title: North-Seeking Magnetotactic Gammaproteobacteria in the Southern Hemisphere.
abstract: Magnetotactic bacteria (MTB) comprise a phylogenetically diverse group of prokaryotes capable of orienting and navigating along magnetic field lines. Under oxic conditions, MTB in natural environments in the Northern Hemisphere generally display north-seeking (NS) polarity, swimming parallel to the Earth's magnetic field lines, while those in the Southern Hemisphere generally swim antiparallel to magnetic field lines (south-seeking [SS] polarity). Here, we report a population of an uncultured, monotrichously flagellated, and vibrioid MTB collected from a brackish lagoon in Brazil in the Southern Hemisphere that consistently exhibits NS polarity. Cells of this organism were mainly located below the oxic-anoxic interface (OAI), suggesting it is capable of some type of anaerobic metabolism. Magnetosome crystalline habit and composition were consistent with elongated prismatic magnetite (Fe3O4) particles. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that this organism belongs to a distinct clade of the Gammaproteobacteria class. The presence of NS MTB in the Southern Hemisphere and the previously reported finding of SS MTB in the Northern Hemisphere reinforce the idea that magnetotaxis is more complex than we currently understand and may be modulated by factors other than O2 concentration and redox gradients in sediments and water columns.
  
  
  
  Magnetotaxis is a navigational mechanism used by magnetotactic bacteria to move along geomagnetic field lines and find an optimal position in chemically stratified sediments. For that, magnetotactic bacteria swim parallel to the geomagnetic field lines under oxic conditions in the Northern Hemisphere, whereas those in the Southern Hemisphere swim antiparallel to magnetic field lines. A population of uncultured vibrioid magnetotactic bacteria was discovered in a brackish lagoon in the Southern Hemisphere that consistently swim northward, i.e., the opposite of the overwhelming majority of other Southern Hemisphere magnetotactic bacteria. This finding supports the idea that magnetotaxis is more complex than previously thought.
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Pedro
authors.initials: P
authors.lastname: Leão
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Lia C R S
authors.initials: LC
authors.lastname: Teixeira
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Jefferson
authors.initials: J
authors.lastname: Cypriano
authors.affiliation: Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Marcos
authors.initials: M
authors.lastname: Farina
authors.affiliation: Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Abreu
authors.affiliation: School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, Nevada, 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, Rio de Janeiro, Brazil ulins@micro.ufrj.br.
authors.forename: Ulysses
authors.initials: U
authors.lastname: Lins
mesh_terms: D000693:Anaerobiosis; D001938:Brazil; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D020563:Gammaproteobacteria / Q000737:chemistry / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D008124:Locomotion; D008280:Magnetics; D055944:Magnetosomes; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D014871:Water Microbiology
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S