Two soils from temperate sites (UK; arable and grassland) were incubated ae
robically at 0, 5, 15 or 25 degrees C for up to 23 days. During this period
both soils were analysed for soil microbial biomass carbon (biomass C) and
adenosine 5' triphosphate contents (ATP). Biomass C did not change signifi
cantly in either soil at any temperature throughout, except during days 0 t
o 1 in the grassland soil. Soil ATP contents increased slowly throughout th
e 23 days of incubation, from 2.2 to a maximum of 3.1 nmol ATP g(-1) soil i
n the arable soil (a 40% increase) and from 6.2 to a maximum of 11.2 nmol A
TP g(-1) soil in the grassland soil tan increase of 81%), both at 25 degree
s C. Since biomass C did not change either with increasing temperature or i
ncreasing time of incubation, it was concluded that an increase in ATP was
either due to an increase in adenylate energy charge or de novo synthesis o
f ATP, or both. During the incubation, biomass ATP concentrations ranged fr
om about 5 to 12 mu mol ATP g(-1) biomass C but trends between biomass ATP
and incubation temperatures were not very obvious until about day 13. On da
y 23, biomass ATP concentrations were positively and linearly related to te
mperature: (mu mol ATP g(-1) biomass C = 6.98 +/- 0.35 + 0.134 +/- 0.023 T-
0 (r(2) = 0.77) with no significant difference in the slope between the gra
ssland and arable soils. At 25 degrees C the biomass ATP concentration was
10.3 mu mol g(-1) biomass C, remarkably close to many other published value
s. It was concluded that, although the biomass increased its ATP concentrat
ion in response to increasing temperature, the increase was comparatively s
mall. Also, at all temperatures tested, the biomass maintained its ATP conc
entration within the range commonly reported for micro-organisms growing ex
pontentially in vitro. This is despite the fact that the biomass normally e
xhibits other features more typical of a "resting" or dormant population -
a paradox which still is not resolved. (C) 2000 Elsevier Science Ltd. All r
ights reserved.