Treponema Endosymbionts are the Dominant Bacterial Members with Ureolytic Potential in the Gut of the Wood-Feeding Termite, Reticulitermes Hesperus

Termites are remarkable for their ability to digest cellulose from wood as their main energy source, but the extremely low nitrogen (N) content of their diet presents a major challenge for N acquisition. Besides the activity of N 2 -fixing bacteria in the gut, the recycling of N from waste products by symbiotic microbes as a complementary N-provisioning mechanism in termites remains poorly understood. In this study, we used a combination of high-throughput amplicon sequencing, quantitative PCR, and cultivation to characterize the microbial community capable of degrading urea, a common waste product, into ammonia in the guts of termites ( Reticulitermes hesperus ) from a wild and laboratory-reared colony. Taxonomic analysis indicated that a majority of the urease ( ureC ) genes in the termite gut (53.0%) matched with a Treponema endosymbiont of gut protists previously found in several other termites, suggesting an important contribution to the nutrition of essential cellulolytic protists. Furthermore, analysis of both the 16S rRNA and ureC amplicons revealed that the laboratory colony had decreased diversity and altered community composition for both prokaryotic and ureolytic microbial communities in the termite gut. Estimation by quantitative PCR showed that microbial ureC genes decreased in abundance in the laboratory-reared colony compared to the wild colony. In addition, most of our cultivated isolates appeared to originate from non-gut environments. Together, our results underscore a more important role for ureolysis by endosymbionts within protists than by free-swimming bacteria in the gut lumen of R. hesperus .

Aspergillus sclerotiorum fungus is lethal to both Western drywood (Incisitermes minor) and Western subterranean (Reticulitermes hesperus)termites

Termite control costs $1.5 billion per year in the United States alone, and methods for termite control usually consist of chemical pesticides. However, these methods have their drawbacks, which include the development of resistance, environmental pollution, and toxicity to other organisms. Biological termite control, which employs the use of living organisms to combat pests, offers an alternative to chemical pesticides. This study highlights the discovery of a fungus, termed “APU strain,” that was hypothesized to be pathogenic to termites. Phylogenetic and morphological analysis showed that the fungus is a strain of Aspergillus sclerotiorum, andexperiments showed that both western drywood (Incisitermes minor) and western subterranean (Reticulitermes hesperus) termites die in a dose-dependent manner exposed to fungal spores of A. sclerotiorum APU strain. In addition, exposure to the A. sclerotiorum Huber strain elicited death in a similar manner as the APU strain. The mechanism by which the fungus caused termite death is still unknown and warrants further investigation. While these results support that A. sclerotiorum is a termite pathogen, further studies are needed to determine whether the fungal species has potential as a biological control agent.

MEASUREMENT OF TERMITE (ISOPTERA: RHINOTERMITIDAE) FEEDING ON PAPER BY VIDEO IMAGE ANALYSIS

We describe a method of rapidly measuring the area removed by termites feeding on paper disks by microcomputer controlled video image analysis. The utility of this technique is demonstrated in a short-term (15 day) assay in which Reticulitermes hesperus Banks workers fed on filter paper, on rice paper containing a synthetic binder and on rice papers manufactured with natural starch from Lycoris radiata (Amaryllidaceae). Termites fed least on rice paper containing natural starch washed only with hot water during the manufacturing process. Greatest feeding occurred on rice paper containing the synthetic binder. Video image analysis is an efficient means of measuring termite feeding activity and comparing feeding on thin substrates of equivalent density and thickness.