Impact of zinc and zinc transporters in Mycobacterium avium ssp. paratuberculosis pathogenicity

鸟分枝杆菌亚种副结核（MAP）是反刍动物的一种慢性肉芽肿性肠炎——约翰氏病（JD，副结核）的病原体。JD是畜牧业中传播最广的细菌性疾病之一，具有重要的经济影响。然而，MAP的病理生物学在很大程度上尚未解决。在我们的研究中，我们旨在通过MAP与密切相关的鸟分枝杆菌ssp的比较来阐明MAP与其他分枝杆菌的病理生物学差异。或者是非致病性分枝杆菌。我们最近对锌饥饿后MAP培养的RNA进行了深度测序分析，发现70个基因对锌限制有反应。值得注意的是，这些基因中有45个位于一个约90 kb的大基因组岛（ZnGI）上，其中包括两个MAP特异性长序列多态性LSP14和LSP15。预计其中35个基因受锌的主要转录调控因子FurB的控制。这种锌反应基因的聚类只在MAP中发现，而在其他分枝杆菌中没有发现。此外，与其他分枝杆菌相比，MAP具有三种推定的锌转运蛋白，其中两种是MAP独有的，可能是通过水平基因转移获得的。对于其中一种转运蛋白MptABC，证实了FurB依赖性调控。因此，锌似乎在MAP的代谢中起重要作用。这一特殊方面可能对反刍动物JD的疾病进展具有重要意义，因为MAP诱导的炎症最常见于宿主主要的锌吸收部位回肠远端。该项目旨在确定锌和锌转运体与MAP代谢和病理生物学的相关性。

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease (JD, paratuberculosis), a chronic, granulomatous enteritis in ruminants. JD is one of the most widespread bacterial diseases of animal husbandry with significant economic impact. However, pathobiology of MAP is largely unresolved. In our studies, we aimed to clarify differences in MAP pathobiology to other mycobacteria by comparison of MAP with the closely related Mycobacterium avium ssp. or nonpathogenic mycobacteria. Our recent deep sequencing analysis of RNA from MAP cultures after zinc starvation revealed that 70 genes responded to zinc limitation. Remarkably, 45 of these genes were located on a large genomic island (ZnGI) of approximately 90 kb which included the two MAP specific long sequence polymorphisms LSP14 and LSP15. Thirty-five of these genes were predicted to be controlled by the major transcriptional regulator for zinc, FurB. This clustering of zinc responsive genes was exclusively found in MAP and not in other mycobacteria. Furthermore, in contrast to other mycobacteria, MAP possesses three putative zinc transporters, of which two are unique to MAP and possibly acquired via horizontal gene transfer. For one of the transporters, MptABC, a FurB dependent regulation was demonstrated. Thus, zinc seems to play an important role in the metabolism of MAP. This particular aspect might be of main importance for disease progression of JD in ruminants as MAP induced inflammation is most frequently found in the distal ileum, the major site of zinc absorption of the host. The project aims to identify the relevance of zinc and zinc transporters for MAP metabolism and pathobiology.