A CHEMOTAXIS CLUSTER FROM AGROBACTERIUM-TUMEFACIENS

We report the DNA sequence of a 9.6-kb region of the Agrobacterium tum efaciens chromosome containing a putative 8-kb chemotaxis operon. The putative operon begins with orf1, whose predicted protein product show s strong sequence identity to methyl-accepting chemotaxis proteins (MC Ps), followed by orf2, che Y1, cheA, cheR, cheB, che Y2, orf9, orf10. All of the identified homologues show a high degree of sequence conser vation with their counterparts in the che operons from Sinorhizobium m eliloti and Rhodobacter sphaeroides, and are arranged in a similar ord er. Mutations in orf1 and cheA result in impaired chemotaxis, whereas deletion of orf10, appears to have no effect on chemotaxis or motility . Although the putative operon does not contain a cheW homologue, hete rologous probing and PCR using consensus primers indicates that cheW m aps elsewhere in the Agrobacterium genome. (C) 1998 Elsevier Science B .V. All rights reserved.