Past Research
Impact of ion concentration on cyanobacterial scum formation
|
Cyanobacterial scums at the surface of the lakes are potentially harmful phenomena with increasing occurrence in the last decades, and the causes that lead to their formation are still an unresolved issue. In order to better understand what triggers the scums, we investigated the effect of several Mg2+ and Ca2+ ion concentrations in promoting them in eight Microcystis aeruginosa strains. The possibility to prevent scum formation by using the ion chelator EDTA was also explored. We found that different ion concentrations have divergent effects on cell aggregation, and that they can select for certain strains to form a scum from a complex community. |
Effect of various ion concentration on scum formation in cyanobacteria
|
The scum formation was highly correlated to the amount of extracellular polymeric substances produced by cells. The toxin-producing lineages required longer time to develop a scum and higher nutrient concentration compared to the non-toxic ones. EDTA failed to prevent the scum formation in most strains, but in turn, it caused cell lysis followed by the release of cellular content into the culture medium. We emphasize the relevance of these results for cyanobacterial scum formation in the environment and we also suggest a potentially efficient method for biomass harvesting in large ponds/tanks.
Drugă B, Buda D-M, Szekeres E, Chiş C, Chiş I, Sicora C, 2019. The impact of cation concentration on Microcystis (cyanobacteria) scum formation. Scientific Reports. 9: 3017. Doi: 10.1038/s41598-019-39619-y.
Drugă B, Buda D-M, Szekeres E, Chiş C, Chiş I, Sicora C, 2019. The impact of cation concentration on Microcystis (cyanobacteria) scum formation. Scientific Reports. 9: 3017. Doi: 10.1038/s41598-019-39619-y.
Interaction between wastewater microorganisms and a new generation of cements
|
Biofilm formation and its interaction with concrete surfaces often results in severe deterioration mechanisms while harming structures like sewer piping systems and wastewater treatment plants. The aim of this project was to compare the biofilm formation during field exposure to real municipal wastewaters on geopolymer and copper-doped geopolymer mortar, with plain Portland cement and calcium aluminate cement as controls.
After 35 days of wastewater exposure, the biofilm was characterized by community DNA analysis, and also by measuring the protein concentration and bacterial respiration at the sample surface. The protein concentration on the Portland cement samples was 50 % higher as compared to the geopolymer mortars, while the respiration rates on the Portland/calcium aluminate cement samples was 2.5 times higher than on the geopolymer doped with copper, suggesting a lower bioreceptivity for the latter material. Scanning electron microscopy revealed the presence of biofilm on mortar surfaces, especially on the samples exposed to organic-rich wastewaters. DNA tests have revealed that the structure of the bacterial communities was different on the four materials, and that copper-doped geopolymer, even though developed less biofilm at its surface as compared to other materials, seems to select for several potential highly pathogenic microorganisms. Drugă B, Ukrainczyk N, Weise K, Koenders E, Lackner S, 2018. Interaction between wastewater microorganisms and geopolymer or cementitious materials: Biofilm characterization and deterioration characteristics of mortars. International Biodeterioration & Biodegradation, 134: 58–67. |
SEM images with the biofilm developed on sample surface
|
Impact of cyanobacteria on fitness and genetic structure of zooplankton populations
|
Zooplankton communities can be strongly affected by cyanobacterial blooms, especially species of genus Daphnia, which are key-species in lake ecosystems. This project explored the effect of microcystin/nonmicrocystin (MC/non-MC) producing cyanobacteria in the diet of mixed Daphnia galeata populations. During a 10-week project, we measured the expression of nine genes potentially involved in Daphnia acclimation to cyanobacteria. The expression pattern of one protease and the ubiquitin-conjugating enzyme genes was positively correlated with the increased fitness of competing clones in the presence of cyanobacteria, suggesting physiological plasticity. The genotype dynamics in mixed populations was only partially related to the growth rates of clones in monocultures and varied strongly with the food. Our results revealed strong intraspecific differences in the tolerance of D. galeata clones to MC/non-MC-producing cyanobacteria in their diet, suggesting microevolutionary effects.
|
|
Drugă B, Turko P, Spaak P, Pomati F, 2016. Cyanobacteria affect fitness and genetic structure of experimental Daphnia populations. Environmental Science & Technology, 50: 3416-3424.
This project was supported by funding from the SCIEX Program (Switzerland), Project Code 13.259/2014.
This project was supported by funding from the SCIEX Program (Switzerland), Project Code 13.259/2014.