Microarray-Based Characterization of theListeria monocytogenesCold Regulon in Log- and Stationary-Phase Cells

Abstract

Whole-genome microarray experiments were performed to define the Listeria monocytogenes cold growth regulon and to identify genes differentially expressed during growth at 4 and 37°C. Microarray analysis using a stringent cutoff (adjusted P < 0.001; >2.0-fold change) revealed 105 and 170 genes that showed higher transcript levels in logarithmic-and stationary-phase cells, respectively, at 4°C than in cells grown at 37°C. A total of 74 and 102 genes showed lower transcript levels in logarithmic-and stationary-phase cells, respectively, grown at 4°C. Genes with higher transcript levels at 4°C in both stationary-and log-phase cells included genes encoding a two-component response regulator (lmo0287), a cold shock protein (cspL), and two RNA helicases (lmo0866 and lmo1722), whereas a number of genes encoding virulence factors and heat shock proteins showed lower transcript levels at 4°C. Selected genes that showed higher transcript levels at 4°C during both stationary and log phases were confirmed by quantitative reverse transcriptase PCR. Our data show that (i) a large number of L. monocytogenes genes are differentially expressed at 4 and 37°C, with more genes showing higher transcript levels than lower transcript levels at 4°C, (ii) L. monocytogenes genes with higher transcript levels at 4°C include a number of genes and operons with previously reported or plausible roles in cold adaptation, and (iii) L. monocytogenes genes with lower transcript levels at 4°C include a number of virulence and virulenceassociated genes as well as some heat shock genes.

The lmo0501 gene coding for a putative transcription activator protein in Listeria monocytogenes promotes growth under cold, osmotic and acid stress conditions

“…In agreement with previous reports (Chan et al, 2007;Liu et al, 2002), cold stress dependent lmo0501 mRNA induction could also be detected in the present study. In addition an lmo0501 transcriptional induction was detected in response to lactic acid and NaCl osmotic stresses.…”

“…One of the putative cold adaptation genes identified in this bacterium is the lmo0501 locus of L. monocytogenes EGDe, which codes for the putative transcription activator protein Lmo0501. An increase in lmo0501 mRNA is observed in transcriptomes of cold acclimated L. monocytogenes cells (Chan et al, 2007;Liu et al, 2002). The aim of the present study was to examine lmo0501 gene functional contributions in adaptation of L. monocytogenes cells to cold, NaCl salt and organic acid stress associated with preserved food.…”

“…In addition several other putative cold, osmotic, acid and alkaline stress protection genes and proteins are known from gene expression analysis, which now allows rationalized creation of deletion mutants for functional studies ( Bowman et al, 2010;Chan et al, 2007;Giotis et al, 2008;Giotis et al, 2010;Liu et al, 2002). One of the putative cold adaptation genes identified in this bacterium is the lmo0501 locus of L. monocytogenes EGDe, which codes for the putative transcription activator protein Lmo0501.…”

A Listeria monocytogenes RNA Helicase Essential for Growth and Ribosomal Maturation at Low Temperatures Uses Its C Terminus for Appropriate Interaction with the Ribosome

“…Among these are compatible solute transporters encoded by the opu and gbu operons; oligopeptide permease encoded by oppA; ferritin (Fri); and phosphohydrolase, encoded by pgpH and involved in ppGpp turnover (7,9,20,23,28,41,42,45,46). L. monocytogenes harbors 4 putative DExD-box RNA helicases, and in a previous study, the genes encoding three RNA helicases (lmo0866, lmo1450, and lmo1722) were found to be induced at low temperatures (11). A transposon insertion in a region directly upstream of a putative RNA helicase gene (homologous to lmo1722) in L. monocytogenes strain F2365 induced a cold-sensitive growth phenotype and reduced swarming motility on soft agar plates (4).…”

ppGpp Conjures Bacterial Virulence

“…Likewise, L. monocytogenes strains that harbor a transposon insertion in pghH, encoding a putative metal-dependent phosphohydrolase (118), are cold sensitive and contain increased levels of ppGpp. Furthermore, at 4°C, stationary-phase L. monocytogenes cells contain lower levels of relA transcript than do their log-phase counterparts rather than the higher levels usually associated with stress tolerance (42). Therefore, L. monocytogenes may decrease its ppGpp pool to adapt to the cold temperatures encountered in refrigerated food products.…”