Some Carbon-Dioxide Requiring Mutants of Neurospora crassa

Abstract

SUMMARYThis paper describes some Neurospora mutants which grow on minimal medium when the gas-phase contains 30 yo CO, (v/v); they are referred to as 'CO, mutants'. One is an arginine mutant (arg-2; 33442) having a mutation at a different locus from the other arginine CO, mutant (arg-3; 30300) ; a second (arg-11 ; 30820) requires arginine + a purine + a pyrimidine for growth in the absence of CO,; a third (44601) requires arginine + a purine + a pyrimidine + a carboxylic acid for growth in the absence of CO,.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 CO, mutants described here were isolated directly from wild-type Neurospora, and their nutritional requirements in the absence of CO, 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 CO, mutants. Another two of these new CO, mutants, which may be allelic, require carboxylic acids in the absence of CO,; these mutants are similar in their nutritional requirements to the succinate mutants described by Lewis (1948) and Strauss (1956).

Chromosomal loci of Neurospora crassa

“…Strains with some (all?) of the alleles can grow on minimal medium in 30%6 CO2 (108). Leakiness is decreased if CO2 is removed or if uridine is added (880).…”

“…The arginine/citrulline requirement can be suppressed by pyr-3 (CPS' ACI-) (236, 658); see pyr-3. Strains carrying allele 30300 can grow on minimal media in 40% CO2 (108,191). Translocation MEP35 is inseparable from arg-3 (R. H. Davis, personal communication; PB) Called cit-1.…”

“…At 0% CO2 or with small inocula, the requirement for all three supplements is absolute; with increasing CO2 concentration or inoculum size, pyrimidine and then purine can be omitted; at 30% C02, all three supplements can be omitted. (108,192,754) Growth rate and morphology are highly variable among progeny from arg-11 x wild type crosses (754). Grows spasmodically in growth tubes (0.…”

Observations on the Tube Method of Measuring Growth Rate in Neurospora crassa

“…In one mutant strain of Neurospora crassa arg-1 I (30820) which requires either 30 o/o (v/v) carbon dioxide or arginine +purine +pyrimidine for normal growth (Broadbent & Charles, 1965), an inoculum doubling-time of 15 hr for 'leaky growth' on minimal medium was observed as compared with an inoculum doubling-time of 3 hr on complete medium. Once growth was established after the lag on these media the density of growth and the linear growth rates were in the same range.…”

PHYSIOLOGICAL PROPERTIES OF ARGININE SENSITIVE MUTANTS OF <i>SALMONELLA TYPHIMURIUM</i>

“…Growth of some pyrimidine mutants in Neurospora crassa (Broadbent and Charles, 1965) and E. coli (Charles and Roberts, 1968) which require both arginine and uracil in air is known to be stimulated by CO2 on minimal medium.…”