The response of three strains of Anacystis nidulans (cyanobacteria) to ultraviolet‐B radiation

Abstract

The influnce of UV-B irradiance was examined on three strains of a cyanobacterium, Anacystis nidulam.These include wild type A. nidulans (An) and strains resistant to cadmium (Cd? and cyanophage As-1 (As-1"). The results indicated that although, the UV-B radiation considered in the present study was damaging to all the three strains, As-1' offered some degree of protection from UV-BLas far as changes in chlorophyll, phycocyanin, "CO, uptake and photosynthetic O2 evolution were concerned. Cadmium resistant strain appeared to be most sensitive to UV-B among the three. The observations form the first report of UV-B effects on a metal resistant and a cyanophage resistant strain of cyanobacterium.SAFFERMAN and M o w s (1963) discovered that the cyanophages could play important role in irradicating waterbloom forming cyanobacteria. Since then, cyanophages have successfully been deployed for cleaning water bodies from bloom forming cyanobacterial species. At the same time, however, some of the cyanophages were also found to kill economically important cyanobacterial strains. Since the in situ protection of such strains from these viruses could not possible, attempts were made to develop mutants of these organisms that could resist to their respective cyanophages (SINGH 1975, AMLA 1976, MISHRA et al. 1993, PANDEY and PANDEY 1994a, and 1994b. The question, however, that appears more interesting at this stage is that what would be the fate of such cyanophage resistant cyanobacterial strains when exposed to environmental stresses. Since the possibility of simultaneous Occurrence of a number of stress factors in aquatic systems cannot be ruled out, this could form an interesting part of scientific investigation.Among the several factors heavy metal pollution (VENKATARAMAN et al. 1992) and increasingly high level of W -B radiation reaching to the earth surface ( M m 1991), are the most important stress factors that received attention worldwide. The adverse effects of both, W -B (TERAMURA et al. 1990, SEARLES et al. 1995, MADRONICH 1995 and cadmium ( GREGER and ORGEN 1989, BORNMAN and DUBE 1991, JULES and SHAW 1994, PANDEY and PANDEY 1994aand 1994b