No abstract

The gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria is the causative agent of bacterial spot disease in pepper and tomato plants, which leads to economically important yield losses. This pathosystem has become a well-established model for studying bacterial infection strategies. Here, we present the whole-genome sequence of the pepper-pathogenic Xanthomonas campestris pv. vesicatoria strain 85-10, which comprises a 5.17-Mb circular chromosome and four plasmids. The genome has a high G؉C content (64.75%) and signatures of extensive genome plasticity. Whole-genome comparisons revealed a gene order similar to both Xanthomonas axonopodis pv. citri and Xanthomonas campestris pv. campestris and a structure completely different from Xanthomonas oryzae pv. oryzae. A total of 548 coding sequences (12.2%) are unique to X. campestris pv. vesicatoria. In addition to a type III secretion system, which is essential for pathogenicity, the genome of strain 85-10 encodes all other types of protein secretion systems described so far in gramnegative bacteria. Remarkably, one of the putative type IV secretion systems encoded on the largest plasmid is similar to the Icm/Dot systems of the human pathogens Legionella pneumophila and Coxiella burnetii. Comparisons with other completely sequenced plant pathogens predicted six novel type III effector proteins and several other virulence factors, including adhesins, cell wall-degrading enzymes, and extracellular polysaccharides. Xanthomonas campestris pv. vesicatoria (also designatedXanthomonas axonopodis pv. vesicatoria [101] or Xanthomonas euvesicatoria [46]) is a gram-negative, rod-shaped ␥-proteobacterium with a high genomic GϩC content. Members of the genus Xanthomonas represent an omnipresent group of plantpathogenic bacteria which infect most economically important crop plants and cause a broad variety of diseases (54). X. campestris pv. vesicatoria, the causative agent of bacterial spot disease on pepper (Capsicum spp.) and tomato (Lycopersicon spp.) plants, enters the plant tissue through stomata and wounds. Bacterial colonization of plant intercellular spaces is locally restricted and induces macroscopically visible disease symptoms, so-called water-soaked lesions that later become necrotic (91). The disease results in defoliation and severely spotted fruits, both of which cause massive yield losses. Bacterial spot disease occurs worldwide but is most pernicious in regions with a warm and humid climate.Pathogenicity of X. campestris pv. vesicatoria depends on a type III protein secretion system (TTSS) (11, 17), which is highly conserved among plant and animal pathogenic bacteria (24, 97). In X. campestris pv. vesicatoria, the TTSS is encoded by the chromosomal hrp gene cluster (hypersensitive response and pathogenicity) (11) and translocates effector proteins into the plant cell (96). Once inside the plant cytoplasm, the effectors modulate host cell processes, such as suppression of the plant basal defense mechanisms, for the benefit of the pathog...

The genus Sorangium synthesizes approximately half of the secondary metabolites isolated from myxobacteria, including the anti-cancer metabolite epothilone. We report the complete genome sequence of the model Sorangium strain S. cellulosum So ce56, which produces several natural products and has morphological and physiological properties typical of the genus. The circular genome, comprising 13,033,779 base pairs, is the largest bacterial genome sequenced to date. No global synteny with the genome of Myxococcus xanthus is apparent, revealing an unanticipated level of divergence between these myxobacteria. A large percentage of the genome is devoted to regulation, particularly post-translational phosphorylation, which probably supports the strain's complex, social lifestyle. This regulatory network includes the highest number of eukaryotic protein kinase-like kinases discovered in any organism. Seventeen secondary metabolite loci are encoded in the genome, as well as many enzymes with potential utility in industry.Natural products and their derivatives provide the basis for medicines targeting a wide range of human diseases. The Gram-negative myxobacteria, members of the d-subgroup of proteobacteria, are an important source of novel classes of secondary metabolites 1 . Of these, the genus Sorangium is particularly valuable, as 46% of metabolites isolated from myxobacteria 1 , including the potent antitumor compound epothilone 2 , derive from this group. The majority of myxobacterial metabolites are polyketides, nonribosomal polypeptides or hybrids of the two structures, many of which are synthesized on gigantic molecular assembly lines composed of polyketide synthase (PKS) and nonribosomal polypeptide synthetase (NRPS) multienzymes 3 . Sorangium strains exhibit additional characteristic features, including 'social behavior' , cell movement by gliding, biofilm formation and morphological differentiation culminating in complex multicellular structures called fruiting bodies 4 . Three myxobacterial suborders are known 5 and the availability of the genome sequence of Myxococcus xanthus (Cystobacterineae) 6 enables comparative analysis with the Sorangium cellulosum (Sorangiineae) genome to illuminate the basis for several important behavioral and metabolic differences. These include the ability of Sorangium strains to degrade complex plant materials (Fig. 1). S. cellulosum So ce56, an obligate aerobe, was established previously as a model Sorangium strain 7 by virtue of its favorable growth characteristics and ability to differentiate reproducibly under laboratory conditions. It synthesizes the cytotoxic chivosazoles 7 and the catecholate-type siderophores myxochelins 8 . Comparison of the complete genome sequence of strain S. cellulosum

Clavibacter michiganensis subsp. michiganensis is a plant-pathogenic actinomycete that causes bacterial wilt and canker of tomato. The nucleotide sequence of the genome of strain NCPPB382 was determined. The chromosome is circular, consists of 3.298 Mb, and has a high G؉C content (72.6%). Annotation revealed 3,080 putative protein-encoding sequences; only 26 pseudogenes were detected. Two rrn operons, 45 tRNAs, and three small stable RNA genes were found. The two circular plasmids, pCM1 (27.4 kbp) and pCM2 (70.0 kbp), which carry pathogenicity genes and thus are essential for virulence, have lower G؉C contents (66.5 and 67.6%, respectively). In contrast to the genome of the closely related organism Clavibacter michiganensis subsp. sepedonicus, the genome of C. michiganensis subsp. michiganensis lacks complete insertion elements and transposons. The 129-kb chp/tomA region with a low G؉C content near the chromosomal origin of replication was shown to be necessary for pathogenicity. This region contains numerous genes encoding proteins involved in uptake and metabolism of sugars and several serine proteases. There is evidence that single genes located in this region, especially genes encoding serine proteases, are required for efficient colonization of the host. Although C. michiganensis subsp. michiganensis grows mainly in the xylem of tomato plants, no evidence for pronounced genome reduction was found. C. michiganensis subsp. michiganensis seems to have as many transporters and regulators as typical soil-inhabiting bacteria. However, the apparent lack of a sulfate reduction pathway, which makes C. michiganensis subsp. michiganensis dependent on reduced sulfur compounds for growth, is probably the reason for the poor survival of C. michiganensis subsp. michiganensis in soil.

Background: Bordetella petrii is the only environmental species hitherto found among the otherwise host-restricted and pathogenic members of the genus Bordetella. Phylogenetically, it connects the pathogenic Bordetellae and environmental bacteria of the genera Achromobacter and Alcaligenes, which are opportunistic pathogens. B. petrii strains have been isolated from very different environmental niches, including river sediment, polluted soil, marine sponges and a grass root. Recently, clinical isolates associated with bone degenerative disease or cystic fibrosis have also been described.