Lateral Gene Transfer between Bacteria and Trichoderma reesei

Abstract

Lateral gene transfer (LGT) has played an important role in shaping the `tree of life'. It has promoted evolution by generating gene redundancies, which allow for more freedom in terms of allowed mutations in a genome, and by introducing new metabolic abilities to organisms. An example, with practical implications, is the cellulase activity of the fungus Trichoderma reesei which degrades cellulose in biofuel production, environmental waste cleanup, and paper processing. While partial optimization of conditions for T. reesei to express enzymes might be achieved through controlling experimental conditions, potentially the most effective approach would be to bring the power of genetic engineering to bear. If the digestive enzymes in T. reesei are the result of LGT, inserting bacterial copies of these genes or their regulators into the T. reesei genome may increase enzymatic activity. Furthermore, an appropriate examination of the entire genome for LGT could lead to insights into the evolution of T. reesei. This study performed phylogenomic analyses to identify LGT in the genome of T. reesei, specifically those genes transferred from bacteria. Three computational programs were used to identify LGT candidates. All identified LGT candidates were subject to further rigorous phylogenetic analyses to assess their evolutionary origins. We detected several cases of LGT between fungi and bacteria, only one of which was recently transferred to T. reesei. This leads us to conclude that LGT probably did not play a significant role in the recent evolution of T. reesei.