Comparative Analysis Of Herbivore Insect Symbionts And Biotechnology Applications

Comparative metagenome analysis was carried out both to study the evolution ofinsect gut symbioints for food adaptation and to discover novel biocatalysts for biorefineryapplications. Grasshopper and cutworm gut symbionts have been sequenced to comparewith the published termite gut symbiotic microbiota, representing three insect orders andspecies fed on different food types. The comparative analysis revealed dramaticallydifferent insect gut symbiont distribution and abundance among the three species. Thesymbiont composition correlates with the function to degrade and utilize different types offood. The overview of functional annotation revealed more enriched and diversecarbonhydrate metabolism and transport genes in cutworm and grasshopper. In particular,the metabolic pathway reconstruction indicated that cutworm gut symbionts have muchmore diverse Glycosyl Hydrolase (GH) enzymes for carbonhydrate utilization andPhosphotransferase System (PTS) for carbonhydrate transport, even though termite gutsymbionts are highly enriched in the GH enzymes relevant to lignocellosic biomassdegradation. On the other hand, termite gut symbionts are more enriched with nitrogenfixation genes assumingly due to the adaptation to the high fiber and less nutritious foodtypes. The results highlighted the insect gut symbionts evolve to adapt to different foodtypes at microbiota composition, species distribution, metabolic pathway, and individualgene levels. In order to explore the insect symbionts for biotechnology applications, wefurther cloned and characterized multiple biomass degrading enzymes including twoendoglucanase, two xylanase, and two glycoside hydrolase family43(GH43) enzymespresented. The GH43enzymes also applied for switchgrass based biomass treatment, andfound grasshopper sourced GH43enzymes has a huge potential to remove thexylooligomers and reduce the loading of cellulase. The data verified the sequencequality and highlighted the functional relevance of insect gut symbionts can be furtherexplored for biorefinery processing.