Culture-independent characterization of novel psychrophilic magnetotactic cocci from Antarctic marine sediments

Fernanda Abreu, Ana Carolina, V. Araujo, Pedro Leao, Karen Tavares Silva, Fabiola Marques de Carvalho, Oberdan de Lima Cunha, Luiz Gonzaga Almeida, Corey Geurink, Marcos Farina, Daniel Rodelli, Luigi Jovane, Vivian H. Pellizari, Ana Tereza de Vasconcelos, Dennis A. Bazylinski, Ulysses Lins*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

18 Citations (Scopus)

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 (628230S 588270W) 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 degrees 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.

Original languageEnglish
Pages (from-to)4426-4441
Number of pages16
JournalEnvironmental Microbiology
Volume18
Issue number12
DOIs
Publication statusPublished - Dec-2016
Externally publishedYes

Keywords

  • CANDIDATUS MAGNETOGLOBUS MULTICELLULARIS
  • ISOTHERMAL REMANENT MAGNETIZATION
  • TARGETED OLIGONUCLEOTIDE PROBES
  • BACTERIAL COMMUNITIES
  • MAGNETOSOME FORMATION
  • AQUATIC ENVIRONMENTS
  • HYPERSALINE LAGOON
  • ACQUISITION CURVES
  • GEOMAGNETIC-FIELDS
  • PROKARYOTE

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