A polyphasic approach to assess the cyanobacterial diversity of summer samples from Czech reservoirs

We used a polyphasic approach combining data from microscopic assessment of fresh biomass and from clone libraries and DGGE fingerprints based on 16S rRNA gene sequences to investigate the cyanobacterial diversity of Czech reservoirs during the summer in 2001 and 2002. In total, 15 genera were identified using the microscopic analysis in 38 samples analysed. They were Aphanizomenon, Anabaena, Anabaenopsis, Aphanocapsa, Aphanothece, Pseudanabaena, Planktothrix, Planktolyngbya, Limnothrix, Woronichinia, Snowella, Romeria, Microcystis, Merismopedia, and Coelomoron. We recovered 113 DGGE band sequences from the same samples. In addition, 128 partial 16S rRNA sequences were obtained from two clone libraries of reservoirs Pilská and Orlík. The phylogenetic comparison with the currently available rRNA sequences in databases showed that our sequences belonged to 8 clusters: Woronichinia, Microcystis, Synechococcus, Snowella, Planktothrix, Anabaena/Aphanizomenon, Limnothrix and a plastid related to Chrysochromulina polylepis. The microscopic enumeration and the molecular results were generally congruent concerning the major populations determined in these samples (for 32 samples among 38). Anabaena/Aphanizomenon, Microcystis and Woronichinia were the major genera in the Czech reservoirs during summer, and were present in most of the samples. This study showed some discrepancies between the genera retrieved by the traditional method and the molecular analyses. Differences concerned the presence of minor populations belonging to Aphanothece, Romeria, Merismopedia, Synechococcus, Snowella and Pseudanabena. These differences could be explained by biases specific to each method (competitive amplification, difficulty to obtain sequences from DGGE bands, not precise microscopic observation of the small-sized genera).MIDI-CHI

Diversity of planktonic cyanobacteria and microcystin occurrence in Polish water bodies investigated using a polyphasic approach

peer reviewedMicroscopic measurements of fresh biomass and 16S rRNA gene sequences from clone libraries and denaturing gradient gel electrophoresis (DGGE) were used to investigate cyanobacterial diversity in Polish water bodies in 2002. In addition, measurements of microcystin (MC) concentrations were made. Thirty water samples were taken from 11 water bodies; of these samples, 18 were obtained from the Sulejow Reservoir during regular monitoring from June to October. Intraand extracellular MC concentrations in Sulejow samples were measured by high performance liquid chromatography (HPLC). The extracellular MC concentration was assessed using a protein phosphatase inhibition assay (PPIA) in additional lakes. Additionally, physicochemical parameters were measured (total nitrogen [TN], total phosphorus [TP], TN:TP ratio, chlorophyll a concentration, temperature). In Sulejow, high intracellular MC concentrations corresponded to large cyanobacterial biovolumes and to low TN:TP ratios. In the other lakes, extracellular MCs were not linked to any measured parameters. The combination of the microscopic and molecular data showed that Aphanizomenon and Microcystis were the dominant genera during the summer period in the Sulejow Reservoir. At the genetic level, there was a succession of 2 different operational taxonomic units (OTUs) belonging to the lineage Anabaena/Aphanizomenon. In the other water bodies, the most frequent populations were Aphanizomenon, Anabaena, Microcystis and Planktothrix. Small populations of Romeria, Snowella, Woronichinia, Limnothrix and Pseudanabaena were observed, and an enigmatic cluster affiliated with Prochlorothrix was genetically retrieved. Anabaena and Microcystis were presumed to be the main genera responsible for the MC production.MIDI-CHI