C. Wagner et al., ACETOGENIC CAPACITIES AND THE ANAEROBIC TURNOVER OF CARBON IN A KANSAS PRAIRIE SOIL, Applied and environmental microbiology, 62(2), 1996, pp. 494-500
To assess the anaerobic capacities of a temperate grassland soil, a Ka
nsas prairie soil was incubated anaerobically as either soil-water (1:
2) suspensions or as soil microcosms at 78% soil water-holding capacit
y. Prairie soil formed acetate and CO2 as the two main initial carbona
ceous products from the anaerobic turnover of endogenous organic matte
r, Metabolic capacities of soil suspensions and microcosms were simila
r. Rates of acetate formation from endogenous organic matter in soil-w
ater suspensions incubated at 40, 30, and 15 degrees C approximated 3.
3, 2.4, and 1.1 mu g of acetate per g (dry weight) of soil per h, resp
ectively, Supplemental H-2 and CO2 were subject to consumption with th
e apparent concomitant synthesis of acetate in both soil suspensions a
nd soil microcosms. In soil microcosms, rates of H-2-dependent acetoge
nesis at 30 and 55 degrees C were nearly equivalent, The uptake of sup
plemental H-2 was not coupled to methanogenesis under any condition ex
amined. These anaerobic activities were relatively stable when sails w
ere subjected to either aerobic drying or alternating periods of O-2 e
nrichment, On the basis of the formation of nitrogen (N-2), denitrific
ation was engaged during anaerobic incubation periods; nitrous oxide (
N2O) was also formed under certain conditions. Although extended incub
ation of soil induced the delayed methanogenic turnover of acetate, ac
etate was subject to immediate turnover under either O-2- or nitrate-e
nriched conditions, These studies support the following concepts: (i)
obligately anaerobic bacteria such as acetogenic bacteria are stable t
o periods of aerobiosis and are active in the anaerobic microsites of
oxic soils, and (ii) acetate synthesized in anaerobic microsites of ox
ic terrestrial soils constitutes a trophic link to both aerobic and an
aerobic microbial communities.