CYANOPHYCIN AND GLYCOGEN-SYNTHESIS IN A CYANOBACTERIAL SCYTONEMA SPECIES IN RESPONSE TO SALT STRESS

The response to salinity of a Scytonema species isolated from the cent ral Australian desert was studied. Under nitrogen fixing conditions th e addition of increasing concentrations of salt (NaCl) caused progress ive inhibition of growth, with growth ceasing at 150 mM NaCl. This cor related with a progressive loss of nitrogenase activity, a low level o f activity being retained at 150 mM NaCl. The inhibition of growth was overcome when KNO3 (10 mM) was added to the growth medium. In respons e to the salt stress, cells accumulated the reserve compounds cyanophy cin and glycogen. Time course experiments showed that they were steadi ly synthesized over 48 h, after which the concentrations stabilized. C yanophycin synthesis was enhanced in salt-stressed cells grown in nitr ate. When cells were restored to their normal growth medium the conten t of these substances decreased towards control levels. (C) 1998 Feder ation of European Microbiological Societies. Published by Elsevier Sci ence B.V.