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Appl. Environ. Microbiol., Feb 1996, 494-500, Vol 62, No. 2
C Wagner, A GriessHammer and HL Drake
To assess the anaerobic capacities of a temperate grassland soil, a Kansas
prairie soil was incubated anaerobically as either soil-water (1:2)
suspensions or as soil microcosms at 78% soil water-holding capacity.
Prairie soil formed acetate and CO(inf2) as the two main initial
carbonaceous products from the anaerobic turnover of endogenous organic
matter. Metabolic capacities of soil suspensions and microcosms were
similar. Rates of acetate formation from endogenous organic matter in
soil-water suspensions incubated at 40, 30, and 15(deg)C approximated 3.3,
2.4, and 1.1 (mu)g of acetate per g (dry weight) of soil per h,
respectively. Supplemental H(inf2) and CO(inf2) were subject to consumption
with the apparent concomitant synthesis of acetate in both soil suspensions
and soil microcosms. In soil microcosms, rates of H(inf2)-dependent
acetogenesis at 30 and 55(deg)C were nearly equivalent. The uptake of
supplemental H(inf2) was not coupled to methanogenesis under any condition
examined. These anaerobic activities were relatively stable when soils were
subjected to either aerobic drying or alternating periods of O(inf2)
enrichment. On the basis of the formation of nitrogen (N(inf2)),
denitrification was engaged during anaerobic incubation periods; nitrous
oxide (N(inf2)O) was also formed under certain conditions. Although
extended incubation of soil induced the delayed methanogenic turnover of
acetate, acetate was subject to immediate turnover under either O(inf2)- or
nitrate-enriched conditions. These studies support the following concepts:
(i) obligately anaerobic bacteria such as acetogenic bacteria are stable to
periods of aerobiosis and are active in the anaerobic microsites of oxic
soils, and (ii) acetate synthesized in anaerobic microsites of oxic
terrestrial soils constitutes a trophic link to both aerobic and anaerobic
microbial communities.
Copyright © 1996, American Society for Microbiology
Acetogenic Capacities and the Anaerobic Turnover of Carbon in a Kansas Prairie Soil
Lehrstuhl fur Okologische Mikrobiologie, BITOK, Universitat Bayreuth, 95440 Bayreuth, Germany
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