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Characterization of the ecological role of genes mediating acid resistance in L actobacillus reuteri during colonization of the gastrointestinal tract
Author(s) -
Krumbeck Janina A.,
Marsteller Nathan L.,
Frese Steven A.,
Peterson Daniel A.,
RamerTait Amanda E.,
Hutkins Robert W.,
Walter Jens
Publication year - 2016
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13108
Subject(s) - biology , colonization , microbiology and biotechnology , gene , gastric acid , urease , bacteria , mutant , secretion , omeprazole , biochemistry , enzyme , genetics , pharmacology
Summary Rodent‐derived strains of L actobacillus reuteri densely colonize the forestomach of mice and possess several genes whose predicted functions constitute adaptations towards an acidic environment. The objective of this study was to systematically determine which genes of L . reuteri 100‐23 contribute to tolerance towards host gastric acid secretion. Genes predicted to be involved in acid resistance were inactivated, and their contribution to survival under acidic conditions was confirmed in model gastric juice. Fitness of five mutants that showed impaired in vitro acid resistance were then compared through competition experiments in ex‐germ‐free mice that were either treated with omeprazole, a proton‐pump inhibitor that suppresses acid secretion in the stomach, or left untreated. This analysis revealed that the urease cluster was the predominant factor in mediating resistance to gastric acid production. Population levels of the mutant, which were substantially decreased in untreated mice, were almost completely restored through omeprazole, demonstrating that urease production in L . reuteri is mainly devoted to overcome gastric acid. The findings provide novel information on the mechanisms by which L . reuteri colonizes its gastric niche and demonstrate that in silico gene predictions and in vitro tests have limitations for predicting the ecological functions of colonization factors in bacterial symbionts.