Dietary S. maltophilia promotes fat storage by enhancing lipogenesis and ER-LD contacts in C. elegans

Dietary and symbiotic bacteria can exert powerful influence on metazoan lipid metabolism. Here, we demonstrate that feeding Caenorhabditis elegans (C. elegans) with the opportunistic pathogenic bacteria Stenotrophomonas maltophilia (S. maltophilia) retards growth and promotes excessive fat storage. Gene expression analysis reveals that dietary S. maltophilia induces a lipogenic transcriptional response that includes the SREBP ortholog SBP-1, and fatty acid desaturases FAT-6 and FAT-7. Live imaging and ultrastructural analysis suggest that excess fat is stored in greatly expanded lipid droplets (LDs), as a result of enhanced endoplasmic reticulum-LD interaction. We also report that loss of function mutations in cyp-35B1 or dpy-9 in C. elegans confers resistance to S. maltophilia. Our work delineates a new model for understanding microbial regulation of metazoan physiology.