Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
FEMS Microbiol Lett. 2013 Jan;338(1):1-9. doi: 10.1111/1574-6968.12011. Epub 2012 Oct 19.
Multicellular organisms limit the availability of free iron to prevent the utilization of this essential nutrient by microbial pathogens. As such, bacterial pathogens possess a variety of mechanisms for obtaining iron from their hosts, including a number of examples of vertebrate pathogens that obtain iron directly from host proteins. Recently, two novel members of the colicin M bacteriocin family were discovered in Pectobacterium that suggest that this phytopathogen possesses such a system. These bacteriocins (pectocin M1 and M2) consist of a cytotoxic domain homologous to that of colicin M fused to a horizontally acquired plant-like ferredoxin. This ferredoxin domain substitutes the portion of colicin M required for receptor binding and translocation, presumably fulfilling this role by parasitizing an existing ferredoxin-based iron acquisition pathway. The ability of susceptible strains of Pectobacterium to utilize plant ferredoxin as an iron source was also demonstrated, providing additional evidence for the existence of such a system. If this hypothesis is correct, it represents the first example of iron piracy directly from a host protein by a phytopathogen and serves as a testament of the flexibility of evolution in creating new bacteriocin specificities.
多细胞生物会限制游离铁的可用性，以防止微生物病原体利用这种必需的营养物质。因此，细菌病原体拥有多种从宿主获取铁的机制，包括一些从宿主蛋白质中直接获取铁的脊椎动物病原体的例子。最近，在果胶杆菌中发现了两种新型的 colicin M 细菌素家族成员，这表明这种植物病原体拥有这样的系统。这些细菌素（pectocin M1 和 M2）由细胞毒性结构域和水平获得的植物样铁氧还蛋白融合而成，与 colicin M 的结构域同源。这个铁氧还蛋白结构域取代了 colicin M 中受体结合和易位所必需的部分，可能通过寄生现有的基于铁氧还蛋白的铁获取途径来发挥此作用。还证明了易感果胶杆菌菌株能够利用植物铁氧还蛋白作为铁源，这为该系统的存在提供了额外的证据。如果这个假设是正确的，那么它代表了植物病原体直接从宿主蛋白中窃取铁的第一个例子，并且证明了进化在创造新的细菌素特异性方面的灵活性。
