文章较难，大家听写填空即可~
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
我们在细菌抗药性的研究上取得了意想不到的进步。进化论就是大家公认的一个最简单的实例了。当一个具有相当数量的细菌种群与一种杀菌剂“狭路相逢”时，只有少数幸运的细菌可以基因突变从而存活下来。他们得以继续生存繁殖，不过余下的都将“灰飞烟灭”。很快，整个菌落全都是当初拥有抗药性的细菌们的后代了。 但是一项新的研究发现，仅有几种基因突变可以保护大部分普通的细菌，使其对药物治疗免疫。这项研究发表在《自然》杂志上。 而免疫的关键就在于这些抗药性的变异菌种可以产生大量的化学物质，名为吲哚，它可以帮助细菌顽强的度过难关。变异菌种们产生的吲哚使那些普通的，毫无抵抗力的细菌们逃过一劫。而变种们此时就扮演着完全利他主义者的角色---制造吲哚使它们自身的成长变得缓慢。 此项发现让我们可以研究新的策略来对付抗药性。此外，它还完善了我们进化动力学，以及在物竞天择压力下的个体与群体的生物系统。