Search

Cyanobacteria are the most primitive photosynthetic organisms on the Earth. Their classification is traditionally based on morphological characters in both botanical and bacteriological systems. Due to the enormous diversity and the lack of clear diacritic morphological features between the closely related species, for resolving the evolutionary relationships and classification of Cyanobacteria during the last years is used a polyphasic approach including sequencing data. Although many molecular markers are improved, new suitable markers for resolving relationships within cyanobacteria at species and generic level are still needed. Our objective was to examine whether the sequences of the photosystem II proteins CP43 and CP47 are suitable markers for such purposes. Phylogenetic analyses based on the CP43 and CP47 amino acid sequences showed that most of the cyanobacterial species/strains belonging to different genera are clustered in separate clades supported by high bootstrap values. The comparison between the CP43 and CP47 trees, and the 16S phylogenetic trees showed that the CP43 and CP47 proteins are more suitable markers in resolving phylogenetic relationships within Cyanobacteria at generic and species level than the conserved 16S rRNA gene sequence. The correct taxonomic classification and identification of the cyanobacterial strains is very important for all studies related to the biological activity of cyanobacteria, their biotechnological application or in the management and monitoring of water. [ABSTRACT FROM AUTHOR]

SUMMARY: Taxonomy of Cyanobacteria, the oldest phototrophic prokaryotes, is problematic for many years due to their simple morphology, high variability and adaptability to diverse ecological niches. After introduction of the polyphasic approach, which is based on the combination of several criteria (molecular sequencing, morphological and ecological), the whole classification system of these organisms is subject to reorganization. The aim of this study was to evaluate whether the outer membrane efflux protein (OMEP) sequences can be used as a molecular marker for resolving the phylogeny and taxonomic status of closely related cyanobacteria. We have performed phylogenetic analyses based on the amino acid sequences of the OMEP and the DNA sequences of the 16S rRNA gene from 86 cyanobacterial species/strains with completely sequenced genomes. Phylogenetic trees based on the OMEP showed that most of the cyanobacterial species/strains belonging to different genera are clustered in separate clades supported by high bootstrap values. Comparing the OMEP trees with the 16S rDNA tree clearly showed that the OMEP is more suitable marker in resolving phylogenetic relationships within Cyanobacteria at generic and species level. [ABSTRACT FROM AUTHOR]

The polyphasic approach is the most progressive system that has been suggested for distinguishing and phylogenetically classifying Cyanoprokaryota (Cyanobacteria/Cyanophyta). Several oscillatorialean genera (Lyngbya, Phormidium, Plectonema, and Leptolyngbya) have problematic phylogenetic position and taxonomic state because of their heterogeneity and polyphyletic nature. To accurately resolve the phylogenetic relationship of some filamentous species (Nodosilinea bijugata, Phormidium molle, Phormidium papyraceum), we have performed phylogenetic analyses based on 16S rRNA gene and the phycocyanin operon (PC-IGS) by using maximum-likelihood (ML) tree inference methods. These analyses were combined with morphologi-cal re-evaluation. Our phylogenetic analyses support the taxonomic separation of genus Nodosilinea from the polyphyletic genus Leptolyngbya. Investigated Nodosilinea strains always formed a coherent genetic cluster supported with a high bootstrap value. The molecular phylogeny confirmed also the monophyly of the Wilmottia group. In addition, data reveal that although P. papyraceum is morphologically similar to Wilmottia murrayi, this species is genetically distinct. Strains from the newly formed genus Phormidesmis and some Phormidium priestleyi strains were clustered in a separate clade different from the typical Phormidium species, but without strong bootstrap support. [ABSTRACT FROM AUTHOR]

The accurate determination of species ofCyanoprokaryota/Cyanophyceaehas many important applications. These include the assessment of risk with regard to blooms in water reservoirs as well as the identification of species capable of producing valuable bioactive compounds. Commonly,Cyanoprokaryotaare classified based on their morphology. However, morphological criteria are not always reliable because they may change, for example, due to environmental factors. Thus, genetic and molecular analyses are a promising additional approach, but their application has so far been limited to relatively few genera. In light of this, we present here the first characterization of species and strains of the genusPhormidiumKütz. based on the cpcB-IGS-cpcA locus of the phycocyanin operon. In phylogenetic analyses using deduced amino acid sequences of the cpcB-cpcA regions,Phormidiumwas found to be polyphyletic. This analysis appeared to be dominated by the cpcB region, which is characterized by a relatively high percentage of informative substitutions. The percentage of variable positions within the cpcB-IGS-cpcA locus overall was 16.5%, thereby indicating a level of divergence remarkably higher than that reported forNodulariaandArthrospirain previous studies relying on cpcB-IGS-cpcA. Further, alignment of informative nucleotide substitutions in the cpcB-IGS-cpcA sequences revealed a mosaic distribution, which may be indicative of genetic recombination events. Finally, the length and sequences of the IGS region alone proved useful as markers to differentiate the cyanobacterial genusPhormidium. However, whether the IGS regionper seis sufficiently discriminatory to differentiate betweenPhormidiumspecies or even strains requires further investigation using newly identifiedPhormidiumsequence data. [ABSTRACT FROM AUTHOR]