Parallel metatranscriptome analyses of host and symbiont gene expression in the gut of the termite Reticulitermes flavipes

Differential impacts of juvenile hormone, soldier head extract and alternate caste phenotypes on host and symbiont transcriptome composition in the gut of the termite Reticulitermes flavipes

BACKGROUND

Termites are highly eusocial insects and show a division of labor whereby morphologically distinct individuals specialize in distinct tasks. In the lower termite Reticulitermes flavipes (Rhinotermitidae), non-reproducing individuals form the worker and soldier castes, which specialize in helping (e.g., brood care, cleaning, foraging) and defense behaviors, respectively. Workers are totipotent juveniles that can either undergo status quo molts or develop into soldiers or neotenic reproductives. This caste differentiation can be regulated by juvenile hormone (JH) and primer pheromones contained in soldier head extracts (SHE). Here we offered worker termites a cellulose diet treated with JH or SHE for 24-hr, or held them with live soldiers (LS) or live neotenic reproductives (LR). We then determined gene expression profiles of the host termite gut and protozoan symbionts concurrently using custom cDNA oligo-microarrays containing 10,990 individual ESTs.

RESULTS

JH was the most influential treatment (501 total ESTs affected), followed by LS (24 ESTs), LR (12 ESTs) and SHE treatments (6 ESTs). The majority of JH up- and downregulated ESTs were of host and symbiont origin, respectively; in contrast, SHE, LR and LS treatments had more uniform impacts on host and symbiont gene expression. Repeat "follow-up" bioassays investigating combined JH + SHE impacts in relation to individual JH and SHE treatments on a subset of array-positive genes revealed (i) JH and SHE treatments had opposite impacts on gene expression and (ii) JH + SHE impacts on gene expression were generally intermediate between JH and SHE.

CONCLUSIONS

Our results show that JH impacts hundreds of termite and symbiont genes within 24-hr, strongly suggesting a role for the termite gut in JH-dependent caste determination. Additionally, differential impacts of SHE and LS treatments were observed that are in strong agreement with previous studies that specifically investigated soldier caste regulation. However, it is likely that gene expression outside the gut may be of equal or greater importance than gut gene expression.

Termite hindguts and the ecology of microbial communities in the sequencing age

Advances in high-throughput nucleic acid sequencing have improved our understanding of microbial communities in a number of ways. Deeper sequence coverage provides the means to assess diversity at the resolution necessary to recover ecological and biogeographic patterns, and at the same time single-cell genomics provides detailed information about the interactions between members of a microbial community. Given the vastness and complexity of microbial ecosystems, such analyses remain challenging for most environments, so greater insight can also be drawn from analysing less dynamic ecosystems. Here, we outline the advantages of one such environment, the wood-digesting hindgut communities of termites and cockroaches, and how it is a model to examine and compare both protist and bacterial communities. Beyond the analysis of diversity, our understanding of protist community ecology will depend on using statistically sound sampling regimes at biologically relevant scales, transitioning from discovery-based to experimental ecology, incorporating single-cell microbiology and other data sources, and continued development of analytical tools.

Comparative metatranscriptomic signatures of wood and paper feeding in the gut of the termite Reticulitermes flavipes (Isoptera: Rhinotermitidae)

Termites are highly eusocial insects that thrive on recalcitrant materials like wood and soil and thus play important roles in global carbon recycling and also in damaging wooden structures. Termites, such as Reticulitermes flavipes (Rhinotermitidae), owe their success to their ability to extract nutrients from lignocellulose (a major component of wood) with the help of gut-dwelling symbionts. With the aim to gain new insights into this enzymatic process we provided R. flavipes with a complex lignocellulose (wood) or pure cellulose (paper) diet and followed the resulting differential gene expression on a custom oligonucleotide-microarray platform. We identified a set of expressed sequence tags (ESTs) with differential abundance between the two diet treatments and demonstrated the source (host/symbiont) of these genes, providing novel information on termite nutritional symbiosis. Our results reveal: (1) the majority of responsive wood- and paper-abundant ESTs are from host and symbionts, respectively; (2) distinct pathways are associated with lignocellulose and cellulose feeding in both host and symbionts; and (3) sets of diet-responsive ESTs encode putative digestive and wood-related detoxification enzymes. Thus, this study illuminates the dynamics of termite nutritional symbiosis and reveals a pool of genes as potential targets for termite control and functional studies of termite-symbiont interactions.

Evidence of a conserved functional role for DNA methylation in termites

Many organisms are capable of developing distinct phenotypes from the same genotype. This developmental plasticity is particularly prevalent in insects, which can produce alternate adaptive forms in response to distinct environmental cues. The ability to develop divergent phenotypes from the same genotype often relies on epigenetic information, which affects gene function and is transmitted through cell divisions. One of the most important epigenetic marks, DNA methylation, has been lost in several insect lineages, yet its taxonomic distribution and functional conservation remain uninvestigated in many taxa. In the present study, we demonstrate that the signature of high levels of DNA methylation exists in the expressed genes of two termites, Reticulitermes flavipes and Coptotermes formosanus. Further, we show that DNA methylation is preferentially targeted to genes with ubiquitous expression among morphs. Functional associations of DNA methylation are also similar to those observed in other invertebrate taxa with functional DNA methylation systems. Finally, we demonstrate an association between DNA methylation and the long-term evolutionary conservation of genes. Overall, our findings strongly suggest DNA methylation is present at particularly high levels in termites and may play similar roles to those found in other insects.

Comparative genomic analysis of the microbiome [corrected] of herbivorous insects reveals eco-environmental adaptations: biotechnology applications

Metagenome analysis of the gut symbionts of three different insects was conducted as a means of comparing taxonomic and metabolic diversity of gut microbiomes to diet and life history of the insect hosts. A second goal was the discovery of novel biocatalysts for biorefinery applications. Grasshopper and cutworm gut symbionts were sequenced and compared with the previously identified metagenome of termite gut microbiota. These insect hosts represent three different insect orders and specialize on different food types. The comparative analysis revealed dramatic differences among the three insect species in the abundance and taxonomic composition of the symbiont populations present in the gut. The composition and abundance of symbionts was correlated with their previously identified capacity to degrade and utilize the different types of food consumed by their hosts. The metabolic reconstruction revealed that the gut metabolome of cutworms and grasshoppers was more enriched for genes involved in carbohydrate metabolism and transport than wood-feeding termite, whereas the termite gut metabolome was enriched for glycosyl hydrolase (GH) enzymes relevant to lignocellulosic biomass degradation. Moreover, termite gut metabolome was more enriched with nitrogen fixation genes than those of grasshopper and cutworm gut, presumably due to the termite's adaptation to the high fiber and less nutritious food types. In order to evaluate and exploit the insect symbionts for biotechnology applications, we cloned and further characterized four biomass-degrading enzymes including one endoglucanase and one xylanase from both the grasshopper and cutworm gut symbionts. The results indicated that the grasshopper symbiont enzymes were generally more efficient in biomass degradation than the homologous enzymes from cutworm symbionts. Together, these results demonstrated a correlation between the composition and putative metabolic functionality of the gut microbiome and host diet, and suggested that this relationship could be exploited for the discovery of symbionts and biocatalysts useful for biorefinery applications.

Lignin-associated metagene expression in a lignocellulose-digesting termite

Lignin is a component of plant biomass that presents a significant obstacle to biofuel production. It is composed of a highly stable phenylpropanoid matrix that upon degradation, releases toxic metabolites. Termites have specialized digestive systems that overcome the lignin barrier in wood lignocellulose to efficiently release fermentable simple sugars; however, how termites specifically degrade lignin and tolerate its toxic byproducts remains unknown. Here, using the termite Reticulitermes flavipes and its symbiotic (protozoan) gut fauna as a model system, we used high throughput Roche 454-titanium pyrosequencing and proteomics approaches to (i) experimentally compare the effects of diets containing varying degrees of lignin complexity on host-symbiont digestome composition, (ii) deeply sample host and symbiont lignocellulase diversity, and (iii) identify promising lignocellulase candidates for functional characterization. In addition to revealing over 9500 differentially expressed transcripts related to a wide range of physiological processes, our findings reveal two detoxification enzyme families not generally considered in connection with lignocellulose digestion: aldo-keto reductases and catalases. Recombinant versions of two host enzymes from these enzyme families, which apparently play no roles in cellulose or hemicellulose digestion, significantly enhance lignocellulose saccharification by cocktails of host and symbiont cellulases. These hypothesis-driven results provide important new insights into (i) dietary lignin as a xenobiotic challenge, (ii) the complex mechanisms used by termites to cope with their lignin-rich diets, and (iii) novel lignin-targeted enzymatic approaches to enhance biofuel and biomaterial production.

Molecular cloning and characterization of an endogenous digestive β-glucosidase from the midgut of the fungus-growing termite Macrotermes barneyi

β-glucosidase from the midgut of the fungus-growing termite Macrotermes barneyi was first cloned and characterized to gain a better understanding of cellulolytic systems in fungus-growing termites. β-glucosidase activity was proven to present primarily in the midgut of M. barneyi and two β-glucosidases were partially purified from the midgut. Based on the N-terminus sequence of one of the β-glucosidases, a full-length cDNA fragment of 1708 bp was obtained. This sequence encodes a 493 amino acid protein belonging to glycoside hydrolase family 1. Quantitative real-time PCR analysis proved that the β-glucosidase gene was primarily expressed in the midgut. β-glucosidase was expressed heterologously and biochemically characterized. Results indicate that β-glucosidase is an endogenous, midgut-origin termite digestive enzyme. It may have applications in understanding the mechanism of lignocellulose degradation in fungus-growing termites.

Endogenous Plant Cell Wall Digestion: A Key Mechanism in Insect Evolution

The prevailing view that insects lack endogenous enzymes for plant cell wall (PCW) digestion had led to the hypothesis that PCW digestion evolved independently in different insect taxa through the establishment of symbiotic relationships with microorganisms. However, recent studies reporting endogenous PCW-degrading genes and enzymes for several insects, including phylogenetically basal insects and closely related arthropod groups, challenge this hypothesis. Here, we summarize the molecular and biochemical evidence on the mechanisms of PCW digestion in insects to analyze its evolutionary pathways. The evidence reveals that the symbiotic-independent mechanism may be the ancestral mechanism for PCW digestion. We discuss the implications of this alternative hypothesis in the evolution of plant-insect interactions and suggest that changes in the composition of lignocellulolytic complexes were involved in the evolution of feeding habits and diet specializations in insects, playing important roles in the evolution of plant-insect interactions and in the diversification of insects.

Evidence for lignin oxidation by the giant panda fecal microbiome

The digestion of lignin and lignin-related phenolic compounds from bamboo by giant pandas has puzzled scientists because of the lack of lignin-degrading genes in the genome of the bamboo-feeding animals. We constructed a 16S rRNA gene library from the microorganisms derived from the giant panda feces to identify the possibility for the presence of potential lignin-degrading bacteria. Phylogenetic analysis showed that the phylotypes of the intestinal bacteria were affiliated with the phyla Proteobacteria (53%) and Firmicutes (47%). Two phylotypes were affiliated with the known lignin-degrading bacterium Pseudomonas putida and the mangrove forest bacteria. To test the hypothesis that microbes in the giant panda gut help degrade lignin, a metagenomic library of the intestinal bacteria was constructed and screened for clones that contained genes encoding laccase, a lignin-degrading related enzyme. A multicopper oxidase gene, designated as lac51, was identified from a metagenomic clone. Sequence analysis and copper content determination indicated that Lac51 is a laccase rather than a metallo-oxidase and may work outside its original host cell because it has a TAT-type signal peptide and a transmembrane segment at its N-terminus. Lac51 oxidizes a variety of lignin-related phenolic compounds, including syringaldazine, 2,6-dimethoxyphenol, ferulic acid, veratryl alcohol, guaiacol, and sinapinic acid at conditions that simulate the physiologic environment in giant panda intestines. Furthermore, in the presence of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), syringic acid, or ferulic acid as mediators, the oxidative ability of Lac51 on lignin was promoted. The absorbance of lignin at 445 nm decreased to 36% for ABTS, 51% for syringic acid, and 51% for ferulic acid after incubation for 10 h. Our findings demonstrate that the intestinal bacteria of giant pandas may facilitate the oxidation of lignin moieties, thereby clarifying the digestion of bamboo lignin by the animal.

The complexities of hydrolytic enzymes from the termite digestive system

The main challenge in second generation bioethanol production is the efficient breakdown of cellulose to sugar monomers (hydrolysis). Due to the recalcitrant character of cellulose, feedstock pretreatment and adapted hydrolysis steps are needed to obtain fermentable sugar monomers. The conventional industrial production process of second-generation bioethanol from biomass comprises several steps: thermochemical pretreatment, enzymatic hydrolysis and sugar fermentation. This process is undergoing continuous optimization in order to increase the bioethanol yield and reduce the economic cost. Therefore, the discovery of new enzymes with high lignocellulytic activity or new strategies is extremely important. In nature, wood-feeding termites have developed a sophisticated and efficient cellulose degrading system in terms of the rate and extent of cellulose hydrolysis and exploitation. This system, which represents a model for digestive symbiosis has attracted the attention of biofuel researchers. This review describes the termite digestive system, gut symbionts, termite enzyme resources, in vitro studies of isolated enzymes and lignin degradation in termites.

Defining host-symbiont collaboration in termite lignocellulose digestion: "The view from the tip of the iceberg"

Termites have the unique ability to exploit lignocellulose as a primary nutrition source. Traditionally, termite lignocellulose digestion has been considered as a gut-symbiont-mediated process; however, in recent years the importance of host digestive capabilities have become apparent. Despite this growing understanding, how digestive enzymes from different origins specifically collaborate (i.e., additively or synergistically) has remained largely unknown. In a recent study, we undertook translational-genomic studies to address these questions in the lower termite Reticulitermes flavipes (Isoptera: Rhinotermitidae) and its symbiotic gut fauna. We used a combination of native gut tissue preparations and recombinant enzymes derived from the host gut transcriptome to identify synergistic collaborations between host and symbiont, and also among enzymes produced exclusively by the host termite. These findings provided important new evidence of synergistic collaboration among enzymes in the release of fermentable monosaccharides from wood lignocellulose, and laid a foundation for future integrative studies into termite digestion, symbiosis and eusociality.

Investigation into the physiologies of Aeromonas veronii in vitro and inside the digestive tract of the medicinal leech using RNA-seq

Host-associated microbial communities are widespread in nature and vital to the health and fitness of the host. Deciphering the physiology of the microbiome in vivo is critical to understanding the molecular basis of the symbiosis. Recently, the development and application of high-throughput sequencing techniques, particularly RNA-seq, for studying microbial communities has enabled researchers to address not only which microbes are present in a given community but also how the community functions. For microbes that can also be cultivated in the laboratory, RNA-seq provides the opportunity to identify genes that are differentially expressed during symbiosis by comparing in vitro to in vivo transcriptomes. In the current study, we used RNA-seq to identify genes expressed by the digestive-tract microbiome of the medicinal leech, Hirudo verbana, and by one of the two dominant symbionts, Aeromonas veronii, in a rich medium. We used a comparative approach to identify genes differentially expressed during symbiosis and gain insight into the symbiont's physiology in vivo. Notable findings include evidence for the symbionts experiencing environmental stress, performing arginine catabolism, and expressing noncoding RNAs that are implicated in stationary phase survival, a state in which A. veronii persists for months within the host.

Bacillus subtillis RTSBA6 6.00, a new strain isolated from gut of Helicoverpa armigera (Lepidoptera: Noctuidae) produces chymotrypsin-like proteases

Exploring bacterial communities with proteolytic activity from the gut of the Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) insect pests was the purpose of this study. As initial efforts to achieve this goal here we report the isolation of new Bacillus subtillis RTSBA6 6.00 strain from the gut of H. armigera and demonstrated as proteases producer. Zymographic analysis revealed 12 proteolytic bands with apparent molecular weights ranging from 20 to 185 kDa. Although some activity was detected at acidic pH, the major activity was observed at slight alkaline pH (7.8). The optimum temperature was found to be 35 °C with complete loss of activity at 70 °C. All proteases were completely inactivated by PMSF (phenylmethylsulfonyl fluoride) and TPCK (N-tosyl-l-phenylalanine chloromethyl ketone), suggesting that proteases secreted by B. subtillis RTSBA6 6.00 belong to serine proteases class with chymotrypsin-like activity. The occurrence of protease producing bacterial community in the gut of the H. armigera advocates its probable assistance to insect in proteinaceous food digestion and adaptation to protease inhibitors of host plants.

Cyp15F1: a novel cytochrome P450 gene linked to juvenile hormone-dependent caste differention in the termite Reticulitermes flavipes

Termites are eusocial insects that jointly utilize juvenile hormone (JH), pheromones, and other semiochemicals to regulate caste differentiation and achieve caste homeostasis. Prior EST sequencing from the symbiont-free gut transcriptome of Reticulitermes flavipes unexpectedly revealed a number of unique cytochrome P450 (Cyp) transcripts, including fragments of a Cyp15 family gene (Cyp15F1) with homology to other insect Cyp15s that participate in JH biosynthesis. The present study investigated the role of Cyp15F1 in termite caste polyphenism and specifically tested the hypothesis that it plays a role in JH-dependent caste differentiation. After assembling the full-length Cyp15F1 cDNA sequence, we (i) determined its mRNA tissue expression profile, (ii) investigated mRNA expression changes in response to JH and the caste-regulatory primer pheromones γ-cadinene (CAD) and γ-cadinenal (ALD), and (iii) used RNA interference (RNAi) in combination with caste differentiation bioassays to investigate gene function at the phenotype level. Cyp15F1 has ubiquitous whole-body expression (including gut tissue); is rapidly and sustainably induced from 3 h to 48 h by JH, CAD, and ALD; and functions at least in part by facilitating JH-dependent soldier caste differentiation. These findings provide the second example of a termite caste regulatory gene identified through the use of RNAi, and significantly build upon our understanding of termite caste homeostatic mechanisms. These results also reinforce the concept of environmental caste determination in termites by revealing how primer pheromones, as socioenvironmental factors, can directly influence Cyp15 expression and caste differentiation.

Carbohydrate-active enzymes revealed in Coptotermes formosanus (Isoptera: Rhinotermitidae) transcriptome

Coptotermes formosanus is one of the most destructive wood-feeding termites. To understand the molecular mechanisms that regulate the development of the termite, a normalized C. formosanus cDNA library was constructed using mixed RNA isolated from workers, soldiers, nymphs and alates of both sexes. The sequencing of this library generated 131 636 expressed sequence tags (ESTs) and 25 939 assembled unigenes. The carbohydrate-active enzymes (CAZymes) revealed in this library were analysed in the present report. A total of 509 putative CAZymes were identified. Diverse cellulolytic enzymes were uncovered from both the host termite and from symbionts harboured by the termite, which were possibly the result of the high efficiency of cellulose utilization. CAZymes associated with trehalose biosynthetic and metabolic pathways were also identified, which are potential regulators of the physiological activities of trehalose, an important insect blood sugar. Representative CAZyme coding genes in glycoside hydrolase family 1 (GH1) were quantitatively analysed. The results showed that the five GH1 β-glucosidase genes were expressed differentially among different castes and one of them was female alate-specific. Overall, the normalized EST library provides a comprehensive genetic resource of C. formosanus and will serve a diverse range of research areas. The CAZymes represent one of the repositories of enzymes useful for physiological studies and applications in sugar-based biofuel production.

Metabolism of polycyclic aromatic hydrocarbons by the wood-feeding termite Coptotermes formosanus (Shiraki)

Polycyclic aromatic hydrocarbons (PAHs) are among the most prevalent and persistent pollutants in the environment. In this study, the wood-feeding termite (WFT) Coptotermes formosanus (Shiraki) was studied regarding the potential ability to degrade two selected low-molecular-weight PAHs, phenanthrene and anthracene. Pyrolysis-gas chromatography/mass spectrometry was employed for analysis of in vivo PAH degradation by three gut segments (fore-, mid-, and hindgut) of the WFT. The results revealed the capability of lower termite for PAH metabolism, which started from the foregut and mainly occurred in the midgut region. Remediation of phenanthrene by the termite has been proposed to be initiated via hydroxylation at the C-10 position. Anthracene metabolism first occurred at the C-3, C-5, and C-12 positions with the addition of aldehyde and carbonyl groups. Ring hydroxylation, methoxylation, esterification, carboxylation, and methylation were detected on both the PAHs for ring fission, suggesting the existence of effective PAH modification activity in the alimentary canal of C. formosanus . This new PAH degradation system of the WFT provides new insights for potential technologies for bioremediation of PAH-contaminated soil and sediment based on the related lingolytic enzymes.

Profiling the metatranscriptome of the protistan community in Coptotermes formosanus with emphasis on the lignocellulolytic system

The symbiotic protists in the hindgut of lower termites are critical for lignocellulose decomposition. Due to the unculturability of these protists, information on lignocellulases and their abundance within the gut is unavailable. The advent of high-throughput sequencing technologies enables an investigation of the gene expression profile in this community without culturing these organisms. Here, we carried out 454 pyrosequencing to profile the metatranscriptome of the protistan community in Coptotermes formosanus. In total, 223,477 reads were obtained by sequencing the enriched protistan mRNA. Phagocytosis and cytoskeletal homeostasis pathways were highly represented in the metatranscriptome. Among the metabolic pathways, starch and sucrose metabolism were dominant. A detailed analysis combining Pfam and KEGG annotation identified 118 glycosyl hydrolases belonging to 18 different glycosyl hydrolase families (GHFs). Subsequently, a novel GHF10 endo-1,4-beta-xylanase was functionally characterized to complement our understanding of the protistan hemicellulases.

Metatranscriptomics reveals the diversity of genes expressed by eukaryotes in forest soils

Eukaryotic organisms play essential roles in the biology and fertility of soils. For example the micro and mesofauna contribute to the fragmentation and homogenization of plant organic matter, while its hydrolysis is primarily performed by the fungi. To get a global picture of the activities carried out by soil eukaryotes we sequenced 2×10,000 cDNAs synthesized from polyadenylated mRNA directly extracted from soils sampled in beech (Fagus sylvatica) and spruce (Picea abies) forests. Taxonomic affiliation of both cDNAs and 18S rRNA sequences showed a dominance of sequences from fungi (up to 60%) and metazoans while protists represented less than 12% of the 18S rRNA sequences. Sixty percent of cDNA sequences from beech forest soil and 52% from spruce forest soil had no homologs in the GenBank/EMBL/DDJB protein database. A Gene Ontology term was attributed to 39% and 31.5% of the spruce and beech soil sequences respectively. Altogether 2076 sequences were putative homologs to different enzyme classes participating to 129 KEGG pathways among which several were implicated in the utilisation of soil nutrients such as nitrogen (ammonium, amino acids, oligopeptides), sugars, phosphates and sulfate. Specific annotation of plant cell wall degrading enzymes identified enzymes active on major polymers (cellulose, hemicelluloses, pectin, lignin) and glycoside hydrolases represented 0.5% (beech soil)–0.8% (spruce soil) of the cDNAs. Other sequences coding enzymes active on organic matter (extracellular proteases, lipases, a phytase, P450 monooxygenases) were identified, thus underlining the biotechnological potential of eukaryotic metatranscriptomes. The phylogenetic affiliation of 12 full-length carbohydrate active enzymes showed that most of them were distantly related to sequences from known fungi. For example, a putative GH45 endocellulase was closely associated to molluscan sequences, while a GH7 cellobiohydrolase was closest to crustacean sequences, thus suggesting a potentially significant contribution of non-fungal eukaryotes in the actual hydrolysis of soil organic matter.

Cellulolytic environment in the midgut of the wood-feeding higher termite Nasutitermes takasagoensis

Unlike lower termites, xylophagous higher termites thrive on wood without the aid of symbiotic protists. In the higher termite Nasutitermes takasagoensis, both endogenous endo-β-1,4-glucanase and β-glucosidase genes are expressed in the midgut, which is believed to be the main site of cellulose digestion. To further explore the detailed cellulolytic system in the midgut of N. takasagoensis, we performed immunohistochemistry and digital light microscopy to determine distributions of cellulolytic enzymes in the salivary glands and the midgut as well as the total cellulolytic activity in the midgut. Although cellulolytic enzymes were uniformly produced in the midgut epithelium, the concentration of endo-β-1,4-glucanase activity and luminal volume in the midgut were comparable to those of the wood-feeding lower termite Coptotermes formosanus, which digests cellulose with the aid of hindgut protists. However, the size of ingested wood particles was considerably larger in N. takasagoensis than that in C. formosanus. Nevertheless, it is possible that the cellulolytic system in the midgut of N. takasagoensis hydrolyzes highly crystalline cellulose to a certain extent. The glucose produced did not accumulate in the midgut lumen. Therefore, the present study suggests that the midgut of the higher termite provides the necessary conditions for cellulolysis.

Functional analyses of the digestive β-glucosidase of Formosan subterranean termites (Coptotermes formosanus)

The research was to elucidate the function of the β-glucosidase of Formosan subterranean termites in vitro and in vivo. The gene transcript was detected predominantly in the salivary gland tissue, relative to the midgut and the hindgut of the foraging worker caste, indicating salivary glands were the major expression sites of the β-glucosidase. Using recombinant β-glucosidase produced in Escherichia coli, the enzyme showed higher affinity and activity toward cellobiose and cellotriose than other substrates tested. In assessing impacts of specific inhibitors, we found that the β-glucosidase could be irreversibly inactivated by conduritol B epoxide (CBE) but not gluconolactone. Termite feeding assays showed that the CBE treatment reduced the glucose supply in the midgut and resulted in the body weight loss while no effect was observed for the gluconolactone treatment. These findings highlighted that the β-glucosidase is one of the critical cellulases responsible for cellulose degradation and glucose production; inactivation of these digestive enzymes by specific inhibitors may starve the termite.

Effective gene collection from the metatranscriptome of marine microorganisms

Background

Metagenomic studies, accelerated by the evolution of sequencing technologies and the rapid development of genomic analysis methods, can reveal genetic diversity and biodiversity in various samples including those of uncultured or unknown species. This approach, however, cannot be used to identify active functional genes under actual environmental conditions. Metatranscriptomics, which is similar in approach to metagenomics except that it utilizes RNA samples, is a powerful tool for the transcriptomic study of environmental samples. Unlike metagenomic studies, metatranscriptomic studies have not been popular to date due to problems with reliability, repeatability, redundancy and cost performance. Here, we propose a normalized metatranscriptomic method that is suitable for the collection of genes from samples as a platform for comparative transcriptomics.

Results

We constructed two libraries, one non-normalized and the other normalized library, from samples of marine microorganisms taken during daylight hours from Hiroshima bay in Japan. We sequenced 0.6M reads for each sample on a Roche GS FLX, and obtained 0.2M genes after quality control and assembly. A comparison of the two libraries showed that the number of unique genes was larger in the normalized library than in the non-normalized library. Functional analysis of genes revealed that a small number of gene groups, ribosomal RNA genes and chloroplast genes, were dominant in both libraries. Taxonomic distribution analysis of the libraries suggests that Stramenopiles form a major taxon that includes diatoms. The normalization technique thus increases unique genes, functional categories of genes, and taxonomic richness.

Conclusions

Normalization of the marine metatranscriptome could be useful in increasing the number of genes collected, and in reducing redundancies among highly expressed genes. Gene collection through the normalization method was effective in providing a foundation for comparative transcriptomic analysis.

Functional characterization and target discovery of glycoside hydrolases from the digestome of the lower termite Coptotermes gestroi

BACKGROUND

Lignocellulosic materials have been moved towards the forefront of the biofuel industry as a sustainable resource. However, saccharification and the production of bioproducts derived from plant cell wall biomass are complex and lengthy processes. The understanding of termite gut biology and feeding strategies may improve the current state of biomass conversion technology and bioproduct production.

RESULTS

The study herein shows comprehensive functional characterization of crude body extracts from Coptotermes gestroi along with global proteomic analysis of the termite's digestome, targeting the identification of glycoside hydrolases and accessory proteins responsible for plant biomass conversion. The crude protein extract from C. gestroi was enzymatically efficient over a broad pH range on a series of natural polysaccharides, formed by glucose-, xylose-, mannan- and/or arabinose-containing polymers, linked by various types of glycosidic bonds, as well as ramification types. Our proteomic approach successfully identified a large number of relevant polypeptides in the C. gestroi digestome. A total of 55 different proteins were identified and classified into 29 CAZy families. Based on the total number of peptides identified, the majority of components found in the C. gestroi digestome were cellulose-degrading enzymes. Xylanolytic enzymes, mannan- hydrolytic enzymes, pectinases and starch-degrading and debranching enzymes were also identified. Our strategy enabled validation of liquid chromatography with tandem mass spectrometry recognized proteins, by enzymatic functional assays and by following the degradation products of specific 8-amino-1,3,6-pyrenetrisulfonic acid labeled oligosaccharides through capillary zone electrophoresis.

CONCLUSIONS

Here we describe the first global study on the enzymatic repertoire involved in plant polysaccharide degradation by the lower termite C. gestroi. The biochemical characterization of whole body termite extracts evidenced their ability to cleave all types of glycosidic bonds present in plant polysaccharides. The comprehensive proteomic analysis, revealed a complete collection of hydrolytic enzymes including cellulases (GH1, GH3, GH5, GH7, GH9 and CBM 6), hemicellulases (GH2, GH10, GH11, GH16, GH43 and CBM 27) and pectinases (GH28 and GH29).

High throughput screening of hydrolytic enzymes from termites using a natural substrate derived from sugarcane bagasse

BACKGROUND

The description of new hydrolytic enzymes is an important step in the development of techniques which use lignocellulosic materials as a starting point for fuel production. Sugarcane bagasse, which is subjected to pre-treatment, hydrolysis and fermentation for the production of ethanol in several test refineries, is the most promising source of raw material for the production of second generation renewable fuels in Brazil. One problem when screening hydrolytic activities is that the activity against commercial substrates, such as carboxymethylcellulose, does not always correspond to the activity against the natural lignocellulosic material. Besides that, the macroscopic characteristics of the raw material, such as insolubility and heterogeneity, hinder its use for high throughput screenings.

RESULTS

In this paper, we present the preparation of a colloidal suspension of particles obtained from sugarcane bagasse, with minimal chemical change in the lignocellulosic material, and demonstrate its use for high throughput assays of hydrolases using Brazilian termites as the screened organisms.

CONCLUSIONS

Important differences between the use of the natural substrate and commercial cellulase substrates, such as carboxymethylcellulose or crystalline cellulose, were observed. This suggests that wood feeding termites, in contrast to litter feeding termites, might not be the best source for enzymes that degrade sugarcane biomass.

Transcriptome profiling of female alates and egg-laying queens of the Formosan subterranean termite

Termites are known to have an extraordinary reproductive plasticity and capacity, but the underlying genetic patterns of termite reproductive biology are relatively understudied. The goal of this study was to identify genes for which expression levels differ between dealated precopulatory females (virgins) and egg-laying queens of the Formosan subterranean termite, Coptotermes formosanus Shiraki. We constructed a normalized polyphenic expressed sequence tag (EST) library that represents genomic material from most of the castes and life stages of the Formosan subterranean termite. Microarrays were designed using probes from this EST library and public genomic resources. Virgin females and queens were competitively hybridized to these microarrays and differentially expressed candidate genes were identified. Differential expression of eight genes was subsequently confirmed via reverse transcriptase quantitative PCR (RT-QPCR). When compared to virgins, queens had higher expression of genes coding for proteins related to immunity (gram negative binding protein), nutrition (e.g., termite-derived endo-beta-1,4-glucanase), protein storage, regulation of caste differentiation and reproduction (hexamerin, juvenile hormone binding protein). Queens also had higher transcript levels for genes involved in metabolism of xenobiotics, fat, and juvenile hormone (glutathione-S-transferase-like proteins, and cytochrome P450), among others. In particular, hexamerin, juvenile hormone binding protein, and a cytochrome P450 from the 4C subfamily are likely to be involved in initiating the inactive period during the reproductive cycle of the queen. Vice versa, virgins had higher expression than queens of genes related to respiration, probably due to recent flight activity, and several genes of unknown function.

Dynamic gut microbiome across life history of the malaria mosquito Anopheles gambiae in Kenya

The mosquito gut represents an ecosystem that accommodates a complex, intimately associated microbiome. It is increasingly clear that the gut microbiome influences a wide variety of host traits, such as fitness and immunity. Understanding the microbial community structure and its dynamics across mosquito life is a prerequisite for comprehending the symbiotic relationship between the mosquito and its gut microbial residents. Here we characterized gut bacterial communities across larvae, pupae and adults of Anopheles gambiae reared in semi-natural habitats in Kenya by pyrosequencing bacterial 16S rRNA fragments. Immatures and adults showed distinctive gut community structures. Photosynthetic Cyanobacteria were predominant in the larval and pupal guts while Proteobacteria and Bacteroidetes dominated the adult guts, with core taxa of Enterobacteriaceae and Flavobacteriaceae. At the adult stage, diet regime (sugar meal and blood meal) significantly affects the microbial structure. Intriguingly, blood meals drastically reduced the community diversity and favored enteric bacteria. Comparative genomic analysis revealed that the enriched enteric bacteria possess large genetic redox capacity of coping with oxidative and nitrosative stresses that are associated with the catabolism of blood meal, suggesting a beneficial role in maintaining gut redox homeostasis. Interestingly, gut community structure was similar in the adult stage between the field and laboratory mosquitoes, indicating that mosquito gut is a selective eco-environment for its microbiome. This comprehensive gut metatgenomic profile suggests a concerted symbiotic genetic association between gut inhabitants and host.

Analysis of the workers head transcriptome of the Asian subterranean termite, Coptotermes gestroi

The lower termite, Coptotermes gestroi (Isoptera: Rhinotermitidae), is originally from Southeast Asia and has become a pest in Brazil. The main goal of this study was to survey C. gestroi transcriptome composition. To accomplish this, we sequenced and analyzed 3003 expressed sequence tags (ESTs) isolated from libraries of worker heads. After assembly, 695 uniESTs were obtained from which 349 have similarity with known sequences. Comparison with insect genomes demonstrated similarity, primarily with genes from Apis mellifera (28%), Tribolium castaneum (28%) and Aedes aegypti (10%). Notably, we identified two endogenous cellulases in the sequences, which may be of interest for biotechnological applications. The results presented in this work represent the first genomic study of the Asian subterranean termite, Coptotermes gestroi.

Multiple levels of synergistic collaboration in termite lignocellulose digestion

In addition to evolving eusocial lifestyles, two equally fascinating aspects of termite biology are their mutualistic relationships with gut symbionts and their use of lignocellulose as a primary nutrition source. Termites are also considered excellent model systems for studying the production of bioethanol and renewable bioenergy from 2nd generation (non-food) feedstocks. While the idea that gut symbionts are the sole contributors to termite lignocellulose digestion has remained popular and compelling, in recent years host contributions to the digestion process have become increasingly apparent. However, the degree to which host and symbiont, and host enzymes, collaborate in lignocellulose digestion remain poorly understood. Also, how digestive enzymes specifically collaborate (i.e., in additive or synergistic ways) is largely unknown. In the present study we undertook translational-genomic studies to gain unprecedented insights into digestion by the lower termite Reticulitermes flavipes and its symbiotic gut flora. We used a combination of native gut tissue preparations and recombinant enzymes derived from the host gut transcriptome to identify synergistic collaborations between host and symbiont, and also among enzymes produced exclusively by the host termite. Our findings provide important new evidence of synergistic collaboration among enzymes in the release of fermentable monosaccharides from wood lignocellulose. These monosaccharides (glucose and pentoses) are highly relevant to 2^nd-generation bioethanol production. We also show that, although significant digestion capabilities occur in host termite tissues, catalytic tradeoffs exist that apparently favor mutualism with symbiotic lignocellulose-digesting microbes. These findings contribute important new insights towards the development of termite-derived biofuel processing biotechnologies and shed new light on selective forces that likely favored symbiosis and, subsequently, group living in primitive termites and their cockroach ancestors.

In situ lignocellulosic unlocking mechanism for carbohydrate hydrolysis in termites: crucial lignin modification

BACKGROUND

Termites are highly effective at degrading lignocelluloses, and thus can be used as a model for studying plant cell-wall degradation in biological systems. However, the process of lignin deconstruction and/or degradation in termites is still not well understood.

METHODS

We investigated the associated structural modification caused by termites in the lignin biomolecular assembly in softwood tissues crucial for cell-wall degradation. We conducted comparative studies on the termite-digested (i.e. termite feces) and native (control) softwood tissues with the aid of advanced analytical techniques: 13C crosspolarization magic angle spinning and nuclear magnetic resonance (CP-MAS-NMR) spectroscopy, flash pyrolysis with gas chromatography mass spectrometry (Py-GC/MS), and Py-GC-MS in the presence of tetramethylammonium hydroxide (Py-TMAH)-GC/MS.

RESULTS

The 13C CP/MAS NMR spectroscopic analysis revealed an increased level of guaiacyl-derived (G unit) polymeric framework in the termite-digested softwood (feces), while providing specific evidence of cellulose degradation. The Py-GC/MS data were in agreement with the 13C CP/MAS NMR spectroscopic studies, thus indicating dehydroxylation and modification of selective intermonomer side-chain linkages in the lignin in the termite feces. Moreover, Py-TMAH-GC/MS analysis showed significant differences in the product distribution between control and termite feces. This strongly suggests that the structural modification in lignin could be associated with the formation of additional condensed interunit linkages.

CONCLUSION

Collectively, these data further establish: 1) that the major β-O-4' (β-aryl ether) was conserved, albeit with substructure degeneracy, and 2) that the nature of the resulting polymer in termite feces retained most of its original aromatic moieties (G unit-derived). Overall, these results provide insight into lignin-unlocking mechanisms for understanding plant cell-wall deconstruction, which could be useful in development of new enzymatic pretreatment processes mimicking the termite system for biochemical conversion of lignocellulosic biomass to fuels and chemicals.

Toward the functional analysis of uncultivable, symbiotic microorganisms in the termite gut

Termites thrive on dead plant matters with the aid of microorganisms resident in their gut. The gut microbiota comprises protists (single-celled eukaryotes), bacteria, and archaea, most of which are unique to the termite gut ecosystem. Although this symbiosis has long been intriguing researchers of both basic and applied sciences, its detailed mechanism remains unclear due to the enormous complexity and the unculturability of the microbiota. In the effort to overcome the difficulty, recent advances in omics, such as metagenomics, metatranscriptomics, and metaproteomics have gradually unveiled the black box of this symbiotic system. Genomics targeting a single species of the unculturable microbial members has also provided a great progress in the understanding of the symbiotic interrelationships among the gut microorganisms. In this review, the symbiotic system organized by wood-feeding termites and their gut microorganisms is outlined, focusing on the recent achievement in omics studies of this multilayered symbiotic system.

Chemical signaling in the gastrointestinal tract

Chemical signaling via the production of small molecules such as hormones has been studied in detail in higher organisms. These molecules have important functions in maintaining physiological homeostasis as well as allowing organisms to respond to external insults. Virtually every living cell produces hormone-like diffusible small molecules that can be used to convey messages to neighboring cells-a vital step in adaptation, development, and survival within populations. Although most of our knowledge on cellular chemical communication comes from studies of multicellular eukaryotes, it is now understood that bacteria can also communicate using sophisticated signaling systems, in a way analogous to those used by higher organisms. Many of these microbes live in close association with higher eukaryotes, in mutualistic or commensal relationships. We suggest that there may be a wealth of unidentified bioactive small molecules in the human body, originating from both microbial and human cells and that have important biological functions. Because chemical signaling has important roles for the biology of both microbes and humans, detecting, identifying, and studying these chemical signals can further our understanding of the chemical interplay between microbiota and their hosts and provide us with an unexplored source of molecules that could be used for human benefit.

Metagenomic analyses: past and future trends

Metagenomics has revolutionized microbiology by paving the way for a cultivation-independent assessment and exploitation of microbial communities present in complex ecosystems. Metagenomics comprising construction and screening of metagenomic DNA libraries has proven to be a powerful tool to isolate new enzymes and drugs of industrial importance. So far, the majority of the metagenomically exploited habitats comprised temperate environments, such as soil and marine environments. Recently, metagenomes of extreme environments have also been used as sources of novel biocatalysts. The employment of next-generation sequencing techniques for metagenomics resulted in the generation of large sequence data sets derived from various environments, such as soil, the human body, and ocean water. Analyses of these data sets opened a window into the enormous taxonomic and functional diversity of environmental microbial communities. To assess the functional dynamics of microbial communities, metatranscriptomics and metaproteomics have been developed. The combination of DNA-based, mRNA-based, and protein-based analyses of microbial communities present in different environments is a way to elucidate the compositions, functions, and interactions of microbial communities and to link these to environmental processes.

Diversity of beetle genes encoding novel plant cell wall degrading enzymes

Plant cell walls are a heterogeneous mixture of polysaccharides and proteins that require a range of different enzymes to degrade them. Plant cell walls are also the primary source of cellulose, the most abundant and useful biopolymer on the planet. Plant cell wall degrading enzymes (PCWDEs) are therefore important in a wide range of biotechnological processes from the production of biofuels and food to waste processing. However, despite the fact that the last common ancestor of all deuterostomes was inferred to be able to digest, or even synthesize, cellulose using endogenous genes, all model insects whose complete genomes have been sequenced lack genes encoding such enzymes. To establish if the apparent "disappearance" of PCWDEs from insects is simply a sampling problem, we used 454 mediated pyrosequencing to scan the gut transcriptomes of beetles that feed on a variety of plant derived diets. By sequencing the transcriptome of five beetles, and surveying publicly available ESTs, we describe 167 new beetle PCWDEs belonging to eight different enzyme families. This survey proves that these enzymes are not only present in non-model insects but that the multigene families that encode them are apparently undergoing complex birth-death dynamics. This reinforces the observation that insects themselves, and not just their microbial symbionts, are a rich source of PCWDEs. Further it emphasises that the apparent absence of genes encoding PCWDEs from model organisms is indeed simply a sampling artefact. Given the huge diversity of beetles alive today, and the diversity of their lifestyles and diets, we predict that beetle guts will emerge as an important new source of enzymes for use in biotechnology.

Metagenomic analyses: past and future trends

Metagenomics has revolutionized microbiology by paving the way for a cultivation-independent assessment and exploitation of microbial communities present in complex ecosystems. Metagenomics comprising construction and screening of metagenomic DNA libraries has proven to be a powerful tool to isolate new enzymes and drugs of industrial importance. So far, the majority of the metagenomically exploited habitats comprised temperate environments, such as soil and marine environments. Recently, metagenomes of extreme environments have also been used as sources of novel biocatalysts. The employment of next-generation sequencing techniques for metagenomics resulted in the generation of large sequence data sets derived from various environments, such as soil, the human body, and ocean water. Analyses of these data sets opened a window into the enormous taxonomic and functional diversity of environmental microbial communities. To assess the functional dynamics of microbial communities, metatranscriptomics and metaproteomics have been developed. The combination of DNA-based, mRNA-based, and protein-based analyses of microbial communities present in different environments is a way to elucidate the compositions, functions, and interactions of microbial communities and to link these to environmental processes.

Functional and translational analyses of a beta-glucosidase gene (glycosyl hydrolase family 1) isolated from the gut of the lower termite Reticulitermes flavipes

This research focused on digestive beta-glucosidases from glycosyl hydrolase family (GHF) 1 from the gut of the lower termite Reticulitermes flavipes. In preceding studies on R. flavipes, we characterized beta-glucosidase activity across the gut and its inhibition by carbohydrate-based inhibitors, and subsequently we identified two partial beta-glucosidase cDNA sequences from a host gut cDNA library. Here, we report on the full-length cDNA sequence for one of the R. flavipes beta-glucosidases (RfBGluc-1), the expression of its mRNA in the salivary gland and foregut, the production of recombinant protein using a baculovirus-insect expression system, optimal recombinant substrate specificity profiles and parameters, and significant inhibition by the established beta-glucosidase inhibitor cellobioimidazole. We also report the partial cDNA sequence for a second gut beta-glucosidase (RfBGluc-2), and show that like RfBGluc-1 its mRNA is localized mainly in the salivary gland. Other results for RfBGluc-1 showing activity against laminaribose, a component of microbial cell walls, suggest that RfBGluc-1 may serve dual functions in cellulose digestion and immunity. These findings provide important information that will enable the testing of hypotheses related to collaborative host-symbiont lignocellulose digestion, and that contributes to the development of next-generation termiticides and novel biocatalyst cocktails for use in biomass-to-bioethanol applications.

Gut Microbiota in Health and Disease

Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual's lifetime and susceptible to both exogenous and endogenous modifications. Recent renewed interest in the structure and function of this “organ” has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond. The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but include elaboration of signaling molecules and recognition of bacterial epitopes by both intestinal epithelial and mucosal immune cells. The advances in modeling and analysis of gut microbiota will further our knowledge of their role in health and disease, allowing customization of existing and future therapeutic and prophylactic modalities.

Production and characterization of a recombinant beta-1,4-endoglucanase (glycohydrolase family 9) from the termite Reticulitermes flavipes

Cell-1 is a host-derived beta-1,4-endoglucanase (Glycohydrolase Family 9 [GHF9]) from the lower termite Reticulitermes flavipes. Here, we report on the heterologous production of Cell-1 using eukaryotic (Baculovirus Expression Vector System; BEVS) and prokaryotic (E. coli) expression systems. The BEVS-expressed enzyme was more readily obtained in solubilized form and more active than the E. coli-expressed enzyme. K(m) and V(max) values for BEVS-expressed Cell-1 against the model substrate CMC were 0.993% w/v and 1.056 micromol/min/mg. Additional characterization studies on the BEVS-expressed enzyme revealed that it possesses activity comparable to the native enzyme, is optimally active around pH 6.5-7.5 and 50-60 degrees C, is inhibited by EDTA, and displays enhanced activity up to 70 degrees C in the presence of CaCl(2). These findings provide a foundation on which to begin subsequent investigations of collaborative digestion by coevolved host and symbiont digestive enzymes from R. flavipes that include GHF7 exoglucanases, GHF1 beta glucosidases, phenol-oxidizing laccases, and others.

Socio-environmental and endocrine influences on developmental and caste-regulatory gene expression in the eusocial termite Reticulitermes flavipes

BACKGROUND

Strict regulation of caste differentiation, at the molecular level, is thought to be important to maintain social structure in insect societies. Previously, a number of extrinsic and intrinsic factors have been shown to influence caste composition in termite colonies. One important factor is the influence of nestmates; in particular, soldier termites are known to inhibit hormone-dependent worker-to-soldier differentiation. However, soldier influences on nestmates at the molecular level are virtually unknown. Here, to test the hypothesis that soldiers can influence nestmate gene expression, we investigated the impact of four treatments on whole-body gene expression in totipotent Reticulitermes flavipes workers: (i) juvenile hormone III (JHIII; a morphogenetic hormone), (ii) soldier head extracts (SHE), (iii) JHIII+SHE, and (iv) live soldiers.

RESULTS

Using quantitative-real-time PCR we determined the expression patterns of 49 previously identified candidate genes in response to the four treatments at assay days 1, 5, and 10. Thirty-eight total genes from three categories (chemical production/degradation, hemolymph protein, and developmental) showed significant differential expression among treatments. Most importantly, SHE and live soldier treatments had a significant impact on a number of genes from families known to play roles in insect development, supporting previous findings and hypotheses that soldiers regulate nestmate caste differentiation via terpene primer pheromones contained in their heads.

CONCLUSIONS

This research provides new insights into the impacts that socio-environmental factors (JH, soldiers, primer pheromones) can have on termite gene expression and caste differentiation, and reveals a number of socially-relevant genes for investigation in subsequent caste differentiation research.

Characterization of four esterase genes and esterase activity from the gut of the termite Reticulitermes flavipes

Four esterase genes and general esterase activity were investigated in the gut of the termite Reticulitermes flavipes. Two genes (RfEst1 and RfEst2) share significant translated identity with a number of insect JH esterases. The two remaining genes (RfEst3 and RfEst4) apparently code for much shorter proteins with similarity to fungal phenolic acid esterases involved in hemicellulose solubilization. All four genes showed consistently high midgut expression. This result was further supported by colorimetric activity assays and Native polyacrylamide gel electrophoresis, which showed significant esterase activity and a number of isoforms in the midgut. The greatest esterase activity and isoform composition were detected when alpha-naphthyl propionate was used as a substrate. Moreover, esterase activity and diverse isoforms were present in gut mitochondrial, microsomal, and cytosolic sub-cellular protein fractions, as well as in the hindgut lumen. These findings reveal an agreement between gut esterase gene expression and activity distributions, and support the idea that R. flavipes gut esterase activity is host (not symbiont)-derived. In addition, these findings support the hypotheses that termite gut esterases may play important roles in lignocellulose digestion and caste differentiation. This study provides important baseline data that will assist ongoing functional-genomic efforts to identify novel genes with roles in semiochemical, hormone, and lignocellulose processing in the termite gut.