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Cyanobacteria; Toxicity testing


In the past toxin production by blue-green algae has been demonstrated by feeding large quantities of algae to vertebrates and observing symptoms leading to animal death. It was the purpose of this investigation to develop a more convenient way to test for the presence of an alga toxin using instead of vertebrates, other algae and those organisms with which it lives and competes in fresh water habitats. Using axenic algae cultures and three different agar media MBL, DAA and NA, the latter to check for bacterial contamination, algae were streaked on the agar surface in petri dishes to form a cross. The alga being tested for toxin production was streaked in a vertical line from top to bottom on the surface of the agar. The second alga formed the horizontal part of the cross and was streaked from left to right. The passing of the second alga across the vertical or first alga provided many close associations of the two algae in the right part of the horizontal streak, supplementing the overall growth and interactions occurring on the agar surface. In this way many combinations of seven species of blue-greens, four species of green algae, Euglena gracilis, and Tetrahymena pyriformis were made. From macroscopic and microscopic examinations it was found that three algae Scytonema hofmanni, Anabaena cylindrica and Anabaena 7119 inhibited the growth of other microorganisms. As a result of this study toxin production by axenic blue-green algae can now be detected qualitatively using microorganisms.

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