etli and other rhizobia like R. leguminosarum bv. trifolii[7], S.meliloti[5],

and B. japonicum[2]. As shown in Figure 3B, the resulting phylogenetic tree showed four separated branches, with a generally homogeneous distribution of phylogenetic groups. The first branch was formed by OtsA proteins from β- and γ -proteobacteria, including OtsA from E. coli and Salmonella enterica. The second cluster was mainly composed of OtsA proteins from γ-proteobacteria, including some halophilic check details representatives such as C. salexigens and Halorhodospira halophila. The third branch grouped OtsAs from α-proteobacteria, including the two R. etli OtsA proteins. Whereas R. etli OtsAch grouped with OtsAs from R. leguminosarum, S. meliloti, Rhizobium sp. NGR234 and Agrobacterium vitis, R. etli OtsAa constituted a separated sub-group within the α-proteobacterial branch. The fourth branch was composed by OtsA proteins from δ-protobacteria. Some incongruences were found, as B. japonicum and Mesorhizobium proteins did not clustered with OtsA proteins from other rhizobia. In summary, this phylogenetic analysis supports the hypothesis that otsAa was transferred to R. etli or its ancestor from a related α-proteobacteria, which did not belong to the Rhizobium/Agrobacterium group. Figure 3 In silico analysis of the two trehalose-6-phosphate synthases (OtsA) encoded by the R. etli

genome. (A) Genomic context of the otsAch (GSK872 cost chromosomal) and otsAs (plasmid p42a) genes, and construction of an otsAch mutant. otsAch was inactivated by the insertion of a BamHI (Bm)-digested Ω cassette, selleck products which carried resistance genes for streptomycin/spectinomycin, into its unique site BglII (Bg), next giving the plasmid pMotsA6 (see text for details). (B) Neighbor-joining tree based on OtsA proteins from α-, β-,γ and δ-proteobacteria. The

tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. The Bacteroides/Chlorobi representative S. ruber was used as outgroup. The evolutionary distances were computed using the Poisson correction method and are in the units of the number of amino acid substitutions per site. The rate variation among sites was modeled with a gamma distribution (shape parameter = 1). All positions containing gaps and missing data were eliminated from the dataset (complete deletion option). Bootstrap probabilities (as percentage) were determined from 1000 resamplings. Inactivation of R. etli otsAch totally suppresses trehalose synthesis from mannitol From the above phylogenetic analysis, otsAch was chosen as the most promising candidate to encode a functional trehalose-6-P-synthase. To check this, the corresponding mutant (strain CMS310) was constructed by insertion of an omega cassette within otsAch (Figure 3A), followed by double recombination in the chromosome of the wild-type strain.