Unusual radioresistance of nitrogen-fixing cultures of Anabaena strains.
Nitrogen-fixing cultures of two species of the filamentous, heterocystous cyanobacterium Anabaena, namely Anabaena sp. strain L-31 and Anabaena torulosa were found to be highly tolerant to 60Co gamma radiation. No adverse effect on diazotrophic growth and metabolism were observed up to a dose of 5 kGy. At higher doses, radiation tolerance showed a correspondence with the inherent osmotolerance, with Anabaena L-31 being the more radiation tolerant as well as osmotolerant strain. In Anabaena L-31, exposure to 6 kGy of gamma rays resulted in genome disintegration, but did not reduce viability. Irradiation delayed heterocyst differentiation and nitrogen fixation, and marginally affected diazotrophic growth. All the affected parameters recovered after a short lag, without any discernible postirradiation phenotype. The radiation tolerance of these Gram-negative photoautodiazotrophs is comparable with that of the adiazotrophic photoautotrophic cyanobacterium Chroococcidiopsis or adiazotrophic heterotroph Deinococcus radiodurans. This is the first report of extreme radioresistance in nitrogen-fixing Anabaena cultures.
Singh
Harinder
H
Molecular Biology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
Fernandes
Tonina
T
Apte
Shree Kumar
SK
D017033:Anabaena / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair; D004269:DNA, Bacterial; D005720:Gamma Rays; D009586:Nitrogen Fixation; D011836:Radiation Tolerance
D004269:DNA, Bacterial
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