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Updated: Jan 21, 2026

Extraction and Analysis of Microbial Phospholipid Fatty Acids in Soils
Published on: August 26, 2016
Drought-induced soil microbial amino acid and polysaccharide change and their implications for C-N cycles in a
Madhavi L Kakumanu1,2, Li Ma1,3, Mark A Williams4
1School of Plant and Environmental Sciences, 301 Latham Hall, Virginia Polytechnic and State University, Blacksburg, VA, 24060, USA.
Abstract:
High microbial carbon (MBC) demand, a proxy for energy demand (cost), during soil microbial response to stressors such as drought are a major gap in understanding global biogeochemical cycling of carbon (C) and nitrogen (N). The dynamics of two dominant microbial pools (amino acids; AA and exopolymeric substances; EPS) in soils exposed to drying and C and N amendment to mimic both low and high nutrient soil habitats were examined. It was hypothesized that dynamics of EPS and AA (osmolytes) would be greater when soil drying was preceded by a pulse of bioavailable C and N. Drying reduced AA content, even as overall soil MBC increased (~35%). The increase in absolute amounts and mol% of certain AA (eg: Taurine, glutamine, tyrosine, phenylalanine) in the driest treatment (-10 MPa) were similar in both soils regardless of amendment suggesting a common mechanism underlying the energy intensive acclimation across soils. MBC and EPS, both increased ~1.5X and ~3X due to drying and especially drying associated with amendment. Overall major pools of C and N based microbial metabolites are dynamic to drying (drought), and thus have implications for earth's biogeochemical fluxes of C and N, perhaps costing 4-7% of forest fixed photosynthetic C input during a single drying (drought) period.
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Work Done During Volume Change
Consider a gas confined to a cylinder fitted with a movable piston at one end. If the gas expands from volume V1 to volume V2, it exerts a force on the piston, such that the piston moves by a distance dr.
The work done by the gas on the piston can be expressed as
Net Change Theorem
Standard Entropy Change for a Reaction

