title: The first complete genome sequences of the acI lineage, the most abundant freshwater Actinobacteria, obtained by whole-genome-amplification of dilution-to-extinction cultures.
abstract: The acI lineage of the phylum Actinobacteria is the most abundant bacterial group in most freshwater lakes. However, due to difficulties in laboratory cultivation, only two mixed cultures and some incomplete single-amplified or metagenome-derived genomes have been reported for the lineage. Here, we report the initial cultivation and complete genome sequences of four novel strains of the acI lineage from the tribes acI-A1, -A4, -A7, and -C1. The acI strains, initially isolated by dilution-to-extinction culturing, eventually failed to be maintained as axenic cultures. However, the first complete genomes of the acI lineage were successfully obtained from these initial cultures through whole genome amplification applied to more than hundreds of cultured acI cells. The genome sequences exhibited features of genome streamlining and showed that the strains are aerobic chemoheterotrophs sharing central metabolic pathways, with some differences among tribes that may underlie niche diversification within the acI lineage. Actinorhodopsin was found in all strains, but retinal biosynthesis was complete in only A1 and A4 tribes.
authors.affiliation: Department of Biological Sciences, Inha University, Incheon 22212, Republic of Korea.
authors.forename: Ilnam
authors.initials: I
authors.lastname: Kang
authors.affiliation: Department of Biological Sciences, Inha University, Incheon 22212, Republic of Korea.
authors.forename: Suhyun
authors.initials: S
authors.lastname: Kim
authors.affiliation: Department of Biological Sciences, Inha University, Incheon 22212, Republic of Korea.
authors.forename: Md Rashedul
authors.initials: MR
authors.lastname: Islam
authors.affiliation: Department of Biological Sciences, Inha University, Incheon 22212, Republic of Korea.
authors.forename: Jang-Cheon
authors.initials: JC
authors.lastname: Cho
mesh_terms: D039903:Actinobacteria / Q000235:genetics* / Q000302:isolation & purification; D001343:Autophagy; D001426:Bacterial Proteins / Q000235:genetics; D001483:Base Sequence; D053898:Biosynthetic Pathways / Q000235:genetics; D005618:Fresh Water; D005784:Gene Amplification; D016680:Genome, Bacterial; D058977:Molecular Sequence Annotation; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins