Four metagenome-assembled genomes representing this species were assembled from sequence data obtained from samples taken from a lake in Kiruna (Sweden), referred to as Ki2, Swedish lake code: 754378-169136. Completeness estimates for genomes, as determined by CheckM (v1.1.3; ‘lineage_wf’), are 94.86%–96.97%, with 1.94%–4.47% estimated contamination. Genomes assemblies range between 4.57–4.64 Mbp, comprising 279–357 contigs, with a G+C content of 68.83%–68.84%. Estimated complete genome sizes from CheckM range between 4.73–4.81 bp. ANI and AAI values between these genomes are 99.9%–100% and 99.9–100%, respectively, while such pairwise comparisons to closely related taxa are below 81.0% and 78.8%, respectively. Phylogenomic analysis of 72 conserved alphaproteobacterial single-copy genes places this species in the genus Acaudatibacter, in the family Caulobacteraceae. The species corresponds to GTDB taxonomy (R220) species “Palsa-881 sp903923135”.
Genomes lack multiple genes for flagellar motility, chemotaxis, holdfast adhesin production, and for the caulobacterial obligate dimorphic cell developmental program. Genomes contain genes for type IV tight-adhesion pili; for carotenoid pigment production; for complete biosynthesis pathways of all standard amino acids; for aerobic respiration using cytochrome c oxidases cytochrome aa3 (coxABC) and cytochrome cbb3 (ccoNOPQ), and for ubiquinol oxidase cytochrome bd (cydA; partial genetic potential); for biosynthesis and degradation of polyphosphate, polyhydroxybutyrate, and starch/glycogen; for the high-affinity PstABCS phosphate, PhnDEC phosphonate, and SsuABC sulfonate transporters. In addition, they have genetic potential for photoautotrophy, containing genes for type II anoxygenic photosynthesis using a light-harvesting II (LH2) complex and a reaction center–light-harvesting I supercomplex (RC–LH1), as well as carbon fixation using the Calvin-Benson-Bassham (CBB) cycle, including the accessory genes for red-type RuBisCO activase (cbbX) and XuBP phosphatase (cbbY). The species has been detected in both oxic and anoxic strata of stratified freshwater bodies in Finland and Sweden. Likely a psychrophilic/mesophilic facultative anaerobe, based on its genetic repertoire and environmental distribution.
The proposed nomenclatural type for the species is the genome Kiruna2_bin-0871^Ts, available under the NCBI WGS assembly accession number GCA_903923135.1^Ts (BioProject ID PRJEB38681), recovered as a coassembly from samples taken 27 July 2018 from a stratified lake in Kiruna, Sweden (lat. 67.92, long. 20.37; from the metagenomes ERS4600421–424). It comprises 279 contigs with a total of 4,636,946 bp, and has an estimated completeness of 96.47% and contamination of 2.20%.