From cantaloupe to cattle: Pseudomonas alabamensis sp. nov. described from diseased cantaloupe (Cucumis melo) foliage and a bovine (Bos taurus) nasopharynx.

Abstract

In 2022, a fluorescent bacterial isolate, designated 22-AL-CL-001, was isolated from diseased cantaloupe (Cucumis melo) foliage collected in Alabama, USA, displaying marginal necrosis and general blighting. Whole-genome sequencing and subsequent comparisons to publicly available bacterial genomes identified Pseudomonas isolate USDA-ARS-USMARC-56711, isolated from a clinically healthy calf (Bos taurus) in Kansas, USA, as genetically similar to isolate 22-AL-CL-001. The two isolates were then characterized using phenotypic and genetic analyses, including fluorescence on King's medium B; LOPAT reactions; pathogenicity assays on cantaloupe, watermelon and squash plants; 16S rRNA gene sequence analysis; phylogeny based on multi-locus sequence analysis (MLSA) of four housekeeping genes; average nucleotide identity based on blast (ANIb); in silico DNA-DNA hybridization (isDDH) including comparison to the Type Genome Server and biochemical profiling using the Biolog Gen III microplate system. MLSA phylogeny placed both isolates into a single clade within the genus Pseudomonas, distant from all included reference strains. ANIb and isDDH analyses definitively identified the isolates as members of the same species (ANIb, 97.25; isDDH, 78.5%), though comparison scores to reference strains were all below the accepted thresholds for species determination. Biolog biochemical profiling, as well as MALDI-TOF mass spectrometry of isolate 22-AL-CL-001, was also unable to identify the isolate as a member of any existing bacterial species. Using a combination of genetic and phenotypic data, we conclude that the two isolates belong to a new species of Pseudomonas, for which we propose the name Pseudomonas alabamensis. The specific epithet, alabamensis, was chosen to represent the location where the type strain 22-AL-CL-001^T (NCPPB 4760^T=LMG 33363^T) was isolated, Alabama, USA. Taxonomic classification of the two isolates by the Genome Taxonomy Database revealed other previously sequenced bacterial strains that, according to ANI and isDDH results, also belong to P. alabamensis.