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.

The Effect of Variables on Laboratory Termite Testing: Part I—Worker:Soldier Ratio

The objective of this study was to determine if the same soldier:worker ratio could be used in the eastern subterranean termite (Reticulitermes flavipes) and the Formosan subterranean termite (Coptotermes formosanus) in standard tests. Native (R. flavipes) and introduced (C. formosanus) subterranean termite species were tested in an American Wood Protection Association E1 standard laboratory test. Statistically equivalent weight losses were found as long as the ratio was within 10 percent of the rate required by the standard.

Temporal Changes in Cuticular Hydrocarbons During Worker-Reproductive Transition in the Eastern Subterranean Termite (Blattodea: Rhinotermitidae)

In social insects, the reproductive division of labor is often regulated through communication using cuticular hydrocarbons (CHCs) that indicate caste identity and reproductive status. In many termites, workers retain reproductive potential and can differentiate into ergatoid reproductives, and this process is mediated by the presence of reproductives in sex- and age-specific patterns. However, little is known about the variation of CHCs profiles during this transition. In this study, we analyzed the CHC profiles of workers in comparison with ergatoids of different age, sex, and mating status in the eastern subterranean termite, Reticulitermes flavipes (Kollar) (Blattodea: Rhinotermitidae), one of the most widely distributed termite species in the world. Both female and male ergatoids were characterized by the presence of tricosane and a group of long-chain and methyl-branched hydrocarbons (chain length ≥ 33), which were found in significantly lower quantities from workers. In addition, CHC profiles differed between newly differentiated (3–4 d) and old (20–25 d) ergatoids, but no difference in CHC signatures was found between females and males based on identified compounds. Heneicosane, a previously reported royal recognition pheromone in R. flavipes, was not detected in ergatoids examined in this study. The results of caste- and age-dependent variations suggest that CHCs may act as releaser pheromones that mediate caste recognition and age-related interactions between reproductives, but analytical results of identified compounds in this study do not support CHCs as sex-specific primer pheromones that regulate nestmate fertility. Royal pheromones in termites may involve complex hydrocarbon blends and non-hydrocarbon substances that await further investigation.

Experimental warming reduces gut prokaryotic diversity, survival and thermal tolerance of the eastern subterranean termite, Reticulitermes flavipes (Kollar)

Understanding the effects of environmental disturbances on the health and physiology of insects is crucial in predicting the impact of climate change on their distribution, abundance, and ecology. As microbial symbionts have been shown 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. Previous studies have shown that temperature affects the diversity of protists in termite gut, but less is known about the bacterial symbionts. 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 showed low temperature exposed termites had significantly lower CTmin and significantly higher SCP values compared to termites from medium or high temperature groups. This suggests 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 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.

Cooperative policing behaviour regulates reproductive division of labour in a termite

Reproductive conflicts are common in insect societies where helping castes retain reproductive potential. One of the mechanisms regulating these conflicts is policing, a coercive behaviour that reduces direct reproduction by other individuals. In eusocial Hymenoptera (ants, bees and wasps), workers or the queen act aggressively towards fertile workers, or destroy their eggs. In many termite species (order Blattodea), upon the death of the primary queen and king, workers and nymphs can differentiate into neotenic reproductives and inherit the breeding position. During this process, competition among neotenics is inevitable, but how this conflict is resolved remains unclear. Here, we report a policing behaviour that regulates reproductive division of labour in the eastern subterranean termite, Reticulitermes flavipes . Our results demonstrate that the policing behaviour is a cooperative effort performed sequentially by successful neotenics and workers. A neotenic reproductive initiates the attack of the fellow neotenic by biting and displays alarm behaviour. Workers are then recruited to cannibalize the injured neotenic. Furthermore, the initiation of policing is age-dependent, with older reproductives attacking younger ones, thereby inheriting the reproductive position. This study provides empirical evidence of policing behaviour in termites, which represents a convergent trait shared between eusocial Hymenoptera and Blattodea.

Cooperative policing behavior regulates reproductive division of labor in a termite

Reproductive conflicts are common in insect societies where helping castes retain reproductive potential. One of the mechanisms regulating the conflicts is policing, a coercive behavior that reduces direct reproduction by other individuals. In eusocial Hymenoptera (ants, bees, and wasps), workers or the queen act aggressively toward fertile workers, or destroy their eggs. In many termite species (order Blattodea), upon the death of primary queen and king, workers or nymphs can differentiate into neotenic reproductives and inherit the breeding position. During this process, competition among neotenics is inevitable, but how this conflict is resolved remains unclear. Here, we report a policing behavior that regulates reproductive division of labor in the eastern subterranean termite, Reticulitermes flavipes. Our results demonstrate that the policing behavior is a cooperative effort performed sequentially by successful neotenics and workers. A neotenic reproductive initiates the attack of the fellow neotenic by biting and displays alarm behavior. Workers are then recruited to cannibalize the injured neotenic. Furthermore, the initiation of policing is age-dependent, with older reproductives attacking younger ones, thereby inheriting the reproductive position. This study provides empirical evidence of policing behavior in termites, which represents a convergent trait shared between eusocial Hymenoptera and Blattodea.

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.