Enhancing Microbial Carbon Use Efficiency Analysis: Insights from Soil-Free Cell Extract Studies

Milan Varsadiya1, Fatemeh Abadi2, Blagodatskaya Evgenia2, Lueders Tillmann1
1 Chair of Ecological Microbiology, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Dr-Hans-Frisch-Str. 1-3, 95448 Bayreuth, Germany
2 Department of Soil Ecology, UFZ-Helmholtz Centre for Environmental Research, Halle (Saale), Germany

P 3.12 in Zooming in: Small scale findings

The fate of soil organic matter hinges on microbial carbon (C) use efficiency (CUE): the ratio of C assimilated by microorganisms and retained within them, versus that released as CO2 during decomposition. To understand the factors (e.g., nutrient chemistry) influencing CUE and assess metabolic activity and C utilization, soil-free microbial cell extract (SFCE) offers a per-cell perspective, distinct from studying microorganisms within complex soil.

SFCE directly quantifies microbial biomass and activity in a near-natural soil microbiome, essential for CUE calculation. Isolating microbial cells from soil, we gauge C absorbed and its efficiency. Microbial cell suspensions from agricultural soil, extracted via a Nycodenz density gradient, were maintained in pre-extracted dissolved organic matter. Cells stained with Syto9 were quantified using flow cytometry. Suspensions, supplied with glucose and substrates, had metabolic activity assessed via microcalorimeter (TAM Air), compared to intact soil.

Preliminary findings suggest SFCE biomass is valuable for studying relative CUE of microbial groups and identifying key drivers, without soil complexities. Data from SFCE studies inform models simulating microbial processes and CUE dynamics in soil ecosystems. These models predict how environmental changes or climate scenarios might impact microbial CUE and carbon cycling in soils.

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