Lactobacillus reuteri is a gram-positive bacterial species that commonly inhabits the gut of mice, poultry, and pigs as a member of the normal microbiota. These bacteria are autochthonous (indigenous) to the gut of these animals because they persist throughout the life of the host at characteristic population sizes in specific regions of the gut. Moreover, L. reuteri strains exhibit host specificity. The genetic attributes and the mechanisms that enable the bacteria to persist in the gut are unknown; therefore, this research focuses on the molecular mechanisms of autochthony. Two L. reuteri strains, 100-23 and DSM20016T will be sequenced. Strain 100-23 is a rodent-specific strain that researchers are using, in combination with Lactobacillus-free mice, as a model organism to study normal microbiota-host interactions. Strain DSM20016T (the type strain of L. reuteri), which is of human origin, does not persist in the gut of mice. The researchers postulate that the genome of strain 100-23 contains genes that are lacking or nonfunctional in DSM20016T and thus differentiate the strains with respect to life in the murine gut. Comparison of the two genomes will yield candidate genes for complementation in DSM20016T or mutation in 100-23. Postsequencing plans include assessment of the ecological performance of complemented or mutated derivatives using Lactobacillus-free mice, studies of in-vivo gene expression using DNA microarrays, and investigations of the L. reuteri secretome.
CSP project participants: Gerald W. Tannock (proposer), Nicholas C.K. Heng, and Jens Walter (Univ. of Otago, New Zealand).