Rectal bacteria produce sex pheromones in the male oriental fruit fly.

Volatile molecules produced by the microbiota play a primary role in chemical communication between insects, and direct production of pheromone components by the microbiota is one of the most obvious mechanisms. Here, we investigated the production of male-borne sex pheromones of the oriental fruit fly, Bactrocera dorsalis. As observed in previous studies, 2,3,5-trimethylpyrazine (TMP) and 2,3,5,6-tetramethylpyrazine (TTMP) are sex pheromones produced in the male rectum. Mature virgin females are strongly attracted to TMP and TTMP. 16S rRNA sequencing results show that the rectal bacteria are dominated by Bacilli that harbor the pathway to produce TMP and TTMP. The levels of Bacilli, TMP, and TTMP in the male rectum can be significantly decreased by feeding male flies with antibiotics. In vitro assays show that Bacillus species isolated from the male rectum can produce TMP and TTMP when provided with the substrates glucose and threonine, the levels of which are significantly higher in the rectum of mature males. These findings highlight the influence of microbial symbionts on insect pheromones and provide an example of direct bacterial production of pheromones in insects.