Dysbiosis: a potential novel strategy for control of subterranean termites

Abstract

Although alternative control strategies using biocontrol agents have reduced populations of many pest insects, biocontrol of termites has met with limited success. Termite living conditions—crowded colonies in moist soil—are seemingly ripe for epizootic outbreaks, yet, termite colonies rarely succumb to disease. The source of their immunity comes from a multi-tiered defense system involving cellular, physiological, and behavioral mechanisms, the combination of which protects termites at individual and colony levels. Defeating termite immunity, however, may be possible by chemically inducing microbial imbalance or dysbiosis. In this study, treating solution (2% chitosan or control) and weather exposure (88 days or 0 days) were tested in a factorial design (four treatments total) to determine sublethal effects on hindgut bacterial diversity in the subterranean termite, Reticulitermes flavipes. The bioassay was set up according to the AWPA E1 single-choice feeding experiment. After four weeks, DNA was extracted from termite hindguts. Species abundance and richness were based on sequence analysis of the V3 and V4 region of the 16S ribosomal RNA gene using the Illumina 16S metagenomics workflow. After pre-processing the data by using data-driven methods to set thresholds for signal to noise ratio and removal of rare species, multivariate analysis was performed using the statistical package PC-ORD. Visualization of the phyla abundance data in a two-way cluster analysis indicated that the four treatments (CTW, chitosan-treated wood not exposed to weathering; CTW_E, chitosan-treated wood exposed to weathering; WTW, water-treated wood not exposed to weathering; and WTW_E, water-treated wood exposed to weathering) separated into two clusters, one uniquely comprised of CTW and the second formed by the other three groups. Association of CTW_E with the two controls (WTW and WTW_E) was presumably due to environmental leaching. PerMANOVA showed that treatment exerted a significant effect on phyla diversity with all four treatments being significantly different from each other. Indicator species analysis (Indicator Value ≥90) detected nine species specific to CTW. These species demonstrated both high relative abundance (>97% of total reads found were found in CTW) and constancy (species found in more than 90% of CTW DNA samples). Five have been isolated from human tissue infections or human tissue infections with comorbidities. Three species—Mycobacterium abscessus, M. franklinii, and Sphingobacterium multivorum— are ubiquitously found in nature and considered to be opportunistic pathogens. Based on these data, we hypothesize that antimicrobials like chitosan can chemically induce dysbiosis to allow establishment of disease-causing pathogens.

Citation

Tang, Juliet D.; Raji, Olan; Peterson, Daniel G.; Jeremic-Nikolic, Dragica. 2018. Dysbiosis: a potential novel strategy for control of subterranean termites. In: Proceedings, 114th annual meeting of the American wood protection association. Birmingham, AL: American Wood Protection Association: 81-91.