TABLE 2.

Growth rates of RNase R Walker motif mutant strains in minimal medium

Overnight cultures of the strains used in Table 1 were subcultured into M9/glucose minimal medium and grown at the indicated temperatures. Periodic measurements of A₆₀₀ were made within the exponential growth phase. Cell doubling times and standard deviations were calculated based on data from five replicate experiments. * denotes p < 0.05 and ** denotes p < 0.0001 by a two-tailed Student's t test as compared with the WT strain.

Growth temperature	Doubling time (min)
	WT	R−	R736A	R D168A,D169A
42 °C	79 ± 5	81 ± 6	80 ± 5	80 ± 5
37 °C	63 ± 4	65 ± 5	67 ± 5	66 ± 5
31 °C	119 ± 6	126 ± 6	129 ± 7*	127 ± 6*
25 °C	135 ± 6	183 ± 7	189 ± 7**	184 ± 6**
15 °C	963 ± 8	1402 ± 10	1421 ± 11**	1410 ± 11**