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, 9 (1), e1003131

Comparative Genomic Analysis of the Microbiome [Corrected] of Herbivorous Insects Reveals Eco-Environmental Adaptations: Biotechnology Applications


Comparative Genomic Analysis of the Microbiome [Corrected] of Herbivorous Insects Reveals Eco-Environmental Adaptations: Biotechnology Applications

Weibing Shi et al. PLoS Genet.

Erratum in

  • PLoS Genet. 2013 Feb;9(2). doi: 10.1371/annotation/91a25db3-8127-42c7-baa0-ce398a2857a6


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.

Conflict of interest statement

The authors have declared that no competing interests exist.


Figure 1
Figure 1. Abundance of bacterial phyla based on the predicted gene models in the gut microbiota of grasshopper (GH), cutworm (CW), and termite (TM), respectively.
The relative abundance ranged from 0–26%. Except for the three most abundant bacteria phyla, all other phyla are less than 5%. To better visualize, the heat map scale set from 0–5%.
Figure 2
Figure 2. Composition of grasshopper (G) and cutworm (C) gut microbiomes as revealed by 16S analysis.
From a PCR-based library, 54 and 56 nearly complete sequences of the 16S rRNA V3–V9 region belonging to different bacterial species were obtained from the gut microbiomes of grasshopper and cutworm, respectively. These were used in a Maximum Likelihood analysis (RA×ML). Species identification was determined based on sequence similarity greater than 97% using the 16S rRNA sequences available in NCBI GenBank. Genbank accession numbers are given. The strains belonging to different group were indicated using different color, i.e. red (γ-proteobacteria/Enterobacteriales), magentas (γ-proteobacteria/Xanthomanadales), brown (α-proteobacteria), cyans (β-proteobacteria), blue (Cyanobacteria), yellow (Bacteroidetes), and green (Firmicutes).
Figure 3
Figure 3. COG analysis reveals metabolic functions that are enriched or under-represented in grasshopper and cutworm gut.
Gene categories with D-Rank values greater than indicated by the dashed line are significantly enriched in the cutworm and grasshopper gut symbiotic metagenome as compared to that of termite (P<0.05); Asterisks indicate categories that are significantly different between grasshopper and cutworm gut microbiomes (P<0.05).
Figure 4
Figure 4. Cluster analysis of genes in three metabolic pathways in the gut microbiomes of grasshopper (GH), cutworm (CW), and termite (TM).
A. biomass degradation enzymes in carbohydrate transport and metabolism; B. Phosphotransferase system; and C. Defense mechanism.
Figure 5
Figure 5. Comparison of the specific activities of enzymes important for biomass deconstruction from grasshopper and cutworm gut microbiomes.
**means P<0.01 and *means P<0.05 in student t-test.

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Grant support

The research is funded by SouthCentral Sungrant and Texas Agrilife Bioenergy Research Initiative. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.