Fuchs Thilo M, Bresolin Geraldine, Marcinowski Lisa, Schachtner Joachim, Scherer Siegfried
Zentralinstitut für Ernährungs- und Lebensmittelforschung, Abteilung Mikrobiologie, Germany.
BMC Microbiol. 2008 Dec 8;8:214. doi: 10.1186/1471-2180-8-214.
Toxin complex (Tc) proteins termed TcaABC, TcdAB, and TccABC with insecticidal activity are present in a variety of bacteria including the yersiniae.
The tc gene sequences of thirteen Yersinia strains were compared, revealing a high degree of gene order conservation, but also remarkable differences with respect to pseudogenes, sequence variability and gene duplications. Outside the tc pathogenicity island (tc-PAIYe) of Y. enterocolitica strain W22703, a pseudogene (tccC2'/3') encoding proteins with homology to TccC and similarity to tyrosine phosphatases at its C-terminus was identified. PCR analysis revealed the presence of the tc-PAIYe and of tccC2'/3'-homologues in all biotype 2-5 strains tested, and their absence in most representatives of biotypes 1A and 1B. Phylogenetic analysis of 39 TccC sequences indicates the presence of the tc-PAIYe in an ancestor of Yersinia. Oral uptake experiments with Manduca sexta revealed a higher larvae lethality of Yersinia strains harbouring the tc-PAIYe in comparison to strains lacking this island. Following subcutaneous infection of Galleria mellonella larvae with five non-human pathogenic Yersinia spp. and four Y. enterocolitica strains, we observed a remarkable variability of their insecticidal activity ranging from 20% (Y. kristensenii) to 90% (Y. enterocolitica strain 2594) dead larvae after five days. Strain W22703 and its tcaA deletion mutant did not exhibit a significantly different toxicity towards G. mellonella. These data confirm a role of TcaA upon oral uptake only, and suggest the presence of further insecticidal determinants in Yersinia strains formerly unknown to kill insects.
This study investigated the tc gene distribution among yersiniae and the phylogenetic relationship between TccC proteins, thus contributing novel aspects to the current discussion about the evolution of insecticidal toxins in the genus Yersinia. The toxic potential of several Yersinia spp. towards M. sexta and G. mellonella demonstrated here for the first time points to insects as a natural reservoir for yersiniae.
具有杀虫活性的毒素复合体（Tc）蛋白，即TcaABC、TcdAB和TccABC，存在于包括耶尔森氏菌属在内的多种细菌中。
比较了13株耶尔森氏菌的tc基因序列，发现基因顺序高度保守，但在假基因、序列变异性和基因重复方面也存在显著差异。在小肠结肠炎耶尔森氏菌菌株W22703的tc致病岛（tc-PAIYe）之外，鉴定出一个假基因（tccC2'/3'），其编码的蛋白与TccC具有同源性，且在其C末端与酪氨酸磷酸酶具有相似性。PCR分析显示，在所有测试的生物型2-5菌株中都存在tc-PAIYe和tccC2'/3'同源物，而在生物型1A和1B的大多数代表菌株中不存在。对39个TccC序列的系统发育分析表明，耶尔森氏菌的一个祖先中存在tc-PAIYe。用烟草天蛾进行的口服摄取实验表明，与缺乏该岛的菌株相比，携带tc-PAIYe的耶尔森氏菌菌株对幼虫的致死率更高。在用5种非人类致病性耶尔森氏菌和4株小肠结肠炎耶尔森氏菌对大蜡螟幼虫进行皮下感染后，我们观察到它们的杀虫活性差异显著，5天后死亡幼虫的比例从20%（克里斯滕森耶尔森氏菌）到90%（小肠结肠炎耶尔森氏菌菌株2594）不等。菌株W22703及其tcaA缺失突变体对大蜡螟的毒性没有显著差异。这些数据证实了TcaA仅在口服摄取时起作用，并表明在以前未知的具有杀虫作用的耶尔森氏菌菌株中存在其他杀虫决定因素。
本研究调查了耶尔森氏菌中tc基因的分布以及TccC蛋白之间的系统发育关系，从而为当前关于耶尔森氏菌属中杀虫毒素进化的讨论提供了新的内容。本文首次证明了几种耶尔森氏菌对烟草天蛾和大蜡螟的潜在毒性，表明昆虫是耶尔森氏菌的天然宿主。
