Serratia montpellierensis sp. nov., Isolated from Laboratory-Reared Parasitic Wasps Psyttalia lounsburyii Silvestri and Psyttalia ponerophaga Silvestri (Hymenoptera: Braconidae)

Abstract

Two strains of bacteria, PsyLou2A^T and PsyPon4B, were isolated from adult braconid wasps Psyttalia lounsburyii and Psyttalia ponerophaga, respectively. These laboratory-reared wasps were investigated as agents for biological control of the olive fruit fly, Bactrocera oleae. Analysis of 16S rRNA genes of the two isolates demonstrated that they were highly related and belonged to the genus Serratia. Genomic sequencing of these isolates revealed genomes of 5,152,551 bp and 5,154,385 bp for PsyLou2A^T and PsyPon4B, respectively, and both genomes had a mol% G+C content of 59.6%. Phylogenetic analyses using BLAST-based average nucleotide identity (ANIb), and digital DNA-DNA hybridization methods indicated that PsyLou2A^T was most closely related to Serratia nevei S15^T, producing ANIb and dDDH values of 96.11% and 70.2%, respectively. Since these values were literally on the species cutoff threshold, additional S. nevei genome assemblies were analyzed using ANIb and dDDH calculations. This revealed that among assemblies that were clearly identifiable as S. nevei, S. nevei S15^T was the most closely related to PsyLou2A^T, and that a majority of assemblies produced dDDH values of 68.3-68.7% relative to PsyLou2A^T. Additionally, PsyLou2A^T differed biochemically from S. nevei S15^T in that it produced positive Voges Proskauer tests, produced protease, lacked arginine dihydrolase, and did not utilize D-lactose. Hence, PsyLou2A^T represents a novel taxon within the Serratia, for which we propose the name Serratia montpellierensis sp. nov. The type strain is PsyLou2A^T (=LMG 32817^T =NRRL B-65689^T).