Gene expression in Escherichia coli treated with human PGRP, gentamicin, and CCCP

Human Peptidoglycan Recognition Proteins (PGRPs) kill bacteria, likely by over-activating stress responses in bacteria. To gain insight into the mechanism of PGRP killing of Escherichia coli and bacterial defense against PGRP killing, gene expression in E. coli treated with a control protein (bovine serum albumin, BSA), human recombinant PGRP (PGLYRP4), gentamicin (aminoglycoside antibiotic), and CCCP (membrane potential decoupler) were compared. Each treatment induced unique and somewhat overlapping pattern of gene expression. PGRP highly increased expression of genes for oxidative and disulfide stress, detoxification and efflux of Cu, As, and Zn, repair of damaged proteins and DNA, methionine and histidine synthesis, energy generation, and Fe-S clusters repair. PGRP also caused marked decrease in the expression of genes for Fe uptake and motility. Gene expression microarray in E. coli exposed to a human bactericidal innate immunity protein, PGRP, showed induction of oxidative stress response and defense genes, with different expression pattern than E. coli exposed to an aminoglycoside antibiotic and a membrane potential decoupler. E. coli was treated with PGRP (human recombinant PGLYRP4), gentamicin, or CCCP (carbonyl cyanide 3-chlorophenylhydrazone). RNA was obtained from each culture and assayed for gene expression using whole genome Affymetrix E. coli Genome 2.0 Array. Each experiment was repeated 3 times.