Type species is Hahnella lacustris MsE-M47 (GCA_965194655.1), isolated from 5 m depth from Lake Most, Czechia (date: 2019-10-01), via high-throughput dilution to extinction cultivation. MsE-M47 has a genome size of 2.2 Mbp with a genomic GC content of 59.2%, contains 3 rRNA genes and 42 tRNAs. The genome is complete, consisting of a circular chromosome. The genome is complete, consisting of a circular chromosome. The genome contains genes encoding anoxygenic aerobic phototrophy (pufABLM) and the complete Calvin cycle for carbon fixation via RuBisCO. Genes for flagellar assembly and chemotaxis were annotated. Pathways for taurine degradation, thiosulfate oxidation (Sox pathway), glycolate oxidation, and the biosynthesis of all amino acids were predicted. Further, pathways for riboflavin, NAD, pantothenate, coenzyme A, biotin, THF, and heme biosynthesis were identified. The closest cultivated relative is the undescribed Burkholderiales bacterium LSUCC0115 (GCA_009646425.1), with an average amino acid identity of 67% and average nucleotide identity of 70.6% and another newly proposed species, Hahnella aquatica MiE-11 (GCA_965194505.1), with an AAI of 65.8% and an ANI of 70.4%. The closest validly described relative is Limnobacter thiooxidans CS-K2 (GCF_036323495.1) with an AAI of 53.55% and an ANI of 66.44%. Current GTDB classification (R220): d__Bacteria; p__Pseudomonadota; c__Gammaproteobacteria; o__Burkholderiales; f__Burkholderiaceae_A; g__UBA2463; s__UBA2463 sp945862985.