TABLE 1.

Intracellular amounts of nucleoside triphosphates, NAD, and PRPP in H. volcanii and H. halobium^a

Compound	Amt (nmol/ml) inb:
	H. volcanii (doubling time, 3.8 h)	H. halobium (doubling time, 8.5 h)
ATP	1.77 ± 0.07	0.82 ± 0.08
GTP	0.79 ± 0.08	0.28 ± 0.01
CTP	0.58 ± 0.14	0.12 ± 0.03
UTP	0.72 ± 0.05	0.29 ± 0.05
dATP	0.06 ± 0.01	0.02 ± 0.01
dGTP	0.04 ± 0.02	0.02 ± 0.01
dCTP	0.05 ± 0.01	0.02 ± 0.01
dTTP	0.06 ± 0.03	0.03 ± 0.02
PRPP	0.98 ± 0.06	0.38 ± 0.10
NAD	0.12 ± 0.04	0.12 ± 0.02

^aCells growing exponentially in liquid medium at 40°C were analyzed as described in Materials and Methods. Data are based on the following growth characteristics at an OD₄₃₆ of 1. H. volcanii: cell numbers, (5.3 ± 0.5) × 10⁹ per ml; protein content, 176 ± 13 μg/ml; RNA content, 31 ± 5 μg/ml. H. halobium: cell numbers, (5.4 ± 0.5) × 10⁹ per ml; protein content, 197 ± 17 μg/ml; RNA content, 26 ± 4 μg/ml. A Burker counting chamber and a light microscope with a magnification of ×400 were used to determine total cell numbers. 

^bValues are means of at least four experiments ± standard deviations. OD₄₃₆, 1.