The VanRS Homologous Two-Component System VnlRS(Ab) of the Glycopeptide Producer Amycolatopsis balhimycina Activates Transcription of the vanHAX(Sc) Genes in Streptomyces coelicolor, but not in A. balhimycina

In enterococci and in Streptomyces coelicolor, a glycopeptide nonproducer, the glycopeptide resistance genes vanHAX are colocalized with vanRS. The two-component system (TCS) VanRS activates vanHAX transcription upon sensing the presence of glycopeptides. Amycolatopsis balhimycina, the producer of the vancomycin-like glycopeptide balhimycin, also possesses vanHAX(Ab) genes. The genes for the VanRS-like TCS VnlRS(Ab), together with the carboxypeptidase gene vanY(Ab), are part of the balhimycin biosynthetic gene cluster, which is located 2 Mb separate from the vanHAX(Ab). The deletion of vnlRS(Ab) did not affect glycopeptide resistance or balhimycin production. In the A. balhimycina vnlR(A)(b) deletion mutant, the vanHAX(Ab) genes were expressed at the same level as in the wild type, and peptidoglycan (PG) analyses proved the synthesis of resistant PG precursors. Whereas vanHAX(Ab) expression in A. balhimycina does not depend on VnlR(Ab), a VnlR(Ab)-depending regulation of vanY(Ab) was demonstrated by reverse transcriptase polymerase chain reaction (RT-PCR) and RNA-seq analyses. Although VnlR(Ab) does not regulate the vanHAX(Ab) genes in A. balhimycina, its heterologous expression in the glycopeptide-sensitive S. coelicolor ΔvanRS(Sc) deletion mutant restored glycopeptide resistance. VnlR(Ab) activates the vanHAX(Sc) genes even in the absence of VanS. In addition, expression of vnlR(Ab) increases actinorhodin production and influences morphological differentiation in S. coelicolor.