Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, Montana, United State of America.
PLoS Pathog. 2021 Oct 14;17(10):e1009995. doi: 10.1371/journal.ppat.1009995. eCollection 2021 Oct.
Yersinia murine toxin (Ymt) is a phospholipase D encoded on a plasmid acquired by Yersinia pestis after its recent divergence from a Yersinia pseudotuberculosis progenitor. Despite its name, Ymt is not required for virulence but acts to enhance bacterial survival in the flea digestive tract. Certain Y. pestis strains circulating in the Bronze Age lacked Ymt, suggesting that they were not transmitted by fleas. However, we show that the importance of Ymt varies with host blood source. In accordance with the original description, Ymt greatly enhanced Y. pestis survival in fleas infected with bacteremic mouse, human, or black rat blood. In contrast, Ymt was much less important when fleas were infected using brown rat blood. A Y. pestis Ymt- mutant infected fleas nearly as well as the Ymt+ parent strain after feeding on bacteremic brown rat blood, and the mutant was transmitted efficiently by flea bite during the first weeks after infection. The protective function of Ymt correlated with red blood cell digestion kinetics in the flea gut. Thus, early Y. pestis strains that lacked Ymt could have been maintained in flea-brown rat transmission cycles, and perhaps in other hosts with similar blood characteristics. Acquisition of Ymt, however, served to greatly expand the range of hosts that could support flea-borne plague.
鼠伤寒沙门氏菌毒素 (Ymt) 是一种由鼠疫耶尔森菌在其最近从假结核耶尔森菌祖先进化后获得的质粒上编码的磷脂酶 D。尽管它的名字叫 Ymt，但它并不是毒力所必需的，而是有助于增强细菌在跳蚤消化道中的存活。在青铜时代循环的某些鼠疫耶尔森菌菌株缺乏 Ymt，表明它们不是通过跳蚤传播的。然而，我们表明 Ymt 的重要性因宿主血液来源而异。与最初的描述一致，Ymt 极大地增强了感染菌血症鼠、人或黑鼠血液的跳蚤中的鼠疫耶尔森菌的存活。相比之下，当使用褐鼠血液感染跳蚤时，Ymt 的重要性要小得多。在感染菌血症褐鼠血液后，携带 Ymt 突变的鼠疫耶尔森菌感染的跳蚤与 Ymt+亲本菌株几乎一样好，并且在感染后的头几周内，通过跳蚤叮咬有效地传播了突变体。Ymt 的保护功能与跳蚤肠道中的红细胞消化动力学相关。因此，早期缺乏 Ymt 的鼠疫耶尔森菌菌株可能在跳蚤-褐鼠传播循环中得到维持，并且可能在具有类似血液特征的其他宿主中得到维持。然而，Ymt 的获得极大地扩展了可以支持跳蚤传播鼠疫的宿主范围。
