2023年经济学人 超级细菌的秘密(2)（在线收听）

    But such “transductions” cannot fully explain the speed with which bacteria evolve resistance either.

    但是这种“转导”也不能完全解释细菌进化出耐药性的速度。

    It happens rarely, and transfers only small chunks of DNA when it does.

    这种情况很少发生，即使发生，也只会转移一小块DNA。

    In 2018 Dr Chen identified another mechanism, known as lateral transduction.

    2018年，陈博士发现了另一种机制，即侧向转导。

    This happens when phages, rather than killing their hosts immediately, integrate their genomes into those of their prey.

    当噬菌体不是立即杀死宿主，而是将自己的基因组整合到猎物的基因组中时，就会发生这种情况。

    When the phages replicate, they read their own genes from the bacteria’s genome, but sometimes grab copies of long neighbouring stretches of bacterial DNA too, which they carry to infect new hosts.

    当噬菌体复制时，它们利用细菌的基因组读取自己的基因，但有时也会拷贝邻近细菌的长片段DNA，它们携带这些复制品来感染新的宿主。

    Dr Chen reckons that phages could in this way end up stealing up to a quarter of their host’s genome.

    陈博士认为噬菌体可以通过这种方式窃取四分之一的宿主基因组。

    He estimates that lateral transduction is thousands of times faster than other mechanisms, making it a candidate as the chief driver of microbial drug resistance.

    他估计，横向转导比其他机制快数千倍，已经成为了微生物耐药性的主要驱动因素。

    In practice, this means a bacterium with no previous exposure to antibiotics could acquire the genes necessary for resistance in a matter of minutes.

    实际上，这意味着以前没有接触过抗生素的细菌可以在几分钟内获得耐药性所需的基因。

    But the story does not end there.

    但故事并没有就此结束。

    Dr Chen examined Staphylococcus aureus, a bacterium that is usually harmless but which can occasionally cause serious illnesses.

    陈医生检查了金黄色葡萄球菌，这种细菌通常是无害的，但偶尔也会引起严重的疾病。

    Particular chunks of its genome, called “pathogenicity islands” (or Sapis), seem to behave like genetic parasites; bits of DNA that replicate selfishly without regard for the well-being of their host.

    其基因组的特定部分，称为“致病性岛”(或致病岛)，似乎表现得像是遗传寄生物; 这些DNA片段会自私地复制，不顾宿主的健康。

    In one sense, that makes them an even more primitive form of replicator than a virus.

    从某种意义上说，这会使它们成为比病毒更原始的复制因子。

    When a bacterial cell playing host to a Sapi is infected by a phage, the Sapis can command the cell to produce a protein called small transferase.

    当作为致病岛宿主的细菌细胞被噬菌体感染时，致病岛可以命令细胞产生一种称为小转移酶的蛋白质。

    This is similar to the protein that the attacking phage uses as a signal to begin packing its DNA into newly produced phages.

    这类似于攻击型噬菌体的蛋白质，它会作为信号，开始将自身DNA打包到新产生的噬菌体中。

    That biochemical trick can cause new phages to be packaged not with viral DNA at all, but with long chunks of bacterial genome.

    这种生化技巧可以导致新的噬菌体完全不是用病毒DNA包装的，而是用长段细菌基因组包装的。

    “It completely replaces the phage genome,” says Dr Chen.

    “它完全取代了噬菌体基因组，”陈博士说。