2) response. Breath H(2) responses to 2 other canned and 2 other dry-type diets were evaluated in 8 adult females using a 4 x 4 Latin-square design. Peak and AUC responses to the canned diets were similar but approximately 2 times greater (p < 0.05) than responses to the dry diets. Relative to dry-type diets, canned diets induce a substantially greater breath H(2) production, and therefore appear to support a greater intestinal microbial population. (+info)
Anaerobic cellulitis as the result of Clostridium perfringens: a rare cause of vascular access graft infection.
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Infection of prosthetic vascular access grafts is the second most common complication of vascular access and represents a challenge encountered by the vascular surgeon. Anaerobic graft infections are rare. We report on a case of a prosthetic vascular access graft infection with Clostridium perfringens. To our knowledge, only one other case with an infected arteriovenous shunt caused by C perfringens has been reported. The patient, a 67-year-old woman with end-stage renal failure as the result of polycystic renal disease, was seen with an infected pseudoaneurysm at the arterial puncture site of the loop graft on the left arm. There was associated purulence at the time of operation. Surgical management consisted of complete graft removal because of the presence of small tunnel abscesses. C perfringens was found in the resected pseudoaneurysm and graft material. Infected pseudoaneurysms most likely are attributable to repetitive punctures in one small area and to a break in sterile technique. A compromised vascular supply, not infrequent in patients for hemodialysis, may lower the oxidation reduction potential, which allows anaerobic bacteria, such as C perfringens, to cause infection. (+info)
Distribution of genes encoding the trypsin-dependent lantibiotic ruminococcin A among bacteria isolated from human fecal microbiota.
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Fourteen bacterial strains capable of producing a trypsin-dependent antimicrobial substance active against Clostridium perfringens were isolated from human fecal samples of various origins (from healthy adults and children, as well as from adults with chronic pouchitis). Identification of these strains showed that they belonged to Ruminococcus gnavus, Clostridium nexile, and Ruminococcus hansenii species or to new operational taxonomic units, all from the Clostridium coccoides phylogenetic group. In hybridization experiments with a probe specific for the structural gene encoding the trypsin-dependent lantibiotic ruminococcin A (RumA) produced by R. gnavus, seven strains gave a positive response. All of them harbored three highly conserved copies of rumA-like genes. The deduced peptide sequence was identical to or showed one amino acid difference from the hypothetical precursor of RumA. Our results indicate that the rumA-like genes have been disseminated among R. gnavus and phylogenetically related strains that can make up a significant part of the human fecal microbiota. (+info)
Organization of the plasmid cpe Locus in Clostridium perfringens type A isolates.
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Clostridium perfringens type A isolates causing food poisoning have a chromosomal enterotoxin gene (cpe), while C. perfringens type A isolates responsible for non-food-borne human gastrointestinal diseases carry a plasmid cpe gene. In the present study, the plasmid cpe locus of the type A non-food-borne-disease isolate F4969 was sequenced to design primers and probes for comparative PCR and Southern blot studies of the cpe locus in other type A isolates. Those analyses determined that the region upstream of the plasmid cpe gene is highly conserved among type A isolates carrying a cpe plasmid. The organization of the type A plasmid cpe locus was also found to be unique, as it contains IS1469 sequences located similarly to those in the chromosomal cpe locus but lacks the IS1470 sequences found upstream of IS1469 in the chromosomal cpe locus. Instead of those upstream IS1470 sequences, a partial open reading frame potentially encoding cytosine methylase (dcm) was identified upstream of IS1469 in the plasmid cpe locus of all type A isolates tested. Similar dcm sequences were also detected in several cpe-negative C. perfringens isolates carrying plasmids but not in type A isolates carrying a chromosomal cpe gene. Contrary to previous reports, sequences homologous to IS1470, rather than IS1151, were found downstream of the plasmid cpe gene in most type A isolates tested. Those IS1470-like sequences reside in about the same position but are oppositely oriented and defective relative to the IS1470 sequences found downstream of the chromosomal cpe gene. Collectively, these and previous results suggest that the cpe plasmid of many type A isolates originated from integration of a cpe-containing genetic element near the dcm sequences of a C. perfringens plasmid. The similarity of the plasmid cpe locus in many type A isolates is consistent with horizontal transfer of a common cpe plasmid among C. perfringens type A strains. (+info)
Genomic analysis of Clostridium perfringens bacteriophage phi3626, which integrates into guaA and possibly affects sporulation.
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Two temperate viruses, phi3626 and phi8533, have been isolated from lysogenic Clostridium perfringens strains. Phage phi3626 was chosen for detailed analysis and was inspected by electron microscopy, protein profiling, and host range determination. For the first time, the nucleotide sequence of a bacteriophage infecting Clostridium species was determined. The virus belongs to the Siphoviridae family of the tailed phages, the order Caudovirales. Its genome consists of a linear double-stranded DNA molecule of 33,507 nucleotides, with invariable 3'-protruding cohesive ends of nine residues. Fifty open reading frames were identified, which are organized in three major life cycle-specific gene clusters. The genes required for lytic development show an opposite orientation and arrangement compared to the lysogeny control region. A function could be assigned to 19 gene products, based upon bioinformatic analyses, N-terminal amino acid sequencing, or experimental evidence. These include DNA-packaging proteins, structural components, a dual lysis system, a putative lysogeny switch, and proteins that are involved in replication, recombination, and modification of phage DNA. The presence of genes encoding a putative sigma factor related to sporulation-dependent sigma factors and a putative sporulation-dependent transcription regulator suggests a possible interaction of phi3626 with onset of sporulation in C. perfringens. We found that the phi3626 attachment site attP lies in a noncoding region immediately downstream of int. Integration of the viral genome occurs into the bacterial attachment site attB, which is located within the 3' end of a guaA homologue. This essential housekeeping gene is functionally independent of the integration status, due to reconstitution of its terminal codons by phage sequence. (+info)
Molecular epidemiology of Clostridium perfringens related to food-borne outbreaks of disease in Finland from 1984 to 1999.
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From 1975 to 1999, Clostridium perfringens caused 238 food-borne disease outbreaks in Finland, which is 20% of all such reported outbreaks during these years. The fact that C. perfringens is commonly found in human and animal stools and that it is also widespread in the environment is a disadvantage when one is searching for the specific cause of a food-borne infection by traditional methods. In order to strengthen the evidence-based diagnostics of food poisonings suspected to be caused by C. perfringens, we retrospectively investigated 47 C. perfringens isolates by PCR for the cpe gene, which encodes enterotoxin; by reversed passive latex agglutination to detect the enterotoxin production; and by pulsed-field gel electrophoresis (PFGE) to compare their genotypes after restriction of DNA by the enzymes SmaI and ApaI. The strains were isolated during 1984 to 1999 from nine food-borne outbreaks of disease originally reported as having been caused by C. perfringens. In seven of the nine outbreaks our results supported the fact that the cause was C. perfringens. Our findings emphasize the importance of a more detailed characterization of C. perfringens isolates than mere identification to the species level in order to verify the cause of an outbreak. Also, to increase the probability of finding the significant cpe-positive C. perfringens strains, it is very important to isolate and investigate more than one colony from the fecal culture of a patient and screen all these isolates for the presence of the cpe gene before further laboratory work is done. (+info)
Two novel oligosaccharides formed by 1F-fructosyltransferase purified from roots of asparagus (Asparagus officinalis L.).
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Two novel oligosaccharides, tetra-and penta-saccharides were synthesized by fructosyl transfer from 1-kestose to 4G-beta-D-galactopyranosylsucrose with a purified 1F-fructosyltransferase of asparagus roots and identified as 1F-beta-D-fructofuranosyl-4G-beta-D-galactopyranosylsucrose, O-beta-D-fructofuranosyl-(2-->1)-beta-D-fructofuranosyl-O-[beta-D-galactopyranosy l-(1-->4)]-alpha-D-glucopyranoside and 1F(1-beta-D-fructofuranosyl)2-4G-beta-D-galactopyranosylsucrose, [O-beta-D-fructofuranosyl-(2-->1)]2-beta-D-fructofuranosyl-O-[beta-D-galactopyran osyl-(1-->4)]-alpha-D-glucopyranoside, respectively. Both oligosaccharides were scarcely hydrolyzed by carbohydrase from rat small intestine. Human intestinal bacterial growth by 1F-beta-D-fructofuranosyl-4G-beta-D-galactopyranosylsucrose was compared with that by the tetrasaccharides, stachyose and nystose. Bifidobacteria utilized 1F-beta-D-fructofuranosyl-4G-beta-D-galactopyranosylsucrose to the same extent as stachyose or nystose. On the other hand, the unfavorable bacteria, Clostridium perfringens, Escherichia coli and Enterococcusfaecalis, that produce mutagenic substances did not use the synthetic oligosaccharide. (+info)