Study of mutation, mutants, and repair in the blue-green alga Agmenellum quadruplicatum



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The study of induced mutation in blue-green algae can be expected to yield significant information in several areas. First, it is desirable to know which mutagens are capable of causing stable mutations in blue-greens. Several mutagens have been reported to cause mutation in blue-green algae; but in only a few of these cases were stable mutant clones isolated from the wild type (3, 24). Once it is known that an agent is mutagenic, it becomes useful to study the way in which it affects a cell. For instance, what are the optimum conditions for survival and mutagenesis? Can the lethal or mutagenic effect be reversed by some prior, coincident, or post treatment given a population of cells? The blue-green algae provide a new biological system in which mutagenic agents and the theories of mutagenesis may be checked and correlated with other biological systems. The second area concerns the study of the mutants themselves. It is anticipated that mutants may be useful in studying the reaction mechanisms in photosynthesis (12). The use of mutants may allow closer scrutiny of the presumed nature of obligate photoautotrophy in blue-green algae (7, 10, 21). As a new biological system, new biochemical pathways may be discovered. And then too, perhaps the role of light in cellular processes other than photosynthesis (9) can be more clearly elucidated with mutants. The last area is blue-green algal genetics. It has been reported that some form of recombination occurs in blue-green algae (3, 20). However, blue-green algal genetics is for the most part an unknown area, yet to be studied. Stable mutants with well defined metabolic blocks are necessary experimental tools for such studies. The purpose of this study was multifold. First, to confirm the earlier work of Van Baalen (24) in regard to N-methyl-N'-nitro-N-nitrosoguanidine induction of stable mutants of blue-green algae. Second, to define the optimum conditions of survival and mutagenesis of blue-green algal cells treated with this same chemical mutagen. Third, to isolate and characterize selected visible mutants induced by this potent mutagen. In the process of fulfilling the original purpose of the study a repair phenomenon was discovered and preliminary characterization of this is reported