D3410: Burkholderia gut symbiont provides vitamin b1 to insect hosts via up-regulated thiamine biosynthetic pathway

Gut microorganisms serve the host with necessary nutrients and maintain a symbiotic relationship. In this study, the relative expression of genes in the thiamine biosynthetic pathway was compared between cultured and gut-colonized bacteria. The expression levels of thiC and thiE2 genes were significantly higher in gut-colonized symbiont. When insects were fed mutant bacteria lacking the thiC and thiE2 genes, the host's growth rate was reduced to a level comparable to that of insects without symbiotic bacteria. Interestingly, complemented mutant symbiont restored host fitness. These results suggest that gut symbiotic bacteria provide vitamin b1 to host insects to support host nutrition.