Importance of substrate quality and clay content on microbial extracellular polymeric substances production and aggregate stability in soils

• Published in: Biology and fertility of soils Vol. 58; no. 4; pp. 435 - 457
• Main Authors: Olagoke, Folasade K., Bettermann, Antje, Nguyen, Phuong Thi Bich, Redmile-Gordon, Marc, Babin, Doreen, Smalla, Kornelia, Nesme, Joseph, Sørensen, Søren J., Kalbitz, Karsten, Vogel, Cordula
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2022; Springer Nature B.V
• Subjects: Aggregates; Agriculture; Archaea; Biomass; Biomedical and Life Sciences; Carbon dioxide; Cellulose; Clay; Community structure; Extracellular; Extracellular polymers; Gene sequencing; Life Sciences; Microbial activity; Microorganisms; Montmorillonite; Montmorillonites; Original Paper; Polysaccharides; Proteins; Respiration; rRNA 16S; Size distribution; Soil; Soil aggregates; Soil investigations; Soil Science & Conservation; Soil stability; Soils; Stability; Starch; Substrates; Clay minerals; Organic matter; 16S rRNA gene sequencing; Extracellular polymeric substances (EPS); Soil aggregates stability; Microbial community composition
• ISSN: 0178-2762; 1432-0789
• DOI: 10.1007/s00374-022-01632-1

We investigated the effects of substrate (cellulose or starch) and different clay contents on the production of microbial extracellular polymeric substances (EPS) and concomitant development of stable soil aggregates. Soils were incubated with different amounts of montmorillonite (+ 0.1%, + 1%, + 10%) both with and without two substrates of contrasting quality (starch and cellulose). Microbial respiration (CO 2 ), biomass carbon (C), EPS-protein, and EPS-polysaccharide were determined over the experimental period. The diversity and compositional shifts of microbial communities (bacteria/archaea) were analysed by sequencing 16S rRNA gene fragments amplified from soil DNA. Soil aggregate size distribution was determined and geometric mean diameter calculated for aggregate formation. Aggregate stabilities were compared among 1–2-mm size fraction. Starch amendment supported a faster increase than cellulose in both respiration and microbial biomass. Microbial community structure and composition differed depending on the C substrate added. However, clay addition had a more pronounced effect on alpha diversity compared to the addition of starch or cellulose. Substrate addition resulted in an increased EPS concentration only if combined with clay addition. At high clay addition, starch resulted in higher EPS concentrations than cellulose. Where additional substrate was not provided, EPS-protein was only weakly correlated with aggregate formation and stability. The relationship became stronger with addition of substrate. Labile organic C thus clearly plays a role in aggregate formation, but increasing clay content was found to enhance aggregate stability and additionally resulted in the development of distinct microbial communities and increased EPS production.