Putative VanRS-like two-component regulatory system associated with the inducible glycopeptide resistance cluster of Paenibacillus popilliae.

Paenibacillus popilliae contains vanF encoding a putative D-Ala:D-lactate (D-Lac) ligase, VanF, as part of the vanY(F)Z(F)H(F)FX(F) cluster that is similar in structure to the enterococcal vanA and vanB clusters. Using growth curves, we demonstrated that vancomycin resistance in P. popilliae is inducible. Using degenerate oligonucleotides targeted at bacterial cell wall ligases, we identified a second ligase gene with features of a D-Ala:D-Ala ligase in both P. popilliae and the related, vancomycin-susceptible, Paenibacillus lentimorbus. The 3,380-bp region upstream of vanY(F)Z(F)H(F)FX(F) in P. popilliae ATCC 14706 was sequenced and found to contain genes encoding a putative two-component regulator, VanR(F)S(F), similar to VanRS but more closely related to a family of two-component regulators linked to VanY-like carboxypeptidases in several glycopeptide-susceptible Bacillus species. This upstream region also included a transposase similar to a transposase found in Bacillus halodurans and, in some strains, a 99-bp insertion of unknown function with 95% nucleotide identity to a portion of the Tn1546 transposase gene. Analysis of glycopeptide resistance-associated clusters from soil and/or insect-dwelling organisms may provide important clues to the molecular evolution of acquired glycopeptide resistance elements in human pathogens.