Bacteria producing the bioplastic polyhydroxybutyrate kill the nematode Caenorhabditis elegans

Bacteria, both individually and as symbionts of other organisms, significantly influence ecosystems by providing nutrients and metabolizing exogenous compounds. Some bacteria polymerize small organic acids such as lactate, pyruvate, and β-or 3-hydroxybutyrate when there is an excess of carbon relative to other elements. One such polymer, poly-β-hydroxybutyrate (PHB) is a biodegradable bioplastic. While the role of PHB as energy/carbon-storage in bacteria is well documented, the effects of PHB on interactions between bacteria and their hosts remain unclear. Here, we discover that PHB-producing bacteria can kill the nematode Caenorhabditis elegans. Death results from a combination of pharyngeal deformation, intestinal distention, disruption of the intestinal barrier, and defecation defects. Remarkably, mutations in C. elegans nuc-1, which encodes DNAse II, partially alleviate PHB-induced lethality. Altogether, our findings illustrate that PHB-producing bacteria can affect host-physiology and survival.