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Appl. Environ. Microbiol., Jun 1997, 2224-2231, Vol 63, No. 6
A Frostegard, SO Petersen, E Baath and TH Nielsen
Microbial community dynamics associated with manure hot spots were studied
by using a model system consisting of a gel-stabilized mixture of soil and
manure, placed between layers of soil, during a 3-week incubation period.
The microbial biomass, measured as the total amount of phospholipid fatty
acids (PLFA), had doubled within a 2-mm distance from the soil-manure
interface after 3 days. Principal-component analyses demonstrated that this
increase was accompanied by reproducible changes in the composition of
PLFA, indicating changes in the microbial community structure. The effect
of the manure was strongest in the 2-mm-thick soil layer closest to the
interface, in which the PLFA composition was statistically significantly
different (P < 0.05) from that of the unaffected soil layers throughout
the incubation period. An effect was also observed in the soil layer 2 to 4
mm from the interface. The changes in microbial biomass and community
structure were mainly attributed to the diffusion of dissolved organic
carbon from the manure. During the initial period of microbial growth,
PLFA, which were already more abundant in the manure than in the soil,
increased in the manure core and in the 2-mm soil layer closest to the
interface. After day 3, the PLFA composition of these layers gradually
became more similar to that of the soil. The dynamics of individual PLFA
suggested that both taxonomic and physiological changes occurred during
growth. Examples of the latter were decreases in the ratios of 16:1 omega
7t to 16:1 omega 7c and of cyclopropyl fatty acids to their respective
precursors, indicating a more active bacterial community. An inverse
relationship between bacterial PLFA and the eucaryotic 20:4 PLFA
(arachidonic acid) suggested that grazing was important.
Copyright © 1997, American Society for Microbiology
Dynamics of a microbial community associated with manure hot spots as revealed by phospholipid fatty acid analyses
Department of Microbial Ecology, Lund University, Sweden. asa.frostegard@mbioekol.lu.se
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