title: Speciation and ecological success in dimly lit waters: horizontal gene transfer in a green sulfur bacteria bloom unveiled by metagenomic assembly.
abstract: A natural planktonic bloom of a brown-pigmented photosynthetic green sulfur bacteria (GSB) from the disphotic zone of karstic Lake Banyoles (NE Spain) was studied as a natural enrichment culture from which a nearly complete genome was obtained after metagenomic assembly. We showed in situ a case where horizontal gene transfer (HGT) explained the ecological success of a natural population unveiling ecosystem-specific adaptations. The uncultured brown-pigmented GSB was 99.7% identical in the 16S rRNA gene sequence to its green-pigmented cultured counterpart Chlorobium luteolum DSM 273T. Several differences were detected for ferrous iron acquisition potential, ATP synthesis and gas vesicle formation, although the most striking trait was related to pigment biosynthesis strategy. Chl. luteolum DSM 273Tsynthesizes bacteriochlorophyll (BChl) c, whereas Chl. luteolum CIII incorporated by HGT a 18-kbp cluster with the genes needed for BChl e and specific carotenoids biosynthesis that provided ecophysiological advantages to successfully colonize the dimly lit waters. We also genomically characterized what we believe to be the first described GSB phage, which based on the metagenomic coverage was likely in an active state of lytic infection. Overall, we observed spread HGT and we unveiled clear evidence for virus-mediated HGT in a natural population of photosynthetic GSB.
authors.affiliation: Integrative Freshwater Ecology Group, Centro de Estudios Avanzados de Blanes, CEAB-CSIC. Accés Cala Sant Francesc, Girona, Spain.
authors.forename: Tomàs
authors.initials: T
authors.lastname: Llorens-Marès
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, State College, PA USA.
authors.forename: Zhenfeng
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, CA, USA.
authors.forename: Lisa Zeigler
authors.initials: LZ
authors.lastname: Allen
authors.affiliation: Informatics Group, J. Craig Venter Institute, Rockville, MD, USA.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Rusch
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, CA, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Craig
authors.affiliation: Microbial and Environmental Genomics, J. Craig Venter Institute, San Diego, CA, USA.
authors.forename: Chris L
authors.initials: CL
authors.lastname: Dupont
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, State College, PA USA.|Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, USA.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Bryant
authors.affiliation: Integrative Freshwater Ecology Group, Centro de Estudios Avanzados de Blanes, CEAB-CSIC. Accés Cala Sant Francesc, Girona, Spain.
authors.forename: Emilio O
authors.initials: EO
authors.lastname: Casamayor
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001429:Bacteriochlorophylls / Q000378:metabolism; D041883:Chlorobium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017753:Ecosystem; D022761:Gene Transfer, Horizontal; D060106:Lakes / Q000382:microbiology*; D056186:Metagenomics; D010788:Photosynthesis; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013030:Spain; D013455:Sulfur / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D012336:RNA, Ribosomal, 16S; C120930:bacteriochlorophyll e; C002084:bacteriochlorophyll c; D013455:Sulfur