微生物学：1つのスイッチによって、大腸菌が昆虫にとって有益なパートナーになる

Beneficial — or symbiotic — interactions between stinkbugs and a laboratory strain of Escherichia coli can be rapidly engineered via a single mutation in the latter, according to a paper published in Nature Microbiology. The findings may help improve our understanding of how beneficial microbes develop with their hosts and the molecular mechanisms driving these relationships.

Microbes often live with hosts in symbiosis, meaning that both partners benefit from the relationship. Symbiosis is prevalent across nature, from humans and their gut microbiome, to plants and the microbes that colonize their roots, and to insects that often live with one or two microbial partners. However, it is unclear how the symbiotic relationship between host and microbe develops.

Ryuichi Koga, Takema Fukatsu and colleagues used stinkbugs (Plautia stali) to study the evolution of E. coli, a type of bacteria that doesn’t normally live in these insects. The authors colonized the gut of stinkbugs with a rapidly-evolving strain of E. coli and allowed them to evolve over 12 insect generations (approximately two years). Initially, E. coli colonization reduced insect survival rates and body size, and caused them to be brown rather than green. However, from generation seven onwards (after around one year), the evolved E. coli supported healthy stinkbugs. Further investigation revealed that these microbes all had a single mutation that allowed them to become beneficial to the insects.

The authors conclude that their findings indicate that host-beneficial symbiotic relationships can develop rapidly and may explain why microbial relationships of this kind are prevalent in nature.

In an associated News & Views article, Martin Kaltenpoth highlights that this study “makes a leap” in the direction of creating “a set of tractable systems that represents this natural diversity and allows us to dissect and manipulate host–symbiont interactions from the molecular to the organismic level.”