The fate of carbon utilized by the subterranean termite Reticulitermes flavipes

Understanding the Role of Free-Living Bacteria in the Gut of the Lower Termite Coptotermes gestroi Based on Metagenomic DNA Analysis

Termites' digestive systems, particularly in lower termites with the presence of protozoa, are unique ecological niches that shelter a diverse microbiota with a variety of functions for the host and the environment. In 2012, the metagenomic DNA (5.4 Gb) of the prokaryotes that freely live in the gut of the lower termite Coptotermes gestroi were sequenced. A total of 125,431 genes were predicted and analyzed in order to mine lignocellulolytic genes. however, the overall picture of the structure, diversity, and function of the prokaryotic gut microbiota was not investigated. In the present study, these 125,431 genes were taxonomically classified by MEGAN and functionally annotated by the Kyoto Encyclopedia of Genes and Genomes (KEGG) and by the Carbohydrate-Active enZYmes (CAZy) and HMMER databases. As a result, 95,751 bacterial genes were classified into 35 phyla. The structure of the bacteria, typified by a high ratio of Firmicutes to Bacterioidetes, was distinct from the structure of the entirety of the bacteria in the lower or higher termites' guts. The archaea (533 genes) were distributed into 4 phyla, 10 classes, 15 orders, 21 families, 47 genera, and 61 species. Although freely living in the guts, the prokaryotic community was formed, developed, and adapted to exhibit unique interactions in order to perform mutual roles of benefit to their hosts. Methanobacteriales, accounting for 61% of the archaea symbionts, seem to play an important role in methanogenesis. Concomitantly, bacterial methanotrophs in the gut utilize methane and combine with other bacterial groups, including potential lignocellulolytic degraders, acetogens, sulfur bacteria, and nitrogen-recycling bacteria, to efficiently convert wood with little nitrogen into acetates via certain pathway modules specified by prokaryotes that freely live in the gut. This forms an important energy source for the termites. Furthermore, bacteria carry 2223 genes involved in the biosynthesis of 17 antibiotic groups. The gut bacteria also possess genes for the degradation of 18 toxic aromatic compounds, of which four are commercial pesticides against termites commonly used for the preservation of wooden constructions. Eight of the eighteen pathways were the first to be reported from the termite gut. Overall, this study sheds light on the roles of the freely living bacteria and archaea in the C. gestroi gut, providing evidence that the gut microbiome acts as the second host genome, contributing both nutrients and immunity to support the host's existence, growth, and development.

Termites are the main dung removals in a degraded landscape in Brazil

Termites are one of the most relevant groups for recycling nutrients and keeping the flow of energy in ecosystems. Although their role as lignocellulose decomposers is the focus of studies, they also act as dung recyclers, but their importance in this process is poorly understood. Here we performed manipulation experiments to determine dung removal by termites in forest remnants and cattle pastures in a fragmented Atlantic Forest landscape. We used wire bags of different mesh sizes placed along transects in three forest fragments and pastures for 10 days to compare the contribution of termites and other coprophagous macrodetritivores to dung removal. Our results indicated that termites removed more dung in pastures than in the forest fragments. In addition, dung beetle exclusion significantly reduced the percentage of dung removal within forest fragments, but not on pastures, indicating termites are important dung recyclers in pastures.