Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/30351
標題: The virulence and antimicrobial activity of symbiotic bacterium in the entomopathogenic nematode, Steinernema abbasi (Rhabditida: Steinernematidae)
蟲生線蟲Steinernem aabbasi(Rhabditida目:Steinernematidae科)之共生菌毒力及抗菌活性
作者: 劉婉君
Liu, Wan-Chun
關鍵字: Steinernema abbasi;Steinernema abbasi;Xenorhabdus sp.;virulence;antimicrobial activity;共生菌;毒力;抗菌活性
出版社: 昆蟲學系
摘要: 
The virulence of a symbiotic bacterium, Xenorhabdus sp., of entomopathogenic nematode, Steinernema abbasi, was compared with Xenorhabdus nematophilus of Steinernema carpocapsae, to Spodoptera litura larvae was conducted in this study. The larvae were killed after injection with five doses of two symbionts, and the mortality rate was increased depending on post injection times. The LD50 values at 24 h and 48 h post incubation time were 99 and 146.5 cells/larva with Xenorhabdus sp., and 10 or lower and 6,037 cells/larva with X. nematophilus, respectively. When injected with 105 cells of Xenorhabdus sp., the haemocytes count of S. litura larvae was reduced with the incubation time. In the time sequences of invading test S. carpocapsae invaded first followed by S. abbasi, and S. carpocapsae symbiont was recovered from S. litura dead larvae. In contrast, when S. abbasi invaded earlier than S. carpocapsae, Xenorhabdus sp. would recover from dead insects while Xenorhabdus sp. could inhibit the growth of X. nematophilus in a co-culture test. Some 6th instar larvae of S. litura were dead when injected with Xenorhabdus sp. cultured for 72 h. Even though the culture was treated with heat, few injected larvae were dead. In addition to insecticidal activity, the culture of Xenorhabdus sp. could inhibit the growth of four human pathogenic bacteria including Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Vibrio parahaemolyticus. Using Biolog and API 20E tests, two symbionts differed in 10 carbon source exhibitions and 1 Gelatin reaction, respectively. Xenorhabdus sp. showed brown colonies on YDC agar while X. nematophilus was off-white ones. All of these assays indicated that the symbiont in S. abbasi varied with X. nematophilus.

本試驗主要探討本地所分離之蟲生線蟲Steinernema abbasi的共生菌Xenorhabdus sp. 對斜紋夜蛾(Spodoptera litura)幼蟲之致病力,並以S. carpocapsae及其共生菌(X. nematophilus)作為比較。將兩種共生菌以10、102、103、104、及105 cells注入斜紋夜蛾五齡幼蟲體內,結果顯示培養24或48小時之菌體皆可造成蟲體死亡,且死亡率隨著接種時間及接種菌量的增加而上升。此外,兩種共生菌Xenorhabdus sp. 及X. nematophilus 24及48小時培養之菌體對五齡幼蟲之LD50分別為99和146.5 cells/larva及 ≦ 10和6,037 cells/larva。注入Xenorhabdus sp. 105 cells至斜紋夜蛾幼蟲體內,其體內血球量隨幼蟲發育時間增加而減少。以兩種蟲生線蟲共同感染同一寄主,則S. carpocapsae於接觸1小時即已侵入寄主內,S. abbasi於2小時後才侵入昆蟲寄主。由死亡蟲體所分離之共生菌皆為X. nematophilus;另進行線蟲先後入侵試驗,顯示線蟲侵入之先後決定幼蟲體內共生菌之種類,且比較共生菌之共同培養試驗發現Xenorhabdus sp. 較X. nematophilus具生長優勢。以Xenorhabdus sp. 培養72小時之10倍濃縮培養液10 μl注入斜紋夜蛾六齡體內可殺死幼蟲;當培養液加熱處理後,仍可造成較低之幼蟲死亡率,推測此共生菌含具熱不穩定之殺蟲物質。另外,Xenorhabdus sp. 經培養48及72 h後之10倍濃縮培養液,對人體病原菌例如金黃葡萄球菌(Staphylococcus aureus)、大腸桿菌(Escherichia coli)、克雷伯氏菌(Klebsiella pneumoniae)及腸炎弧菌(Vibrio para- haemolyticus)等皆具抑菌效果。Xenorhabdus sp. 及X. nematophilus進行生理生化測試發現,兩者利用相異的碳素源共有10種,且Xenorhabdus sp. 於Gelatin測試中為陽性反應;Xenorhabdus sp. 於YDC agar上菌落呈褐色,X. nematophilus則呈灰白色;因此推測S. abbasi之共生菌應非X. nematophilus 。
URI: http://hdl.handle.net/11455/30351
Appears in Collections:昆蟲學系

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