P-005. Transcriptional Analysis of the Growth of Listeria monocytogenes 10403S and a ΔsigB Mutant Strain Following Exposure to Dinitrophenol or Sodium Arsenite

B. Lungu1, S. E. Dowd2, A. Muthaiyan1, S. C. Ricke1, M. G. Johnson1;
1Univ. of Arkansas, Fayetteville, AR, 2USDA-ARS-LIRU, Lubbock, TX.

In Listeria monocytogenes (L. m) SigB activation has been shown to occur through a common pathway during both environmental and energy stress conditions. However, little is known about the role of SigB when sudden interruptions in energy supply occur during active growth. The effects of an inhibitor of proton motive force (PMF) and an inhibitor of pyruvate dehydrogenase (PD) on transcriptional changes in L. m and its sigB mutant were compared. 2, 4-dinitrophenol (DNP) was used to inhibit PMF while sodium arsenite (SAs) was used to inhibit PD. These inhibitors were added individually in separate experiments to L. m 10403S wild type and a sigB mutant strain growing at log phase (23°C) in Brain Heart Infusion broth. The resulting transcriptomes after 2 hours of exposure to the inhibitors were analyzed using Pathogen Functional Genomics Resource Center (PFGRC) microarrays and protocols. During growth in the presence of DNP 193 and 223 genes were differentially expressed (P < 0.05) for the wild type and ΔsigB mutant, respectively. The data shows that cellular processes involving cell division or DNA metabolism appear to be PMF-dependent while those involving the phosphotransferase system appear to be PMF-independent. Repression of genes related to cell division or synthesis/degradation of cellular components occurred following PMF loss. During growth in the presence of SAs, differential expression of 742 and 134 genes were exhibited by the wild type and ΔsigB mutant, respectively. The results indicate that most of the genes involved in regulation during growth of L. m may be sigB-dependent. Induction of protein synthesis genes also occurred following the addition of SAs. Interestingly, the reaction catalyzed by SAs may provide an energy source for protein synthesis. In addition, energy stress induced by SAs led to induction of the fur and prfA genes. This suggests that metabolic pathways involving PD may be linked to pathogenesis in this organism.