Abstract
In many gram negative bacilli, AmpD plays a key role in both cell well-recycling pathway and β-lactamase regulation, inactivation of the ampD causes the accumulation of 1,6-anhydromuropeptides, and results in the ampC overproduction. In Yersinia enterocolitica, the regulation of ampC expression may also rely on the ampR-ampC system, the role of AmpD in this species is still unknown. In this study, three AmpD homologs (AmpD1, AmpD2, and AmpD3) have been identified in complete sequence of strain Y. enterocolitica subsp. palearctica 105.5R(r). To understand the role of three AmpD homologs, several mutant strains were constructed and analyzed where a rare ampC regulation mechanism was observed: low-effective ampD2 and ampD3 cooperate with the high-effective ampD1 in the three levels regulation of ampC expression. Enterobacteriaceae was used to be supposed to regulate ampC expression by two steps, three steps regulation was only observed in Pseudomonas aeruginosa. In this study, we first reported that Enterobacteriaceae Y. enterocolitica can also possess a three steps stepwise regulation mechanism, regulating the ampC expression precisely.
Highlights
Yersinia enterocolitica is a human enteric pathogen with worldwide distribution
Strains were routinely grown in Luria Bertani (LB) broth or on LB plates at 28◦C (Y. enterocolitica) and 37◦C (E. coli)
All three AmpD homologs in Y. enterocolitica have four common residues at positions 34(H), 69(H), 154(H), and 165(P) shown by Jacobs et al (1995); and six essential residues 34(H), 116(E), and 154(H), 162(K), 164(D) for C. freundii AmpD activity reported by Genereux et al were found (Genereux et al, 2004)
Summary
Yersinia enterocolitica is a human enteric pathogen with worldwide distribution. It is a highly heterogeneous species with six biovars (1A, 1B, 2, 3, 4, and 5) that has more than fifty serotypes with different geographical distribution, ecological niches, and pathogenic properties (Wang et al, 2009; Liang et al, 2012). The resulting plasmid was introduced into E. coli S17 λpir and transferred into the wild-type strain 105.5R(r) and the seven derivate ampD mutants with or without cefoxitin. Luminescence values showed an obvious elevation when the ampD1 inactivated strain, YE D1, was examined; and the ampC promoter activity of double inducible conditions.
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