Roseomonas hellenica sp. nov., isolated from roots of wild-growing Alkanna tinctoria.

Two Gram-negative, aerobic, rod-shaped and yellow-orange pigmented bacterial strains (LMG 31523T and LMG 31524) were isolated from roots of wild-growing Alkanna tinctoria plants collected near Thessaloniki, Greece. Analysis of their 16S rRNA gene sequences revealed that they form a separate cluster related to the genus Roseomonas. A comparative whole genome analysis of the two strains and the type strains of related Roseomonas species revealed average nucleotide identity values from 78.84 and 80.32%. The G + C contents of the genomic DNA of strains LMG 31523T and LMG 31524 were 69.69% and 69.74%, respectively. Combined data from phenotypic, phylogenetic and chemotaxonomic studies indicated that the strains LMG 31523T and LMG 31524 represent a novel species of the genus Roseomonas. Genome analysis of the new strains showed a number of genes involved in survival in the rhizosphere environment and in plant colonization and confirmed the endophytic characteristics of LMG 31523T and LMG 31524. Since the strains LMG 31523T and LMG 31524 were isolated from a plant collected in Greece the name Roseomonas hellenica sp. nov. is proposed. The type strain is LMG 31523T (=CECT 30032T).

First-in-human topical microbiome transplantation with Roseomonas mucosa for atopic dermatitis.

The underlying pathology of atopic dermatitis (AD) includes impaired skin barrier function, susceptibility to Staphylococcus aureus skin infection, immune dysregulation, and cutaneous dysbiosis. Our recent investigation into the potential role of Gram-negative skin bacteria in AD revealed that isolates of one particular commensal, Roseomonas mucosa, collected from healthy volunteers (HVs) improved outcomes in mouse and cell culture models of AD. In contrast, isolates of R. mucosa from patients with AD worsened outcomes in these models. These preclinical results suggested that interventions targeting the microbiome could provide therapeutic benefit for patients with AD. As a first test of this hypothesis in humans, 10 adult and 5 pediatric patients were enrolled in an open-label phase I/II safety and activity trial (the Beginning Assessment of Cutaneous Treatment Efficacy for Roseomonas in Atopic Dermatitis trial; BACTERiAD I/II). Treatment with R. mucosa was associated with significant decreases in measures of disease severity, topical steroid requirement, and S. aureus burden. There were no adverse events or treatment complications. We additionally evaluated differentiating bacterial metabolites and topical exposures that may contribute to the skin dysbiosis associated with AD and/or influence future microbiome-based treatments. These early results support continued evaluation of R. mucosa therapy with a placebo-controlled trial.

Roseomonas deserti sp. nov., isolated from crude oil contaminated desert sand.

Two dark pink pigmented bacterial strains (M3T and M11) were isolated from crude oil contaminated desert sand from Kuwait. Both strains were Gram-stain-negative and small-rod to oval-shaped bacteria. Strains M3T and M11 grew at 13-42 °C (optimum, 30-35 °C) and pH 6.5-9.0 (optimum, 7.0-7.5). No additional NaCl was required for the growth of both strains. The genomic DNA G+C content of strains M3T and M11 were 69.5 and 69.0 mol%, respectively. Both strains were closely related and the mean DNA-DNA hybridization value was 92±1 %. 16S rRNA gene sequence comparisons of both strains indicated that they belong to the genus Roseomonas. Strains M3T and M11 had a sequence similarity of 97.3 and 97.4 % with Roseomonas oryzae JC288T, respectively. Both strains had <97 % 16S rRNA gene sequence similarity with other members of the genus Roseomonas. Strain M3T showed 18±2 and 13±2 % reassociation (based on DNA-DNA hybridization) with R. oryzae KCTC 42542T and Roseomonas cervicalis KACC 11686T, respectively. The major cellular fatty acids (>5 %) were identified as C18 : 1ω6c/C18 : 1ω7c, C16 : 1ω6c/C16 : 1ω7c and C16 : 0 in both strains. Both strains showed diphosphatidylglycerol, phosphatidylglycerol, phosphatidyl-ethanolamine, phosphatidylcholine and unidentified glycolipid as major polar lipids. Based on distinct phenotypic, genotypic and phylogenetic differences from the previously described taxa, we propose the classification of strains M3T and M11 as representative of a novel species in the genus Roseomonas, for which the name Roseomonas deserti sp. nov. is suggested. The type strain is M3T (=KEMB 2255-459T=JCM 31275T).