191
Mutation Research, 61 (1979) 191--196 © Elsevier/North-Holland Biomedical Press
SODIUM AZIDE-INDUCED MUTAGENESIS IN Saccbaromyces cerevisiae
L. ~ILH.~NKOV.~, V. SMIOVSK.h, and J. VELEM[NSK~ a Department o f Biochemistry and Microbiology, Institute o f Chemical Technology, 16628 Praha 6, Suchbdtarova 5, and a Institute o f Experimental Botany, Czechoslovak Academy o f Sciences, 160 O0 Praha 6, Flemingovo 2 (Czechoslovakia) (Received 21 July 1978) (Revision received 13 February 1979) (Accepted 27 February 1979)
Summary Sodium azide (0.5--2.0 X 10 -5 M), applied for 24 h on cells growing in complete medium, increased up to 26 times the frequency of reversions and locusspecific suppressor mutations of allele ilvl-92 in diploid strain D7 of Saccharomyces cerevisiae. Similarly, it enhanced the frequency of reversions and/or mitotic gene conversions of alleles trp5-12/trp5-27 up to 19 times. Reconstruction experiments showed that the increase of mutations in complete medium was not due to a selection of prototrophic types under growth conditions and, therefore, that sodium azide acts as a weak mutagen in S. cerevisiae under growth conditions at a low pH. No mutagenic or convertogenic effect was observed when azide was applied to resting cells in buffer at pH 4.2.
Sodium azide is widely used in agriculture as a nematocide, herbicide, stimulator of seed germination, disinfectant of grain, and soil sterilant. It is also used as a preservative in medical diagnostic products or as an anti-hypertension agent, as a bactericide or metabolic inhibitor in biochemical laboratories etc. [11]. Thus, several groups of professionals could be exposed to this agent. Although it is n o t likely to be cancerogenic [7], azide is a very strong mutagen at low pH in some organisms [9,11] and non-mutagenic in others [1]. For instance, in barley it induced as many mutations as ethyl methanesulphonate and other strong mutagens [9]. However, the most efficient doses inducing point (chlorophyll) mutations did not increase the frequency of chromosomal aberrations [8] or DNA single-strand breaks [13] above the spontaneous level. Aberrant metaphases and DNA breaks were induced only by sub-lethal doses [13]. In Salmonella typhimurium and Escherichia coli, azide was mutagenic preferentially in excision
Mutation Research, 61 (1979) 191--196 © Elsevier/North-Holland Biomedical Press
SODIUM AZIDE-INDUCED MUTAGENESIS IN Saccbaromyces cerevisiae
L. ~ILH.~NKOV.~, V. SMIOVSK.h, and J. VELEM[NSK~ a Department o f Biochemistry and Microbiology, Institute o f Chemical Technology, 16628 Praha 6, Suchbdtarova 5, and a Institute o f Experimental Botany, Czechoslovak Academy o f Sciences, 160 O0 Praha 6, Flemingovo 2 (Czechoslovakia) (Received 21 July 1978) (Revision received 13 February 1979) (Accepted 27 February 1979)
Summary Sodium azide (0.5--2.0 X 10 -5 M), applied for 24 h on cells growing in complete medium, increased up to 26 times the frequency of reversions and locusspecific suppressor mutations of allele ilvl-92 in diploid strain D7 of Saccharomyces cerevisiae. Similarly, it enhanced the frequency of reversions and/or mitotic gene conversions of alleles trp5-12/trp5-27 up to 19 times. Reconstruction experiments showed that the increase of mutations in complete medium was not due to a selection of prototrophic types under growth conditions and, therefore, that sodium azide acts as a weak mutagen in S. cerevisiae under growth conditions at a low pH. No mutagenic or convertogenic effect was observed when azide was applied to resting cells in buffer at pH 4.2.
Sodium azide is widely used in agriculture as a nematocide, herbicide, stimulator of seed germination, disinfectant of grain, and soil sterilant. It is also used as a preservative in medical diagnostic products or as an anti-hypertension agent, as a bactericide or metabolic inhibitor in biochemical laboratories etc. [11]. Thus, several groups of professionals could be exposed to this agent. Although it is n o t likely to be cancerogenic [7], azide is a very strong mutagen at low pH in some organisms [9,11] and non-mutagenic in others [1]. For instance, in barley it induced as many mutations as ethyl methanesulphonate and other strong mutagens [9]. However, the most efficient doses inducing point (chlorophyll) mutations did not increase the frequency of chromosomal aberrations [8] or DNA single-strand breaks [13] above the spontaneous level. Aberrant metaphases and DNA breaks were induced only by sub-lethal doses [13]. In Salmonella typhimurium and Escherichia coli, azide was mutagenic preferentially in excision
