Moraxella salivae sp. nov., isolated from the saliva of a healthy human volunteer

Abstract

Abstract Background Strain I5GT was isolated from the saliva of a healthy volunteer and polyphasic taxonomic approaches were applied for its systematic identification to clarify its taxonomic position within the genus Moraxella. Methods A polyphasic taxonomic study was performed, including morphological observation, physiological and biochemical characterisation, chemotaxonomic analyses (fatty acid profile, respiratory quinone, polar lipids), 16S rRNA gene phylogeny, and whole-genome-based phylogenetic and comparative genomic analyses. Results Strain I5GT is a Gram-stain-negative, aerobic, rod-shaped bacterium. Growth occurs at 25–37 °C (optimum 37 °C), pH 7.0–9.0 (optimum pH 8.0), and 0–1.0% (w/v) NaCl (optimum 0.5%). 16S rRNA gene analysis placed it in the genus Moraxella, with highest similarity (96.17%) to Moraxella oblonga IAM 14971ᵀ. Whole-genome phylogeny supported a distinct novel lineage. The maximum average nucleotide identity (ANI) (85.9%) and the highest digital DNA-DNA hybridisation (dDDH) (24.8%) values were well below species thresholds. DNA G + C content was 37.5 mol%. Major fatty acids were C₁₈:₁ ω9c, C₁₆:₀, C₁₈:₀ and Summed Feature 3 (C₁₆:₁ ω7c and/or C₁₆:₁ ω6c), major quinone was CoQ-8, major polar lipids were phosphatidylglycerol, diphosphatidylglycerol and phosphatidylethanolamine. Conclusion Strain I5GT represents a novel species within the genus Moraxella, for which the name Moraxella salivae sp. nov. is proposed. The type strain is I5GT (= KCTC 18404ᵀ = GDMCC 1.5953ᵀ).