Stick insects stole digestive enzyme genes from their microbiome

Although many organisms—including humans—rely on their gut microbiome to help digest the complex polysaccharides found in leafy greens, stick insects have opted for a do-it-yourself strategy. More than 60 million years ago, these critters stole the DNA blueprint for pectinase enzymes from their microbiome, incorporating the bacterial genes in their own genome, according to a study led by Matan Shelomi of the Max Planck Institute for Chemical Ecology (Sci. Rep. 2016, DOI: 10.1038/srep26388). Being able to break down pectin found in the cell walls of leafy plants without having to rely on assistance from the microbiome helped stick insects in the Phasmatodea order expand their number of species to the thousands. When the team’s members analyzed the pectinase DNA in the genomes of several stick insect species, they found that the critters probably stole the skill from Gammaproteobacteria, a common stick insect gut bacteria. Curiously, of the several pectinase genes nabbed by the stick insect, not all still break down pectin. Some pectinases evolved, and their current functions remain unknown.