Effects Of Environmental Factors On The Biosynthesis Of Hemolytic Toxins By The Marine Cyanobacterium Synechococcus ('sp') Miami Bgii6s (blue-Green Algae, Florida)

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Doctor of Philosophy (Ph.D.)


The effects of environmental factors upon growth and hemolytic compound biosynthesis by Synechococcus sp. Miami BGII6S were studied. This strain was previously isolated from an area in Biscayne Bay, Florida, where a massive fish kill occurred.Synechococcus sp. Miami BGII6S was found to be a fast growing strain (maximum growth rate 0.188 h('-1), equivalent to 5.3 h doubling time). It was also characterized by tolerance to a broad range of salinities, growing very well in seawater salinities from 20 to 5('o)/oo. Its optimal temperature for growth was around 28(DEGREES)C. Growth saturation light intensity was 90 (mu)Em('-2)s('-1). Its optimal pH (7.5-9.5) was well within the prevalent range in the marine environment.Production of hemolysins by Synechococcus sp. Miami BGII6S was found to be influenced by light intensity, temperature and salt concentration, as well as by cell age. Optimal conditions for hemolytic active compounds production by S sp. Miami BGII6S, in artificial seawater were found to be around 25(DEGREES)C, 50 (mu)Em('-2)s('-1) light intensity, and 16('o)/oo. Production of hemolytic active substances increases sharply when the cells are in late stationary phase. Little hemolytic substance was produced in the lag or exponential growth phases.It was found that there were at least two different hemolytic active compounds produced by this strain. One is water soluble and heat labile, while the other is ethanol soluble and heat stable. The hemolytic active substances did not show either antibacterial or mutagenic properties. Both living cells and extracts of Synechococcus sp. Miami BGII6S were toxic to Artemia II instar nauplii, but not to the rotifer Brachionus plicatilis.


Biology, Oceanography

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