Polyphasic characterization of a thermo-tolerant filamentous cyanobacterium isolated from the Euganean thermal muds (Padova, Italy)

In this paper we report a morphological, ultrastructural, biochemical and molecular (16S rRNA, 16S–23S ITS, rbcL and rpoC1 gene sequencing) survey on a very thin, non-heterocystous, filamentous cyanobacterium, isolated from mats covering several mud maturation tanks of the Euganean Thermal District, at temperatures ranging from 26 to 59°C. Denaturing gradient gel electrophoresis results, obtained using cyanobacterial primers targeting the 16S rRNA gene, confirmed that this cyanobacterium is one of the commonest taxa growing in the mud tanks. Comparison with Geitlerinema sp. PCC 8501 (=Phormidium laminosum Gomont ex Gomont strain OH-1-p Cl 1), a thin thermobiotic species isolated from hot springs of Oregon and morphologically similar to our isolate, led us to hypothesize that the Euganean and PCC 8501 strains are either very similar sister species or ecotypes of the same species in a yet to be defined clade, clearly distinct within the paraphyletic Leptolyngbya group.