Lactococcus lactis mutants resistant to lactococcin A and garvicin Q reveal missense mutations in the sugar transport domain of the mannose phosphotransferase system

Lactococcin A is a bacteriocin from Lactococcus lactis that permeabilizes the membrane of sensitive lactococcal cells and requires the presence of the membrane-bound components IIC and IID of the mannose phosphotransferase system (man-PTS). Recently, it was reported through cryo-electron microscopy analyses of man-PTS and several bacteriocins fused to a maltose-binding protein, including lactococcin A, that these bacteriocins create pores by inserting themselves between the Core and Vmotif domains of man-PTS. In our study, we obtained a dozen spontaneous mutants of L. lactis IL1403 resistant to lactococcin A. All but one of the mutants of IL1403 have mutations located in the genes encoding the IIC or IID proteins. These mutations also resulted in resistance to garvicin Q, a bacteriocin from Lactococcus garvieae with a broad inhibition spectrum and very little sequence homology to lactococcin A. Missense mutations were found in the sugar transport domain of man-PTS of bacteriocin-resistant IL1403 mutants, which also impeded the uptake of mannose. When lactococcin A, garvicin Q, or pediocin PA-1, an anti-listerial bacteriocin, were fused to a maltose-binding protein, we observed reduced or no antibacterial activity. Taken together, the precise mechanism of action of bacteriocins using the man-PTS remains to be fully understood

Response of Methicillin-Resistant Staphylococcus aureus to Amicoumacin A

Amicoumacin A exhibits strong antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA), hence we sought to uncover its mechanism of action. Genome-wide transcriptome analysis of S. aureus COL in response to amicoumacin A showed alteration in transcription of genes specifying several cellular processes including cell envelope turnover, cross-membrane transport, virulence, metabolism, and general stress response. The most highly induced gene was lrgA, encoding an antiholin-like product, which is induced in cells undergoing a collapse of Δψ. Consistent with the notion that LrgA modulates murein hydrolase activity, COL grown in the presence of amicoumacin A showed reduced autolysis, which was primarily caused by lower hydrolase activity. To gain further insight into the mechanism of action of amicoumacin A, a whole genome comparison of wild-type COL and amicoumacin A-resistant mutants isolated by a serial passage method was carried out. Single point mutations generating codon substitutions were uncovered in ksgA (encoding RNA dimethyltransferase), fusA (elongation factor G), dnaG (primase), lacD (tagatose 1,6-bisphosphate aldolase), and SACOL0611 (a putative glycosyl transferase). The codon substitutions in EF-G that cause amicoumacin A resistance and fusidic acid resistance reside in separate domains and do not bring about cross resistance. Taken together, these results suggest that amicoumacin A might cause perturbation of the cell membrane and lead to energy dissipation. Decreased rates of cellular metabolism including protein synthesis and DNA replication in resistant strains might allow cells to compensate for membrane dysfunction and thus increase cell survivability

Ribosomally synthesized and post-translationally modified peptide natural products: Overview and recommendations for a universal nomenclature

Covering: 1988 to 2012 This review presents recommended nomenclature for the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs), a rapidly growing class of natural products. The current knowledge regarding the biosynthesis of the >20 distinct compound classes is also reviewed, and commonalities are discussed

Studies on tridecaptin B(1), a lipopeptide with activity against multidrug resistant Gram-negative bacteria

Tridecaptin B1is a new lipopeptide with activity against Gram-negative bacteria.</p