Inactivation of the Lactobacillus reuteri 100-23 ureC gene affects in vitro acid tolerance, and impairs ecological fitness in vivo

ABSTRACT: Lactobacillus reuteri 100-23 is an autochthonous inhabitant of the rodent gastrointestinal system that adheres to the non-secretory epithelium of the forestomach and forms biofilms. Microarray analysis of the expression profile of L. reuteri 100-23 cells harvested from the stomach of ex-Lactobacillus-free mice, compared to those of L. reuteri 100-23 in laboratory culture, revealed an in vivo upregulation of a urease gene cluster by greater than 50-fold. Genes for urease production were absent in all publically available Lactobacillus genome sequences except L. reuteri 100-23 and have recently been identified as specific to rodent strains of L. reuteri (Frese et al. 2011). In the current study, the urease enzyme was shown to be functional. Supplementation with 2% urea allowed L. reuteri 100-23 to increase the pH of the culture medium. A mutant strain of L. reuteri 100-23 was developed by insertional inactivation of the ureC gene, which encodes the largest subunit of the urease enzyme. The mutant strain was unable to hydrolyze urea to increase the pH of culture medium, and did not survive acid stress at pH 2.5 for 6 h, even in the presence of urea. In contrast, the wild type strain was still viable after 6 h when 2% urea supplementation was included. When mice free of lactobacilli were inoculated with a mixture of equal numbers of wild type L. reuteri 100-23 and ureC mutant cells, the wild type constituted 99% of the resulting Lactobacillus population in the stomach, caecum and jejunum after one week (108 cells/gram of sample). This study has therefore shown the importance of a functional urease enzyme in the ecological fitness of L. reuteri 100-23. Analysis of the microarray data was obtained from two independent biological replicates.

ORGANISM(S): Lactobacillus reuteri 100-23

SUBMITTER: Charlotte Wilson 

PROVIDER: E-GEOD-36286 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress