Dynamics of competitive population abundance of Lactobacillus plantarum ivi gene mutants in faecal samples after passage through the gastrointestinal tract of mice

Aim: This study aims to evaluate the impact of mutation of previously identified in vivo- induced ( ivi) genes on the persistence and survival of Lactobacillus plantarum WCFS1 in the gastrointestinal ( GI) tract of mice. Methods and Results: Nine Lact. plantarum ivi gene replacement mutants were constructed, focussing on ivi genes that encode proteins with a predicted role in cell envelope functionality, stress response and regulation. The in vitro growth characteristics of the mutants appeared identical to those observed for the wild- type strain, which agrees with the recombination- based in vivo expression technology suggestion that these genes are not transcribed in the laboratory. Quantitative PCR experiments demonstrated differences in the relative population dynamics of the Lact. plantarum ivi mutants in faecal samples after passage through the GI tract of mice. Conclusions: The in situ competition experiments revealed a 100- to 1000- fold reduction of the relative abundance of three of the ivi gene mutants, harbouring deletions of genes predicted to encode a copper transporter, an orphan IIC cellobiose PTS and a cell wall anchored extracellular protein. Significance and Impact of the Study: These experiments clearly establish that the proteins encoded by these three genes play a key role in Lact. plantarum performance during passage of the GI tract.