Georghiou P E, Blagden P A, Winsor L, Williams D T
Department of Chemistry, Memorial University of Newfoundland, St. John's, Canada.
Mutat Res. 1989 Jan-Feb;225(1-2):33-9. doi: 10.1016/0165-7992(89)90029-8.
It has been proposed that increases in the number of bacteria applied to each plate can enhance the sensitivity of the Ames S. typhimurium mutagenicity assay. These procedures have the potential to elevate the number of spontaneous revertants (SR) by increasing the contribution of pre-existing revertants (PER) present before application of the bacteria to the limited histidine test plates. We have investigated the contribution of PER when 10(9) bacteria are applied to the plates and found that the number of PER is dependent on the handling and storage of the cultures used to inoculate the overnight broth. The average number of PER/10(9) viable bacteria after overnight growth in broths inoculated from a frozen permanent, lyophilized permanent, master plate, and an isolated colony, of TA98 were 267, 188, 57 and 13 respectively. The resultant elevation of the number of SR for a strain may result in a failure to identify a mutagenic response. It is recommended that the number of PER be monitored in any modification of the Ames test that makes use of elevated numbers of bacteria.
有人提出，增加每个平板上所接种细菌的数量可以提高鼠伤寒沙门氏菌艾姆斯致突变性试验的灵敏度。这些操作有可能通过增加在将细菌接种到有限的组氨酸试验平板之前就已存在的预先存在的回复突变体（PER）的贡献，来提高自发回复突变体（SR）的数量。我们研究了向平板接种10⁹个细菌时PER的贡献，发现PER的数量取决于用于接种过夜肉汤的培养物的处理和储存方式。从冷冻永久平板、冻干永久平板、主平板和一个分离菌落接种肉汤过夜培养后，TA98每10⁹个活细菌中PER的平均数量分别为267、188、57和13。菌株SR数量的这种增加可能导致无法识别诱变反应。建议在艾姆斯试验的任何利用增加细菌数量的改进方法中监测PER的数量。
