TABLE 1.

Rates of spontaneous mutation in H. volcanii pyrE2

	Fluctuation test (quartile method)a
Basis	Equal growth	Slower growth	P0 methodb	MA methodc
Quartile 1	1.43 ± 0.84	1.32 ± 0.72
Median	1.72 ± 0.62	2.01 ± 0.53
Quartile 3	2.29 ± 0.87	2.63 ± 0.95
Meand	1.81 ± 0.84	1.99 ± 86	1.97 ± 0.57	5.87

^aValues are for eight sets of 20 cultures, incorporating two types of replicates to smooth experimental variability: (i) four different culture sets were inoculated on different days, with different inocula and batches of medium, and (ii) within each, two culture sets differed with respect to the number of cells in the inocula (10³ vs. 10⁴). Calculations shown for slower growth are based on k^m/k^w = 0.9 (Koch 1982).

^bValues are from six independent samples drawn at various cell densities from four cultures for a total of 24 measurements of N and f.

^cMedian of the six component rates 4.30, 4.97, 5.02, 6.73, 23.9, and 26.5 (all ×10⁻⁸).

^dGlobal mean of all 24 determinations (three estimates from each of eight fluctuation tests) are listed in the two quartile columns.