Mycobacterium bovis is the causative agent of bovine tuberculosis and the predominant cause of zoonotic tuberculosis in people. Bovine tuberculosis occurs in farmed cattle but also in a variety of wild animals, which form a reservoir of infection. Although direct transmission of tuberculosis occurs between mammals, the low frequency of contact between different host species and abundant shedding of bacilli by infected animals suggests an infectious route via environmental contamination. Other intracellular pathogens that transmit via the environment deploy strategies to survive or exploit predation by environmental amoebae. To explore if M. bovis has this capability, we investigated its interactions with the soil and dung-dwelling amoeba, Dictyostelium discoideum. We demonstrated that M. bovis evades phagocytosis and destruction by D. discoideum and actively transits through the amoeba using the ESX-1 Type VII Secretion System as part of a programme of mechanisms, many of which have been co-opted as virulence factors in the mammalian host. This capacity of M. bovis to utilise an environmental stage between mammalian hosts may enhance its transmissibility. In addition, our data provide molecular evidence to support an evolutionary role for amoebae as training grounds for the pathogenic M. tuberculosis complex.

中文翻译：

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牛分枝杆菌使用 ESX-1 VII 型分泌系统来逃避土壤中的变形虫盘基网柄菌的捕食。

牛分枝杆菌是牛结核病的病原体，也是人畜共患结核病的主要原因。牛结核病发生在养殖的牛身上，但也发生在各种野生动物身上，它们形成了感染的宿主。尽管结核病在哺乳动物之间发生直接传播，但不同宿主物种之间的接触频率低以及受感染动物大量脱落的杆菌表明通过环境污染进行感染途径。通过环境传播的其他细胞内病原体部署策略以生存或利用环境变形虫的捕食。为了探索 M. bovis 是否具有这种能力，我们研究了它与土壤和粪便中的变形虫盘基网柄菌的相互作用。我们证明 M. bovis 逃避 D. bovis 的吞噬作用和破坏。discoideum 并使用 ESX-1 VII 型分泌系统作为机制程序的一部分积极通过变形虫，其中许多已被选为哺乳动物宿主中的毒力因子。牛分枝杆菌利用哺乳动物宿主之间环境阶段的这种能力可能会增强其传播能力。此外，我们的数据提供了分子证据来支持变形虫作为致病性结核分枝杆菌复合体的训练场的进化作用。