Twelve metagenome-assembled genomes representing this species were assembled from sequence data obtained from samples taken from lakes Björntjärnen (Sweden), Alinen Mustajärvi (Finland), Keskinen Rajajärvi (Finland), and Valkea Kotinen (Finland). Completeness estimates for genomes, as determined by CheckM (v1.1.3; ‘lineage_wf’), are 69.50–97.53%, with 1.62–4.21% estimated contamination. Genome assemblies range between 3.06–4.56 Mbp in size, comprising 100–973 contigs, with a G+C content of 67.37%–67.58%. Estimated complete genome sizes from CheckM range between 4.40–4.68 Mbp. ANI and AAI values between these genomes are 97.8%–100% and 99.3–100%, respectively, while such pairwise comparisons to closely related taxa are below 81.0% and 78.8%, respectively. Phylogenomic analysis of 72 concatenated 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 sp903872075”.
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); for thiosulfate oxidation using thiosulfate dehydrogenase TsdA; for biosynthesis and degradation of polyphosphate and polyhydroxybutyrate; and for high-affinity PstABCS phosphate and PhnDEC phosphonate transporters. In addition, they have genetic potential for photoautotrophy, containing genes for bacteriochlorophyll synthesis, 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 Umea_bin-04329^Ts, available under the NCBI WGS assembly accession number GCA_903872075.1^Ts (BioProject ID PRJEB38681), recovered as a metagenome coassembly from samples taken in autumn of 2018 from the stratified lakes Björntjärnen (lat. 64.12, long. 18.78) and Nästjärnen (lat. 64.15, long. 18.80), both in Umeå, Sweden (metagenomes ERS4600559–565 and ERS4600568–570). It comprises 100 contigs with a total of 4,361,582 bp, and has an estimated completeness of 95.32% and contamination of 1.62%.