Thus, rpoB has become an important proxy in studies aiming for the discrimination of closely-related strains and species. A comparison of the rpoB gene sequences of all six strains and their closest neighbours (Figure 2) revealed that all novel sequences were less than
98% similar to any of the described sequences. Given the fact that the 98% level of rpoB gene sequence similarity represents the proposed cut-off level for the definition of species within the family Enterobacteriaceae, this yielded a second piece of evidence for the contention that the two groups of new strains constitute novel species within the Enterobacteriaceae. Figure 2 further ML323 research buy showed that the rpoB sequences of strains of group-I (REICA_142T, REICA_084
and REICA_191) were identical to each other, grouping distantly with a cluster containing sequences of E. radicincitans D5/23T (97.5% similarity), E. arachidis Ah-143T (96.6%) and E. cowanii CIP 107300T (92.8%). The rpoB gene sequences of the group-II strains were also virtually identical, with those of strains REICA_032 and REICA_211 being the same and 99.8% similar to that of REICA_082T. As these sequences were quite divergent from those of any other group (as well as from the first group), a HDAC inhibitor separate cluster was defined in the tree (Figure 2). The sequence of the proposed group-II type strain REICA_082T was most closely related to that of E. radicincitans D5/23T (92.4% sequence similarity), E. arachidis EPZ-6438 mw Ah-143T (92.0%) and strain REICA_142T (91.9%). Phylogenetic inference on the basis of maximum likelihood corroborates the results obtained with the MP based
trees (Additional file 2: Figure S2). Additionally, the rpoB gene based analyses were supported by those of the predicted proteins; in these nucleotide sequence based analyses, the strains of groups I and II again clustered tightly together within a main cluster encompassing a range of Enterobacter (next to Cronobacter) strains including the same close relatives as above (data not shown). Figure 2 Maximum parsimony (MP) consensus tree based on the rpoB gene sequence of selected Enterobacteriaceae Lepirudin . Tree wasconstructed using CNI with a search level of 3, and initial trees by random addition (100 reps). The consensus tree inferred from 5600 most parsimonious trees is shown. Branches corresponding to partitions reproduced in less than 50% of the trees are collapsed. The percentage of parsimonious trees in which the associated taxa cluster together in the bootstrap test (1000 replications) are shown next to the branches. The analyses involved 45 sequences. All positions containing gaps and missing data were eliminated. There was a total of 495 positions in the final dataset, 136 of which are informative under the parsimony criterion. Evolutionary analyses were conducted in MEGA5.