title: Remarkable diversity of phototrophic purple bacteria in a permanently frozen Antarctic lake.
abstract: Although anoxygenic photosynthesis is thought to play an important role in the primary productivity of permanently frozen lakes in the Antarctic dry valleys, the bacterial communities responsible for this metabolism remain uncharacterized. Here we report the composition and activity of phototrophic purple bacteria in Lake Fryxell, Antarctica, as determined by analysis of a photosynthesis-specific gene, pufM. The results revealed an extensive diversity and highly stratified distribution of purple nonsulfur bacteria in Lake Fryxell and showed which phylotypes produced pufM transcripts in situ. Enrichment cultures for purple bacteria yielded two morphotypes, each with a pufM signature identical to signatures detected by environmental screening. The isolates also contained gas vesicles, buoyancy structures previously unknown in purple nonsulfur bacteria, that may be necessary for these organisms to position themselves at specific depths within the nearly freezing water column.
authors.affiliation: Department of Microbiology, Southern Illinois University, Carbondale, Illinois 62901-6508, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Karr
authors.forename: W Matthew
authors.initials: WM
authors.lastname: Sattley
authors.forename: Deborah O
authors.initials: DO
authors.lastname: Jung
authors.forename: Michael T
authors.initials: MT
authors.lastname: Madigan
authors.forename: Laurie A
authors.initials: LA
authors.lastname: Achenbach
mesh_terms: D000864:Antarctic Regions; D001419:Bacteria / Q000302:isolation & purification*; D001426:Bacterial Proteins; D005615:Freezing; D005618:Fresh Water / Q000382:microbiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D016133:Polymerase Chain Reaction; D020560:Proteobacteria / Q000302:isolation & purification*; D012333:RNA, Messenger / Q000032:analysis
chemical_list: D001426:Bacterial Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C098543:PufM protein, Bacteria; D012333:RNA, Messenger