Determining potential glutamine synthetase and glutamate dehydrogenase activity in soil

Geisseler, Daniel; Doane, Timothy A.; Horwáth, William R.

doi:10.1016/j.soilbio.2009.06.002

Cited by 17 publications

(13 citation statements)

References 36 publications

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“…Assimilation of NH 4 –N occurs via two major pathways: the glutamine synthetase/glutamate synthase (GS/GOGAT) system and glutamate dehydrogenase (GDH; Payne, 1980 ), both resulting in the production of Glu, and thus contributing to Glx. Importantly, both GS and GDH processes are intracellular ( Geisseler et al., 2009 ) which concurs with the current findings of highest TSP 15 N enrichment in Glx ( Fig. 1 a) while Glx 15 N enrichment was less notable in the extracts of EPS ( Fig.…”

Section: Discussionsupporting

confidence: 91%

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Soil organic matter and the extracellular microbial matrix show contrasting responses to C and N availability

Redmile-Gordon

Evershed

Hirsch

et al. 2015

Soil Biology and Biochemistry

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An emerging paradigm in soil science suggests microbes can perform ‘N mining’ from recalcitrant soil organic matter (SOM) in conditions of low N availability. However, this requires the production of extracellular structures rich in N (including enzymes and structural components) and thus defies stoichiometric expectation. We set out to extract newly synthesised peptides from the extracellular matrix in soil and compare the amino acid (AA) profiles, N incorporation and AA dynamics in response to labile inputs of contrasting C/N ratio. Glycerol was added both with and without an inorganic source of N (10% 15N labelled NH4NO3) to a soil already containing a large pool of refractory SOM and incubated for 10 days. The resulting total soil peptide (TSP) and extracellular pools were compared using colorimetric methods, gas chromatography, and isotope ratio mass spectrometry. N isotope compositions showed that the extracellular polymeric substance (EPS) contained a greater proportion of products formed de novo than did TSP, with hydrophobic EPS-AAs (leucine, isoleucine, phenylalanine, hydroxyproline and tyrosine) deriving substantially more N from the inorganic source provided. Quantitative comparison between extracts showed that the EPS contained greater relative proportions of alanine, glycine, proline, phenylalanine and tyrosine. The greatest increases in EPS-peptide and EPS-polysaccharide concentrations occurred at the highest C/N ratios. All EPS-AAs responded similarly to treatment whereas the responses of TSP were more complex. The results suggest that extracellular investment of N (as EPS peptides) is a microbial survival mechanism in conditions of low N/high C which, from an evolutionary perspective, must ultimately lead to the tendency for increased N returns to the microbial biomass. A conceptual model is proposed that describes the dynamics of the extracellular matrix in response to the C/N ratio of labile inputs.

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Section: Discussionsupporting

confidence: 91%

“…In the present study, the N-induced increase of Glx concentration and 15 N enrichment in TSP indicates N assimilation by the microbial biomass. This anabolic process requires energy and generally results in an efflux of CO 2 ( Geisseler et al., 2009 ). In the absence of light the bulk of C must be derived from cellular reserves or SOM.…”

Section: Discussionmentioning

confidence: 99%

Soil organic matter and the extracellular microbial matrix show contrasting responses to C and N availability

Redmile-Gordon

Evershed

Hirsch

et al. 2015

Soil Biology and Biochemistry

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“…In preliminary experiments, the addition of the cocktail had no effect on urease activity in the nonfumigated soils (data not shown). The inhibitory effects of the cocktail on soil protease were similar to those observed by Renella et al (2002) and Geisseler et al (2009). These results indicated that the cocktail was effective in preventing urease degradation via proteolysis during the chloroform fumigation procedure.…”

Section: Responses Of Soil Urease Activity To Chloroform Fumigationsupporting

confidence: 77%

Tillage Effects on Intracellular and Extracellular Soil Urease Activities Determined by an Improved Chloroform Fumigation Method

Qin

Hu²,

Wang³

et al. 2010

Soil Science

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The intracellular urease activity in soils determined by the chloroform fumigation method is underestimated because of urease degradation by soil protease and denaturation by chloroform. The objectives of this study were to correct this underestimation and to investigate the responses of intracellular, extracellular, and total urease activities to notillage, reduced tillage, and moldboard plowing treatments. Surface layer soils (0Y20 cm) after 8-year different tillage treatments were collected. First, the soil samples were fumigated with ethanol-free chloroform in the presence of a protease inhibitor. Subsequently, a urease addition experiment was conducted to determine what percentage of soil urease was denatured during the fumigation procedure. Our results showed that the corrected intracellular urease activities in soils under no-tillage, reduced tillage, and moldboard plowing accounted for 58.2%, 62.3%, and 51.7% of the total urease activity, respectively. Both no-tillage and reduced tillage significantly increased the intracellular, extracellular, and total urease activities compared with moldboard plowing. The ratio between intracellular and extracellular urease activities was not significantly different between no-tillage and reduced tillage probably because the soil ammonia content was similar under these treatments. The three urease activity pools were significantly correlated with soil organic C, microbial biomass C and N, and available P. These results indicate that both the intracellular and extracellular urease activities were sensitive indicators for monitoring soil quality under different tillage practices.

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“…Hoch & Bronk (2007) found that amendments of amino acids and ammonium to marine bacterioplankton increased growth and repressed GS and assimilatory nitrate reductase activities. Similarly, Geisseler et al (2009) found that the GDH:GS activity ratio for soil microbial communities was inversely related to the C:N availability.…”

Section: Nitrogenmentioning

confidence: 86%

Ecoenzymatic Stoichiometry and Ecological Theory

Sinsabaugh¹,

Shah²

2012

Annu. Rev. Ecol. Evol. Syst.

710

461

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and peroxide, respectively, as electron acceptors, catalyze the oxidative degradation of lignin and the formation of humus. These choices are partially methodological; it is easier to assay activities using soluble substrates that yield soluble products than to study the degradation of insoluble polymers or humic complexes. This bias has value in that reactions that yield assimilable products are the ones most directly linked to microbial metabolism (Meyer-Reil 1987, Hoppe et al. 1988, Münster 1991). In the molecular sieve model (Burns 1978), such enzymes are intermediate agents in reaction pathways that connect the activities of polymer-degrading enzymes distributed throughout the environmental matrix and cell membrane permeases that transport substrates into the cell. In many cases, the enzymes that catalyze the terminal reactions in polymer degradation are localized on cell surfaces and periplasmic spaces.

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Determining potential glutamine synthetase and glutamate dehydrogenase activity in soil

Cited by 17 publications

References 36 publications

Soil organic matter and the extracellular microbial matrix show contrasting responses to C and N availability

Soil organic matter and the extracellular microbial matrix show contrasting responses to C and N availability

Tillage Effects on Intracellular and Extracellular Soil Urease Activities Determined by an Improved Chloroform Fumigation Method

Ecoenzymatic Stoichiometry and Ecological Theory

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