Single Cyanobacteria Research Articles

Effects of chronic radiation exposure on phytoplankton communities in special industrial reservoirs of Mayak PA

A comparative study of phytoplankton communities inhabiting six reservoirs in the Southern Urals with different levels of radioactive contamination is presented. Along with increasing the level of radioactive contamination, the diversity of the phytoplankton species is decreases, however the abundance of surviving species and their biomass did not depend on the level of radiation contamination in the studied reservoirs. There were found no signs of ecological regression of phytoplankton communities caused by radioactive contamination up to 6.5 kBq l-1 in the reservoirs of the Techa river Reservoir Cascade R-11, R-10, R-4 and R-3. Ecological regression of the phytoplankton community was observed in reservoirs R-17 and R-9, with a total activity of β-emitting radionuclides 470 kBq l-1 and higher, a total activity of α-emitting radionuclides 220 kBq l-1 and higher. Ecological regression of communities was registered as a decrease in species diversity, fluctuations in the number of algae in the high ranges, and the predominant development of one species. Reduction of species diversity in adverse conditions and violations of interspecies relationships in the community often leads to sharp fluctuations in the biomass and abundance. Moreover, the highest biomass of the algal communities can result from either excessive species gain or species loss. In the most contaminated R-9 (Karachai Lake) species diversity is dramatically decreased to monoculture of a single cyanobacteria species, dominant species could vary in different years of the study.

Effects of microcystin-producing and microcystin-freeMicrocystis aeruginosa on enzyme activity and nutrient content in the rotifer Brachionus calyciflorus.

Toxic cyanobacterial blooms disrupt freshwater recreation and adversely affect zooplankton. The freshwater cyanobacterium Microcystis aeruginosa produces microcystins, which are compounds toxic to rotifers. This study evaluated the effects of M. aeruginosa on enzyme activity and nutrient content in the rotifer Brachionus calyciflorus Pallas. The rotifers were fed on Chlorella pyrenoidosa, Scenedesmus obliquus, microcystin-producing and microcystin-free M. aeruginosa alone, and mixtures of green algae combined with toxic and nontoxic cyanobacteria, respectively. Activities of amylase, pepsase, trypsin, cellulase, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were assessed after rotifer exposure to an environmental stressor. Nutrients analyzed were glycogen, protein, and triglyceride (TG). Single cyanobacteria and mixtures combined with toxic M. aeruginosa inhibited SOD activity. CAT and GPx activities significantly increased in rotifers fed with the mixture of Chlorella and toxic cyanobacteria. The activity of digestive enzymes increased compared with the Chlorella group in single and mixed diets. Glycogen and protein decreased in Microcystis mixtures, whereas TG content increased. The grazing rate (G) of the rotifers decreased with grazing time. High G value was observed with green algae in every treatment group. Although the toxins released after grazing on Microcystis affected rotifer enzyme activity and nutrient content, B. calyciflorus changed its physiological performance and grazing intensity with food type in response to eutrophic conditions.

Circadian Gating of the Cell Cycle Revealed in Single Cyanobacterial Cells

Although major progress has been made in uncovering the machinery that underlies individual biological clocks, much less is known about how multiple clocks coordinate their oscillations. We simultaneously tracked cell division events and circadian phases of individual cells of the cyanobacterium Synechococcus elongatus and fit the data to a model to determine when cell cycle progression slows as a function of circadian and cell cycle phases. We infer that cell cycle progression in cyanobacteria slows during a specific circadian interval but is uniform across cell cycle phases. Our model is applicable to the quantification of the coupling between biological oscillators in other organisms.