Effects of climate variability on interactions between cyanobacteria and associated microheterotrophs-consequences for development of toxic cyanobacterial blooms
Final Report Abstract
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.
Publications
- Bacterial diversity associated with freshwater Zooplankton. Environmental Microbiology Reports, Vol. 1. 2009, Issue 1, pp. 50–55.
Hans-Peter Grossart, Claudia Dziallas, and Kam W. Tang
(See online at https://dx.doi.org/10.1111/j.1758-2229.2008.00003.x) - Diversity and abundance of freshwater Actinobacteria along environmental gradients in the brackish northern Baltic Sea.
Environmental Microbiology, Vol. 11. 2009, Issue 8, pp. 2042–2054.
Karin Holmfeldt, Claudia Dziallas, Josefin Titelmann, Kirsten Pohlmann, Hans-Peter Grossart, Lasse Riemann
(See online at https://dx.doi.org/10.1111/j.1462-2920.2009.01925.x) - Effects of food on bacterial community composition associated with the copepod Acartia tonsa Dana. Biology Letters, Vol. 5. 2009, Nr. 4, pp. 549 - 553.
Kam Tang, Claudia Dziallas, Kristine Hutalle-Schmelzer, and Hans-Peter Grossart
(See online at https://dx.doi.org/10.1098/rsbl.2009.0076) - Microbial activities accompanying decomposition of cladoceran and copepod carcasses under different environmental conditions. Aquatic Microbial Ecology, Vol. 57. 2009, pp. 89-100.
Kam W. Tang, Samantha L. Bickel. Claudia Dziallas, and Hans-Peter Grossart
(See online at https://dx.doi.org/10.3354/ame01331) - Sommercamp für Bakterien. IGB Annual Report 2008, S. 24.
Claudia Dziallas, Hans-Peter Grossart
- Bacterial dispersal by hitchhiking on Zooplankton. Proceedings of the National Academy of Sciences of the United States of America - PNAS, Vol. 107. 2010, Nr. 26, pp. 11959 - 11964.
Hans-Peter Grossart, Claudia Dziallas, Franziska Leunert, Kam W. Tang
(See online at https://dx.doi.org/10.1073/pnas.1000668107) - Similar bacterial community composition in acidic mining lakes with different pH and lake chemistry. Microbial Ecology, Vol. 60. 2010, Issue 3, pp. 618-627.
Heike Kampe, Claudia Dziallas, Hans-Peter Grossart, Norbert Kamjunke
(See online at https://dx.doi.org/10.1007/s00248-010-9679-5) - Increasing Oxygen Radicals and Water Temperature Select for Toxic Microcystis sp. PLOS one, 2011.
Claudia Dziallas, Hans-Peter Grossart
(See online at https://dx.doi.org/10.1371/journal.pone.0025569) - Quantification of toxic and toxin-producing cyanobacterial cells by RING-FISH in combination with flow cytometry. Limnology and Oceanography: Methods, Vol. 9. 2011, Issue 2, pp. 67–73.
Claudia Dziallas, Solvig Pinnow, and Hans-Peter Grossart
(See online at https://dx.doi.org/10.4319/lom.2011.9.67) - Temperature and biotic factors influence bacterial communities associated with Microcystis sp. (cyanobacteria). Environmental Microbiology, Vol. 13. 2011, Issue 6, pp. 1632–1641.
Claudia Dziallas, Hans-Peter Grossart
(See online at https://dx.doi.org/10.1111/j.1462-2920.2011.02479.x) - Zooplankton and aggregates as refuge for aquatic bacteria: Protection from UV, heat and ozone stresses used for water treatments. Environmental Microbiology, Vol. 13. 2011, Issue 2, pp. 378–390.
Kam Tang, Claudia Dziallas, Hans-Peter Grossart
(See online at https://dx.doi.org/10.1111/j.1462-2920.2010.02335.x) - UV irradiation of natural organic matter (NOM): impact on organic
carbon and on bacteria. Aquatic Sciences, Vol. 74. 2012, Issue 3, pp. 443-454.
Andrea Paul, Claudia Dziallas, Elke Zwirnmann, Egil T. Gjessing, Hans-Peter Grossart
(See online at https://doi.org/10.1007/s00027-011-0239-y)
