Exploring the pathogenicity of Oscheius sp. KHA501 and its potential in association with entomopathogenic bacteria

Abstract

Nematodes have developed a range of abilities to more effectively acquire food resources throughout their evolution. Entomopathogenic nematodes (EPNs), by using entomopathogenic bacteria, are known to efficiently utilize insect bodies as valuable food resources. Nematodes of the genus Oscheius are recognized as freeliving, and certain species display the entomopathogenic trait like EPNs. Pathogenicity of Oscheius nematodes is believed to depend on associations with entomopathogenic bacteria. However, the interrelationship between entomopathogenic bacteria and Oscheius nematodes remains insufficiently elucidated. In this study an undescribed Oscheius nematode, designated as Oscheius sp. KHA501, was isolated using a Galleria mellonella bait trap method. Oscheius sp. KHA501 exhibited a free-living behavior and was culturable with both Escherichia coli OP50 and a bacterium that was predominantly isolated from G. mellonella carcasses after infection of Oscheius sp. KHA501. The isolated bacterium, identified as Serratia marcescens bKHA501, exhibited pronounced virulence and played a pivotal role in the entomopathogenic attributions of Oscheius sp. KHA501. Furthermore, S. marcescens bKHA501 demonstrated the capability to impede the growth and propagation of the free-living soil nematode Caenorhabditis elegans. While Oscheius sp. KHA501 does not display high but moderate entomopathogenicity, its ability to harness pathogenic bacteria enhances its role as a superior scavenger. Entomopathogenic bacteria use nematodes as a vector for dissemination, suggesting the presence of a mutualistic relationship between S. marcescens bKHA501 and Oscheius KHA501.