Variable responses of the soil microbial biomass to trace concentrations of ¹³C‐labelled glucose, using ¹³C‐PLFA analysis

Abstract

13 C-labelled glucose was applied to arable (Broadbalk NPK) and permanent grassland (Woburn Grassland) soils to investigate the response of the soil microbial biomass (SMB) to carbon (C) applied at trace concentrations. Phospholipid fatty acids (PLFA) were used as biomarkers for G+ve (odd-chained and iso/anteiso FA) and G−ve bacteria (mono-unsaturated and cyclic FA), actinobacteria (10-methyl-branched FA), fungi (octadecadienoic acid) and general membrane lipids [16:0,18:0]. Gas chromatography-combustion-stable isotope ratio mass spectrometry (GC-C-IRMS) was used to determine the incorporation of 13 C into individual PLFA in two experiments: first, after application of a single concentration (15 μg C g −1 ) of 13 C-glucose over a time sequence (0, 8, 24, 48, 120 and 240 hours), and second after application at three concentrations (25, 83, 416 μg C g −1 soil after 120 hours). 13 C incorporation into PLFA over time was similar in both soils. However, in the permanent grassland soil, 13 C incorporation was increased in actinobacteria PLFA at 120 hours when [16:0,18:0] was reduced. At 240 hours, 13 C incorporation increased in [16:0,18:0] concurrently with a reduction in G+ve bacteria PLFA. Increasing glucose concentration caused different responses in the SMB of both soils. In the arable soil, all biomarker PLFA concentrations increased at all rates of application. In contrast, in the permanent grassland soil PLFA concentrations were similar to the control in all SMB groups, except G+ve bacteria after the greatest rate of application. However, the δ 13 C values of the same PLFA indicated that uptake of applied 13 C-glucose was proportional to the applied concentration in all groups of soil bacteria in both soils.

Comparison of characterization and microbial communities in rice straw- and wheat straw-based compost forAgaricus bisporusproduction

“…Fatty acid nomenclature was used as described by Frostegard et al [13]. The fatty acids i15:0, a15:0, 15:0, i16:0, 17:0, a17:0, i17:0, cy17:0, 16:1ω9c and cy19:0 were chosen to represent bacterial PLFAs [8], while 18:2ω6, 9c and 18:1ω9c were used as indicators of fungal community [1]. Actinomycetes biomarkers were 10 Me17:0 and 10 Me18:0 [29,43]; Gram-positive bacteria were represented by the sum of all branched PLFAs [14]; and Gram-negative bacteria were represented by the sum of all monounsaturated PLFAs [21].…”

Influence of cropping system management and crop residue addition on soil carbon turnover through the microbial biomass

“…Several studies have used 13 C-glucose to determine its consumption, modification, and accumulation as soil organic C through time (Aoyama et al 2000;Fontaine et al 2004;Evershed et al 2006;Dungait et al 2011). Addition of C substrates to soil can change the turnover of SOM, accelerating or retarding mineralization of native organic C with the supply of organic inputs; this is called, respectively, positive or negative priming effect (PE).…”

13C PLFAs: a key to open the soil microbial black box?

“…Often the labelled compounds added to soil are chosen to mimic soil organic matter mineralization products or plant inputs. A range of 13 C enriched low molecular weight compounds typical of those lost by plants in rhizodeposition, such as glucose, glycine, acetate, amino acid mixtures, and water extracts of plants, have all been successfully traced into soil PLFA pools (Paterson et al 2008a;Rinnan and Bååth 2009;Dungait et al 2011Dungait et al , 2013Andresen et al 2014;Lemanski and Scheu 2014). More recalcitrant fractions typical of those entering soil through leaf litter and root residues have been added to soil and traced into soil PLFA pools.…”