Type genome is Planktophila dulcis MMS-IIA-65 (GCF_002288225.1), which was isolated via dilution-to-extinction cultivation from Lake Zurich, Switzerland. Curved rods with lengths of 0.44±0.09 μm and diameters of 0.26±0.03 μm. The initial pure culture was lost after a few propagations to fresh medium; no growing culture is available. The initial culture grew well in sterile lake water amended with minimal carbon medium, vitamins and amino acids. Planktophila dulcis MMS-IIA-65 has a genome size of 1.35 Mbp and a genomic GC content of 48.0%. The genome is complete, consisting of a circular chromosome and contains 3 rRNA genes and 40 tRNAs. It is auxotrophic for reduced sulfur sources, betaine, and several vitamins (B1, B5, B7, B12) and possesses rhodopsins. Basis for the assignment is a phylogenomic tree of 476 concatenated protein sequences, phylogenetic analysis of 16S rRNA, 23S rRNA, and rhodopsin genes, as well as average nucleotide and amino acid identities presented in Neuenschwander et al. (2018, ISMEJ, doi: 10.1038/ismej.2017.156). The closest cultivate relatives are Planktophila rubra IMCC25003 (GCA_002284855) and Planktophila sulfonica MMS-IA-56 (GCF_002288065.1) with average amino acid identities of 89.6 and 89.4%, respectively, and average nucleotide identities of 82.1 and 81.9%, respectively.