Endosymbiotic interactions in freshwater invertebrates: what are the microbes doing?

Most species of insect carry heritable microbes, i.e. bacteria which pass from a female to her progeny. Studies have shown these symbionts are important drivers of host biology, ecology and evolution – improving resistance to parasites, changing sex ratio, and allowing use of nutritionally poor food. Most studies of heritable microbes have focused on terrestrial hosts, which have revealed common infections in arthropods, some infections in nematodes, but none in other taxa. In contrast, heritable microbes are found in a much wider range of freshwater taxa – including leeches, hydra and snails as well as arthropods. The symbionts are a bit distinct too –some bacterial symbionts, such as torix Rickettsia, are much more commonly found in freshwater than terrestrial species.

Nevertheless, we know very little about the biology of these symbioses. Do the symbionts have the same maternal-only inheritance, or is the biparental transmission seen in one case study widespread? What is the impact of the symbiont on the host individuals, and more widely, on the ecology and evolution of freshwater species?

The student will develop one or more study systems from freshwater communities as a laboratory model, and characterize the transmission biology of the symbiont, the effect of the symbiont on host biology, and ecological impacts. The student will be trained in techniques for assaying for/identifying symbionts; in FISH analysis of infection within individuals, and in experimental analysis of impact in cultured specimens.

The most important criterion is that the student is fascinated by symbiotic interactions, and enjoys invertebrate model systems. They should be happy performing basic molecular techniques (for which they will be trained), field sampling and animal husbandry. They will benefit from complementary supervisor expertise: Greg Hurst, an expert on symbiotic interactions, and David Atkinson, an expert in freshwater biology.