Comparative Transcriptome Analysis Reveals Differentially Expressed Genes Related to Antimicrobial Properties of Lysostaphin in Staphylococcus aureus.

Xianghe Yan,Andrew Gehring,Peter Irwin,Yiping He,Yanping Xie,Charles Li,David M Donovan

doi:10.3390/antibiotics11020125

Abstract

Comparative transcriptome analysis and de novo short-read assembly of S. aureus Newman strains revealed significant transcriptional changes in response to the exposure to triple-acting staphylolytic peptidoglycan hydrolase (PGH) 1801. Most altered transcriptions were associated with the membrane, cell wall, and related genes, including amidase, peptidase, holin, and phospholipase D/transphosphatidylase. The differential expression of genes obtained from RNA-seq was confirmed by reverse transcription quantitative PCR. Moreover, some of these gene expression changes were consistent with the observed structural perturbations at the DNA and RNA levels. These structural changes in the genes encoding membrane/cell surface proteins and altered gene expressions are the candidates for resistance to these novel antimicrobials. The findings in this study could provide insight into the design of new antimicrobial agents.

Highlights

Lysostaphin [1], classified as a prototype III bacteriocin, is a glycyl-glycine bacteriocin peptidoglycan hydrolase (PGH) secreted by Staphylococcus simulans
PGH is known to degrade the peptidoglycans in Staphylococcus aureus cell walls, resulting in cell lysis [2]
We have identified the genetic mechanisms of resistance to peptidoglycan hydrolases via repeated exposure of S. aureus Newman_2010 strain (cultured wild-type (WT) S. aureus Newman in the year of 2010) to sublethal concentrations of a genetically engineered, triple-acting, staphylolytic, peptidoglycan hydrolase (PGH1801) [2,12]

Summary

Introduction

Lysostaphin [1], classified as a prototype III bacteriocin, is a glycyl-glycine bacteriocin peptidoglycan hydrolase (PGH) secreted by Staphylococcus simulans. PGH is known to degrade the peptidoglycans in Staphylococcus aureus cell walls, resulting in cell lysis [2]. Several mechanisms of resistance to lysostaphin have been proposed: for example, reduced S. aureus fitness [4]; mutations in lysostaphin-resistant S. aureus femA [5]; replacing the Gly of the pentaglycine ligand by serine in the peptidoglycan pentaglycine cross bridge or a shortened cross-bridge [6,7,8,9,10]; alterations in the plasmid-borne lss (lysostaphin endopeptidase) and lif (pACK1) genes [9,11]. We have identified the genetic mechanisms of resistance to peptidoglycan hydrolases via repeated exposure of S. aureus Newman_2010 strain (cultured wild-type (WT) S. aureus Newman in the year of 2010) to sublethal concentrations of a genetically engineered, triple-acting, staphylolytic, peptidoglycan hydrolase (PGH1801) [2,12]. The resultant mutant strain S. aureus Newman 1801_2010 has resistance to lysostaphin with a

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