Characterization of an intertidal cyanobacterium that constitutes a separate clade together with thermophilic strains

This work reports the characterization of a unicellular cyanobacterium (LEGE 06123) isolated from an intertidal diazotrophic mat at Luz, a rocky beach in southern Portugal. This organism aggregates to form colonies held together by extracellular polymeric substances (EPS). Cells or cell groups are surrounded by a laminated sheath, and division occurs by binary fission, often in irregular planes. Dispersion is achieved by liberation of daughter cells from the ruptured mother sheath. LEGE 06123 is halotolerant, withstands a considerable range of iron concentrations, and favours growth at moderately high temperatures (35, 40 degrees C). According to the criteria defined in 1998 by Komarek and Anagnostidis, LEGE 06123 could belong to the species Gloeocapsopsis crepidinum (Thuret) Geitler ex Komarek 1993. However, our phylogenetic analyses clearly show that LEGE 06123 is closely related to three cyanobacteria isolated from the Great Yellowstone and Zerka Ma'in hot springs, one of them (5.2 s.c.1) being described as a new genus and a new species - Chroogloeocystis siderophila Brown, Mummey et Cooksey. The polyphasic characterization performed here has exposed the unusual features of LEGE 06123, which along with the three thermophilic strains, forms a distinct clade deserving further investigation.