A subset of naturally isolated Bacillus strains show extreme virulence to the free-living nematodes Caenorhabditis elegans and Pristionchus pacificus
A subset of naturally isolated Bacillus strains show extreme virulence to the free-living nematodes Caenorhabditis elegans and Pristionchus pacificus
复制标题
DOI：
10.1111/j.1462-2920.2010.02278.x
复制
发表时间：
2010-11-01
影响因子：
5.1
通讯作者：
Sommer, Ralf J.
中科院分区：
文献类型：
--
作者：
Rae, Robbie;Iatsenko, Igor;Sommer, Ralf J.
土壤环境中自由生活线虫的主要食物来源是细菌，细菌能影响线虫的发育、繁殖和存活。为了占据可靠的细菌食物来源，一些线虫与一系列无脊椎动物宿主（一旦宿主死亡，细菌就会繁殖）形成特定的关系，从而形成线虫，细菌和昆虫或其他无脊椎动物的三营养系统。我们从土壤（来自德国和英国）、马粪和蜣螂中分离出768株芽孢杆菌菌株，并将其喂给遗传上易处理的自由生活线虫秀丽隐杆线虫和太平洋棱纹线虫以分离杀线虫菌株。而C.线虫是一种食菌性土壤线虫，太平洋拟单胞菌是一种杂食性蠕虫，经常与金龟子甲虫一起发现。共分离到20株芽孢杆菌（由B.蜡状芽孢杆菌（B. cereus）、B. weihenstephanensis，B.真菌和芽孢杆菌属）对C.秀丽隐杆线虫和太平洋隐杆线虫在5天内导致70%至100%的死亡率，并显著影响发育和育雏大小。致病性最强的菌株是3株B。从蜣螂中分离到的蜡样菌对C. elegans在不到24小时内，但P. pacificus仍然耐药。C.线虫Bre突变体对B也高度敏感。蜡样菌株表明其毒素使用与B不同的毒力机制。苏云金杆菌Cry 5 B毒素此外，daf-2/daf-16胰岛素信号通路的突变不能挽救生存。我们分析了这三种B的毒素基因（bcet、nhe复合物、hbl复合物、pcpl、sph、cytK、pipplc、hly 2、hly 3、entFM和entS）。蜡样菌株，并显示出大多数毒素基因的存在，但没有HBL复合物。综上所述，本研究表明，大多数从土壤、马粪和地栖甲虫中自然分离的芽孢杆菌对C. elegans和P. pacificus。从20个对两种线虫具有不同毒力模式的致病菌株中筛选出3个B型菌株。蜡样菌株研究线虫的抗性和易感性免疫反应。
P>The main food source of free-living nematodes in the soil environment is bacteria, which can affect nematode development, fecundity and survival. In order to occupy a reliable source of bacterial food, some nematodes have formed specific relationships with an array of invertebrate hosts (where bacteria proliferate once the hosts dies), thus forming a tritrophic system of nematode, bacteria and insect or other invertebrates. We isolated 768 Bacillus strains from soil (from Germany and the UK), horse dung and dung beetles and fed them to the genetically tractable free-living nematodes Caenorhabditis elegans and Pristionchus pacificus to isolate nematocidal strains. While C. elegans is a bacteriovorous soil nematode, P. pacificus is an omnivorous worm that is often found in association with scarab beetles. We found 20 Bacillus strains (consisting of B. cereus, B. weihenstephanensis, B. mycoides and Bacillus sp.) that were pathogenic to C. elegans and P. pacificus causing 70% to 100% mortality over 5 days and significantly affect development and brood size. The most pathogenic strains are three B. cereus-like strains isolated from dung beetles, which exhibit extreme virulence to C. elegans in less than 24 h, but P. pacificus remains resistant. C. elegans Bre mutants were also highly susceptible to the B. cereus-like strains indicating that their toxins use a different virulence mechanism than B. thuringiensis Cry 5B toxin. Also, mutations in the daf-2/daf-16 insulin signaling pathway do not rescue survival. We profiled the toxin genes (bcet, nhe complex, hbl complex, pcpl, sph, cytK, piplc, hly2, hly3, entFM and entS) of these three B. cereus-like strains and showed presence of most toxin genes but absence of the hbl complex. Taken together, this study shows that the majority of naturally isolated Bacillus from soil, horse dung and Geotrupes beetles are benign to both C. elegans and P. pacificus. Among 20 pathogenic strains with distinct virulence patterns against the two nematodes, we selected three B. cereus-like strains to investigate resistance and susceptibility immune responses in nematodes.