Molecular Markers Specific for the Pseudomonadaceae Genera Provide Novel and Reliable Means for the Identification of Other Pseudomonas Strains/spp. Related to These Genera

Abstract

Background/Objectives: Taxon-specific conserved signature indels (CSIs) exhibit a strong predictive ability of being found in other members of specific taxa/genera. Recently, multiple exclusively shared CSIs were identified for several newly described Pseudomonadaceae genera (viz. Aquipseudomonas, Atopomonas, Caenipseudomonas, Chryseomonas Ectopseudomonas, Geopseudomonas, Halopseudomonas, Metapseudomonas, Phytopseudomonas, Serpens, Stutzerimonas, Thiopseudomonas, and Zestomonas). This study examines the potential applications of these CSIs for identifying other Pseudomonas spp. (strains) related to these genera. Methods: This work utilized the AppIndels.com server, which uses information regarding the presence of known taxon-specific CSIs in a genome for predicting its taxonomic affiliation. For this purpose, sequence information for different CSIs specific for the Pseudomonadaceae species/genera were added to the server’s database. Results: The AppIndels server was used to predict the taxonomic affiliation of 1972 genomes of unclassified Pseudomonas spp. (strains/isolates). Based upon finding a significant number of CSIs matching a specific taxon, the AppIndels server made positive predictions regarding the taxonomic affiliation of 299 examined genomes into the following clades/genera: Pseudomonas sensu stricto clade (46), Pseudomonas aeruginosa (64), Ectopseudomonas (46), Chryseomonas (32), Stutzerimonas (31), Metapseudomonas (22), Aquipseudomonas (21), Phytopseudomonas (17), Halopseudomonas (9), Geopseudomonas (4), Thiopseudomonas (3), Serpens (2), and Caenipseudomonas and Zestomonas (1 each). Phylogenetic studies confirmed that the taxonomic predictions by the server were 100% accurate. Conclusions: Our results demonstrate that the CSIs specific for Pseudomonadaceae species/genera, in conjunction with the AppIndels server, provides a novel and useful tool for identifying other species/strains affiliated with these species/genera. Phylogenetic studies suggest that many examined Pseudomonas strains constitute novel species in the indicated genera.