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Extracellular cyanobacterial substances inhibit microbial growth
1Department of Marine Microbiology, Center for Environmental Research and Environmental Technology, Faculty of Biology and Chemistry, University of Bremen, Germany. bhs@biotec.uni-bremen.de
Summary
Marine cyanobacteria excrete substances that alter growth media, impacting other cyanobacteria and microbes. These "excreted substances" cause cell lysis, reduced chlorophyll, and affect bacterial and yeast growth.
Area of Science:
- Microbiology
- Phycology
- Biochemistry
Background:
- Cyanobacteria produce extracellular substances with diverse biological activities.
- Specific marine cyanobacteria strains (Anabaena sp. Hi 26, Oscillatoria subtilissima Bo 62) alter media color.
- Other strains (Rivularia sp. Bo 85, Oscillatoria limnetica Flo 1) affect media viscosity.
Purpose of the Study:
- To investigate the impact of cyanobacterial extracellular substances on related cyanobacteria.
- To assess the effects of these substances on heterotrophic microorganisms.
- To understand the bioactivity of excreted substances from marine cyanobacteria.
Main Methods:
- Utilizing sterile-filtered media pre-conditioned with specific cyanobacteria strains.
- Employing a "cyanobacterial assay" to observe effects on filamentous cyanobacteria.
- Conducting an "agar diffusion assay" to test impacts on bacteria and yeast.
Main Results:
- Cyanobacterial excretions induced cell lysis, empty sheaths, altered filament lengths, and single-cell formation.
- A decrease in chlorophyll a and protein content was observed in affected cyanobacteria.
- Pre-cultured media significantly affected the growth of gram-positive bacteria, gram-negative bacteria, and Saccharomyces cerevisiae.
Conclusions:
- Extracellular substances from marine cyanobacteria possess significant bioactivity.
- These substances can inhibit or alter the growth and morphology of other cyanobacteria.
- Cyanobacterial excretions influence the growth of various heterotrophic microorganisms, indicating inter-species interactions.