Genome sequence and characterization of a freshwater photoarsenotroph, Cereibacter azotoformans strain ORIO, isolated from sediments capable of cyclic light-dark arsenic oxidation and reduction

A freshwater photosynthetic arsenite-oxidizing bacterium, Cereibacter azotoformans strain ORIO, was isolated from Owens River, CA, USA.  The waters from Owens River are elevated in arsenic and serve as the headwaters to the Los Angeles Aqueduct.  The complete genome sequence of strain ORIO is 4.8 Mb genome (68 % G+C content) and comprises 2 chromosomes and 6 plasmids. Taxonomic analysis placed ORIO within the Cereibacter genus (formerly Rhodobacter). The ORIO genome contains arxB2AB1CD (encoding an arsenite oxidase), arxXSR (regulators), and several ars arsenic resistance genes all co-localized on a 136 kb plasmid, named pORIO3. Phylogenetic analysis of ArxA, the molybdenum-containing arsenite oxidase catalytic subunit, demonstrated photoarsenotrophy is likely to occur within members of the Alphaproteobacteria. ORIO is a mixotroph, oxidizes arsenite to arsenate photoheterotrophically, and expresses arxA in cultures grown with arsenite. Further ecophysiology studies with Owens River sediment demonstrated the interconversion of arsenite and arsenate was dependent on light-dark cycling. arxA and arrA (arsenate respiratory reductase) genes were detected in the light-dark cycled sediment metagenomes suggesting syntrophic interactions among arsenotrophs. This work establishes Cereibacter azotoformans str. ORIO as a new model organism for studying photoarsenotrophy and light-dark arsenic biogeochemical cycling.

Methods
The published paper describes data generation and collection.  Briefly the methods include:

Enrichment cultring of anoxygenic photosynthetic microbes
Growth curve analyses
Arsenic analyses by HPLC-ICPMS (Thermo X-Series2 ICP-MS and Hamilton PRP-X-100 HPLC column for arsenic speciation)
Genomic DNA sequencing by MiSeq and Oxford Nanopore
Metagenomic DNA sequencing by Oxford Nanopore