Diversity and functional activity of cyanobacteria from King George and Deception Islands, South Shetland Archipelago, Antarctica.

Author(s)

Diego Bonaldo Genuario

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB)
• Defense date: 2014-09-19

Examining board members

Marli de Fatima Fiore; Pio Colepicolo Neto; Itamar Soares de Melo; Regina Teresa Rosim Monteiro

• Advisor: Marli de Fatima Fiore

Abstract

Cyanobacteria are characterized as the most abundant group of photoautotrophic microorganisms found in the polar regions. Members of this group perform oxygenic photosynthesis and many of them can also fix atmospheric nitrogen. Investigations on the cyanobacterial community have been made mainly applying microscopic observations of environmental samples. Cyanobacterial isolation, physiological studies and cultureindependent analyses are scarce. In this study the cyanobacterial community from two oceanic islands in Antarctica was investigated using culture-dependent and independent approaches. Also, the ecological role of this group of microorganisms as nitrogen-fixing organisms and the genetic potential for biosynthesis of natural products were evaluated. Sixty-eight cyanobacterial strains were isolated from different environmental samples. They belong to the orders Chroococcales, Pseudanabaenales, Oscillatoriales and Nostocales, families Xenococcaceae, Dermocarpellaceae, Pseudanabaenaceae, Oscillatoriaceae, Nostocaceae, Microchaetaceae and Rivulariaceae. Phylogenetic analyses based on 16S rRNA sequences of these cyanobacteria revealed the existence of groups: exclusively formed by sequence of strain isolated in this work; intermixed sequences from this and other studies developed in other Antarctic regions; and sequences originated from different regions of the world. Fortyone cultured strains possess the nifH gene fragment encoding the nitrogenase enzyme complex, which is related to the biological nitrogen fixation (BNF). Unicellular (Chroococcales), homocytous (Pseudanabaenales and Oscillatoriales) and heterocytous forms (Nostocales) showed genetic potential for BNF, and 18 of them were subjected to acetylene reduction assay (ARA) coupled with a sensitive laser photoacoustic ethylene detector. All strains tested exhibited some nitrogenase activity in response to different concentrations of oxygen and or irradiance under different temperature conditions. Phylogenetically, the nifH gene sequences showed three distinct grouping patterns that may be related to the evolutionary events involved in the distribution and or maintenance of this gene. The presence of genes and or intergenic regions in these cyanobacterial strains underscores the genetic potential of them to synthesize natural products with biotechnological interest.The abundance of nifH gene copies related to cyanobacteria in biofilm samples highlights the importance of this group of microorganisms as suppliers of N reduced forms for Antarctic environment. The analysis of the cyanobacteria community revealed by 16S rRNA sequencing of metagenomic DNA showed a predominance of OTUs related to orders Nostocales, Oscillatoriales and Pseudanabaenales, families Pseudanabaenaceae, Phormidiaceae, Nostocaceae and Rivulariaceae. The phylogenetic tree containing Antarctic sequences from cultivated and uncultivated cyanobacteria showed that only part of this community in biofilms has been accessed by isolation, indicating the complementarity between the two approaches used in the analysis of cyanobacterial community (AU)

• FAPESP's process: 10/00321-3 - Diversity and functional activity of cyanobacteria isolated from South Shetlands Archipelago, Antarctic Continent
• Grantee: Diego Bonaldo Genuário
• Support Opportunities: Scholarships in Brazil - Doctorate