Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, UK.
BMC Microbiol. 2010 Jun 22;10:177. doi: 10.1186/1471-2180-10-177.
Photorhabdus are Gram negative bacteria that are pathogenic to insect larvae whilst also having a mutualistic interaction with nematodes from the family Heterorhabditis. Iron is an essential nutrient and bacteria have different mechanisms for obtaining both the ferrous (Fe2+) and ferric (Fe3+) forms of this metal from their environments. In this study we were interested in analyzing the role of Fe3+ and Fe2+ iron uptake systems in the ability of Photorhabdus to interact with its invertebrate hosts.
We constructed targeted deletion mutants of exbD, feoABC and yfeABCD in P. luminescens TT01. The exbD mutant was predicted to be crippled in its ability to obtain Fe3+ and we show that this mutant does not grow well in iron-limited media. We also show that this mutant was avirulent to the insect but was unaffected in its symbiotic interaction with Heterorhabditis. Furthermore we show that a mutation in feoABC (encoding a predicted Fe2+ permease) was unaffected in both virulence and symbiosis whilst the divalent cation transporter encoded by yfeABCD is required for virulence in the Tobacco Hornworm, Manduca sexta (Lepidoptera) but not in the Greater Wax Moth, Galleria mellonella (Lepidoptera). Moreover the Yfe transporter also appears to have a role during colonization of the IJ stage of the nematode.
In this study we show that iron uptake (via the TonB complex and the Yfe transporter) is important for the virulence of P. luminescens to insect larvae. Moreover this study also reveals that the Yfe transporter appears to be involved in Mn2+-uptake during growth in the gut lumen of the IJ nematode. Therefore, the Yfe transporter in P. luminescens TT01 is important during colonization of both the insect and nematode and, moreover, the metal ion transported by this pathway is host-dependent.
Photorhabdus 是革兰氏阴性细菌，对昆虫幼虫具有致病性，同时与异小杆线虫科的线虫存在共生关系。铁是一种必需的营养物质，细菌有不同的机制从环境中获取二价（Fe2+）和三价（Fe3+）形式的这种金属。在这项研究中，我们感兴趣的是分析 Photorhabdus 摄取 Fe3+和 Fe2+的系统在其与无脊椎动物宿主相互作用中的作用。
我们构建了 P. luminescens TT01 的 exbD、feoABC 和 yfeABCD 基因的靶向缺失突变体。exbD 突变体预计在获取 Fe3+的能力上受到削弱，我们表明该突变体在缺铁培养基中生长不良。我们还表明，该突变体对昆虫无毒，但对与 Heterorhabditis 的共生作用没有影响。此外，我们表明 feoABC（编码一种预测的 Fe2+渗透酶）的突变在毒力和共生作用中都没有受到影响，而 yfeABCD 编码的二价阳离子转运蛋白是在烟草夜蛾（鳞翅目）中对毒力所必需的，但在大蜡螟（鳞翅目）中则不是。此外，Yfe 转运体似乎在线虫 IJ 阶段的定植中也有作用。
在这项研究中，我们表明铁摄取（通过 TonB 复合物和 Yfe 转运体）对 P. luminescens 对昆虫幼虫的毒力很重要。此外，这项研究还表明，Yfe 转运体似乎参与了 IJ 线虫肠道腔中 Mn2+的摄取。因此，P. luminescens TT01 中的 Yfe 转运体在昆虫和线虫的定植过程中都很重要，而且，该途径运输的金属离子依赖于宿主。
