K. Kusel et Hl. Drake, EFFECTS OF ENVIRONMENTAL PARAMETERS ON THE FORMATION AND TURNOVER OF ACETATE BY FOREST SOILS, Applied and environmental microbiology, 61(10), 1995, pp. 3667-3675
The capacity to form acetate from endogenous matter was a common prope
rty of diverse forest soils when incubated under anaerobic conditions,
At 15 to 20 degrees C, acetate synthesis occurred without appreciable
delay when forest soils were incubated as buffered suspensions or in
microcosms at various percentages of their maximum water holding capac
ity. Rates for acetate formation with soil suspensions ranged from 35
to 220 mu g of acetate per g (dry weight) of soil per 24 h, and maxima
l acetate concentrations obtained in soil suspensions were two- to thr
eefold greater than those obtained with soil microcosms at the average
water holding capacity of the soil, Cellobiose degradation in soil su
spensions yielded H-2 as a transient product. Under anaerobic conditio
ns, supplemental H-2 and CO2 were directed towards the acetogenic synt
hesis of acetate, and enrichments yielded a syringate-H-2-consuming ac
etogenic consortium. At in situ temperatures, acetate was a relatively
stable anaerobic end product; however, extended incubation periods in
duced acetoclastic methanogenesis and sulfate reduction, Higher mesoph
ilic and thermophilic temperatures greatly enhanced the capacity of so
ils to form methane, Although methanogenic and sulfate-reducing activi
ties under in situ-relevant conditions were negligible, these findings
nonetheless demonstrated the occurrence of methanogens and sulfate-re
ducing bacteria in these aerated terrestrial soils, In contrast to the
protracted stability of acetate under anaerobic conditions at 15 to 2
0 degrees C with unsupplemented soils, acetate formed by forest soils
was rapidly consumed in the presence of oxygen and nitrate, and substr
ate-product stoichiometries indicated that acetate turnover was couple
d to oxygen-dependent respiration and denitrification. The collective
results suggest that acetate formed under anaerobic conditions might c
onstitute a trophic link between anaerobic and aerobic processes in fo
rest soils.