Using axenic and gnotobiotic insects to examine the role of different microbes on the development and reproduction of the kissing bug Rhodnius prolixus (Hemiptera: Reduviidae)

Kissing bugs (Hempitera: Reduviidae) are obligately and exclusively blood feeding insects. Vertebrate blood is thought to provide insufficient B vitamins to insects, which rely on obligate symbiotic relationships with bacteria that provision these nutrients. Kissing bugs harbor environmentally acquired bacteria in their gut lumen, without which they are unable to develop to adulthood. Early experiments identified a single bacterial species, Rhodococcus rhodnii , as a symbiont of Rhodnius prolixus , but modern studies of the kissing bug microbiome suggest that R. rhodnii is not always present or abundant in wild-caught individuals. We asked whether R. rhodnii or other bacteria alone could function as symbionts of R. prolixus . Bacteria-free (axenic) insects were produced whose microbiome could be experimentally manipulated to produce insects with known microbiomes (gnotobiotic). We found that gnotobiotic insects harboring R. rhodnii alone developed faster, had higher survival, and laid more eggs than gnotobiotic R. prolixus harboring other bacterial monocultures, including other described symbionts of kissing bugs and several related Rhodococcus species. R. rhodnii grew to high titer in the guts of R. prolixus while other tested species were found at much lower abundance. Rhodococcus species tested had nearly identical B vitamin biosynthesis genes, and dietary supplementation of B vitamins had a relatively minor effect on development and survival of gnotobiotic R. prolixus . Our results indicate that R. prolixus have a higher fitness when harboring R. rhodnii than other bacteria tested, and that symbiont B vitamin synthesis is likely a necessary but not sufficient function of gut bacteria in kissing bugs.