Four novel Planctomicrobium species isolated from sewage sludge or leakage water of a compost heap in Northern Germany

Four non-pigmented, off-white to ivory strains, SH527T, SH661T, SH664T and SH668T, have been isolated from sewage sludge or leakage water of a compost heap in Northern Germany as part of an isolation campaign conducted by Heinz Schlesner, Kiel University in the 1980s-early 2000s. Analyses based on five phylogenetic markers place the novel strains in the genus Planctomicrobium in the family Planctomycetaceae within the phylum Planctomycetota. All four strains are aerobic heterotrophs with a neutrophilic and mesophilic growth profile. Genome sequencing revealed relatively small genomes compared to the relatives in the same family, with strain SH668T having the currently smallest genome (4.81 Mbp) of any described member of the family Planctomycetaceae. The analysis of genome-encoded features suggests a metabolism better adapted to the degradation of polysaccharides rather than of lignocellulose-derived aromatic compounds. The collected data justifies the delineation of the novel isolates from the sole species in the genus, Planctomicrobium piriforme. The four isolates belong to four separate novel species, for which we introduce the names Planctomicrobium limosum sp. nov., Planctomicrobium stercoris sp. nov., Planctomicrobium aquicomposti sp. nov. and Planctomicrobium mucosum sp. nov. The novel taxa are represented by the following isolates as respective type strains: SH527T (= CECT 30937T = KCTC 102136T), SH661T (= DSM 116760T = KCTC 102128T), SH664T (= DSM 116388T = KCTC 102081T) and SH668T (= DSM 116585T = KCTC 102080T).