Microbiome of the Termite Gut and Its Biotechnological Perspective

Lignocellulose is the most abundant renewable biopolymer on Earth, and its deconstruction is observed under a wide range of environmental conditions. Diverse organisms have evolved specialised strategies and enzymes, with termites being the most efficient natural lignocellulose degraders.

The “higher termite” gut is a complex multi-domain system where symbiosis between prokaryotes and the host has established over the evolutionary timescale. The gut microbiome is mainly dominated by Firmicutes, Spirochaetes, Fibrobacteres and Bacteroidetes representatives, most of which are yet uncultured and genetically intractable microorganisms. Our recent metatranscriptomic and metagenomic studies combined with genome re-constructions have showed that only a minor fraction of microbial carbohydrate active enzymes (CAZymes) is shared between the different termite gut microbiomes, making each termite species a unique reservoir of potentially industrially applicable enzymes. As an example, we characterised several GH5_4 multi-functional CAZymes of Spirochaetes origin, which can simultaneously attack cellulose, xylan and mannan backbones. Broad substrate specificity CAZymes are potent and versatile tools for a renewable bioeconomy and could help simplifying the complexity of enzymatic cocktails. In additional to being host-specific, microbial CAZyme gene expression is also gut compartment-specific, showing further niche specialisation of certain microbial populations. For some termite species, the axial and radial gradients of various physical and chemical parameters are very pronounced between the different gut segments, allowing specialisation in efficient utilisation of separate lignocellulose fractions.

Further characterisation and future engineering of the termite gut-compartment specific microbiomes will allow establishing best microbial consortia with enzymatic machinery efficiently processing industrially important lignocellulosic biomasses.