Relations phylogénétiques de souches cyanobactériennes non axéniques sur base de l'analyse du RNA ribosomique 16S

Abstract

In order to determine the nearly complete 16S rRNA gene sequences of cyanobacteria originating from nonaxenic cultures, a cyanobacterium-specific oligonucleotide probe was developed to distinguish polymerase chain reaction (PCR) products of the cyanobacterial rRNA operons from those resulting from amplification of contaminating bacteria. Using this screening method the 16S rRNA genes of four nonaxenic filamentous cyanobacterial strains belonging to the genera Leptolyngbya and OscitIatoria were cloned and sequenced. For the genus Leptolyngbya, the 16S rRNA sequence of the axenic strain PCC 73110 was also determined. Phylogenetic trees were constructed based on complete and partial sequences. The results show that the strains Leptolyngbya Jbveolarum Kom~rek 1964/112, Leptolyngbya sp. VRUC 135 Albertano t985/1, and LeptoIyngbya boryanum PCC 73110 belong to the same cluster. Strain Oscillatoria cf. corallinae SAG 8.92, which contains the rare photosynthetic pigment CUphycoerythrin, is not closely related to other CUphycoerythrin- containing cyanobacteria. Oscillatoria agardhii CYA 18, which is a representative of planktonic Oscillatoria species that form toxic blooms in Norwegian inland waters, has no close relatives in the tree