Inactivation of alternative sigma factor 54 (RpoN) leads to increased acid resistance, and alters locus of enterocyte effacement (LEE) expression in Escherichia coli O157 : H7.
Alternative sigma factor 54 (RpoN) is an important regulator of stress resistance and virulence genes in many bacterial species. In this study, we report on the gene expression alterations that follow rpoN inactivation in Escherichia coli O157 : H7 strain Sakai (Sakai rpoN : : kan), and the influence of RpoN on the acid resistance phenotype. Microarray gene expression profiling revealed the differential expression of 103 genes in SakairpoN : : kan relative to Sakai. This included the growth-phase-dependent upregulation of genes required for glutamate-dependent acid resistance (GDAR) ( gadA, gadB, gadC and gadE), and the downregulation of locus of enterocyte effacement (LEE) genes, which encode a type III secretion system. Upregulation of gad genes in SakairpoN : : kan during exponential growth correlated with increased GDAR and survival in a model stomach system. Complementation of SakairpoN : : kan with a cloned version of rpoN restored acid susceptibility. Genes involved in GDAR regulation, including rpoS (sigma factor 38) and gadE (acid-responsive regulator), were shown to be required for the survival of SakairpoN : : kan by the GDAR mechanism. This study describes the contribution of rpoN to acid resistance and GDAR gene regulation, and reveals RpoN to be an important regulator of stress resistance and virulence genes in E. coli O157 : H7.
Riordan
James T
JT
Department of Cell Biology, Microbiology and Molecular Biology (CMMB), University of South Florida, Tampa, FL 33620, USA.
Tietjen
Jillian A
JA
Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
Walsh
Coilin W
CW
Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
Gustafson
John E
JE
Microbiology Group, Biology Department and Molecular Biology Program, New Mexico State University, Las Cruces, NM 88003, USA.
Whittam
Thomas S
TS
Microbial Evolution Laboratory, National Food Safety and Toxicology Center, Michigan State University, East Lansing, MI 48824, USA.
D000143:Acids / Q000378:metabolism*; D019453:Escherichia coli O157 / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D020411:Oligonucleotide Array Sequence Analysis; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D051877:RNA Polymerase Sigma 54 / Q000235:genetics / Q000378:metabolism*; D018085:Regulon; D014774:Virulence
D000143:Acids; D029968:Escherichia coli Proteins; C457340:LEE protein, E coli; D010750:Phosphoproteins; C497751:rpoN protein, E coli; D051877:RNA Polymerase Sigma 54