Aes may also play a role in the regulation

of raffinose m

Aes may also play a role in the regulation

of raffinose metabolism by inhibiting α-galactosidase [27]. However, these data were obtained from overexpression of aes from plasmids, thus raising the question of their relevance in vivo. An illustration of aes overexpression from the plasmid pACS2 [28] is shown in Additional file 1: Fig. S1. Secondly, a previous study of aes expression in the K-12 strain in vitro did not find significant effects on expression under the various metabolic, stress or environmental Fer-1 conditions tested http://​genexpdb.​ou.​edu/​, with the exception of aes overexpression observed in strains cultured in the presence of acetate [29]. Interestingly, esterase B exhibits Michaelis-Menten kinetics for the hydrolysis of 1-naphtyl acetate [9]. Finally, aes expression was found to be homogeneous see more across 10 representative strains of E. coli/Shigella cultured in 869 medium [30]. Our previous findings from the study of the genetic sequence surrounding aes did not suggest a role for the encoded protein in virulence. Indeed, comparisons, using the MaGe system, of 75 kbp of sequence upstream and downstream from aes in the 20 strains of E. coli [31] showed that aes is not located in/or adjacent to any regions linked to extraintestinal pathogeniCity specific to B2 strains (Additional file 2: Table S1). To gain insight into Aes function we tested the mutants

under different conditions. Firstly, we studied the in vitro growth of parent-type strains and their respective

mutants on several Selleck ARRY-162 carbon sources. We did not observe any difference between parent-type strains K-12 or CFT073 and their respective mutants K-12 Δaes and CFT073 Δaes in competition studies with LB and gluconate minimum media (data not shown). Additionally, growth of the strains CFT073, K-12, CFT073 Δaes and K-12 Δaes, in the presence of different carbon sources, was the same for parent and mutant strains. These results suggested that Aes does not play a role in regulation ioxilan of the growth of the strains in these conditions. Secondly, we studied whether Aes is involved in the virulence of E. coli in vivo using a septicaemia mouse model. Kaplan-Meyer curves obtained for CFT073 and its mutants CFT073 Δaes and CFT073 Δaes:Cm were similar, suggesting that Aes is not involved in the virulence process (p = 0.87) (Additional file 1: Fig. S2). Conclusion Selection tests and phylogenetic analyses indicate that aes is under purifying selection, showing a similar evolutionary history to that of the species. The differences in electrophoretic properties between the variant types B1 and B2 were consistent with analyses of the amino-acid sequence tree for Aes and protein structure models obtained for these variants. These findings illustrated the marked divergence of the B2 phylogenetic group from the A, B1 and D phylogenetic groups in this species.

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