Abstract
Species belonging to the bacterial phylum Planctomycetes are ubiquitous members of the microbial communities in aquatic environments and are frequently isolated from various biotic and abiotic surfaces in marine and limnic water bodies. Planctomycetes have large genomes of up to 12.4 Mb, follow complex lifestyles and display an uncommon cell biology; features which motivate the investigation of members of this phylum in greater detail. As a contribution to the current collection of axenic cultures of Planctomycetes, we here describe strain Pla52T isolated from wood particles in the Baltic Sea. Phylogenetic analysis places the strain in the family Pirellulaceae and suggests two species of the recently described genus Stieleria as current closest neighbours. Strain Pla52nT shows typical features of members of the class Planctomycetia, including division by polar budding and the presence of crateriform structures. Colonies of strain Pla52nT have a light orange colour, which is an unusual pigmentation compared to the majority of members in the phylum, which show either a pink to red pigmentation or entirely lack pigmentation. Optimal growth of strain Pla52nT at 33 °C and pH 7.5 indicates a mesophilic (i.e. with optimal growth between 20 and 45 °C) and neutrophilic growth profile. The strain is an aerobic heterotroph with motile daughter cells. Its genome has a size of 9.6 Mb and a G + C content of 56.0%. Polyphasic analyses justify delineation of the strain from described species within the genus Stieleria. Therefore, we conclude that strain Pla52nT = LMG 29463T = VKM B-3447T should be classified as the type strain of a novel species, for which we propose the name Stieleria varia sp. nov.
Highlights
Planctomycetes is a phylum of mostly aquatic bacteria, which can be found in various limnic and marine water bodies
Colonies of strains confirmed as members of the phylum Planctomycetes were re-streaked on M1H N-acetyl glucosamine (NAG) artificial seawater (ASW) plates, which served as a source for the inoculation of liquid cultures in M1H NAG ASW medium
Maximum likelihood phylogenetic trees based on 16S rRNA genes sequences and multi-locus sequence analysis (MLSA) place strain Pla52nT in the recently introduced family Pirellulaceae (Dedysh et al 2019)
Summary
Planctomycetes is a phylum of mostly aquatic bacteria, which can be found in various limnic and marine water bodies. The sessile cells bud to form flagellated swarmer cells, which swim and relocate before settling down to attach and begin reproduction In this context, Planctomycetes were found to be frequent colonisers of macroalgae (Bengtsson and Øvreas 2010; Faria et al 2018; Lage and Bondoso 2014) and can even be the dominating phylum in microbial communities on biotic surfaces. To extend our knowledge on Plantomycetes in general and the genus Stieleria in particular, we characterise strain Pla52nT by using physiological, microscopic, genomic, and phylogenetic methods Based on these analyses, we propose that strain Pla52nT constitutes the third species of the recently described genus Stieleria
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