Charles Lauren, Carbone Ignazio, Davies Keith G, Bird David, Burke Mark, Kerry Brian R, Opperman Charles H
Center for the Biology of Nematode Parasitism, Department of Plant Pathology, North Carolina State University, Raleigh, NC 27606, USA.
J Bacteriol. 2005 Aug;187(16):5700-8. doi: 10.1128/JB.187.16.5700-5708.2005.
Pasteuria penetrans is a gram-positive, endospore-forming eubacterium that apparently is a member of the Bacillus-Clostridium clade. It is an obligate parasite of root knot nematodes (Meloidogyne spp.) and preferentially grows on the developing ovaries, inhibiting reproduction. Root knot nematodes are devastating root pests of economically important crop plants and are difficult to control. Consequently, P. penetrans has long been recognized as a potential biocontrol agent for root knot nematodes, but the fastidious life cycle and the obligate nature of parasitism have inhibited progress on mass culture and deployment. We are currently sequencing the genome of the Pasteuria bacterium and have performed amino acid level analyses of 33 bacterial species (including P. penetrans) using concatenation of 40 housekeeping genes, with and without insertions/deletions (indels) removed, and using each gene individually. By application of maximum-likelihood, maximum-parsimony, and Bayesian methods to the resulting data sets, P. penetrans was found to cluster tightly, with a high level of confidence, in the Bacillus class of the gram-positive, low-G+C-content eubacteria. Strikingly, our analyses identified P. penetrans as ancestral to Bacillus spp. Additionally, all analyses revealed that P. penetrans is surprisingly more closely related to the saprophytic extremophile Bacillus haladurans and Bacillus subtilis than to the pathogenic species Bacillus anthracis and Bacillus cereus. Collectively, these findings strongly imply that P. penetrans is an ancient member of the Bacillus group. We suggest that P. penetrans may have evolved from an ancient symbiotic bacterial associate of nematodes, possibly as the root knot nematode evolved to be a highly specialized parasite of plants.
穿刺巴氏杆菌是一种革兰氏阳性、形成芽孢的真细菌，显然是芽孢杆菌 - 梭菌分支的成员。它是根结线虫（南方根结线虫属）的专性寄生虫，优先在发育中的卵巢上生长，抑制繁殖。根结线虫是经济上重要的农作物的毁灭性根部害虫，且难以控制。因此，长期以来穿刺巴氏杆菌一直被认为是根结线虫的潜在生物防治剂，但其挑剔的生命周期和寄生的专性性质阻碍了大规模培养和应用方面的进展。我们目前正在对巴氏杆菌的基因组进行测序，并使用40个管家基因的串联，去除插入/缺失（indels）和不进行去除操作，以及分别使用每个基因，对33种细菌（包括穿刺巴氏杆菌）进行了氨基酸水平分析。通过将最大似然法、最大简约法和贝叶斯方法应用于所得数据集，发现穿刺巴氏杆菌在革兰氏阳性、低G + C含量真细菌的芽孢杆菌类中紧密聚类，置信度很高。引人注目的是，我们的分析确定穿刺巴氏杆菌是芽孢杆菌属的祖先。此外，所有分析都表明，穿刺巴氏杆菌与腐生嗜极端微生物哈氏芽孢杆菌和枯草芽孢杆菌的关系比与致病物种炭疽芽孢杆菌和蜡样芽孢杆菌的关系更为密切，令人惊讶。总体而言，这些发现强烈暗示穿刺巴氏杆菌是芽孢杆菌组的古老成员。我们认为，穿刺巴氏杆菌可能从线虫的古老共生细菌伙伴进化而来，可能是随着根结线虫进化成为高度特化的植物寄生虫而发生的。
