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Cytochrome c is not essential for viability of the fungus Aspergillus nidulans


Bradshaw, RE and Bird, DM and Gardiner, RE and Brown, SC and Hirst, P, Cytochrome c is not essential for viability of the fungus Aspergillus nidulans, Molecular Genetics and Genomics , 266, (1) pp. 48-55. ISSN 1617-4615 (2001) [Refereed Article]

DOI: doi:10.1007/s004380100517


The filamentous fungus Aspergillus nidulans is an obligate aerobe, which is capable of anaerobic survival, but not anaerobic growth. Since cytochrome c forms an essential part of the oxidative respiratory pathway it was expected that mutants lacking this component would be non-viable. Gene replacement of one homologue of the cycA (cytochrome c) gene was carried out in a diploid strain. Benomyl-induced haploidisation of this diploid yielded all cycA+ haploid colonies, initially suggesting that loss of cycA was indeed lethal. However, use of an alternative unbiased method to recover haploids yielded viable, but slow-growing, cycA- mutants. Replacement of the cycA locus in the cycA- mutants was verified by Southern blotting. Spectral analysis confirmed the absence of detectable levels of cytochrome c, and respiratory insensitivity to cyanide suggested the absence of cytochrome c-dependent respiration. Growth parameters were consistent with those expected of a cycA- mutant. Compared to the wild type, the mutants grew slowly on fermentable carbon sources, did not grow on non-fermentable carbon sources, and produced higher levels of ethanol. To our knowledge, this is the first report of a filamentous fungus that remains viable after complete elimination of a functional cytochrome c gene. We propose that the mutants are viable due to their ability to ferment and to use alternative respiratory pathways.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Microbiology
Research Field:Microbial genetics
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the environmental sciences
UTAS Author:Brown, SC (Dr Simon Brown)
ID Code:33099
Year Published:2001
Web of Science® Times Cited:10
Deposited By:Health Sciences A
Deposited On:2005-06-22
Last Modified:2011-08-03

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