According to the research appearing in the August 7 online edition of the journal Nature Genetics, fungal microbes can quickly alter the appearance of their cell surfaces, their "skin," disguising themselves in order to slip past the immune system's vigilant defenses. And, for all the world's brewers, the study also helps explain why certain beers are cloudy and others are clear.
"It's all about skin," says Whitehead Member Gerald Fink, who compares the fungal microbe to an M&M--a sugar coating encasing the cell's DNA. "The skin of fungi microbes is what enables them to stick to your organs, and thus become pathogenic. It also enables the fungi to stick together, which is desirable for fermentation in beer."
The genetic core to this study is a DNA phenomenon known as tandem repeats. Here, small units of between 3 and 200 nucleotides form within a gene and repeat sometimes up to about 35 times. (Nucleotides, the building blocks of our genome, are represented by the letters A, C, T, G.) In humans, these tandem repeats received a lot of attention when the gene responsible for Huntington's disease was discovered; a repeat of the letters CAG in a gene called IT-15 causes the condition.
These tandem repeats also occur in fungal microbes. Kevin Verstrepen, a post-doctoral researcher in Fink's lab, decided to find out how often they occur, and what possible functions they might offer, by using baker's yeast as a model. Verstrepen scanned the entire yeast genome with a custom computer program developed by Whitehead's bioinformatics group.
Contact: David Cameron
Whitehead Institute for Biomedical Research