Genetic analysis of zwittermicin A resistance in Escherichia coli: effects on membrane potential and RNA polymerase

Abstract

SummaryZwittermicin A is a novel aminopolyol antibiotic that represents a new structural class of antibiotic and has diverse biological activities, including the suppression of plant disease and the ability to inhibit prokaryotic and eukaryotic cells. To enhance our fundamental understanding and applications of zwittermicin A, we elucidated mechanisms of zwittermicin A resistance in Escherichia coli. Two classes of zwittermicin Aresistant mutants of E. coli were selected and characterized. One class included mutants altered in hemA, hemB, hemL, ubi, cydAB or atp, which were defective in generating a proton motive force (PMF) and resistant to aminoglycosides. The mutant analysis, coupled with physiological data, indicated an association between the electrical membrane potential (⌬⌿) component of PMF and zwittermicin A sensitivity. A second class of zwittermicin A-resistant mutants was aminoglycoside sensitive and was affected in rpoB and rpoC, genes that encode subunits of RNA polymerase. The rpoB and rpoC mutants suggested that zwittermicin A might inhibit transcription, DNA replication, DNA gyrase or topoisomerase I; however, we found no further evidence to support any of these as the target for zwittermicin A. This study elucidated the genetic mechanisms of zwittermicin A resistance in E. coli. The results suggest that ⌬⌿ drives zwittermicin A uptake, and that, unlike other antibiotics for which resistance maps in rpoB or rpoC, zwittermicin A does not cause the rapid cessation of DNA or RNA synthesis, suggesting a unique mechanism of antibiosis.

Genetic Changes That Correlate with Reduced Susceptibility to Daptomycin in Staphylococcus aureus

“…The amino acid changes found in association with increases in the daptomycin MIC have not been described previously. They do not lie within the regions of rpoB known to confer resistance to the RNA polymerase inhibitor rifampin, nor do they overlap with mutations in rpoB and rpoC that confer resistance to other antibiotics, e.g., zwittermicin, streptolydigin, and microcin J25 (6,35,39,42,44,45). Mutations in rpoB and rpoC could reflect direct interaction between daptomycin and the polymerase or could alter global gene expression in ways that alter susceptibility.…”

Escherichia coli RNA Polymerase Is the Target of the Cyclopeptide Antibiotic Microcin J25

“…All known mutations leading to rifampin resistance map to the rpoB gene (reference 14 and references cited therein), while mutations causing streptolydigin resistance have been found in both ␤ and ␤Ј subunits (11,26,27). Recently, rpoB and rpoC mutants of E. coli resistant to a novel aminopolyol antibiotic, zwittermicin A, have been described (32). However, all of these antibiotics are structurally very different from MccJ25, which appears as the first peptide antibiotic affecting RNAP.…”

Genetic basis in plants for interactions with disease-suppressive bacteria

“…Efforts to improve the effectiveness of microbial biocontrol generally have concentrated on identifying or engineering new strains with enhanced attributes expected to increase disease suppression (7)(8)(9)(10). Our goal was to provide a rigorous test of the role of plant genotype in a disease-suppressive microbial biocontrol interaction.…”