Clostridium perfringens is a Gram-positive anaerobic spore-forming bacterium that causes life-threatening gas gangrene and mild enterotoxaemia in humans, although it colonizes as normal intestinal flora of humans and animals. The organism is known to produce a variety of toxins and enzymes that are responsible for the severe myonecrotic lesions. Here we report the complete 3,031,430-bp sequence of C. perfringens strain 13 that comprises 2,660 protein coding regions and 10 rRNA genes, showing pronounced low overall G ؉ C content (28.6%). The genome contains typical anaerobic fermentation enzymes leading to gas production but no enzymes for the tricarboxylic acid cycle or respiratory chain. Various saccharolytic enzymes were found, but many enzymes for amino acid biosynthesis were lacking in the genome. Twenty genes were newly identified as putative virulence factors of C. perfringens, and we found a total of five hyaluronidase genes that will also contribute to virulence. The genome analysis also proved an efficient method for finding four members of the two-component VirR͞VirS regulon that coordinately regulates the pathogenicity of C. perfringens. Clearly, C. perfringens obtains various essential materials from the host by producing several degradative enzymes and toxins, resulting in massive destruction of the host tissues.

The efficiency with which lysis of five strictly anaerobic and six facultatively anaerobic bacterial species, all well-known human colonic commensals, were lysed was tested using a reference method for general metagenomic analysis and an improved method that involves higher levels of lysozyme and proteinase K, as well as the addition of achromopeptidase. Ten species were lysed with an efficiency of >80% by the reference method, while the lytic efficiency for Clostridium ramosum JCM 1298T was <50%. The lytic efficiency of the improved method for C. ramosum JCM 1298 T was 82.5%. Similarly, five samples of human feces were tested with these methods, as well as with the QIAamp DNA stool mini kit. Although the efficiency of lysis of the microbes recovered from the fecal samples fluctuated depending on the sample in the cases of the reference method (13.3-84.6%) and QIAamp DNA stool mini kit (38.8-69.2%), the improved method gave stable and high-level lysis (>90%) for all the fecal samples. Accordingly, since the DNA samples isolated by the improved method can reflect nearly true genomic information in the microbial flora, our improved method should be applicable to metagenomic analyses, not only for bacteria in the human intestine but also for bacteria in other environments.