Photorhabdus aballayi sp. nov. and Photorhabdus luminescens subsp. venezuelensis subsp. nov., isolated from Heterorhabditis amazonensis entomopathogenic nematodes
Ricardo A. R. Machado, Aashaq Hussain Bhat, Carlos Castañeda-Álvarez, Vladimı́r Půža, Ernesto San‐Blas
Abstract
Six Gram-negative, rod-shaped bacterial strains isolated from Heterorhabditis amazonensis entomopathogenic nematodes were characterized to determine their taxonomic position. 16S rRNA and gyrB gene sequences indicate that they belong to the class Gammaproteobacteria , family Morganellaceae and genus Photorhabdus , and that some of them are conspecifics. Two of them, APURE T and JAR T , were selected for further molecular characterization using whole genome- and whole-proteome-based phylogenetic reconstructions and sequence comparisons. Phylogenetic reconstructions using whole genome and whole proteome sequences show that strains APURE T and JAR T are closely related to Photorhabdus luminescens subsp. luminescens ATCC 29999 T and to P. luminescens subsp. mexicana MEX47-22 T . Moreover, digital DNA–DNA hybridization (dDDH) values between APURE T and P. luminescens subsp. luminescens ATCC 29999 T , APURE T and P. luminescens subsp. mexicana MEX47-22 T , and APURE T and JAR T are 61.6, 61.2 and 64.1 %, respectively. These values are below the 70 % divergence threshold that delimits prokaryotic species. dDDH scores between JAR T and P. luminescens subsp. luminescens ATCC 29999 T and between JAR T and P. luminescens subsp. mexicana MEX47-22 T are 71.9 and 74.8 %, respectively. These values are within the 70 and 79 % divergence thresholds that delimit prokaryotic subspecies. Based on these genomic divergence values, APURE T and JAR T represent two different taxa, for which we propose the names: Photorhabdus aballayi sp. nov. with APURE T (=CCM 9236 T =CCOS 2019 T ) as type strain and Photorhabdus luminescens subsp. venezuelensis subsp. nov. with JAR T (=CCM 9235 T =CCOS 2021 T ) as type strain. Our study contributes to a better understanding of the biodiversity of an important bacterial group with enormous biotechnological and agricultural potential.