Genome and transcriptome analysis of the lignite-degrading Trichoderma cf. simile WF8 strain highlights potential degradation mechanisms

Abstract

The biodegradation of lignite (brown coal) by microorganisms has the potential for bioremediation of contaminated mining sites and to generate alternative ways to valorize lignite, such as by producing humic acids or building block chemicals. Previously, a lignite-degrading strain of Trichoderma was isolated, but the genomic and transcriptomic basis of its lignite-degrading ability remained unknown. Here we report that the sequenced genome of the T. cf. simile WF8 strain encoded for enzymes with roles in the degradation of lignite, and potentially tolerance to lignite-breakdown products. There was only a small number of annotated unique genes in the T. cf. simile WF8 genome compared to other fungi, and likely the expression of gene families shared with other fungi is a key factor in lignite biosolubilization by T. cf. simile. The transcriptomes were analyzed of T. cf. simile cultured at two time-points with the lignite-breakdown model compounds 4-phenoxybenzoic acid (which was growth inhibitory), and phenetole and 9-10-dibutoxyanthracene (neither of which inhibited growth), and showed ∼20% of genes up-regulated by one or more of these compounds. The analysis highlights candidates for characterization and engineering enzyme over-expressing T. cf. simile strains with potentially improved degradation capacity, e.g., laccases and peroxidases, or tolerance and catabolism of breakdown products, e.g., cytochrome P450s, and ring cleavage dioxygenases.