School of Science, University of Greenwich, Chatham Maritime, Kent ME4 4TB, UK.
J Invertebr Pathol. 2011 Jun;107(2):132-8. doi: 10.1016/j.jip.2011.03.008. Epub 2011 Mar 30.
Several strains of Bacillus thuringiensis were previously isolated from soil in Antarctica and appeared to have physiological adaptations to this cold, nutrient-poor environment. In spite of this they could produce abnormally large, parasporal crystals under laboratory conditions. Here, they have been further characterised for toxin genes and invertebrate pathogenicity. All of the strains were positive in PCR assays for the cry1Aa and cry2 genes. This was confirmed by sequence analysis and the parasporal crystals of all strains contained polypeptides of about 130kDa. This potential for lepidopteran toxicity was borne out in bioassays of purified δ-endotoxins against larvae of Pieris brassicae: the LD(50) values of B2408 (288μg) were comparable to that of the reference strain, HD-12 (201μg). There was no activity against the nematode Caenorhabditis elegans in spite of the fact that all strains appeared to possess the cry6 gene. PCR screening for genes encoding other nematode-toxic classes of toxins (Cry5, 4 and 21) was negative. B. thuringiensis has never previously been shown to be toxic to Collembola (springtails) but the purified δ-endotoxins of one of the Antarctic strains showed some activity against Folsomia candida and Seira domestica (224μg and 238μg, respectively). It seems unlikely that the level of toxicity demonstrated against springtails would support a pathogenic life-style in nature. All of the strains were positive for genes encoding Bacillus cereus-type enterotoxins. In the absence of higher insects and mammals the ecological value of retaining the toxic capability demonstrated here is uncertain.
先前从南极洲土壤中分离出几种苏云金芽孢杆菌菌株，它们似乎对这种寒冷、营养贫乏的环境具有生理适应性。尽管如此，它们在实验室条件下仍能产生异常大的伴孢晶体。在这里，它们进一步被表征为毒素基因和昆虫病原性。所有菌株在 cry1Aa 和 cry2 基因的 PCR 检测中均呈阳性。这通过序列分析得到了证实，所有菌株的伴孢晶体都含有约 130kDa 的多肽。这对鳞翅目昆虫毒性的可能性在纯化 δ-内毒素对小菜蛾幼虫的生物测定中得到了证实：B2408（288μg）的 LD（50）值与参考菌株 HD-12（201μg）相当。尽管所有菌株似乎都拥有 cry6 基因，但对秀丽隐杆线虫没有活性。针对编码其他线虫毒性类毒素（Cry5、4 和 21）的基因的 PCR 筛选为阴性。苏云金芽孢杆菌以前从未被证明对弹尾目（跳虫）有毒，但其中一种南极菌株的纯化 δ-内毒素对 Folsomia candida 和 Seira domestica 表现出一定的活性（分别为 224μg 和 238μg）。不太可能是针对跳虫表现出的毒性水平会支持其在自然界中的致病生活方式。所有菌株都对编码芽孢杆菌 cereus 型肠毒素的基因呈阳性。在没有高等昆虫和哺乳动物的情况下，保留这里显示的毒性能力的生态价值是不确定的。
