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 omega 7c and/or iso-C-15 :0 2-OH, and C-18:1 omega 7c. 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.