Are gut symbionts involved in presoldier differentiation in Reticulitermes flavipes

Termites are eusocial insects that host a range of prokaryotic and eukaryotic gut symbionts and can also differentiate into a range of caste phenotypes. Soldier caste differentiation from termite workers follows two successive molts that are driven at the endocrine level by juvenile hormone (JH). The first molt is from workers to presoldiers, followed by a second molt where soldiers differentiate from presoldiers. While physiological and eusocial mechanisms tied to JH signaling have been studied, the role of gut symbiota in the caste differentiation process is poorly understood. Here, we used the JH analog-methoprene in combination with the antibiotic kanamycin to manipulate caste differentiation and gut bacterial loads in Reticulitermes flavipes termites via four bioassay treatments: kanamycin, methoprene, kanamycin + methoprene, and an untreated (negative) control. The bacterial 16S rRNA gene sequencing provided alpha-beta diversities that demonstrated significantly different species richness, evenness and diversity between the treatments. The untreated control demonstrated highest species richness, evenness and diversity. The 16S results further revealed that the bacteria from the phyla Actinobacteria, Proteobacteria, Fusobacteria, Patescibacteria, and Bacteroidetes were differentially abundant in the methoprene treatment, suggesting roles for these microbes during the differentiation process. Based on these results we are now able to link specific bacterial groups with caste differentiation outcomes.