The alignment was verified with macclade 4.033 PCC software (Sinauer Associates Inc., Sunderland, MA) and phylogenetic analysis were run with paup*

4.0b10 (Swofford, 2002). Maximum-likelihood (ML) reconstruction considered the Akaike Information Criterion as a model of nucleotidic evolution after a model test analysis (Posada & Crandall, 1998). this website The model with the best fit was GTR+I+G, where I=0.3894 (proportion of invariable sites) and G=0.5246 (gamma distribution). Topologies were also inferred with neighbor-joining (NJ) (Kimura 2 Parameters) and maximum parsimony (MP). Bootstrap considered 500 (ML, NJ) and 1000 (MP) replicates, respectively. Crocosphaera watsonii, a unicellular nitrogen-fixing cyanobacteria, was included as the outgroup. Molecular clock estimates were inferred from a MAP topology calculated from a Bayesian phylogenetic analysis with mrbayes v3.1.2 (Huelsenbeck & Ronquist 2001) using the model with best fit to the data set.

Bayesian analysis consisted of two independent Markov Chain Monte Carlo runs, performed by four differentially heated chains of 5 × 106 generations. Phylograms with a topology identical to the MAP topology were recovered with paup* 4.0b10 and 100 were chosen to conduct age estimates. The timing of phylogenetic divergence was calculated with r8s v1.71 (Sanderson, 2006) with penalized likelihood (Sanderson, 2002). The node defining Cyanobacteria was fixed at 2700 MYA and a minimum age for the heterocystous cyanobacteria was defined at 1618 MYA (Falcón et al., 2010). The outgroup was

Selleck U0126 Phosphatidylinositol diacylglycerol-lyase Chloroflexus aurantiacus, a green nonsulfur bacterium. Sequences generated in this study are deposited in the NCBI database with accession numbers: FJ660972–FJ661026. Sequences FJ660972–FJ660992 correspond to isolates from microbialites in Pozas Azules I, a desert pond in Cuatro Ciénegas, México; FJ660993 and FJ660994 are from a microbial mat on a beach rock in Heron Island at the Great Barrier Reef, Australia; FJ660995–FJ661005 and FJ66101–FJ661021 are from separate isolates obtained from type cultures of Tolypothrix sp. PCC 7504 and Calothrix sp. PCC 7103 maintained in culture at the Department of Botany at Stockholm University, Sweden; and FJ661006–FJ661009 correspond to isolates from the shore line of a rocky islet outside the Stockholm University Marine Research Station at Askö in the Baltic Sea, Sweden. Phylogenetic differentiation was well sustained, suggesting three natural groups pertaining to Calothrix from Askö (Sweden), also including the strain PCC 7103, Rivularia from strains in Pozas Azules I (Mexico) and Tolypothrix including the strain PCC 7504 (Fig. 1). These genera were earlier defined based on molecular identities (Rajaniemi et al., 2005; Taton et al., 2006; Sihvonen et al., 2007).