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There’s been an unexpected development in our understanding of drug resistance in bacteria. The accepted [--1--] was a simple case of [--2--]. In a bacterial population exposed to a killer drug, a few lucky individuals might have a genetic mutation that kept them alive. They survived to reproduce, while the rest of the population [--3--]. In short order, the entire colony consisted only of the offspring of the drug-resistant founders.
But a new study finds that just a few resistant [--4--] can protect large numbers of normal bacteria that would have been thought to be susceptible to the drug therapy. The research appears in the journal Nature.
The key seems to be that the drug-resistant mutants produce large amounts of compounds called indoles, which help bacteria tough out tough times. And the indoles from the mutants [--5--] the regular, nonresistant bacteria. The mutants themselves seem to be acting altruistically—their own growth is slowed by their indole production.
The finding should lead to new strategies to fight drug resistance. And it could also improve our take on evolutionary dynamics, in systems that apparently experience selection pressure at both the individual and group levels.
scenario evolutionary selection perished mutants buck up
我們在細(xì)菌抗藥性的研究上取得了意想不到的進(jìn)步。進(jìn)化論就是大家公認(rèn)的一個(gè)最簡單的實(shí)例了。當(dāng)一個(gè)具有相當(dāng)數(shù)量的細(xì)菌種群與一種殺菌劑“狹路相逢”時(shí)，只有少數(shù)幸運(yùn)的細(xì)菌可以基因突變從而存活下來。他們得以繼續(xù)生存繁殖，不過余下的都將“灰飛煙滅”。很快，整個(gè)菌落全都是當(dāng)初擁有抗藥性的細(xì)菌們的后代了。 但是一項(xiàng)新的研究發(fā)現(xiàn)，僅有幾種基因突變可以保護(hù)大部分普通的細(xì)菌，使其對藥物治療免疫。這項(xiàng)研究發(fā)表在《自然》雜志上。 而免疫的關(guān)鍵就在于這些抗藥性的變異菌種可以產(chǎn)生大量的化學(xué)物質(zhì)，名為吲哚，它可以幫助細(xì)菌頑強(qiáng)的度過難關(guān)。變異菌種們產(chǎn)生的吲哚使那些普通的，毫無抵抗力的細(xì)菌們逃過一劫。而變種們此時(shí)就扮演著完全利他主義者的角色---制造吲哚使它們自身的成長變得緩慢。 此項(xiàng)發(fā)現(xiàn)讓我們可以研究新的策略來對付抗藥性。此外，它還完善了我們進(jìn)化動力學(xué)，以及在物競天擇壓力下的個(gè)體與群體的生物系統(tǒng)。