Ultramicrobacterial Diversity in the Plankton of Lake Baikal

This is the first report on recovery of 82 genomes of ultramicrobacteria, ultra-small cells with genome sizes from 0.58 to 3.2 Mb, from femtobacterioplankton of Lake Baikal by genetic and bioinformatic methods. Ultramicrobacteria belonged to six phyla dominated by the Actinomycetota (35), Pseudomonadota (26), and Bacteroidota (13) genomes, with smaller numbers of the Patescibacteria (Saccharimonadia) (3), Verrucomicrobiota (3), and Chloroflexota (2) genomes. Actinobacteria Planktophila spp. and proteobacteria Polynucleobacter spp. were the most numerous ultramicrobacterial species.