Microbial metabolic specificity controls pelagic lipid export efficiency

Lipids comprise more than 20% of sinking organic matter in the ocean and play a crucial role in the carbon cycle. Despite this, our understanding of the processes that control lipid degradation is limited. Here we combined nano-lipidomics and imaging to study the bacterial degradation of diverse algal lipid droplets. Bacteria isolated from natural marine particles exhibited distinct dietary preferences, ranging from selective to promiscuous degraders. Dietary preference was associated with a distinct set of lipid degradation genes rather than with taxonomic origin. The top degrader, Pseudomonas zhaodongensis, rapidly consumed triacylglycerols (TAGs) from lipid extracts while promoting colonization of kin by chemotaxis toward glycerol, the TAG degradation product. Using synthetic communities composed of isolates with distinct dietary preferences, we demonstrated that lipid degradation is modulated by microbial interactions. A particle export model incorporating these dynamics suggests that metabolic specialization and community dynamics influences lipid transport efficiency in the ocean’s mesopelagic zone.