Diversity of peptidoglycan structure—Modifications and their physiological role in resistance in antibiotic producers

Peptidoglycan (PG) is a bacteria specific cell surface layer that ensures the bacterial shape and integrity. The two actinomycetes Amycolatopsis balhimycina and Microbispora sp. PTA-5024 are producers of PG targeting antibiotics. To prevent the binding of their secreted product to their own PG, they developed specific self-resistance mechanisms. Modifications of PG, which are applied by both strains, are the introduction of amide-residues at the PG precursors and the alternative crosslinks within the nascent PG. The PG modifications found in Microbispora sp. PTA-5024 seemed to be an intrinsic characteristic of the genus Microbispora, rather than a specific mechanism of NAI-107 resistance. In contrast, the modifications in A. balhimycina represent an alternative way to avoid suicide specific for glycopeptide producers. The different PG modifications reflect the fact that antibiotic producing organisms contain not only one but multiple mechanisms to ensure protection against biologically active molecules produced by themselves.