Servicenavigation

Detailseite

Zurück

Projekt Druckansicht

Effects of climate variability on interactions between cyanobacteria and associated microheterotrophs-consequences for development of toxic cyanobacterial blooms

Fachliche Zuordnung Hydrogeologie, Hydrologie, Limnologie, Siedlungswasserwirtschaft, Wasserchemie, Integrierte Wasserressourcen-Bewirtschaftung
Förderung Förderung von 2006 bis 2011
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 28750711
 
Erstellungsjahr 2011

Zusammenfassung der Projektergebnisse

Bacteria in aquatic environments have primarily been regarded as free-living organisms responsible for degradation of dissolved organic matter although the importance of particles and organisms for bacteria, e.g. pathogens, has been well described. There is evidence that a substantial fraction of Bacteria as well as Archaea can be attached to particulate matter and living organisms. They can interact with other microorganisms or their hosts, respectively. Examples for hosts harbouring numerous heterotrophic bacteria are cyanobacteria species. These highly abundant organisms are very important for freshwater and marine ecosystems e.g. the mass developments of cyanobacteria. This project focused on interactions of heterotrophic microorganisms with living cyanobacteria and the ecological consequences for freshwater habitats. The main part of this project was directed towards heterotrophic microbial interactions with cyanobacteria. Cyanobacteria can be unicellular and relatively small like Synechococcus sp. and Microcystis sp., whereas the latter one can also form large colonies. Both genera belong to photoautotrophic prokaryotes which can be responsible for about half of the global primary production and thus represent a unique ecological niche for associated heterotrophic microorganisms. Some strains of Microcystis sp. have the capability to produce toxins such as the hepatotoxin microcystin which can cause severe health and economic problems. In the presented project we have investigated temperature as a structuring factor in these interactions and found that: 1. Temperature affects the microbial community structure associated with cyanobacteria; We found bacterial groups which only occur at high temperatures (32*C e.g. Brevundimonas sp. and Pseudomonas sp.) or at low temperatures (20*C, e.g. Actinobacteria of the Acl cluster, Burkholderiales and Planctomycetes). However, a few bacterial groups such as Sphingomonas sp. occur at a wide range of temperatures. 2. Increasing temperatures lead to a higher ratio of Microcystis aeruginosa cells containing the mcyD gene for microcystin synthetase but a lower ratio of cells actually producing the toxin. However, at 32*0 we found the highest concentrations of microcystins mostly due to higher growth rates and cell-specific toxin production rates. 3. Associated prokaryotes (heterotrophs as well as a non-toxic cyanobacterial strain) affect toxin-production: At all incubation temperatures we found an increase of a more toxic variant of microcystin (MC-LR In relation to MC-YR) in the presence of heterotrophic bacteria and an increase of MC-YR in the presence of the non-toxic cyanobacterial strain. In conclusion, microbial interactions are of great importance for shaping the bacterial community structure or altering toxin production but also by extending bacterial dispersal mechanisms in aquatic ecosystems. These interactions have been neglected for a long time but are substantial for microbial evolution, the identification of new bacterial (anaerobic) processes, and thus for the physiology of interacting partners. Understanding these interactions could be also the key for a successful risk assessment of toxic cyanobacteria blooms or waterborne pathogens in future.

Projektbezogene Publikationen (Auswahl)

 
 

Zusatzinformationen

© 2025 DFG Kontakt / Impressum / Datenschutz

Textvergrößerung und Kontrastanpassung