Abstract

Adaptation to a novel niche requires metabolic machinery suitable for surviving and exploiting a new environment. Horizontal gene transfer - the acquisition of genetic material from another species – can provide new metabolic capabilities instantaneously, allowing rapid response to sudden environmental changes. Here, I investigate the hypothesis that a horizontal transfer from bacteria to an ancient fungal species contributed to the evolution of virulence and invasive growth in fungi.

Organisms from bacteria to mammals use the Pentose Phosphate Pathway to synthesize ribose, the basic building block of DNA and RNA . Surprisingly, in Saccharomyces cerevisiae, ribose can also be synthesized by an alternative route, encoded by the newly characterized gene, SHB17 . Diverse fungal species possess SHB17 ?like genes, but outside of fungi, SHB17 ?like genes are only found in a small group of bacteria. The presence of a SHB17 ?like gene in distantly related bacteria, but not in more closely related animal and plant species, suggests that an ancient fungal species may have acquired SHB17 directly from bacteria. Intriguingly, a Shb17?like gene in the fungal pathogen Candida albicans exhibits increased expression during the infectious process. I will present computational evidence that SHB17 was acquired by horizontal transfer and experimental evidence that SHB17 contributes to virulence in C. albicans. Taken together, these observations suggest that the acquisition of a new gene may have contributed to a novel ecological strategy in fungi.