P-018. Protein Synthesis and Metabolic Energy Strategies in Listeria monocytogenes 10403S and a ΔsigB Mutant during Multiple-Nutrient Starvation

B. Lungu1,2, J. C. Saldivar1, R. P. Story1, S. C. Ricke1, M. G. Johnson1;
1Univ. of Arkansas, Fayetteville, AR, 2Univ. of Georgia, Athens, GA.

Listeria monocytogenes is capable of expressing a starvation survival response (SSR) under conditions of nutrient deprivation. SigB is thought to initiate the transcription of genes in response to starvation, producing the proteins required for an effective SSR by L. monocytogenes. However, it is unclear what source of energy the starved cells utilize for the production of needed proteins and the expression of a SSR. The first objective of this study was to analyze the protein profiles of L. monocytogenes 10403S and a ΔsigB mutant before and during the early hours of multiple-nutrient starvation in an attempt to identify any novel SigB-dependent or SigB-independent proteins produced during starvation. Using two-dimensional gel electrophoresis, protein profiles for L. monocytogenes 10403S, starved for 6 h, showed 12 proteins with increased expression, 4 proteins with decreased expression, and 38 proteins appearing to be unaffected. In the ΔsigB mutant strain, 8 proteins exhibited an increase in expression and 39 proteins appeared to be unaffected. The second objective was to examine the effects of 3 inhibitors of substrate level phosphorylation (0.001M iodoacetate (IA), 0.1M sodium fluoride (SF), 0.01M sodium arsenite (SAs)), 2 inhibitors that uncouple oxidative phosphorylation (0.1M sodium arsenate (SA), 0.01M potassium cyanide (CY)), and 1 inhibitor that dissipates the proton motive force (PMF) (0.01M dinitrophenol (DNP)) on the SSR of L. monocytogenes to provide insights on the metabolic strategies of starved cells. The varying SSRs of both the wild type and mutant strains to the different metabolic inhibitors under aerobic or anaerobic conditions suggested that 1.) energy derived from the PMF is important for an effective SSR, 2.) L. monocytogenes likely utilizes an anaerobic electron transport during multiple-nutrient starvation, and 3.) the glycolytic pathway is a very important energy source during multiple-nutrient starvation when oxygen is available, and less important in anaerobic conditions. Overall, these metabolic strategies may provide the energy used for producing proteins essential to the SSR of L. monocytogenes.