Photorhabdus luminescens subsp. Namnaonensis subsp. nov., isolated from Heterorhabditis baujardi nematodes

A lightly yellowish-pigmented, oxidase-negative bacterial strain (PB45.5^T) isolated from the Nam Nao district of Phetchabun in central Thailand was investigated to determine its taxonomic position. Cells of the isolate showed a rod shaped appearance. The strain stained Gram-negative. Strain PB45.5^T shared highest 16S rRNA gene sequence similarity with the type strains of Photorhabdus luminescens subsp. akhurstii (99.2 %) and Photorhabdus luminescens subsp. hainanensis (99.1 %) and lower similarities to all other Photorhabdus luminescens subspecies (<98.0 %). Multilocus sequence analysis (MLSA) based on concatenated partial recA, dnaN, gltX, gyrB and infB gene sequences confirmed the affiliation obtained by 16S rRNA gene sequence analysis but showed a clear distinction of PB45.5^T from the closest related type strains. Strain PB45.5^T shared only 96.9% sequence similarity (concatenated nucleotide sequences) with P. luminescens subsp. akhurstii FRG04^T and 96.8% with P. luminescens subsp. hainanensis C8404^T. The fatty acid profile of the strain consisted of the major fatty acids C_{14: 0}, C_{16: 0}, C_{17: 0} cyclo, C_{16: 1}ω7c and/or iso-C_{15: 0} 2-OH, and C_{18: 1}ω7c. The MLSA results and the differential biochemical and chemotaxonomic properties showed that strain PB45.5^T represents a novel P. luminescens subspecies, for which the name Photorhabdus luminescens subsp. namnaonensis subsp. nov. (type strain PB45.5^T=LMG 29915^T=CCM 8729^T) is proposed.