TolC is important for bacterial survival and oxidative stress response in Salmonella enterica serovar Choleraesuis in an acidic environment.
The outer membrane protein TolC, which is one of the key components of several multidrug efflux pumps, is thought to be involved in various independent systems in Enterobacteriaceae. Since the acidic environment of the stomach is an important protection barrier against foodborne pathogen infections in hosts, we evaluated whether TolC played a role in the acid tolerance of Salmonella enterica serovar Choleraesuis. Comparison of the acid tolerance of the tolC mutant and the parental wild-type strain showed that the absence of TolC limits the ability of Salmonella to sustain life under extreme acidic conditions. Additionally, the mutant exhibited morphological changes during growth in an acidic medium, leading to the conflicting results of cell viability measured by spectrophotometry and colony-forming unit counting. Reverse-transcriptional-PCR analysis indicated that acid-related molecules, apparatus, or enzymes and oxidation-induced factors were significantly affected by the acidic environment in the null-tolC mutant. The elongated cellular morphology was restored by adding antioxidants to the culture medium. Furthermore, we found that increased cellular antioxidative activity provides an overlapping protection against acid killing, demonstrating the complexity of the bacterial acid stress response. Our findings reinforce the multifunctional characteristics of TolC in acid tolerance or oxidative stress resistance and support the correlative protection mechanism between oxygen- and acid-mediated stress responses in Salmonella enterica serovar Choleraesuis.
Graduate Institute of Veterinary Pathobiology, National Chung Hsing University, Taiwan.
Jen-Jie
JJ
Lee
Graduate Institute of Veterinary Pathobiology, National Chung Hsing University, Taiwan.
Ying-Chen
YC
Wu
Department of Veterinary Medicine, National Chung Hsing University, Taiwan.
Chih-Jung
CJ
Kuo
Graduate Institute of Veterinary Pathobiology, National Chung Hsing University, Taiwan. Electronic address: hsuan@nchu.edu.tw.
Shih-Ling
SL
Hsuan
Graduate Institute of Veterinary Pathobiology, National Chung Hsing University, Taiwan; Graduate Institute of Microbiology and Public Health, National Chung Hsing University, Taiwan. Electronic address: thc@dragon.nchu.edu.tw.
Ter-Hsin
TH
Chen
D000143:Acids; D000975:Antioxidants / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018384:Oxidative Stress; D019779:Salmonella enterica / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D065288:Serogroup; D013312:Stress, Physiological
D000143:Acids; D000975:Antioxidants; D001425:Bacterial Outer Membrane Proteins; D006861:Hydrogen Peroxide
Acid tolerance; Oxidative stress; Salmonella enterica serovar Choleraesuis; TolC