Paludisphaera mucosa sp. nov., a Novel Planctomycete of the Family Isosphaeraceae from a Boreal Fen

Abstract

—Planctomycetes are common inhabitants of northern wetland ecosystems. In this study, a new planctomycete of the genus Paludisphaera, strain Pla2T, was isolated from a boreal fen in Russia. The novel isolate was represented by nonmotile, pink-pigmented, spherical cells that multiplied by budding and occurred singly or were assembled in small aggregates. Strain Pla2T was a chemoorganotrophic, psychrotolerant mesophile with a growth optimum at pH 5.5‒6 and 15‒20°C. The preferred growth substrates were polysaccharides, including xylan, xanthan gum, and phytagel, as well as some sugars. The 16S rRNA gene sequence of strain Pla2T displayed the highest similarity (97.9%) to that of ‘Paludisphaera soli’ JC670T isolated from highland soil of the western Himalayas. With other members of the genus Paludisphaera, ‘P. rhizosphaerae’ JC665T and P. borealis PX4T, this similarity was 97.0 and 93.8%, respectively. The genome of strain Pla2T was 8.21 Mb in size and contained about 6500 protein-coding genes and 3 copies of the rRNA operon. The DNA G + C content was 67 mol %. The average nucleotide identity between the genome sequence of strain Pla2T and those of previously described members of the genus Paludisphaera was between 79.4 and 82.6%. This genotypic distance as well as several phenotypic differences allowed classifying the new planctomycete from a fen as representing a novel species of the genus Paludisphaera, Paludisphaera mucosa sp. nov. with the type strain Pla2T (=KCTC92668T = VKM B-3698T).