Effects of Radiations on Blue-green Algae: II. Effects in Growth

The unicellular blue-green alga Anacystis nidulans was repeatedlytreated with X-rays and radiophosphate (32P) during successivesubcultures. The strains so obtained were characterized by comparisonwith the untreated control strain, with respect to their resistanceto ultraviolet light, X-rays, streptomycin, and isoniazid. The³²P-treated strain was found to be relatively more resistantto streptomycin than the untreated strain and the X-rayed strainwas found to be relatively rnore sensitive to isoniazid thanthe control. In old cultures, cells of the X-rayed strain weresignificantly smaller than those of the untreated strain. The effects of X-rays on cell- and heterocyst dimensions ofthe nitrogen-fixing alga Chlorogloea fritschii Mitra were studied.In the irradiated material the cell diameter and heterocystbreadth were greater, rather than smaller, than in unirradiatedmaterial.