Characterization of the acyl carrier protein gene and the fab gene locus in Xanthomonas albilineans

A genomic region containing the fatty acid biosynthetic (fab) genes was iso lated from the sugarcane leaf-scald pathogen Xanthomonasalbilineans. The or der and predicted products of fabG (beta -ketoacyl reductase), acpP (acyl c arrier protein), fabF(ketoacyl synthase II) and downstream genes in X. albi lineans are very similar to those in Escherichia coli, with one exception. Sequence analysis, confirmed by insertional knockout and specific substrate feeding experiments, shows that the position occupied by pabC (encoding am inodeoxychorismate lyase) in other bacteria is occupied instead by pabB (en coding aminodeoxychorismate synthase component I) in X. albilineans. Downst ream of pabB, X. albilineans resumes the arrangement common to characterize d Gram-negative bacteria, with three transcriptionally coupled genes, encod ing an ORF340 protein of undefined function, thymidylate kinase and delta' subunit of DNA polymerase III holoenzyme (HolB). Different species may obta in a common advantage from coordinated regulation of the same biosynthetic pathways using different genes in this region. (C) 2000 Federation of Europ ean Microbiological Societies. Published by Elsevier Science B.V. All right s reserved.