A region of the Agrobacterium tumefaciens chromosome containing genes required for virulence and attachment to host cells.

A 29 kb region of the circular chromosome of Agrobacterium tumefaciens containing genes required for bacterial attachment to host cells and virulence has been sequenced. Transposon mutants in many of the genes have been obtained. The mutants can be divided into two groups: those which can be complemented by conditioned medium and those whose phenotype is unaffected by conditioned medium. The first group includes mutants in genes with homology to ABC transporters, one possible transcriptional regulator, and some closely linked genes immediately downstream. The second group includes mutants in two possible transcriptional regulators, one ATPase, and a number of biosynthetic genes including a transacetylase required for the formation of an acetylated capsular polysaccharide. There are also several genes with no homology to genes of identified function. The presence of such a large number of genes required for attachment to host cells suggests that the ability of A. tumefaciens to bind to plant cells may play an important role in the life of these bacteria.