GROWTH RESPONSE OF CHLAMYDOMONAS AND HAEMATOCOCCUS TO THE VOLATILE FATTY ACIDS
The first five straight-chain saturated fatty acids were tested to determine their effect on cell division of phytoflagellates. Chlamydomonas reinhardti Danseard and Haematococcus pluvialis Flotow were selected for measurement because of information available from similar studies of the long-chain acids. Cultures were grown at five concentrations of the sodium salt within the range of 0.5 to 10.0 mmoles/liter.Acetate stimulated the rate of cell division, while butyrate, the other acid with an even number of carbons, produced an inconsistent although negligible effect.The fatty acids with an odd number of carbons inhibited division of cells, with propionate being most and valerate least effective. Inhibition in these tests, in which initial pH was kept constant, was proportional to the initial concentration of the acid salt. Additional tests showed propionate inhibition to be approximately proportional to a calculated amount of undissociated acid in the medium. H. pluvialis was 9–12 times more sensitive than was C. reinhardti.The possibility of propionic acid inhibition of algae in acid lakes is discussed.