ORIGINAL PAPER Morphological and phylogenetic diversity of thermophilic cyanobacteria in Algerian hot springs Samia Amarouche-Yala • Ali Benouadah • Abd El Ouahab Bentabet • Purificacio ´n Lo ´pez-Garcı ´a Received: 19 March 2014 / Accepted: 13 July 2014 / Published online: 31 July 2014 Ó Springer Japan 2014 Abstract Geothermal springs in Algeria have been known since the Roman Empire. They mainly locate in Eastern Algeria and are inhabited by thermophilic organ- isms, which include cyanobacteria forming mats and con- cretions. In this work, we have investigated the cyanobacterial diversity of these springs. Cyanobacteria were collected from water, concretions and mats in nine hot springs with water temperatures ranging from 39 to 93 °C. Samples were collected for isolation in culture, microscopic morphological examination, and molecular diversity analysis based on 16S rRNA gene sequences. Nineteen different cyanobacterial morphotypes were iden- tified, the most abundant of which were three species of Leptolyngbya, accompanied by members of the genera Gloeocapsa, Gloeocapsopsis, Stigonema, Fischerella, Synechocystis, Microcoleus, Cyanobacterium, Chroococ- cus and Geitlerinema. Molecular diversity analyses were in good general agreement with classical identification and allowed the detection of additional species in three springs with temperatures higher than 50 °C. They corresponded to a Synechococcus clade and to relatives of the intracellularly calcifying Candidatus Gloeomargarita lithophora. The hottest springs were dominated by members of Lep- tolyngbya, Synechococcus-like cyanobacteria and Gloeo- margarita, whereas Oscillatoriales other than Leptolyngbya, Chroococcales and Stigonematales dominated lower tem- perature springs. The isolation of some of these strains sets the ground for future studies on the biology of thermophilic cyanobacteria. Keywords Cyanobacteria Á Hot spring Á Thermophilic Á Microbial mat Á Biomineralization Á Carbonate Introduction Cyanobacteria constitute a phylum of photosynthetic bac- teria of crucial importance in ecology and evolution. Their ancestor developed oxygenic photosynthesis, thus leading to the oxygenation of the Earth’s atmosphere and imposing novel environmental selective constraints to other groups of organisms (Herrero and Flores 2008). The chloroplasts of eukaryotic plants and algae derived from ancestral cyanobacterial endosymbionts, which led to another major diversification event in the history of terrestrial life (Ne- lissen et al. 1995; Cavalier-Smith 2002). From an ecolog- ical point of view, cyanobacteria are also extremely successful, being able to thrive in a wide variety of eco- systems. These include not only oceans and freshwater systems, but also many extreme environments. Essentially, Communicated by A. Oren. Electronic supplementary material The online version of this article (doi:10.1007/s00792-014-0680-7) contains supplementary material, which is available to authorized users. S. Amarouche-Yala Nuclear Research Center of Algiers, Bd. Frantz Fanon, BP 399 Algiers-RP, 16000 Algiers, Algeria e-mail: sam.wassi.amarouche@gmail.com S. Amarouche-Yala University of Abderhamane Mira, Route de Targa Ouzemmour, Be ´jaia, Algeria A. Benouadah Á A. El Ouahab Bentabet University of Mohamed El Bachir El Ibrahimi, Bordj Bou, Arre ´ridj, Algeria P. Lo ´pez-Garcı ´a (&) Unite ´ d’Ecologie, Syste ´matique et Evolution, CNRS UMR8079, Universite ´ Paris-Sud, 91405 Orsay, France e-mail: puri.lopez@u-psud.fr 123 Extremophiles (2014) 18:1035–1047 DOI 10.1007/s00792-014-0680-7