title: Culture-independent characterization of novel psychrophilic magnetotactic cocci from Antarctic marine sediments.
abstract: Magnetotactic bacteria (MTB) are a heterogeneous group of ubiquitous aquatic microorganisms capable of biomineralizing nano-sized, membrane-bound, magnetic iron-rich mineral particles called magnetosomes. MTB are found in chemically-stratified aquatic sediments and/or water columns with a wide range of salinities, moderate to high temperatures, and pH varying from neutral to strongly alkaline. MTB from very cold environments have not been investigated to any great degree and here we characterize MTB from the low temperature Antarctic maritime region. Sediment samples were collected at nine sampling sites within Admiralty Bay, King George Island (62°23'S 58°27'W) from 2009 to 2013. Samples from five sites contained MTB and those from two of these sites contained large number of magnetotactic cocci that were studied using electron microscopy and molecular techniques. The magnetotactic cocci contained magnetosomes either arranged as two or four chains or as a disorganized cluster. The crystalline habit and composition of all magnetosomes analyzed with high-resolution transmission electron microscopy and energy dispersive X-ray microanalysis were consistent with elongated prismatic crystals of magnetite (Fe3O4). The retrieved 16S rRNA gene sequences from magnetically-enriched magnetotactic cocci clustered into three distinct groups affiliated with the Alphaproteobacteria class of the Proteobacteria. Novel sequences of each phylogenetic cluster were confirmed using fluorescent in situ hybridization. Metagenomic data analysis of magnetically-enriched magnetotactic cocci revealed the presence of mam genes and MTB-specific hypothetical protein coding genes. Sequence homology and phylogenetic analysis indicated that predicted proteins are related to those of cultivated alphaproteobacterial MTB. The consistent and continuous low temperature of the sediment where the magnetotactic cocci are present (always below 1°C) suggests that these MTB from maritime Antarctica are psychrophiles. Moreover, similar morphotypes and 16S gene sequences were retrieved from samples collected from different sites from maritime Antarctica for several years suggesting that these new strains of MTB are indigenous members of Antarctic microbiota.
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, RJ, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Abreu
authors.forename: Ana
authors.initials: A
authors.lastname: Carolina
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, RJ, Brazil.
authors.forename: V
authors.initials: V
authors.lastname: Araujo
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, RJ, Brazil.
authors.forename: Pedro
authors.initials: P
authors.lastname: Leão
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, RJ, Brazil.
authors.forename: Karen Tavares
authors.initials: KT
authors.lastname: Silva
authors.affiliation: Laboratório de Bioinformática, Laboratório Nacional de Computação Científica, 25651-070, Petrópolis, RJ, Brazil.
authors.forename: Fabíola Marques de
authors.initials: FM
authors.lastname: Carvalho
authors.affiliation: Laboratório de Bioinformática, Laboratório Nacional de Computação Científica, 25651-070, Petrópolis, RJ, Brazil.
authors.forename: Oberdan de Lima
authors.initials: OL
authors.lastname: Cunha
authors.affiliation: Laboratório de Bioinformática, Laboratório Nacional de Computação Científica, 25651-070, Petrópolis, RJ, Brazil.
authors.forename: Luiz Gonzaga
authors.initials: LG
authors.lastname: Almeida
authors.affiliation: School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV, 89154-4004, USA.
authors.forename: Corey
authors.initials: C
authors.lastname: Geurink
authors.affiliation: Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, RJ, Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
authors.affiliation: Instituto Oceanográfico, Universidade de São Paulo, 05508-900, São Paulo, SP, Brazil.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rodelli
authors.affiliation: Instituto Oceanográfico, Universidade de São Paulo, 05508-900, São Paulo, SP, Brazil.
authors.forename: Luigi
authors.initials: L
authors.lastname: Jovane
authors.affiliation: Instituto Oceanográfico, Universidade de São Paulo, 05508-900, São Paulo, SP, Brazil.
authors.forename: Vivian H
authors.initials: VH
authors.lastname: Pellizari
authors.affiliation: Laboratório de Bioinformática, Laboratório Nacional de Computação Científica, 25651-070, Petrópolis, RJ, Brazil.
authors.forename: Ana Tereza de
authors.initials: AT
authors.lastname: Vasconcelos
authors.affiliation: School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV, 89154-4004, USA.
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Bazylinski
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, 21941-902, Rio de Janeiro, RJ, Brazil.
authors.forename: Ulysses
authors.initials: U
authors.lastname: Lins
mesh_terms: D020561:Alphaproteobacteria / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D000864:Antarctic Regions; D003470:Culture Media / Q000737:chemistry / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology*; D017404:In Situ Hybridization, Fluorescence; D055944:Magnetosomes; D046529:Microscopy, Electron, Transmission; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D054712:Salinity; D012623:Seawater / Q000737:chemistry / Q000382:microbiology*
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S