microbiome is the genus Treponema (Spirochaetota), which accounted for approximately 32% of sequences in another 16S rRNA study. The same study identified Endomicrobia (phylum:Elusimicrobiota), which are predominant endosymbionts several protozoa in the termtie gut. Artificial defaunation of Reticulitermes species by force-feeding on starch or starvation leads to a loss of flagellates and, by association, these endosymbiotic Endomicrobia, and an increase in abundance of free-living relatives. A rare free-living member of this class, Endomicrobium proavitum, the first Endomicrobia species to be cultured and named, was isolated from sterile-filtered gut homogenates from defaunated (starch-fed) R. flavipes workers. It is believed to play a role in nitrogen fixation. While some gut bacteria live free in the gut lumen or attached to the gut wall, many others live in close association with flagellates. These include uncultured members of Endomicrobia (Elusimicrobiota) and other taxa that live as cytoplasmic symbionts, as well as epibiotic symbionts that attach to the outer surface of cells. In R. flavipes, cytoplasmic symbionts have been identified in flagellates such as Trichonympha agilis (Hypermastigida) and Pyrsonympha vertens (Oxymonadida). The latter is also characterised by spirochaete epibiotic symbionts. In other termite species, members of the spirochaete genus Treponema have been identified as endo- and ectosymbionts of flagellates: similar associations may explain Treponema'''s dominance in the R. flavipes gut. Archaea Archaea isolated from the R. flavipes hindgut include the H2- and CO2-utilizing methanogens Methanobrevibacter cuticularis and curvatus. These two species are believed to be the dominant methanogens in R. flavipes and are found in the peripheral, microxic region of the hindgut, on or in close proximity to the gut wall, where they are sometimes attached to filamentous prokaryotes. Caste-specific differences Although there is a core microbiome shared among castes and colonies, the alate caste gut is characterised by a significantly lower abundances of bacteria in the genus Treponema (Spirochaetota) and the class Endomicrobia (Elusimicrobia) compared to workers and soldiers. Flagellates in the class Parabasalia and the order Oxymonadida are also significantly less abundant in the alate gut, with the latter significantly reduced in dealates as well. Human impact Along with Reticulitermes virginica, R. flavipes is responsible for 80% of the $2.2 billion spent annually in the United States on termite control. Termites feed on wood cellulose, meaning that their presence in human made structures often goes unnoticed for lengthy periods of time. A termite infested timber will appear structurally sound from the outside, while