| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 2006: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 2005: ¥2,400,000 (Direct Cost: ¥2,400,000)
|
|---|
| Research Abstract |
Bacillus cereus is a causative agent of food-borne poisonings. Based on the clinical symptoms, food-borne poisonings are divided into two types, emetic and diarrheal type. Our previous whole genome analysis isolated from emetic type foor poisoning, cereulide which is a responsible toxin for emesis is synthesized by gene cluster located not in the chromosome but on the large plasmid. We further conducted the structural analysis of cereulide biosynthesis gene cluster-carrying plasmids. At the same time, we also investigated the genetic background of such cereulide-producing B. cereus strains. PCR analysis revealed that all cereulide-producing strains possessed large plasmids with no exceptions. We also found the structural similarities among those plasmids. Although cereulide-biosynthesis gene cluster was absent, some cereulide-non producing strains had large plasmids which were partially resemble to those from cereulide-producing strains. These observations led us to explore the genetic background of cereulide-producing strains using multilocus sequence typing. Twenty-five cereulide-producing strains fell into four sequence types (STs). Three out of four STs have already been reported, however, we found the new cluster, namely ST164. To our surprise, this ST164 was much closer to STs such as ST1 or ST135 which were composed of only B.anthracis. Judging from the similar chemical or biological properties, it has long been assumed that B.cereus and B.anthracis were very close to each other. Our current studies have successively demonstrated that not all B.cereus but cereulide-producing B.cereus is genetically close to B.anthracis, and emergence of such emetic type B.cereus is thought to be recent in the history of B.cereus.
|
