An untargeted cultivation approach revealed Pseudogemmatithrix spongiicola gen. nov., sp. nov., and sheds light on the gemmatimonadotal mode of cell division: binary fission.

Members of the phylum Gemmatimonadota can account for up to 10% of the phylogenetic diversity in bacterial communities. However, a detailed investigation of their cell biology and ecological roles is restricted by currently only six characterized species. By combining low-nutrient media, empirically determined inoculation volumes and long incubation times in a 96-well plate cultivation platform, we isolated two strains from a limnic sponge that belong to this under-studied phylum. The characterization suggests that the two closely related strains constitute a novel species of a novel genus, for which we introduce the name Pseudogemmatithrix spongiicola. The here demonstrated isolation of novel members from an under-studied bacterial phylum substantiates that the cultivation platform can provide access to axenic bacterial cultures from various environmental samples. Similar to previously described members of the phylum, the novel isolates form spherical appendages at the cell poles that were believed to be daughter cells resulting from asymmetric cell division by budding. However, time-lapse microscopy experiments and quantitative image analysis showed that the spherical appendages never grew or divided. Although the role of these spherical cells remains enigmatic, our data suggests that cells of the phylum Gemmatimonadota divide via FtsZ-based binary fission with different division plane localization patterns than in other bacterial phyla.

Planctoellipticum variicoloris gen. nov., sp. nov., a novel member of the family Planctomycetaceae isolated from wastewater of the aeration lagoon of a sugar processing plant in Northern Germany.

In the present study, we characterise a strain isolated from the wastewater aeration lagoon of a sugar processing plant in Schleswig (Northern Germany) by Heinz Schlesner. As a pioneer in planctomycetal research, he isolated numerous strains belonging to the phylum Planctomycetota from aquatic habitats around the world. Phylogenetic analyses show that strain SH412T belongs to the family Planctomycetaceae and shares with 91.6% the highest 16S rRNA gene sequence similarity with Planctopirus limnophila DSM 3776T. Its genome has a length of 7.3 Mb and a G + C content of 63.6%. Optimal growth of strain SH412T occurs at pH 7.0-7.5 and 28 °C with its pigmentation depending on sunlight exposure. Strain SH412T reproduces by polar asymmetric division ("budding") and forms ovoid cells. The cell size determination was performed using a semi-automatic pipeline, which we first evaluated with the model species P. limnophila and then applied to strain SH412T. Furthermore, the data acquired during time-lapse analyses suggests a lifestyle switch from flagellated daughter cells to non-flagellated mother cells in the subsequent cycle. Based on our data, we suggest that strain SH412T represents a novel species within a novel genus, for which we propose the name Planctoellipticum variicoloris gen. nov., sp. nov., with strain SH412T (= CECT 30430T = STH00996T, the STH number refers to the Jena Microbial Resource Collection JMRC) as the type strain of the new species.

Gemmata algarum, a Novel Planctomycete Isolated from an Algal Mat, Displays Antimicrobial Activity.

Axenic cultures of two strains, JC673T and JC717, both belonging to the phylum Planctomycetota, were isolated from distinct geographical locations in India. Strain JC673T was obtained from algal mats of a wetland situated in the state of Kerala, India, while strain JC717 originated from the Central Marine Fisheries Research Institute (CMFRI), state of Tamil Nadu, India. The two strains share 99.9% 16S rRNA gene sequence similarity and are most closely related to Gemmata obscuriglobus UQM 2246T (99.3% 16S rRNA gene sequence identity). The newly isolated strains are Gram-negative, grow aerobically and tolerate up to 4% (w/v) NaCl and a pH of up to 9.0. Cells are spherical and form pink-pigmented colonies. The respiratory quinone is MK-6. Major fatty acids are C18:0, C16:1ω5c and C16:0. Polar lipids include phosphatidylcholine, phosphatidylethanolamine, several unidentified amino lipids, unidentified phospholipids, additional unidentified lipids, and an unidentified choline lipid. The polyamine spermidine is produced by the two strains. The strains have a genome size of about 8.2 Mb with a DNA G+C content of 67.6%. Solvent-based culture extracts of the isolates showed antimicrobial activity against three bacterial test strains. Their phylogenetic position along with differences in morphological, physiological, and genomic features support the classification as a new species of the genus Gemmata, for which we propose the name Gemmata algarum sp. nov. Strain JC673T (=KCTC 72851T = NBRC 114340T) and JC717 are the type and non-type strain of the new species, respectively.