Structure and Regulation of a Gene Cluster Involved in Capsule Formation of Y.Pestis

Abstract

It has been known since 1894 that, the causative agent of plague disease, gram-negative bacterium Yersinia pestis, is capable of forming large capsules (Kitazato, 1894). The capsule substance is highly immunogenic for mice and has been under extensive study as a potential component of synthetic vaccine against disease. Chemical analysis of capsule (F1 antigen) has led to the conclusion that it consists of protein (Amies, 1951), lipid and polysaccharide (Glosnicka & Gruszkiewicz, 1980). We have cloned the gene cluster determining synthesis of the capsule protein subunut and shown that this subunit of protein origin can be secreted in E.coli cells with the formation of capsule. The gene, encoding capsule subunit, as well as genes involved in translocation of the protein across bacterial outer membrane have been sequenced. These data together with those of subcloning, mutagenesis and complementation analysis have led to the conclusion that the f1 gene cluster is organised in a similar way to the gene clusters involved in extracellular secretion and assembly of some fimbriae subunits of E.coli and other gram-negative bacteria (Karlyshev et al., 1992a). It has been also shown that the f1 gene cluster contains gene responsible for the regulation of capsule formation.