Comparative Genomic Analysis of the Endosymbionts of Herbivorous Insects Reveals Eco-Environmental Adaptations: Biotechnology Applications

Abstract

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.

Gill bacteria enable a novel digestive strategy in a wood-feeding mollusk

“…At least one shipworm species (Lyrodus pedicellatus) has been shown to grow and reproduce normally using wood as its sole particulate food source (3). However, unlike their terrestrial herbivorous and xylophagous counterparts, whose digestive systems contain complex communities of microbes (4)(5)(6)(7)(8)(9), Bankia setacea and several other shipworm species accumulate and digest wood in the cecum ( Fig. 1 A and B), a region of the foregut that is devoid of any conspicuous microbial community (10).…”

Metagenomic analysis of the pinewood nematode microbiome reveals a symbiotic relationship critical for xenobiotics degradation

“…Metagenomics has been a major approach to study the composition, function, evolution of various microbiota, and interactions between microbiomes and their hosts114142. We aim to examine the metabolic pathways in microbiome metagenomes and compare to that in the PWN genome for understanding the mechanisms underlying detoxification metabolism.…”

The chemical properties and microbial community characterization of the thermophilic microaerobic pretreatment process

“…The proportion of class Clostridia in TMP0 and TMP1 was almost the same, which was 33.9% and 33.81%, respectively, the most of which belong to the order Clostridiales. Clostridia were known to play a key role in biogas-producing process (Briones et al, 2014;Kampmann et al, 2012), members belong to order Clostridiales contributed to the breakdown of polysaccharide molecules and ferment sugars to organic acids (Guo et al, 2015;Shi et al, 2013;Wirth et al, 2012). The relative abundances of class Clostridia and order Clostridiales in TMP0 and TMP1 were more than three times higher than that of inoculum, which indicated the greater ability of TMP0 and TMP1 to breakdown of polysaccharide molecules and ferment sugar to organic acids.…”