Unknown,Transcriptomics,Genomics,Proteomics

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Maltose utilization by Lactobacillus reuteri 100-23

ABSTRACT: Commensal (symbiont) bacteria form communities in various regions of the bodies of vertebrates. Phylogenetic analysis of gut communities is advanced, but the relationships, especially at the trophic level, between commensals that share gut habitats of monogastric animals have not been investigated to any extent. Lactobacillus reuteri strain 100-23 and Lactobacillus johnsonii strain 100-33 cohabit in the forestomach of mice. According to the niche exclusion principle, this should not be possible because both strains utilise the two main fermentable carbohydrates present in the stomach digesta: glucose and maltose. We show, based on gene transcription analysis, in vitro physiological assays, and in vivo experiments that the two strains can co-exist in the forestomach habitat because L. reuteri 100-23 transports maltose into its cells more efficiently than does L. johnsonii 100-33. Conversely, strain 100-33 transports glucose more efficiently than 100-23. As a result, 100-23 shows a preference for growth using maltose, whereas 100-33 prefers glucose. Mutation of the maltose phosphorylase gene (malA) of strain 100-23 prevented its growth on maltose-containing culture medium, and resulted in the numerical dominance of 100-33 in the forestomach. The fundamental niche of L. reuteri 100-23 in the mouse forestomach can be defined in terms of glucose and maltose fermentation. Its realised niche when L. johnsonii 100-33 is present is maltose fermentation. Hence nutritional adaptations provided niche differentiation that enabled cohabitation by the two strains through resource partitioning in the mouse forestomach. This real life, trophic phenomenon conforms to a mathematical model. Analysis of the microarray data was obtained from two independent biological replicates. A dye swap was included in the analysis

ORGANISM(S): Lactobacillus reuteri 100-23

SUBMITTER: Charlotte Wilson

PROVIDER: E-GEOD-24472 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Oxidative stress due to endogenous hydrogen peroxide production by Lactobacillus species is a well-known issue in the food industry. In this study, the transcriptional response to oxygen of Lactobacillus johnsonii, one of the H2O2-producing strains used in the food industry, was analyzed. It was found that aerobic growth conditions led to a more than two-fold downregulation of 45 genes as compared to anaerobic growth, whereas 6 genes were more than twofold upregulated. Among the upregulated genes were two genes that displayed significant homology to NADH-dependent oxidoreductase (NOX). The postulated transcriptional regulation of the nox promoter by oxygen was studied using a GUS-reporter construct, confirming a 2.1-fold upregulated GUS-expression upon aerobic growth. Exposure to sublethal levels of hydrogen peroxide did not result in significant regulation of the nox promoter. In a previous study of hydrogen peroxide production by L. johnsonii, a NADH flavin reductase (NFR) was identified to be involved in hydrogen peroxide production. An NFR-deficient derivative was strongly impaired in H2O2 production, but regained a partial H2O2 producing capacity upon prolonged oxygen exposure. The nox-promoter appeared to be 3.6-fold upregulated under aerobic conditions in the NFR-deficient background, which may imply a role of this gene in the regained H2O2 production. Indeed, deletion of the nox-gene in the NFR-deletion background, resulted in a strain that no longer produced H2O2, also during prolonged exposure to oxygen. The double-mutant (nfr, nox) displayed strongly impaired aerobic growth and oxygenation induced rapid growth stagnation that is not caused by H2O2. We conclude that H2O2 production in L. johnsonii is primarily dependent on NFR but can also involve an oxygen-inducible NADH oxidase under aerobic conditions. Moreover, our results imply that H2O2 production plays a prominent role in oxygen tolerance of L. johnsonii. loop design of the samples including two shortcuts

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Maltose utilization by Lactobacillus reuteri 100-23

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