Microorganisms can increase their host’s ability to adapt to the environment and reproduce – evolutionary biologists are studying how in ever-greater detail. A research team headed by Dr. Fabian Staubach and Yun Wang from the Institute of Biology I at the University of Freiburg has now studied the relationship of gluconobacter bacteria and Drosophila melanogaster (common fruit fly). They have found that specific gluconobacter variants supply the flies with vitamin B1 and so improve their fitness. This involved comparison of different but closely-related varieties of gluconobacter bacteria and the effect they have on fruit flies. Those bacteria that produced vitamin B1 gave rise to the flies having more offspring – because the vitamin promoted reproduction. In addition, the researchers discovered that bacteria can pass on the necessary vitamin-producing genes horizontally – that is, not just to their offspring but also to living relatives. Their microbial genome-wide association study (GWAS) was conducted by the scientists together with researchers from the Max Planck Institute for Evolutionary Biology and the University of Wisconsin La Crosse, USA. Their results are being published in the journal BMC Biology.
“We want a better understanding of how microbes influence the fitness of the host. So we are tracing the evolutionary events that lead to changes in the host’s fitness that are mediated by the bacteria,” explains Staubach.
Amongst other things, the researchers found that the gluconobacters had probably already lost the vitamin-producing genes back in evolutionary history – but then recovered them through horizontal gene transfer from other bacteria. The researchers discovered this by creating a family tree of the bacteria they were studying, which they then used to trace the evolutionary history of the vitamin-producing genes. On one branch of this tree the vitamin-producing genes appeared as a connecting block (Operon), which was very similar to the genes of foreign bacteria. This is a typical trace of horizontal gene transfer.
Putting it briefly, Staubach says, “Our study underscores the importance of genetic variation between closely-related bacteria for the host and shows that horizontal gene transfer can contribute to the flexibility of the microbiome and possibly to the host’s adaptation to its environment.”
Wang, Y., Baumdicker, F., Schweiger, P., Kuenzel, S., Staubach, F. (2021): Horizontal gene transfer-mediated bacterial strain variation affects host fitness in Drosophila. In: BMC Biology. DOI: 10.1186/s12915-021-01124-y