title: Globally distributed uncultivated oceanic N2-fixing cyanobacteria lack oxygenic photosystem II.
abstract: Biological nitrogen (N2) fixation is important in controlling biological productivity and carbon flux in the oceans. Unicellular N2-fixing cyanobacteria have only recently been discovered and are widely distributed in tropical and subtropical seas. Metagenomic analysis of flow cytometry-sorted cells shows that unicellular N2-fixing cyanobacteria in "group A" (UCYN-A) lack genes for the oxygen-evolving photosystem II and for carbon fixation, which has implications for oceanic carbon and nitrogen cycling and raises questions regarding the evolution of photosynthesis and N2 fixation on Earth.
authors.affiliation: Ocean Sciences Department, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA. zehrj@ucsc.edu
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Zehr
authors.forename: Shellie R
authors.initials: SR
authors.lastname: Bench
authors.forename: Brandon J
authors.initials: BJ
authors.lastname: Carter
authors.forename: Ian
authors.initials: I
authors.lastname: Hewson
authors.forename: Faheem
authors.initials: F
authors.lastname: Niazi
authors.forename: Tuo
authors.initials: T
authors.lastname: Shi
authors.forename: H James
authors.initials: HJ
authors.lastname: Tripp
authors.forename: Jason P
authors.initials: JP
authors.lastname: Affourtit
mesh_terms: D000458:Cyanobacteria / Q000166:cytology / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D019143:Evolution, Molecular; D005434:Flow Cytometry; D005798:Genes, Bacterial; D020459:Genes, rRNA; D016680:Genome, Bacterial; D023281:Genomics / Q000379:methods; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics; D010140:Pacific Ocean; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D012623:Seawater / Q000382:microbiology*
chemical_list: D045332:Photosystem II Protein Complex; D010088:Oxidoreductases; C029130:nitrogenase reductase