Sugiyama Taiki, Hasegawa Koichi
Department of Environmental Biology, College of Bioscience & Biotechnology, Chubu University, 1200 Matsumoto, Kasugai, Aichi, 487-8501, Japan.
Sci Rep. 2025 Jul 2;15(1):22550. doi: 10.1038/s41598-025-06488-7.
Entomopathogenic nematodes (EPNs), primarily Steinernema and Heterorhabditis, form symbiotic relationships with bacteria from the genera Xenorhabdus and Photorhabdus, respectively. These bacteria exhibit insecticidal activity and suppress competing microorganisms, allowing EPNs and their symbionts to dominate insect cadavers. While monoxenic associations are fundamental to EPN-bacteria interactions, recent studies suggest that EPNs may harbor a diverse array of symbiotic bacteria with consistent associations. However, the role of these additional symbiotic bacteria in EPN pathogenesis and the complexity of their interactions remain unclear. In this study, Steinernema monticolum KHA701 was newly isolated using the Galleria mellonella bait method. Compared to the highly pathogenic Heterorhabditis bacteriophora TT01, S. monticolum KHA701 demonstrated superior insecticidal activity against G. mellonella larvae and exhibited a broad host range, targeting 63 arthropod species across 18 orders and 41 families. Microbiota analysis of S. monticolum KHA701 infective juveniles identified 34 bacterial species, including Xenorhabdus hominickii, from the nematode body. Five bacteria-Elizabethkingia miricola, Serratia marcescens, Pseudomonas protegens, Staphylococcus sp., and X. hominickii-were confirmed to be highly pathogenic to Zophobas morio and Periplaneta fuliginosa larvae. Notably, the combination of X. hominickii with any of the other four bacteria significantly enhanced the insecticidal activity of S. monticolum KHA701 against G. mellonella. These findings suggest that S. monticolum KHA701 utilizes a diverse community of bacterial symbionts to enhance its insecticidal efficacy, providing novel insights into the ecological strategies of EPNs.
昆虫病原线虫（EPNs），主要是斯氏线虫属（Steinernema）和异小杆线虫属（Heterorhabditis），分别与致病杆菌属（Xenorhabdus）和发光杆菌属（Photorhabdus）的细菌形成共生关系。这些细菌具有杀虫活性，并能抑制竞争性微生物，使昆虫病原线虫及其共生体在昆虫尸体上占据主导地位。虽然单菌共生关系是昆虫病原线虫与细菌相互作用的基础，但最近的研究表明，昆虫病原线虫可能含有多种具有稳定关联的共生细菌。然而，这些额外的共生细菌在昆虫病原线虫致病过程中的作用及其相互作用的复杂性仍不清楚。在本研究中，采用大蜡螟诱饵法新分离出山地斯氏线虫（Steinernema monticolum）KHA701。与高致病性的嗜菌异小杆线虫（Heterorhabditis bacteriophora）TT01相比，山地斯氏线虫KHA701对大蜡螟幼虫表现出更强的杀虫活性，并且具有广泛的宿主范围，针对18个目41个科的63种节肢动物。对山地斯氏线虫KHA701感染性幼虫的微生物群分析确定了34种细菌，包括来自线虫体内的霍氏致病杆菌（Xenorhabdus hominickii）。已证实5种细菌——嗜麦芽窄食单胞菌（Elizabethkingia miricola）、粘质沙雷氏菌（Serratia marcescens）、荧光假单胞菌（Pseudomonas protegens）、葡萄球菌（Staphylococcus sp.）和霍氏致病杆菌——对黄粉虫和黑胸大蠊幼虫具有高致病性。值得注意的是，霍氏致病杆菌与其他四种细菌中的任何一种组合，都显著增强了山地斯氏线虫KHA701对大蜡螟的杀虫活性。这些发现表明，山地斯氏线虫KHA701利用多种细菌共生体群落来提高其杀虫效果，为昆虫病原线虫的生态策略提供了新的见解。
