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Lager von Oscillatoria spec. |
Environmental impacts on cyanobacteria Materials and methods Media An enrichment medium, which was originally for cellulose degrading bacteria turned out very good results with cyanobacteria of the species Oscillatoria. Species used for the experiments The cyanobacteria used in my experiments were isolated out of a eight week old Winogradsky column. The isolated cyanobacteria of the genus Oscillatoria were enriched in a medium for cellulose-degrading bacteria. By transferring the cultures several times in fresh medium the contamination with other algae could be reduced. Description of the experiments/discussion My experiments covered field observation of cyanobacteria (Oscillatoria rubescens) which could show that cyanobacteria can play an indicating role e.g. for water analysis. Laboratory experiments were made with Oscillatoria spec. as noted above. Because of their simple structure and the simple way of cultivation, the used species of Oscillatoria appeared to be very suitable for my observations. Indicating effect of Oscillatoria on copper and zinc The cyanobacteria reacted to copper and zinc salts even in very low concentrations (<=0,1ppm) by changing the filament’s structure and stopping their movement. Supposed to be responsible for this cessation, which in the end leads to the death of the bacteria, are small fractures between the single cells of the filament. With an increasing concentration of copper ions the number of fractures is increases. Long term observation showed that the bacteria incubated with high concentrations of copper lose their intensive blue-green colour, which has probably an influence on their photosynthesis. Bacteria incubated with zinc lose their colour even at very low concentrations, but without occurring any fractures. If the movement of the whole filament is organised by signals throughout the filament, the transduction of these signals is probably interrupted because of the fractures. Structurally seen it is supposed that intercellular conjunctions are disturbed or destroyed. The development of agglomerations between single filaments was definitely interrupted by the heavy metals. Correlation between the movement of Oscillatoria and phototaxis A standard test tube was filled with the enrichment medium and Oscillatoria. The test tube was surrounded by black paper with only three holes for light admittance, two centimetres apart from each other. The experiment took place under "daylight-conditions". The light intensity has not been measured. It could be observed, that the bacteria, first at the bottom of the test tube started to build a growing network of their filaments covering the whole test tube after 7 days. Near the holes for light admittance, they developed agglomerations consisting of a high amount of single filaments. Also the observations of an older, contaminated culture, could show, that the organisation in agglomerations of trichomes probably helped the cyanobacteria to combat potential antagonists, such as rhizopoda or rotatoria. Observations under the microscope showed, that the activity of trichome-movement increased with a higher light intensity. As the poisoning with heavy metals was correlated with a cessation - and this with a stop of agglomeration – it is presumed that the movement of Oscillatoria plays a decisive rolle in the aspiration after better light conditions for photosynthesis. Biotic and abiotic impacts influencing the development of cyanobacteria Oscillatoria rubescens was isolated out of a small lake in late December 1998. The water quality of the lake, highly frequented by people in the summer, could be identified as in a critical trophic condition by water analysis. Oscillatoria rubescens is known as an indicating organism for the enrichment of nutrients in a lake. The high appearance of O. rubenscens in December can be seen as a simple example of how conditions such as temperature, light and e.g. nutrients caused by biotic or abiotic factors can have influence on cyanobacteria. Plans and ideas for further examination My observations referring to an organism that can be used as an indicator for, e.g. heavy metals in aquatic environments caused me to find some other organisms that can also be used as indicators. For one year now I have been preparing experiments with the myxomycete Physarum polycephalum. With the help of a CCD-camera installed on a microscope and a digital image processing system I hope to improve my observations referring to the movement of Oscillatoria and the myxomycete, as the observations can be recorded and evaluated. Martin Etzrodt, * 22.12.1982 Participation at the junior field of "jugend forscht" 1998, 1st. price on regional level, 3rd. place State of Bavaria,Germany. publications: "Blaualgen und Umwelteinflüsse", "young researcher, The European journal of science and technology", issue 56, November 1999 contact: Etzrodt@gmx.net Die Arbeit "Blaualgen und Umwelteinflüsse" siegte auf dem Regionalwettbewerb "Jugend forscht/Schüler experimentieren" im Fachbereich Biologie und erreichte auf dem Landeswettbewerb "Schüler experimentieren" den 3. Platz. Die Arbeit wurde ebenfalls mit zwei Umweltpreisen prämieirt. |