Effect of aluminum and pH on the growth of Anacystis nidulans

Anacystis nidulans cultured in 10 ml Mauro's modified medium (3M) were exposed to 1, 5, 20 and 50 ppm aluminium sulphate with no pH adjustment, to 1, 5, 20, 50 and 100 ppm aluminium at pH 7.9, and pH ranging from 2.4-12.00. Cell growth was eliminated at pH 2.4 and 12.0 and severely reduced at pH 4.5 and 11.5. The optimal growth range was 6.5-7.9. The cyanobacterium could reduce pH values of 4.5 or 11.5 to 7.5-8.6, but had no effect on pH 2.4 or 12.0. The nature of the regulatory mechanism is discussed. Aluminium at all concentrations with no pH adjustment inhibited early growth, with complete inhibition at 20 and 50 ppm. Values for pH at 1, 5, 20 and 50 ppm aluminium were 7.3, 6.65, 3.6 and 3.35, respectively. Results from experiments with pH adjustment to 7.9 indicated that different aluminium concentrations affected algal growth regardless of pH adjustment, and that the effects of aluminium were significantly less in cultures with, than without, pH adjustment. The effects of EDTA on aluminium effects on growth of A. nidulans are discussed.