SSS 2008-05-21

（单词翻译）

This is scientific American's 60-Second Science, I'm Christopher Intagliata. Got a minute?

The yeast¹ Candida albicans ekes² out a quiet living in our gut³. But it’s a tough life. It faces acids and enzymes⁴, and the immune system always bullies⁵ invaders⁶. 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 chromosome⁷. In sexually reproducing organisms like us, a process called meiosis halves this number. Mom’s egg and Pop’s sperm⁸ 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 progeny⁹ have double the normal amount of chromosomes¹⁰, which they randomly¹¹ 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 chromosomal¹² grab bag that results is genetically¹³ diverse, and some strains are resistant¹⁴ to antifungal drugs. Second, normal fungal sexual reproduction usually produces spores¹⁵, which the immune system can easily identify and dispose of. Without spores, Candida can better avoid getting busted¹⁶.

Thanks for the minute, for Scientific American’s 60-Second Science, I'm Christopher Intagliata