Dose-Dependent Effects of a Gut-Derived Bacillus on Survival and Feeding in a Neotropical Termite

The ecological success of termites is closely linked to their associations with gut microbial communities, yet these interactions may also entail potential fitness costs. The effects of gut-associated bacteria on host performance remain poorly understood. Here, we experimentally assessed the effects of a gut-derived Bacillus sp. isolate on the survival and feeding behavior of workers of the termite Constrictotermes cyphergaster (Silvestri, 1901) (Termitidae: Nasutitermitinae), using the opportunistic pathogen Pseudomonas aeruginosa as a reference treatment. Workers were exposed to increasing bacterial doses, and survival analyses revealed that both bacteria induced a significant dose-dependent decline in survival. However, the Bacillus isolate caused a stronger reduction in overall survival compared to controls, whereas P. aeruginosa also reduced survival but with a comparatively weaker effect. Feeding activity was independent of dose, but exposure to Bacillus sp. significantly reduced food consumption, a pattern not observed for P. aeruginosa. These results demonstrate that a gut-derived bacterium can negatively affect host survival and feeding under experimental conditions, highlighting the importance of considering both beneficial and potentially harmful effects of host-associated microorganisms on termite fitness.