松材线虫(Bursaphelenchus xylophilus)耐久型幼虫(LIV)携带的香茅醇假单胞杆菌(Pseudomonas citronellolis)分离与鉴定

目的]目前有关松材线虫与伴生细菌的关系及伴生细菌的病原作用是松树枯萎病研究的重点。为了揭示松材线虫与伴生细菌之间存在的密切关系，作者对松材线虫L_IV幼虫携带的细菌进行了分离鉴定。方法]根据培养性状和16S rDNA序列同源性以及系统发育学等方面进行分析鉴定。结果]确定L_IV幼虫携带的是香茅醇假单胞杆菌（Pseudomonas citronellolis），携带率为100%；每条L_IV幼虫携带量在1.4×10⁵~4.5×10⁵。L_IV幼虫生活在松褐天牛体内，是引起松材线虫病侵染流行的唯一虫态；新发现的香茅醇假单胞杆菌能分解纤维素及降解或合成萜烯和酚类化合物。结论]L_IV幼虫携带香茅醇假单胞杆菌的发现，揭示了松树、松褐天牛、松材线虫、细菌同为一体的紧密关系，并为揭示松树枯萎病机制提供了一种新病原和重要的研究思路。

Isolated and Identified of the Bacteria Pseudomonas citronellolis from the Dauerlarva of Bursaphelenchus xylophilus (LIV)

Objective] This study is to reveal the relationship of pathogenic bacteria associated with the pine wood nematode.Method] The bacteria carried by the dauerlarvae of Bursaphelenchus xylophilus (L_IV) were isolated, and were identified with 16S rDNA sequence homology and phylogenetic analysis.Result] It was showed that L_IV could carry a large amount of bacteria and the carrying rate was as high as 100%; the amount of the bacteria carried was 1.4×10⁵~4.5×10⁵ on each L_IV. The bacteria strain isolated from L_IV was identified as Pseudomonas citronellolis. The 16S rDNA sequence of the strain No.14 was 1 448 bp in length and the similarity of P. citronellolis was 99% comparing with the data in the gene bank.Conclusion] The preliminary conclusion is that the L_IV with P. citronellolis formed a group of the compound pathogen; L_IV is the only one linking pine tree with the longhorned beetle Monochamus alternatus; the bacteria of P. citronellolis could decompose cellulose and degrade or synthesis terpenes and phenolic compounds; The present discovery of L_IV carrying P. citronellolis suggests that the pine tree, Monochamus alternatus, Bursaphelenchus xylophilus and P. citronellolis may be a compacted system, and perhaps it may reveal a part of the mechanisms that the bacteria is a main factor causing pine wilt disease and killing pine tree die finally.