sativa), can improve the fitness of their host plants and are therefore known as plant-growth-promoting bacteria (PGPB; [3, 12, 13]). In a recent study, we assessed the bacterial communities that occur within roots of rice plants by both cultivation-independent (i.e. more than 500 clones containing the 16S rRNA gene were sequenced) and cultivation-dependent approaches . From the directly-obtained clone library, ca. 30% of the sequences were assigned to one unique operational taxonomic unit (OTU), defined at 99% sequence similarity as a member of the genus Enterobacter. In addition, selleck chemical we obtained a high number of bacterial isolates (222) from the same samples,
by serial dilution on R2A agar. After screening these isolates to assess the number of different genotypes via BOX-A1R PCR, 84 distinct fingerprinting patterns were observed across all, using an 80% similarity cut-off level . Preliminary analysis of the 16S rRNA genes of each of these groups revealed a suite of six independent (non-clonal) strains that were closely related to the most abundantly retrieved OTU from the clone library. This clearly demonstrated the predominance of Enterobacter-related types in Napabucasin the rice
root bacterial community and indicated their potential functional importance. The 16S rRNA sequences also matched a sequence obtained from an Enterobacter sp. (denoted CBMB30), a rice endophytic bacterium why isolated in South Korea that was reported to have plant-growth-promoting properties . In the current study, the six strains, divided into two related groups of three strains each, are further characterized. On the basis of the collective results obtained, we propose that they constitute two new species, which we denominate Enterobacter oryziphilus sp. nov. (strains REICA_084, REICA_142T and REICA_191) and Enterobacter oryzendophyticus sp. nov. (strains REICA_032, REICA_082T and REICA_211). Results and discussion Presumptive identification of strains Six isolates, obtained from different rice root samples, were grouped, by preliminary analyses, into two groups of three strains each, which both resembled,
by comparison of their partial 16S rRNA gene sequences, the dominant clones in a directly obtained clone library . Analyses of the full 16S rRNA gene sequences of all isolates then revealed hits, at high levels of homology, with sequences belonging to members of the genus Enterobacter, including the type strains of several different species. Figure 1 gives a depiction of a maximum parsimony (MP) based phylogenetic tree, which used 1125 unambiguously aligned positions, 90 of which are informative under the parsimony criterion. The tree was constructed on the basis of a comparison of the six new isolates with a range of related (mostly Enterobacter) sequences. The topology of the tree was strongly supported by bootstrap analyses (Figure 1).