Effects of L-methionine-DL-Sulphoximine(MSO) and 3-(3,4-dichlorophenyl)- N-N-dimethylurea(DCMU) on Physiological Activity of Cyanobacteria Nostoc species Isolated from Lichen Peltigeracanina


Lichen is a Symbiotic system consist of nitrogen fixing Cyanobacteria or and algae andfungus. Cyanobacteria can fix nitrogen in a peculiar differentiated cells called heterocystunder aerobic conditions, those heterocyst are the loci of nitrogenase activity. The organicnitrogen and carbohydrates produced by cyanobacteria utilized by fungi and the fungussupplying the cyanobacteria and algae by inorganic metals coming from dissolved rocksby acids produced by fungi. Culture of Nostocspp treated with MOS excreted, the newlyfixed nitrogen in form of ammonia into liquid media, which is proportions with theconcentration of the analog and detected after 6 h of treatment. Acetylene reductiontechnique (nitrogenase activity) was not affected by analog (MSO) treatment. The growthof Cyanobacteria Nostocspp was slightly inhibited starting after 6 h of treatment. The ratesof carbon fixation were highly enhanced after treatment leading to increase the number of(PGBS) in the Cyanobacteria cells. The combination treatment of Nostocspp culture byMSO and DCMU showed the following: carbon and nitrogen fixation are dependent ofeach other, slight inhibitions in culture growth, 50% inhibition in ammonia release,complete inhibition of carbon fixation and disappeared of extra PGB. Light intensities andcarbon fixation are dependent even in the presence of MSO. The cultivation of Nostocsppculture under Ar/O2/CO2 in presence of MSO gives reverse relationship between thecellular incorporated carbon and time. Electron micrograph showed an increase in PGBs ofthe lichen P. conina treated with MSO through the first hour of treatment and thendisappeared after 24 h.