Rothia similimucilaginosa sp. nov., isolated from the human nasal cavity

TL;DR

Scientists discovered a new bacterial species, Rothia similimucilaginosa, from nasal samples of children in Wisconsin.

Contribution

The paper introduces a new species in the Rothia genus, distinct from R. mucilaginosa based on genomic and biochemical data.

Findings

The new species shares high 16S rRNA similarity but falls below species demarcation thresholds for ANI and DDH.

RSM42T can use fructose-6-phosphate as a carbon source, a unique trait among Rothia species.

Distinct enzyme activity and fatty acid profiles further differentiate R. similimucilaginosa from R. mucilaginosa.

Abstract

Four strains of a Gram-stain-positive, coccoid, catalase-positive, non-motile bacterium were recovered from nasal lavage samples collected from children in Wisconsin during the Spring of 2008. These strains, designated RSM42T, RSM292, RSM386 and RSM407, were subjected to a comprehensive biochemical and polyphasic taxonomic investigation. Despite the novel bacterium sharing 99.6% 16S rRNA gene sequence identity with Rothia mucilaginosa 5762/67T, BLAST+ average nucleotide identity, MUMmer3 average nucleotide identity and digital DNA–DNA hybridization values of 91.3%, 91.9% and 43.1%, respectively, were below the cut-off values routinely used for species demarcation. Consistent with these findings, phylogenetic and pangenomic comparisons indicated that RSM42T, RSM292, RSM386 and RSM407 form a separate lineage within the genus Rothia. Strain RSM42T is further distinguished from R. mucilaginosa 5762/67T by its unique ability among Rothia species to use fructose-6-phosphate as a sole carbon source. RSM42T also exhibits an enzyme activity profile consistent with R. mucilaginosa, as it is positive for valine arylamidase and negative for C4 esterase, β-glucosidase, pyrazinamidase and trypsin, a combination not observed in other Rothia species. The major fatty acids were anteiso-C15:0 (44.2%) and iso-C16:0 (14.4%), and the moderate fatty acids were anteiso-C13:0 (2.3%), iso-C14:0 (6.0%), C14:0 (2.3%), iso-C15:0 (5.9%), C15:0 (1.9%), C16:0 (9.3%) and anteiso-C17:0 (9.5%). The major polar lipids were aminoglycolipid and diphosphatidylglycerol. Based on biochemical, phylogenetic, genotypic and chemotaxonomic criteria, these isolates represent a novel species within the genus Rothia, closely related to R. mucilaginosa, for which the name Rothia similimucilaginosa sp. nov. is proposed. The type strain is RSM42T (=ATCC TSD-447T=DSM 118581T).

Figures