The Effect of Oxygen on Bile Resistance inListeria monocytogenes.
Listeria monocytogenesis a Gram-positive facultative anaerobe that is the causative agent of the disease listeriosis. The infectious ability of this bacterium is dependent upon resistance to stressors encountered within the gastrointestinal tract, including bile. Previous studies have indicated bile salt hydrolase activity increases under anaerobic conditions, suggesting anaerobic conditions influence stress responses. Therefore, the goal of this study was to determine if reduced oxygen availability increased bile resistance ofL. monocytogenes. Four strains representing three serovars were evaluated for changes in viability and proteome expression following exposure to bile in aerobic or anaerobic conditions. Viability for F2365 (serovar 4b), EGD-e (serovar 1/2a), and 10403S (serovar 1/2a) increased following exposure to 10% porcine bile under anaerobic conditions (P< 0.05). However, HCC23 (serovar 4a) exhibited no difference (P> 0.05) in bile resistance between aerobic and anaerobic conditions, indicating that oxygen availability does not influence resistance in this strain. The proteomic analysis indicated F2365 and EGD-e had an increased expression of proteins associated with cell envelope and membrane bioenergetics under anaerobic conditions, including thioredoxin-disulfide reductase and cell division proteins. Interestingly, HCC23 had an increase in several dehydrogenases following exposure to bile under aerobic conditions, suggesting that the NADH:NAD+ is altered and may impact bile resistance. Variations were observed in the expression of the cell shape proteins between strains, which corresponded to morphological differences observed by scanning electron microscopy. These data indicate that oxygen availability influences bile resistance. Further research is needed to decipher how these changes in metabolism impact pathogenicityin vivoand also the impact that this has on susceptibility of a host to listeriosis.
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA.
Morgan L
ML
Wright
School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ 85721, USA.
Ken
K
Pendarvis
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
Bindu
B
Nanduri
Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA.
Mariola J
MJ
Edelmann
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA.
Haley N
HN
Jenkins
Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS 39762, USA.
Joseph S
JS
Reddy
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA.
Jessica G
JG
Wilson
Institute for Genomics, Biocomputing and Biotechnology, Mississippi State University, Mississippi State, MS 39762, USA.
Xuan
X
Ding
Livestock Issues Research Unit, USDA-ARS, Lubbock, TX 79403, USA.
Paul R
PR
Broadway
School of Animal and Comparative Biomedical Sciences, University of Arizona, Tucson, AZ 85721, USA.
Mais G
MG
Ammari
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA.
Oindrila
O
Paul
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA.
Brandy
B
Roberts
Department of Biological Sciences, Mississippi State University, Mississippi State, MS 39762, USA; The University of Southern Mississippi, 118 College Drive, Box #5018, Hattiesburg, USA.
Janet R
JR
Donaldson
Bile; Listeria monocytogenes; Mass spectrometry; Oxygen; Proteomic; Scanning electron microscopy