Engineering of mutants of Anabaena PCC7120 (cyanobacterium) constructed by DNA-plasmid transfer and UV-radiation resistant to the herbicide Diuron capable of ammonia production

Abstract

Ten mutants of Anabaena PCC7120 were successfully constructed to express two genetic traits, ammonia production and the resistance to the Diuron herbicide, using transposon induced mutagenesis and UV-radiation. The ranges for heterocyst frequency and ammonia production of mutants were 4.2%-6.8% and 2.3-6.6 μmol mg dry wt-1 h-1 respectively. The herbicide-resistance threshold for all mutants was 2.0 mg L-1, above which the mutants started to decline in health as observed microscopically. The dry weight of the mutants reached 300-400 mg L-1 with growth patterns similar to those of the wild-type after 20 days of growth in a batch culture in the presence of Diuron. In contrast, the addition of herbicide to the wild-type has led to a drastic reduction in O2- evolution followed by cellular vaculation, breakdown of filaments and cell death within 24 h (data not shown; microscopic inspection).