ATR-FTIR Study of Alaska Yellow Cedar Extractives and Relationship with Their Natural Durability

New approaches for assessing wood durability are needed to help categorize decay resistance as timber utilization shifts towards plantations or native forest regrowth that may be less durable than original native forest resources. This study evaluated attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy combined with principal component analysis (PCA) for distinguishing between groups of Alaska yellow cedar (Cupressus nootkatensis) wood for susceptibility to two decay fungi (Gloeophyllum trabeum and Rhodonia placenta) and the eastern subterranean termite (Reticulitermes flavipes). Alaska yellow cedar durability varied with test organisms, but the majority of samples were highly resistant to fungal and termite attack. Weight losses and extractives yield using sequential extractions (toluene:ethanol > ethanol > hot water) showed moderate to weak relationships. PCA analysis revealed limited ability to distinguish amongst levels of wood durability to all tested organisms. The absence of non-resistant samples may have influenced the ability of the chemometric methods to accurately categorize durability.

Regulation of host phenotypic plasticity by gut symbiont communities in the Eastern Subterranean termite (Reticulitermes flavipes Kollar)

Termites are eusocial insects that host a range of prokaryotic and eukaryotic gut symbionts and can differentiate into a range of caste phenotypes. Soldier caste differentiation from termite workers follows two successive molts (worker-presoldier-soldier) that are driven at the endocrine level by juvenile hormone (JH). While physiological and eusocial mechanisms tied to JH signaling have been studied, the role of gut symbionts in the caste differentiation process is poorly understood. Here, we used the JH analog-methoprene in combination with the antibiotic kanamycin to manipulate caste differentiation and gut bacterial loads in Reticulitermes flavipes termites via four bioassay treatments: kanamycin, methoprene, kanamycin+methoprene, and an untreated (negative) control. Bioassay results demonstrated a significantly higher number of presoldiers in the methoprene, highest mortality in kanamycin+methoprene, and significantly reduced protist numbers in all treatments except the untreated control. Bacterial 16S rRNA gene sequencing provided alpha and beta diversity results that mirrored bioassay findings. From ANCOM analysis, we found that several bacterial genera were differentially abundant among treatments. Finally, follow-up experiments showed that if methoprene and kanamycin or untreated termites are placed together, zero or rescued presoldier initiation (respectively) occurs. These findings reveal that endogenous JH selects for symbiont compositions required to successfully complete presoldier differentiation. However, if the gut is voided before the influx of JH, it cannot select for the necessary symbionts that are crucial for molting. Based on these results we are able to provide a novel example of linkages between gut microbial communities and host phenotypic plasticity.

Characterization of cellulose-degrading microbiota from the eastern subterranean termite and soil

Background: While there have been a lot of studies on the termite gut microbiota, there has been very little research directly on the cellulose-degrading microbiota in termites or their soil environment. This study addresses this problem by profiling cellulose-degrading bacteria and archaea in the selective cellulose cultures of two samples of the eastern subterranean termite (Reticulitermes flavipes) and one soil sample collected at the same location as one of the termite samples. Methods: All the cultures were examined for cell concentration and remaining cellulose after the culture was completed. The 16S rRNA pyrotag sequencing method was used to identify the prokaryotic microbiota for the three cultures and one termite colony without culture. The MOTHUR, SSU-ALIGN, RDPTools, phyloseq, and other R packages were used for sequence and statistical analyses. Results: Biochemical analyses of the cultures suggested high efficiency of cellulose degradation. Comparative analyses between the cultured and uncultured termite gut microbiota revealed a significant difference. Proteobacteria and Firmicutes were found to be the two most abundant phyla of cellulose-degrading bacteria from the three cultures, but different classes within each phylum dominated the different samples. Shared and sample-specific cellulose-degrading taxa, including a core set of taxa across all the cultures, were identified. Conclusions: Our study demonstrates the importance of using selective cellulose culture to study the cellulose-degrading microbial community. It also revealed that the cellulose-degrading microbiota in the eastern subterranean termite is significantly influenced by the microbiota in the surrounding soil environment. Biochemical analyses showed that the microbial communities enriched from all the selective cultures were efficient in degrading cellulose, and a core set of bacteria have been identified as targets for further functional analyses.

Experimental Warming Reduces Survival, Cold Tolerance, and Gut Prokaryotic Diversity of the Eastern Subterranean Termite, Reticulitermes flavipes (Kollar)

Understanding the effects of environmental disturbances on insects is crucial in predicting the impact of climate change on their distribution, abundance, and ecology. As microbial symbionts are known to play an integral role in a diversity of functions within the insect host, research examining how organisms adapt to environmental fluctuations should include their associated microbiota. In this study, subterranean termites [Reticulitermes flavipes (Kollar)] were exposed to three different temperature treatments characterized as low (15°C), medium (27°C), and high (35°C). Results suggested that pre-exposure to cold allowed termites to stay active longer in decreasing temperatures but caused termites to freeze at higher temperatures. High temperature exposure had the most deleterious effects on termites with a significant reduction in termite survival as well as reduced ability to withstand cold stress. The microbial community of high temperature exposed termites also showed a reduction in bacterial richness and decreased relative abundance of Spirochaetes, Elusimicrobia, and methanogenic Euryarchaeota. Our results indicate a potential link between gut bacterial symbionts and termite’s physiological response to environmental changes and highlight the need to consider microbial symbionts in studies relating to insect thermosensitivity.

Vibratory behaviour produces different vibrations patterns in presence of reproductives in a subterranean termite species

Vibratory behaviours are widespread in social insects, but the produced vibrations remain poorly explored. Communication using vibrations is an efficient way to transmit information in subterranean environments where visual and odorant signals are less efficient. In termites, different vibratory behaviours are performed in different contexts like reproductive regulation and alarm signalling, but only few studies explored the structure of the produced vibrations (i.e., duration, number of pulses, amplitude). Here, we described several types of vibrations produced by a vibratory behaviour widespread in termites (body-shaking), which can be transmitted through the substrate and detected by other colony members. We analysed the structures of the emitted vibrations and the occurrence of the body-shaking events in presence/absence of reproductives and/or in presence/absence of a stress stimuli (flashlight) in the subterranean termite Reticulitermes flavipes. Interestingly, only the presence of the reproductives did influence the number of pulses and the duration of the emitted vibrations. Moreover, the first part of the emitted vibrations seems to be enough to encode reproductive information, but other parts might hold other type of information. Body-shaking occurrence did increase in presence of reproductives but only briefly under a flashlight. These results show that vibratory cues are complex in termites and their diversity might encode a plurality of social cues.

Draft Genome Sequences of Dysgonomonas sp. Strains GY75 and GY617, Isolated from the Hindgut of Reticulitermes flavipes

ABSTRACT Dysgonomonas species are facultative heterotrophs capable of growth on lignocellulose-derived polysaccharides. Dysgonomonas species harbor myriad genes involved in glycan modification and are well suited to the lignocellulose-rich conditions within the termite hindgut. Here, we report draft genome sequences for Dysgonomonas sp. strains GY75 and GY617, isolated from the hindgut of Reticulitermes flavipes.

Concentration-Dependent Feeding Deterrence to 20-Hydroxyecdysone for Three Subterranean Termite Species (Blattodea: Rhinotermitidae)

Effective active ingredients in toxicant bait formulations must be non-deterrent to insect feeding behavior at lethal concentrations. This study evaluated feeding deterrence for Coptotermes formosanus Shiraki, C. gestroi (Wasmann), and Reticulitermes flavipes (Kollar) when provided access to cellulose impregnated with various concentrations of the insect molting hormone, 20-hydroxyecdysone (20E). Termites were exposed to 20E concentrations of 200, 500, 1000 and 2000 ppm and to noviflumuron at 5000 ppm in a 24 h choice-test, and the mass of substrate consumption from treated and untreated media pads was compared for each treatment. 20E feeding deterrence was detected at 500, 1000 and 2000 ppm for C. gestroi, and at 2000 ppm for C. formosanus. No significant differences in consumption of treated and untreated substrate was detected at any concentration for R. flavipes. Potential methods for reducing deterrence are discussed.