Metagenomic assessment of the microbial community associated to the Amazonian dark earth cyanobacterium Nostoc SP. CENA67

Abstract

Nostoc is a cyanobacterial genus with worldwide distribution and ecological, evolutionary, biogeochemical, biotechnological, and ecotoxicological importance. Nostoc spp. are the cyanobacteria most commonly found in symbiotic relationships with other organisms. As a consequence of tight heterotrophic bacteria-cyanobacteria interactions, non-axenic cultures are usually achieved in cyanobacteria isolation. Previously, as part of the project "Genomic sequencing of the cyanobacterium Nostoc sp. CENA67 and annotation of genes encoding secondary metabolites" (FAPESP nº 2011/08092-6), the genome sequencing of the strain CENA67, isolated from Amazonian dark earth soil, revealed a considerable number of nucleotide sequences from other micro-organisms in its culture. This result presents an interesting opportunity for carrying out both genomic and metagenomic studies. Therefore, the aim of this research proposal is to analyze metagenomic sequences from microorganisms associated to Nostoc sp. CENA67 and to evaluate their interactions. For this purpose, cells from Nostoc sp. CENA67 culture will be grown in liquid AA/4 medium for three weeks and used for DNA extraction. The DNA will be used for metagenomic sequencing in Illumina MiSeq. The resulting data set will be preprocessed for the elimination of low quality sequences and contamination and used for metagenome assembly. The assembled contigs will be annotated and binning will be carried out to group similar sequences. After separation of the cyanobacterium genome, diversity analyses will be performed on the associated community contigs, as well as functional analyses comparing cyanobacterium and community sequences. It is expected that the study of both the genome of the Nostoc sp. CENA67 strain and the metagenome of its associated community uncovers a better understanding of the ecological role of cyanobacteria in natural environments and their interactions with other micro-organisms. (AU)