Guest Post: Bugs in bugs in bugs

Symbiotic relationships, where organisms of different species work together for mutual gain, have been studied extensively in numerous biological systems, but modern genomic techniques are revolutionising our understanding of how these interactions work at the molecular level. A recent paper by John McCutcheon and Carol von Dohlen has reported an interesting case of a ‘three-way symbiosis’ between the mealybug (Planococcus citri) – a significant pest of plants – and two species of bacteria.

This interaction shows a high level of metabolic complementarity: the genes for several amino acid biosynthetic pathways that are essential to the mealybug are spread across the genomes of the three different species. This makes the mealybug completely dependent on its bacterial symbionts.