Isolation of Fungi and Bacteria Associated with the Guts of Tropical Wood-Feeding Coleoptera and Determination of Their Lignocellulolytic Activities.

Keilor Rojas-Jiménez,Myriam Hernández

doi:10.1155/2015/285018

Keilor Rojas-Jiménez, Myriam Hernández

Open Access

https://doi.org/10.1155/2015/285018

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Abstract

The guts of beetle larvae constitute a complex system where relationships among fungi, bacteria, and the insect host occur. In this study, we collected larvae of five families of wood-feeding Coleoptera in tropical forests of Costa Rica, isolated fungi and bacteria from their intestinal tracts, and determined the presence of five different pathways for lignocellulolytic activity. The fungal isolates were assigned to three phyla, 16 orders, 24 families, and 40 genera; Trichoderma was the most abundant genus, detected in all insect families and at all sites. The bacterial isolates were assigned to five phyla, 13 orders, 22 families, and 35 genera; Bacillus, Serratia, and Pseudomonas were the dominant genera, present in all the Coleopteran families. Positive results for activities related to degradation of wood components were determined in 65% and 48% of the fungal and bacterial genera, respectively. Our results showed that both the fungal and bacterial populations were highly diverse in terms of number of species and their phylogenetic composition, although the structure of the microbial communities varied with insect host family and the surrounding environment. The recurrent identification of some lignocellulolytic-positive inhabitants suggests that particular microbial groups play important roles in providing nutritional needs for the Coleopteran host.

Highlights

Plant cell walls are predominantly composed of lignin, cellulose, and hemicellulose
We isolated 92 fungal strains and 135 bacterial strains from larvae of five families of Coleoptera that were feeding on decaying wood in tropical wet forests of 10 national parks of Costa Rica
The positive trade-off of this approach was the identification of several isolates with lignocellulose-degrading capabilities, which can be further used for the respective enzyme characterization, for direct degradation assays on residues from agriculture and forestry, for the treatment of industrial effluents, and for bioprospecting novel metabolites with other biotechnological applications

Summary

Introduction

Plant cell walls are predominantly composed of lignin, cellulose, and hemicellulose. Together, these three polymers represent one of the most abundant sources of renewable energy on Earth [1,2,3]. The adaptation of the coleopteran insects to nutrientlimited diets, such as wood constituents, is attributed to the establishment of relationships with microorganisms. These microorganisms, highly prominent in the digestive tracts of the host, perform essential functions including digestion of lignocellulosic biomass, nutrient production, and compound detoxification [6,7,8,9]. From the biotechnological point of view, the coleopteran gut inhabitants represent a novel source for bioprospecting of enzymes related to the conversion of plant biomass into biofuels, production of industrial value-added products, and bioremediation of pollutants [16,17,18]

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