Drosophila Perpetuates Nutritional Mutualism by Promoting the Fitness of Its Intestinal Symbiont Lactobacillus plantarum.

Facultative animal-bacteria symbioses, which are critical determinants of animal fitness, are largely assumed to be mutualistic. However, whether commensal bacteria benefit from the association has not been rigorously assessed. Using a simple and tractable gnotobiotic model- Drosophila mono-associated with one of its dominant commensals, Lactobacillus plantarum-we reveal that in addition to benefiting animal growth, this facultative symbiosis has a positive impact on commensal bacteria fitness.

Pathogen Virulence Impedes Mutualist-Mediated Enhancement of Host Juvenile Growth via Inhibition of Protein Digestion.

The microbial environment impacts many aspects of metazoan physiology through largely undefined molecular mechanisms. The commensal strain Lactobacillus plantarum(WJL) (Lp(WJL)) sustains Drosophila hormonal signals that coordinate systemic growth and maturation of the fly. Here we examine the underlying mechanisms driving these processes and show that Lp(WJL) promotes intestinal peptidase expression, leading to increased intestinal proteolytic activity, enhanced dietary protein digestion, and increased host amino acid levels.