RT Journal Article SR Electronic(1) A1 Gillie, O. J.YR 1970 T1 Methods for the Study of Nuclear and Cytoplasmic Variation in Respiratory Activity of Neurospora crassa, and the Discovery of Three New Genes JF Microbiology, VO 61 IS 3 SP 379 OP 395 DO https://doi.org/10.1099/00221287-61-3-379 PB Microbiology Society, SN 1465-2080, AB SUMMARY Three methods of detecting respiratory variation in Neurospora crassa have been investigated. They involved the addition of dyes (pontamine sky blue and eosin yellowish) tellurite or tetrazolium to a complete medium containing ethionine. The latter prevented conidiation and enabled the colours of the colonies to be seen clearly. These methods were used to distinguish nuclear and cytoplasmic cytochrome mutants (cyt-i, cyt-2, mi-i, mi-3, SG-3 and SG) from wild-type colonies on the basis of colour. Tetrazolium violet (2-5-diphenyl-3-(i-napthyl)-tetrazolium chloride) incorporated into modified Nagai medium with ethionine is recommended for distinguishing cytoplasmic mutants of Neurospora from wild-type. Certain other nuclear mutants were also distinguishable from wild-type in some of these tests. These were ac-i, ac-2, acr-3, ad-4, leu-5, nit-i, oxD-i. Thirty-two wild-type strains in reciprocal crosses were tested on these media to find whether these tests would distinguish any nuclear or cytoplasmic variation. No new cytoplasmic variants were found. Three new nuclear genes, Bm (mauve on dye media), Tet-R (ability to reduce tetrazolium) and sir (suppressor of mi-3) are described and have been mapped. All three loci were linked to the mating type locus on chromosome 1. Tet-R was found in only certain wild-type strains of mating type a (e.g. 74-or8-ia), and Tet-W (unable to reduce tetrazolium) was found in all wild-type strains of mating type A (e.g. 74-or23-i A) and certain wild-types of mating type a;f, a suppressor of mi-i, also suppressed SG-3 and SG, but not mi-3; su− suppressed mi-3, but none of the other cytoplasmic mutants., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-61-3-379