Silvanigrella

Abstract

Abstract Sil.va.ni.grel'la. N.L. fem. dim. n. Silvanigrella named after Silva nigra the Latin geographic name of the Schwarzwald (Black Forest) mountains located in the south‐west of Germany. Proteobacteria / Oligoflexia / Silvanigrellales / Silvanigrellaceae / Silvanigrella The genus Silvanigrella accommodates heterotrophic freshwater bacteria isolated from the water column of circumneutral or slightly acidic (pH 5–7) lakes and ponds with low ion concentrations (conductivity < 30 μS/cm). So far, only the two species Silvanigrella aquatica and Silvanigrella paludirubra have been described. Cells of the type strains have in common red pigmentation, motility, and pleomorphic morphology. In both species, the cell morphology ranges from rod‐shaped cells to filamentous forms, the cell size is variable in length and width. The type strain of S. aquatica in addition forms, densely coiled spirals. The type strains of both species grow at temperatures above 30°C, but only the type strain of S. paludirubra grows at temperatures below 10°C. Growth occurred up to supplementary NaCl concentrations of 1.0–1.1% (w/v). Both type strains utilized various organic substrates including carbohydrates, amino acids, and short‐chain fatty acids; however, the substrate spectra of the two strains differed. The most abundant fatty acid was iso‐C 15:0 for both type strains, contributing 33% to the total fatty acid content. The major respiratory quinone of S. paludirubra is menaquinone MK‐8, while the quinones of S. aquatica remained unidentified. The type strains of S. aquatica and S. paludirubra were both characterized by medium‐sized genomes (3.5 and 3.9 Mb, respectively) with low G + C content (32.6 and 29.3 mol%, respectively). DNA G + C content (mol%) : 29–33 (genome sequencing). Type species : Silvanigrella aquatica Hahn et al. 2017 VP .