A Study of the Gut Bacterial Community of Reticulitermes virginicus Exposed to Chitosan Treatment

A thorough understanding of microbial communities in the gut of lower termites is needed to develop target-specific and environmentally benign wood protection systems. In this study, the bacterial community from Reticulitermes virginicus was examined by Illumina sequencing of 16S ribosomal RNA (rRNA) spanning the V3 and V4 regions. Prior to library preparation, the termites were subjected to five treatments over an 18-day period: three groups were fed on wood treated with 0.5% chitosan, 25% acetic acid, or water, the fourth group was taken directly from the original collection log, and the fifth group was starved. Metagenomic sequences were analyzed using QIIME 2 to understand the treatments’ effects on the dynamics of the gut bacteria. Four dominant phyla were detected: Bacteroidetes (34.4% of reads), Firmicutes (20.6%), Elusimicrobia (15.7%), and Proteobacteria (12.9%). A significant effect of chitosan treatment was observed in two phyla; Firmicutes abundance was significantly lower with chitosan treatment when compared to other groups, while Actinobacteria was lower in unexposed and starved termites. The results suggest that chitosan treatment not only affects the structure of the microbial community in the gut, but other treatments such as starving also cause shifts in termite gut communities.

Trichonympha burlesquei n. sp. from Reticulitermes virginicus and evidence against a cosmopolitan distribution of Trichonympha agilis in many termite hosts

Historically, symbiotic protists in termite hindguts have been considered to be the same species if they are morphologically similar, even if they are found in different host species. For example, the first-described hindgut and hypermastigote parabasalian, Trichonympha agilis (Leidy, 1877) has since been documented in six species of Reticulitermes, in addition to the original discovery in Reticulitermes flavipes. Here we revisit one of these, Reticulitermes virginicus, using molecular phylogenetic analysis from single-cell isolates and show that the Trichonympha in R. virginicus is distinct from isolates in the type host and describe this novel species as Trichonympha burlesque i n. sp. We also show the molecular diversity of Trichonympha from the type host R. flavipes is greater than supposed, itself probably representing more than one species. All of this is consistent with recent data suggesting a major underestimate of termite symbiont diversity.

Asexual queen succession in the subterranean termite Reticulitermes virginicus

Termite colonies are founded by a pair of primary reproductives. In many species, including subterranean termites (family Rhinotermitidae), the primary king and queen can be succeeded by neotenic reproductives that are produced from workers or nymphs within the colony. It is generally believed that these neotenics inbreed within the colony, sometimes for many generations. Here, we show that primary queens of the North American subterranean termite, Reticulitermes virginicus , are replaced by numerous parthenogenetically produced female neotenics. We collected functional female neotenics from five colonies of R. virginicus in North Carolina and Texas, USA. Genetic analysis at eight microsatellite loci showed that 91–100% of the neotenics present within a colony were homozygous at all loci, indicating that they were produced through automictic parthenogenesis with terminal fusion. In contrast, workers, soldiers and alates were almost exclusively sexually produced by mating between the female neotenics and a single king. This is the second termite species shown to undergo asexual queen succession, a system first described in the Japanese species, Reticulitermes speratus . Thus, the conditional use of sexual and asexual reproduction to produce members of different castes may be widespread within Reticulitermes and possibly other subterranean termites.