Studies on mutation in blue-green algae : auxotrophic mutants and mutants impaired in inorganic nitrogen metabolism



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The procaryotic nature of the blue-green algal cell, implying a relative simplicity, coupled with its capacity for carrying out O₂-evolving photosynthesis presents an attractive biological system for the study of the relation between photosynthesis and other cellular processes. To study this relationship three possible choices exist. They are: 1). The study of whole unmodified cells; 2). The study of cell-free systems; and, 3). The study of whole modified cells. I have chosen this last possibility recognizing that two further modifications are available, viz., to use various inhibition techniques to study a given cellular process or to use an induced, but nonetheless natural, event (mutation) followed by elective culture methods to select progeny affected in the process one wishes to study. The latter approach, only recently available with blue-green algae, was chosen. Despite the large background of information on mutation and genetics in other microbial systems, work in this area with blue-green algae has just begun. [...] The purpose of this investigation has been threefold: 1). To study mutation and the resultant mutants in an "obligate" photoautotroph. 2). To obtain auxotrophic mutants which might be useful in the study of intermediary metabolism in the blue-green algae as well as provide a system which could be used to demonstrate unequivocally some mode of sexual recombination. 3). To study the relationship between nitrate reduction and photosynthesis in whole cells without resorting to 2,4-dinitrophenol (DNP) or acid media (Kessler, 1964) to measure the accumulation of the product of nitrate reduction, namely NO₂̄. It is assumed that the process of nitrate assimilation in mutant progeny reflects the process in the parent strain