Speaker
Description
In their natural habitats, bacteria live in close contact with other species. Genomic studies reveal plentiful evidence of horizontal gene transfer across different species. However, little is known about its rates and fitness effects. What are limiting factors of cross-species gene transfer? How does gene transfer affect bacterial fitness? While gene transfer can benefit bacteria during adaptation to new niches, it also bears the potential of reducing fitness by introducing maladapted genes. We study these trade-offs by combining experimental evolution with genomics, transcriptomics, and molecular biology. We measured the rate of gene transfer between closely related Bacillus species and found that the rate of orthologous replacement is remarkably high. We found that gene transfer confers a net fitness increase and that selection has a broad genetic basis. Currently, we are using high-throughput technology for quantifying the distribution of fitness effects (DFE) of horizontal gene transfer between Bacillus species. The DFE shows both small and large effect beneficial transfers, indicating strong potential for fast adaptive evolution. In different growth conditions, strong effect transfers show pleiotropic effects including a fitness trade-off. With increasing complexity of nutrients and growth conditions, transformation becomes increasingly beneficial. We conclude that transformation has a strong potential for speeding up adaptation to varying environments by profiting form a gene-pool shared between closely related species.
