Oscillatoria duplisecta ETS-06

Oscillatoria duplisecta ETS-06 is a filamentous cyanobacterium described by Moro and collaborators in 2007. It shows morphological characteristics identical to those observed as early as 1817 by Pollini in the Euganean thermal springs. At the time, Pollini described an organism he named Conferva duplisecta, which was later renamed Oscillatoria duplisecta by Trevisan in 1871. According to Moro et al., the ETS-06 strain matches the original description precisely, particularly in the morphology of the cell filaments (trichomes).

 

The trichomes of ETS-06 are several centimeters long, straight, cylindrical, unbranched, with rounded ends, and visible to the naked eye due to their green-brown coloration. They are surrounded by a very thin sheath. The cells making up the trichomes are wider than they are long, as shown in Figure 1.

 

Figure 1. Optical microscope images of Oscillatoria duplisecta ETS-06. Scale bar: 100 µm.

 

The strain was isolated from basins containing thermal muds, with water temperatures during maturation of around 40 °C. Genetic analyses revealed a similarity to a group of cyanobacteria isolated from river waters in Thailand. Despite this high similarity, morphological and ecological differences led Moro and Andreoli to consider ETS-06 a distinct species, officially assigning it the name Oscillatoria duplisecta (Pollini) Moro et Andreoli. Its genetic sequence (16S rDNA gene) is registered in international databases (AM398647).

 

The species was also detected using next-generation sequencing techniques (Gris et al. 2020), showing high abundance in clays from thermal ponds and pools, but it was absent in mature thermal muds.

 

In 2023, the species was re-isolated by Dr. Raffaella M. Zampieri at the Department of Biology, University of Padua (in the laboratory of Prof. Nicoletta La Rocca). However, the species did not survive in culture and, for now, can only be observed in its natural environment.

 

 

This record is the result of a long-standing collaboration with the Department of Biology of the University of Padua and is part of the Digital Archive of the Pietro d’Abano Thermal Studies Center, created with the support of the Municipality of Montegrotto Terme (Municipal Council Resolution No. 121 of 17-07-2025).