Immune stimulation induced changes to the native gut microbiota of bumble bees

Understanding factors influencing the maintenance and membership of
beneficial host-associated microbial communities is central to
understanding ecological, evolutionary, and health consequences of these
communities for their hosts. Host immunity is often implicated as a
potential regulator of these microbiota. However, conversely, immunity may
play a disruptive role, with immune responses to infection causing
collateral damage. Such effects may be more prominent from innate immune
responses, with more rapid-acting and relatively non-specific components.
We investigated how upregulation of antibacterial immunity in the bumble
bee Bombus impatiens affects the core gut microbiota, testing the
hypothesis of immunity-induced perturbation of the beneficial microbiota
structure. Freshly emerged adult bees received a native microbiota
inoculation before being subjected to non-pathogenic immune stimulation
treatments. We quantified the microbial community using 16S rRNA amplicon
sequencing and targeted qPCR. We find colonization of the core member
Gilliamella is altered by immune stimulation treatment. Additionally, a
positive association in communities between Gilliamella and another core
bacteria, Snodgrassella alvi, is perturbed. These changes are indicative
of immune-response-induced dysbiosis. As such, the potential for
collateral perturbation of beneficial microbial communities upon a
host's innate immune response may contribute to immune costs, shaping
the evolutionary optimization of immune investment.