Yeast Does DNA Tricks to Live in Us

The yeast Candida albicans does some clever genetic copying and deleting to survive in the harsh environment of the human gut. Christopher Intagliata reports

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[The following is an exact transcript of this podcast.]

The yeast Candida albicans ekes out a quiet living in our gut. But it’s a tough life. It faces acids and enzymes, and the immune system always bullies invaders. So Candida has customized its reproductive cycle for life inside a warm-blooded host. Researchers described it in the journal Public Library of Science Biology.

Human cells have two copies of each chromosome. In sexually reproducing organisms like us, a process called meiosis halves this number. Mom’s egg and Pop’s sperm only have one copy of each chromosome—together they make a whole. That’s you. But Candida doesn’t bother with meiosis when it mates. So its progeny have double the normal amount of chromosomes, which they randomly toss off til they’re near the right number again.

This cycle is useful for a gut-dweller for two reasons. First, Candida often trashes fewer copies of some chromosomes and more of others. The chromosomal grab bag that results is genetically diverse, and some strains are resistant to antifungal drugs. Second, normal fungal sexual reproduction usually produces spores, which the immune system can easily identify and dispose of. Without spores, Candida can better avoid getting busted.

—Christopher Intagliata

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