Resistance of nutrient-deprived Listeria monocytogenes 10403S and a DeltasigB mutant to chemical stresses in the presence or absence of oxygen.
Nutrient-deprived Listeria monocytogenes have increased resistance to processing control measures. Heat-stressed L. monocytogenes cells produce higher counts under anaerobic conditions and SigB reportedly contributes to the survival of environmentally stressed Gram-positive bacteria. In this study, a wild type (wt) strain, L. monocytogenes 10403S, and a DeltasigB mutant, FSLA1-254, were stressed by starvation in phosphate buffered saline coupled with exposure to chemicals with/without oxygen. In the absence of chemicals, the mutant survived starvation almost as well as the wt, suggesting that the starvation survival response (SSR) in L. monocytogenes was SigB-independent. Conversely, in the presence of chemical stresses the SSR results differed depending on the chemical used. In the presence of sodium chloride (SC), both strains were able to express an SSR under aerobic conditions but not under anaerobic conditions. However, in the presence of sodium propionate (SP), the mutant yielded counts that were 2 log CFU/mL lower than the controls and their aerobic counterparts. In the presence of sodium lactate (SL), the mutant yielded counts that were approximately 3 log CFU/mL lower than the wt under anaerobic conditions. Thus, for the chemical stress produced by SC, the SSR appeared to be SigB-independent. The SSR of L. monocytogenes appeared to be SigB-dependent following exposure to SP or SL under anaerobic conditions. Following exposure to sodium diacetate or lauric acid, both strains were unable to express an SSR. No detectable CFUs were observed after 14 to 21 d under either aerobic or anaerobic incubation. Therefore, these 2 chemicals could be used in biocidal formulations against L. monocytogenes cells under aerobic or anaerobic conditions.
Lungu
B
B
Dept of Food Science and Technology, Univ of Georgia, Athens, GA 30602, USA.
Ricke
S C
SC
Johnson
M G
MG
D000332:Aerobiosis; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015169:Colony Count, Microbial; D003470:Culture Media; D005516:Food Microbiology; D005520:Food Preservatives / Q000494:pharmacology*; D007850:Lauric Acids / Q000494:pharmacology; D008089:Listeria monocytogenes / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D011422:Propionates / Q000494:pharmacology; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D019346:Sodium Acetate / Q000494:pharmacology; D012965:Sodium Chloride / Q000494:pharmacology; D019354:Sodium Lactate / Q000494:pharmacology
D001426:Bacterial Proteins; D003470:Culture Media; D005520:Food Preservatives; D007850:Lauric Acids; D011422:Propionates; C480945:SigB protein, Listeria monocytogenes; D012808:Sigma Factor; C030358:lauric acid; D012965:Sodium Chloride; D019346:Sodium Acetate; C514135:sodium propionate; D010100:Oxygen; D019354:Sodium Lactate