Preprints
https://doi.org/10.5194/egusphere-2023-2302
https://doi.org/10.5194/egusphere-2023-2302
10 Nov 2023
 | 10 Nov 2023

Improving measurements of microbial growth, death, and turnover by accounting for extracellular DNA in soils

Jörg Schnecker, Theresa Böckle, Julia Horak, Victoria Martin, Taru Sandén, and Heide Spiegel

Abstract. Microbial respiration, growth and turnover are driving processes in the formation and decomposition of soil organic matter. In contrast to respiration and growth, microbial turnover and death currently lack distinct methods to be determined. Here we propose a new approach to determine microbial death rates and to improve measurements of microbial growth. By combining sequential DNA extraction to distinguish between intracellular and extracellular DNA and 18O incorporation into DNA, we were able to measure microbial death rates. We first evaluated methods to determine and extract intracellular and extracellular DNA separately. We then tested the method by subjecting soil from a temperate agricultural field and a deciduous beech forest to either 20 °C, 30 °C or 45 °C for 24 h. Our results show, that while mass specific respiration and gross growth either increased with temperature or remained stable, microbial death rates strongly increased at 45 °C and caused a decrease in microbial biomass and thus in microbial net growth. We further found that also extracellular DNA pools decreased at 45 °C compared to lower temperatures, further indicating enhanced uptake and recycling of extracellular DNA along with increased respiration, growth and death rates. Additional experiments including soils from more and different ecosystems as well as testing the effects of factors other than temperature on microbial death are certainly necessary to better understand the role of microbial death in soil C cycling. We are nevertheless confident that this new approach to determine microbial death rates and dynamics of intracellular and extracellular DNA separately will help to improve concepts and models of C dynamics in soils in the future.

Jörg Schnecker, Theresa Böckle, Julia Horak, Victoria Martin, Taru Sandén, and Heide Spiegel

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2302', Anonymous Referee #1, 15 Dec 2023
    • AC2: 'Reply on RC1', Jörg Schnecker, 02 Feb 2024
  • RC2: 'Comment on egusphere-2023-2302', Anonymous Referee #2, 05 Jan 2024
    • AC1: 'Reply on RC2', Jörg Schnecker, 02 Feb 2024
Jörg Schnecker, Theresa Böckle, Julia Horak, Victoria Martin, Taru Sandén, and Heide Spiegel
Jörg Schnecker, Theresa Böckle, Julia Horak, Victoria Martin, Taru Sandén, and Heide Spiegel

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Short summary
Microbial processes are driving the formation and decomposition of soil organic matter. In contrast to respiration and growth, microbial death rates currently lack distinct methods to be determined. Here we propose a new approach to measure microbial death rates. This new approach to determine microbial death rates and dynamics of intracellular and extracellular DNA separately will help to improve concepts and models of C dynamics in soils in the future.