Mutation to resistance for virus N-1 in the blue-green alga Nostoc muscorum

Spontaneous and induced host-range mutants of cyanophage N-1

Optimal conditions for the induction of host-range mutants of cyanophage N-1 by acridine orange were established. Induced host-range mutants were isolated with a frequency of 0.1 to 4.0 x 10(-5) over a spontaneous mutation frequency of 0.2-3.6 x 10(-11).

Genetic effects of N-methyl-N'-nitro-N-nitrosoguanidine and its homologs

Since the discovery of the mutagenic activity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in 1960, this compound has become one of the most widely used chemical mutagens. The present paper gives a survey on the chemistry, metabolism, and mode of interaction of MNNG with DNA and proteins, and of the genotoxic effects of this agent on microorganisms, plants, and animals, including human cells cultured in vitro. Data on the carcinogenicity and teratogenicity of MNNG as well as on the genotoxic effects of homologs of MNNG are also presented.

Effects of host aging, ions, and pH on the adsorption of the cyanovirus N-1 to Nostoc muscorum

The adsorption rate of the cyanovirus N-1 infecting the nitrogen-fixing blue-green alga Nostocmuscorum decreased with aging of algal cultures and the virus failed to adsorb to the dead host cells. The adsorption rate declined in saline magnesium chloride solution compared to that in algal growth medium. The addition of amino acids like L-tryptophan and L-phenylalanine failed to enhance the adsorption rate of the virus. Optimal pH of adsorption was 7.6 to 8;1.

Effect of temperature on the adsorption and one-step growth of the Nostoc virus N-1

This study was an attempt to observe the effects of temperature on adsorption and one-step growth of the virus N-1 infecting the nitrogen-fixing cyanobacterium Nostoc muscorum. Adsorption rate was found to maximum at 40 degrees C whereas no adsorption occurred at 10 degrees C. The Q10 value was about 2.03 and the energy of activation, Ea was 16.3 kcal/mole for the adsorption process. The development cycle of the virus was temperature sensitive. With increase in temperature, a gradual increase in inhibition of virus yield i.e. 8.33% at 30 degrees C, 35.3% at 35 degrees C and complete inhibition at 40 degrees C was observed. Out of 7 h latent period, the early 4 h were temperature sensitive and heat treatment had a reversible inhibitory effect on virus development. The temperature treatment did not affect the rise period but burst-size was reduced.