昆虫病原线虫异小杆属新种Heterorhabditis beicherriana共生菌的分离及致病性

昆虫病原线虫共生菌在农业及医药领域已成为一种重要的生物活性资源。本研究通过致死的昆虫血腔和侵染期线虫直接分离线虫Heterorhabditis beicherriana的共生细菌，根据形态学特征、生理生化特性及16S rDNA序列初步鉴定为Photorhabdus luminescens，系统发育分析显示为发光杆菌属新亚种菌株。采用共生菌细菌体稀释液注射接种进行致病性测定，结果显示，每头大蜡螟幼虫接种菌量为600 cfu/mL，72 h时死亡率达到100%；24 h时LC₅₀为213.13 cfu/mL，48 h时LC₅₀为46.87 cfu/mL。这为研究该线虫H.beicherriana的致病机制奠定基础，以期发掘新的具有重要价值的活性资源。

Isolation and Pathogenicity of Symbiotic Bacteriua associated with the Entomopathogenic Nematode Heterorhabditis beicherriana

The symbiotic bacteria associated with entomopathogenic nematodes are potential biological resources in the field of agriculture and medicine. In this study, symbiotic bacteria were isolated directly through infective juveniles or the blood chamber of Galleria mellonella larvae which were infected by Heterorhabditis beicherriana. The symbiotic bacterium was identified as Photorhabdus luminescens based on morphology, physiological and biochemical characteristics and sequence analysis of 16S rDNA; phylogenetic analysis demonstrated the strain was shown to be part of the species of P. luminescens, but it was clearly sperated with clear separation from currently recognized subspecies. It is proposed to be a new subspecies. G. mellonella larvae injected with the cell diluent were used to test pathogenicity of the symbiotic bacterium. The strain C1 exhibited strong pathogenicity to the G. mellonella larvae. Mortality reached 100% at 72 h when one wax moth was inoculated with the concentration of 600 cfu/mL moth. The LC₅₀ was 213.13 cfu/mL at 24 h and 46.87 cfu/mL at 48 h. Our study will lay the foundation for the study of the pathogenic mechanism of H. beicherriana, thus leading to explore a new bacterial strain with important value.