Evolution and regulation of microbial secondary metabolism

Microbes have disproportionate impacts on the macroscopic world. This is
in part due to their ability to grow to large groups and cooperatively
secrete massive amounts of secondary metabolites that impact their
environment. Yet, the conditions enabling secondary metabolism without
compromising primary needs remain unclear. Here we investigated the
biosynthesis of thamnolipids, a secondary metabolite that Pseudomonas
aeruginosa makes to decrease the surface tension of surrounding liquid.
Using a combination of genomics, metabolomics, transcriptomics, and
mathematical modeling we show that biosynthesis of rhamnolipids from
glycerol varies inconsistently across the phylogenetic tree; instead,
non-producer lineages are also those worse at reducing the oxidative
stress of primary glycerol metabolism. The link to oxidative stress
explains the inconsistent distribution across the P. aeruginosa tree,
adding a new layer to the regulation of rhamnolipids—a microbial secondary
metabolite important for fitness in natural and clinical settings.