Some Carbon-Dioxide Requiring Mutants of Neurospora crassa

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Abstract
This paper describes some Neurospora mutants which grow on minimal medium when the gas phase contains 30% CO2 (v/v); they are referred to as "CO2 mutants." One is an arginine mutant (arg-2; 33442) having a mutation at a different locus from the other arginine CO2 mutant (arg-3; 30300); a second (arg-11; 30820) requires arginine + a purine + a pyrimidine for growth in the absence of CO2; a third (44601) requires arginine + a purine + a pyrimidine + a carboxylic acid for growth in the absence of CO2. The mutations in mutants 30820 and 44601 are allelic and the carboxylic-acid requirement of mutant 44601 is attributable to its genetic background. The remaining CO2 mutants described here were isolated directly from wild-type Neurospora. and their nutritional requirements in the absence of CO2 subsequently determined. Two of these mutants, which are allelic, are adenine-requiring mutants sited at the adenine-3 locus, although the adenine-3A and -3B mutants 38709 and Y 112-M2 are not CO2 mutants. Another two of these new CO2 mutants, which may be allelic, require carboxylic acids in the absence of CO2; these mutants are similar in their nutritional requirements to the succinate mutants described by Lewis (1948) and Strauss (1956).