TABLE 1.

Effect of pH on the growth and survival of M. jannaschii, A. profundus, T. fumicolans, and Pyrococcus strain GB-D at optimal (82°C or 90°C) and superoptimal (88°C or 100°C) temperatures with and without nutrients

pH for indicated species	Growtha with growth nutrients at:		Survivalb without growth nutrients at:
	82°C	88°C	82°C	88°C
M. jannaschii
6.5	NDf	ND	6	6
6.0	++	++	3.5c	3c
5.0	++	++	3c	0
4.5	++	++	0	0
A. profundus
6.5	++	++	6	6
6.0	++	++	6c	6c
5.0	−	−	0d	0d
4.5	−	−	ND	ND
	90°C	100°C	90°C	100°C
T. fumicolans
7.5	++	++	6	0
5.5	++	++	6	0
5.0	++	++	6	0
4.5	+	+	0	0
Pyrococcus sp.
7.5	++	++	6	6
5.5	++	++	6e	6
5.0	++	+	6	6
4.5	++	+	6e	6

^aGrowth is indicated by an increase in cell number of greater than or equal to 1 order of magnitude (++), less than 1 order of magnitude (+), or less than one doubling (−).

^bSurvival is indicated by the number of dilution steps in the sixfold dilution series that exhibited regrowth after 24-h exposure to nongrowth conditions.

^cThese numbers are averages from two experiments.

^dAt pH 4.7, good survival was found (5 at 82°C and 6 at 88°C), indicating highly variable results in the pH range of 4.7 to 5.

^eNumber verified by most-probable-number calculation.

^fND, no data collected.