Resumo

The phylum Cyanobacteria belongs to the Bacteria domain, being widely distributed in a vast range of natural environments. These microrganisms occur in unicellular, filamentous or branched filamentous forms, usually surrounded by a mucilaginous matrix or sheath. These extracellular materials have been characterized as a nutritional source that favor the growth and establishment of mutualistic interaction with other organisms (mainly heterotrophic bacteria). However, the microbial community structure associated with diverse cultivated cyanobacteria in highly specific environmental conditions is almost unknown. Therefore, the aim of this study was to show the shifts in the structure and composition of bacterial community associated to several genera of cyanobacteria. In this context, thirty six strains from eight cyanobacterial genera, isolated from six different environments, were randomly selected from a cyanobacterial culture collection belonging to the Cellular and Molecular Biology Laboratory CENA/USP. The DNA of the microbial community associated to each strain was extracted from cells suspensions grown into liquid medium BG11. The bacterial community structure was further depicted by DGGE (Denaturing gradient gel eletrophoresis). The results demonstrated a high diversity of bacterial assemblages associated to each individual cyanobacteria strain. A cluster analysis indicated that the bacterial community majorly differs due to the phylogenetic affiliation of cyanobacteria, as observed by the formation of separated clusters for isolates identified as Microcystis aeruginosa, or the formation of a specific clade of the bacterial community profiles associated to Leptolyngbya sp. In counterpart, no clustering profiles from isolates obtained from the same environments was observed, indicating that the environment has a minor role, when compared to cyanobacteria taxonomy, as a driver on the assemblage of associated bacterial communities. These results highlights some insights on the close relationship of the bacterial community associated with cyanobacteria, supporting the idea that cyanobacteria can structure microbial communities, what possibly indicate a role of such organisms in the cyanobacteria metabolism.