Competition within low-density bacterial populations as an unexpected factor regulating carbon decomposition in bulk soil

Journal Article · 15 September 2021 · Soil Biology and Biochemistry

DOI: https://doi.org/10.1016/j.soilbio.2021.108423 · OSTI ID:1864816

Coche, Alexandre ^[1]; Babey, Tristan ^[2]; Rapaport, Alain ^[3]; Gonod, Laure Vieublé ^[4]; Garnier, Patricia ^[4]; Nunan, Naoise ^[5]; de Dreuzy, Jean-Raynald ^[1]

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1. Univ. Rennes (France)
2. Stanford Univ., CA (United States)
3. French National Research Institute for Agriculture, Food and Environment (INRAE), Montpellier (France); Univ. Montpellier (France)
4. Univ. Paris-Saclay, Thiverval-Grignon (France). AgroParisTech
5. Sorbonne Univ., Paris (France) Inst. of Ecology and Environmental Sciences; Swedish Univ. of Agriculutral Sciences, Uppsala (Sweden)

Bacterial decomposition of organic matter in soils is generally believed to be mainly controlled by the access bacteria have to organic substrate. The influence of bacterial traits on this control has, however, received little attention. Using the substrate-dependent Monod growth model, we develop a bioreactive transport model to screen the interactive impacts of spatial dispersion and bacterial traits on mineralization. Bacterial traits primarily involved in the bacterial response to the substrate concentration, such as the maximum specific uptake rate and efficiency, the adaptation time of the uptake rate and the initial population density, are considered. We compare the model results with two sets of previously performed cm-scale soil-core experiments in which the mineralization of the pesticide 2,4-D was measured under well-controlled initial distributions and transport conditions. Bacterial dispersion away from the initial substrate location induced a significant increase in 2,4-D mineralization. Additionally, it reveals an increase of specific uptake rates at lower bacterial densities, more than compensating the decrease of specific uptake rates caused by substrate dilution. This regulation of bacterial activities by density, caused by the local depletion of substrate by competing bacteria, becomes dominant for bacteria with an efficient uptake of substrate at low substrate concentrations (a common feature of oligotrophs). Such oligotrophs, commonly found in soils, compete with each other for substrate even at remarkably low population densities. The ratio-dependent Contois growth model, which includes a density regulation in the expression of the uptake efficiency, is more accurate and convenient to calibrate than the substrate-dependent Monod model, at least under these conditions. In view of their strong interactions, bioreactive and transport processes cannot be handled independently but should be integrated, in particular when reactive processes of interest are carried out by oligotrophs.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); French National Research Agency (ANR)
• Grant/Contract Number: AC02-76SF00515
• OSTI ID: 1864816
• Journal Information: Soil Biology and Biochemistry, Journal Name: Soil Biology and Biochemistry Vol. 164; ISSN 0038-0717
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English