Fungal–bacterial dynamics and their contribution to terrigenous carbon turnover in relation to organic matter quality

Abstract

Ecological functions of fungal and bacterial decomposers vary with environmental conditions. However, the response of these decomposers to particulate organic matter (POM) quality, which varies widely in aquatic ecosystems, remains poorly understood. Here we investigated how POM pools of substrates of different qualities determine the relative contributions of aquatic fungi and bacteria to terrigenous carbon (C) turnover. To this end, surface sediments were incubated with different POM pools of algae and/or leaf litter. 13C stable-isotope measurements of C mineralization were combined with phospholipid analysis to link the metabolic activities and substrate preferences of fungal and bacterial heterotrophs to dynamics in their abundance. We found that the presence of labile POM greatly affected the dominance of bacteria over fungi within the degrader communities and stimulated the decomposition of beech litter primarily through an increase in metabolic activity. Our data indicated that fungi primarily contribute to terrigenous C turnover by providing litter C for the microbial loop, whereas bacteria determine whether the supplied C substrate is assimilated into biomass or recycled back into the atmosphere in relation to phosphate availability. Thus, this study provides a better understanding of the role of fungi and bacteria in terrestrial–aquatic C cycling in relation to environmental conditions.

Effects of temperature, soil substrate, and microbial community on carbon mineralization across three climatically contrasting forest sites

“…The strong effect of temperature on the rate of soil C mineralization does not rule out the importance of soil microbial community, as it is recognized that climate and environmental factors can mask the influence of decomposer community on decomposition, due to the fact that soil microorganisms may both adapt to and be affected by climate and environments (Canarini, Carrillo, Mariotte, Ingram, & Dijkstra, 2016; Keiser & Bradford, 2017). Moreover, the structure and functions of soil microbial communities are further constrained by soil physiochemical properties and SOM quality (Fabian, Zlatanovic, Mutz, & Premke, 2017; Sun et al., 2016; Xun et al., 2015; You et al., 2014, 2016). Growing evidences show that soil geochemistry and physical structure impose direct effects on SOM stability by creating physiochemical barriers preventing microorganisms to access carbon sources (Bardgett et al., 2008; Chenu & Plante, 2006; Delgado‐Baquerizo et al., 2015; Doetterl et al., 2015; Plante, Conant, Stewart, Paustian, & Six, 2006).…”

Key role of streambed moisture and flash storms for microbial resistance and resilience to long‐term drought

“…For the latter, it has been shown that the reduction of soil moisture can limit enzyme and substrate diffusion (Liu, Zhang, & Wan, 2009) and enzyme efficiencies could be affected, possibly because processes such as enzyme immobilisation are increased while diffusion rates are reduced (Henry, 2013). Fabian, Zlatanovic, Mutz, and Premke (2017) showed that the use of recalcitrant carbon compounds would be F I G U R E 5 Relationships between water content and extracellular polymeric substances (log EPS), bacterial viability (log Live cells), βd-xylosidase (log XYL) and βd-glucosidase (log GLU). Fabian, Zlatanovic, Mutz, and Premke (2017) showed that the use of recalcitrant carbon compounds would be F I G U R E 5 Relationships between water content and extracellular polymeric substances (log EPS), bacterial viability (log Live cells), βd-xylosidase (log XYL) and βd-glucosidase (log GLU).…”

Effects of zooplankton carcasses degradation on freshwater bacterial community composition and implications for carbon cycling

“…Stable isotope analysis of the respired CO 2 provides information on carbon substrates metabolized by the microbial community (Fabian et al, 2017). The ratio of 13 С/ 12 С in the dissolved CO 2 was measured directly in each microcosm by a membrane-inlet mass-spectrometer dissolved gas analyser (HiCube pumping station, Pfeiffer Vacuum and Bay Instruments membrane, USA), controlled by Quickdata software.…”