Current projects

2009–2013, reg. code GAČR 206/09/0309: Competition mechanisms in Cyanobacteria affecting phytoplankton species composition, principal investigator Klára Řeháková.

The phytoplankton composition in European lakes and reservoirs has been investigated for decades. Dense populations of cyanobacteria often dominate phytoplankton. They can build water blooms in summer and autumn, and produce harmful toxins. Therefore, they present potential hazards to public and animal health worldwide, both via blooming of water reservoirs leading to toxin release in drinking water as well as to hypertrophy with consequent oxygen depletion in the natural environments. For these reasons it is necessary to reveal the details in biology of water blooms. The proposed project is focused on the study of competition among dominating species of water bloom. How the co-existence of the species can influence their ecophysiological and biochemical characteristics? How the changes in these characteristics can increase their successfulness to become dominant species of water bloom? Project will be unique in the interface of results from biochemical and physiological point of view.

2011–2013, reg. code GA ČR P504-11-2177: The importance of cell death for freshwater phytoplankton succession, structure and composition, principal investigator Petr Znachor.

Phytoplankton constitute an important component of pelagic food webs in freshwater reservoirs. For a better understanding of phytoplankton dynamics, it is crucial to know the processes that affect both increase and decline of a population. Traditionally, grazing and sedimentation have been considered as the main factors responsible for reducing size of natural phytoplankton population. Recently, cell death was recognized as an additional and important loss process. There are only few field reports on the subject, all indicating cell death is an important determinant of the seasonal variability in abundance and structure of marine phytoplankton; however, scarce data are available from freshwaters. In the proposed project, we intend to use SYTOX Green, which stains specifically dead cells, to study wax and wane of phytoplankton key species. Aim of this project is to explore the role of cell death in a seasonal succession of phytoplankton in a freshwater reservoir, to assess factors affecting cell death and to evaluate its importance over the diurnal cycle.

2011–2014 reg. code GA ČR: Phytoplankton release of dissolved organic carbon and its relationship to bacterioplankton composition, principal investigator Jiří Nedoma.

The aim of the project is to study specific species-to-species interactions between phytoplankton and bacterioplankton mediated by the dissolved organic carbon (DOC) released by phytoplankton in a natural aquatic system. Relationships between environmental factors, phytoplankton composition, biomass, and nutrient status (P-deficiency), the quantity and quality of the DOC released by phytoplankton, and their impact on bacterioplankton assemblage composition, will be studied along to the longitudinal transect in the eutrophic Římov reservoir during three consecutive seasons. P-deficiency will be measured by ³³P phosphorus turnover, phytoplankton physiological status by variable fluorescence, primary production, DOC release and composition using ¹⁴C method, bacterioplankton taxonomical composition by CARDFISH.

2010-2013, reg. č. GAČR EEF/10/E011: Functional role and ecotype divergence in Actinobacteria of the AcI lineage, principal investigator Jan Jezbera.

The high in situ abundances and the cosmopolitan distribution of relatively few phylogenetic lineages of ultramicrobacteria strongly point to their evolutionary success and functional significance at the ecosystem level. Actinobacteria of the AcI lineage represents one of this group. We plan metagenomic sequencing of the cultures of Actinobacteria to revel the following: Firstly, we shall seek for genome-based differences of carbon metabolism and substrate preference. Secondly, we will focus on actinorhodopsin genes in the AcI clades, because they suggest a different role of these groups in ecosystem processes than in other bacteria. Thirdly, genes encoding surface layer proteins seem to convey particularly high predation resistance in Ac1 bacteria. Genes responsible for the development of the S-layer (possibly influencing grazing resistance) will be revealed and grazing experiments will be planned based on the results of metagenomic sequencing. Real-time PCR assays will be developed and applied to reveal the distribution of the AcI bacteria encoding actinorhodopsins and the S-layer.

2013-2017, reg. code GAČR 13-00243S: Unveiling life strategies of selected groups of planktonic Betaproteobacteria in relationship to carbon flow to higher trophic levels, principal investigator Karel Šimek.

We propose investigations of life strategies related to genomic and ecophysiological traits of representative strains of the key groups of freshwater Betaproteobacteria, i.e. the genera Limnohabitans and Polynucleobacter, with contrasting lifestyles and frequently also different habitat preferences. We hypothesize that strains affiliated with these abundant groups differ in growth potential and grazing-induced mortality in situ, thus modulating the role of the groups in carbon flow to higher trophic levels. Notably, a large collection of representative strains from both groups is available that facilitates examination of diversity in ecophysiologic and genomic traits of these bacteria. Specific in situ experimental designs are proposed for testing of eco-physiological characteristics of the bacteria and estimating of their taxon-specific roles in carbon transfer to bacterivorous flagellates in five different habitats. Important new insights into distinct bacterial lifestyles are assumed, including implications for refinement of existing concepts of bacterial life strategies.