Lactiplantibacillus plantarum strains with enhanced animal growth promoting capabilities in well fed animals

The gut microbiota has a profound impact on animal physiology, improving organ function and promoting growth under different nutritional conditions. Complex mechanisms underlying growth-promotion by the gut microbiota have been described. In particular, strains of the same bacterial species within different genera exhibit strain-specific growth promotion. In a previous study, we used artificial selection on a poorly growth-promoting strain of Lactiplantibacillus plantarum (NIZO2877) and isolated evolved strains with enhanced growth-promoting capabilities in insects. However, it remains unclear to what extent existing growth-promoting strains can further optimise their benefits and whether these effects persist in well-fed mammals. Here, we experimentally evolved a Drosophila growth-promoting strain of L. plantarum (WJL) under conditions of nutrient deprivation. This strain had not undergone any prior evolutionary adaptation. Our aim was to maximize its growth-promoting benefits while evaluating the translation of this phenotype in different animal models. After artificial selection across ten Drosophila generations, we identified an evolved strain (L. plantarum IGFL1) that significantly improved Drosophila juvenile growth compared to the ancestral strain. Administration of IGFL1 to conventional C57Bl/6j male mice under both nutrient deprivation and normal dietary conditions significantly increased body length and weight growth rates compared to placebo-fed animals. These effects were comparable to those of the ancestral strain, suggesting a context-dependent phenotype. Genome sequencing of IGFL1 revealed the presence of four mutations that may be related to more effective utilization of nutrients. Our results demonstrate the high adaptive potential of L. plantarum, although functional improvements in promoting animal growth are strictly context-dependent. Despite this specificity in adaptation, both strains (the ancestral WJL and the evolved IGFL1) show transferable potential in terms of animal growth promotion, as they are both highly beneficial in flies and mice. These results pave the way for testing these strains to enhance the growth performance of agricultural target species.