Proteolytic activity under nitrogen or sulfur limitation

Soil Science Society of America Journal, 1983

Soil enzyme activities are often used as indices of microbial growth and activity in soils. Quantitative information concerning which soil enzymes most accurately reflect microbial growth and activity is lacking. Relationships between the activities of 11 soil enzymes and microbial respiration, biomass, viable plate counts, and soil properties were determined in surface samples of 10 diverse soils. Correlation analyses showed that alkaline phosphatase, amidase, a-glucosidase, and dehydrogenase activities were significantly (P < 0.01) related to microbial respiration as measured by CO 2 evolution in soils which had received glucose amendments. Phosphodiesterase, arylsulfatase, invertase, a-galactosidase, and catalase activities were correlated at the 5% level while acid phosphatase and urease activities were not significantly correlated to microbial respiration. There was no significant correlation between the 11 soil enzymes assayed and CO 2 evolution in the 10 unamended soils. Only phosphodiesterase and a-galactosidase activities were significantly (P < 0.05) related to microbial numbers obtained on some selective culture media. Alkaline phosphatase, amidase, and catalase were highly correlated (P < 0.01) with microbial biomass as determined by CO 2

European Journal of Soil Biology, 2020

Proteinaceous material constitute the main source of nitrogen in soil organic matter. Use of this nitrogen is limited by the breakdown of proteins into peptides and free amino acids. Proteases, therefore, are important in the use of protein N. The aim of this study is to assess the effect of subtilisin, which is a soil extracellular endopeptidase from Bacillus sp., both on soil microbial biostimulation and biodiversity. In addition to the protease, keratins, an insoluble-protein and low-bioavailable substrate, was added to enhance the effect of protease in soil. Protease, both on its own and in combination with keratins, has a biostimulant effect on soil microbial activity that was reflected in the protease, dehydrogenase and phosphatase activities. DNA metabarcoding analysis further revealed specific changes in soil biodiversity, mainly defined by the enrichment of plant-growth promoting microorganisms, specifically those producing hydrolase enzymes such as phosphatase and ammonifiers. Surprisingly, the addition of keratins specifically showed a rapid stimulation of soil proteolytic bacteria. Thus, the present work supports the use of subtilisin as biofertiliser and values the recycling of keratinous industrial waste in the field of biofertilisation.

Journal of Plant Nutrition and Soil Science, 2002

Within different land-use systems such as agriculture, forestry, and fallow, the different morphology and physiology of the plants, together with their specific management, lead to a system-typical set of ecological conditions in the soil. The response of total, mobile, and easily available C and N fractions, microbial biomass, and enzyme activities involved in C and N cycling to different soil management was investigated in a sandy soil at a field study at Riesa, Northeastern Germany. The management systems included agricultural management (AM), succession fallow (SF), and forest management (FM). Samples of the mineral soil (0±5, 5±10, and 10±30 cm) were taken in spring 1999 and analyzed for their contents on organic C, total N, NH 4 +-N and NO 3 ±-N, KCl-extractable organic C and N fractions (Corg (KCl) and Norg (KCl)), microbial biomass C and N, and activities of b-glucosidase and L-asparaginase. With the exception of Norg (KCl) , all investigated C and N pools showed a clear relationship to the land-use system that was most pronounced in the 0±5 cm profile increment. SF resulted in greater contents of readily available C (Corg (KCl)), NH 4 +-N, microbial biomass C and N, and enzyme activities in the uppermost 5 cm of the soil compared to all other systems studied. These differences were significant at P £ 0.05 to P £ 0.001. Comparably high C mic :C org ratios of 2.4 to 3.9 % in the SF plot imply a faster C and N turnover than in AM and FM plots. Forest management led to 1.5-to 2-fold larger organic C contents compared to SF and AM plots, respectively. High organic C contents were coupled with low microbial biomass C (78 mg g ±1) and N contents (10.7 mg g ±1), extremely low C mic : C org ratios (0.2±0.6 %) and low b-glucosidase (81 mg PN g ±1 h ±1) and L-asparaginase (7.3 mg NH 4-N g ±1 2 h ±1) activities. These results indicate a severe inhibition of mineralization processes in soils under locust stands. Under agricultural management, chemical and biological parameters expressed medium values with exception for NO 3 ±-N contents which were significantly higher than in SF and FM plots (P £ 0.005) and increased with increasing soil depth. Nevertheless, the depth gradient found for all studied parameters was most pronounced in soils under SF. Microbial biomass C and N were correlated to b-glucosidase and Lasparaginase activity (r ³ 0.63; P £ 0.001). Furthermore, microbial biomass and enzyme activities were related to the amounts of readily mineralizable organic C (i.e. Corg (KCl)) with r ³ 0.41 (P £ 0.01), suggesting that (1) KCl-extractable organic C compounds from field-fresh prepared soils represent an important C source for soil microbial populations, and (2) that microbial biomass is an important source for enzymes in soil. The Norg (KCl) pool is not necessarily related to the size of microbial biomass C and N and enzyme activities in soil.

Soil & Tillage Research, 2011

Revista de la ciencia del suelo y nutrición vegetal, 2008

Biology and Fertility of Soils, 2012

It is still problematic to use enzyme activities as indicators of soil functions because: (1) enzyme assays determine potential and not real enzyme activities; (2) the meaning of measured enzyme activities is not known; (3) the assumption that a single enzyme activity is an indicator of nutrient dynamics in soil neglects that the many enzyme activities are involved in such dynamic processes; (4) spatio-temporal variations in natural environments are not always considered when measuring enzyme activities; and (5) many direct and indirect effects make difficult the interpretation of the response of the enzyme activity to perturbations, changes in the soil management, changes in the plant cover of soil, etc. This is the first review discussing the links between enzyme-encoding genes and the relative enzyme activity of soil. By combining measurements of enzyme activity in soil with expression (transcriptomics and proteomics) of genes, encoding the relative enzymes may contribute to understanding the mode and timing of microbial communities' responses to substrate availability and persistence and stabilization of enzymes in the soil.

Soil Biology and Biochemistry, 1998

Two arable soils and one pasture soil had previously been air-dried for 6 d and stored at room temperature. The enzyme activities remaining after this treatment were constant. The soils were then extracted with 140 mM sodium pyrophosphate at pH 7.1. Amino acid N and total organic C contení of soils and soil extracts, together with humic and fulvic acids contení of soil extraéis were determined. Total organic C was determined in soil residues obtained after extraction. Chemical characterization of the organic matter of soils, soil extracts and soil residues was carried out by pyrolysis gas chromatography (Py-GC). Protease activity was determined in soil extracts and soil residues by using three different substrates: N-benzoyl-Largininamide (BAA), specific for trypsin; N-benzyloxy-carbonyl-L-phenylalanyl L-leucine (ZPL), specific for carboxypeptidases, and casein, essentially non-specific. Comparative studies between specific activities referred to organic C in soils, soil extracts and soil residues and their corresponding pyrogram composition, and also between total extracted or residual activity and the humine or unhumified organic matter contení of the corresponding soil, allowed us to establish hypotheses about the type of organic matter the enzymes are associated with. From 12% to 21% of the soil organic C (33% to 39% of which were humic acids) and from 3% and 18% of amino acid N were extracted from soil using pyrophosphate. Py-GC analyses showed that pyrophosphate was effective in extracting condensed humic substances and glycoproteins and that the organic matter present in soil extracts was especially rich in intact or partially-decomposed fresh residues of carbohydrate origin and also in certain humus-associated proteins. Extracted BAA-hydrolysing activity accounted for 11% to 36% of the soil activity, depending on soil type. Extracted ZPL-and casein-hydrolysing activities were, with one exception, remarkably high, accounting for about 100% or even more of the soil activity, depending on soil type. According to the results BAA-hydrolysing proteases are probably mostly associated with highly condensed humus, ZPL-hydrolysing proteases with less condensed humic substances and casein-hydrolysing proteases with fresh organic matter.

Nutrient Cycling in Agroecosystems, 2004

A field experiment was conducted to determine the effects of surface applications of dairy shed effluent (DSE) (effluent collected from a dairy milking shed and consists of dung, urine and water) or chemical fertilizer (NH4Cl) on N dynamics, microbial biomass C and N and extracellular enzyme activities (protease, deaminase and urease) in different soil depths. The DSE and NH4Cl were applied to pasture soil at an equivalent rate of 200 kg N ha−1in May and November 1996, as autumn and late spring applications, respectively. Soil samples taken from different soil depths following the autumn application were analyzed for inorganic N, microbial biomass C and N and enzyme activities, while soil samples taken following the late spring application were analyzed for inorganic N only. The soil NH4+concentration, soluble organic C, protease, deaminase and urease activities, and microbial biomass C and N significantly increased in the 0–5 cm soil depth soon after the application of DSE. During ...

Soil Biology and Biochemistry, 2002

Anthropogenic N deposition affects litter decomposition and soil organic matter (SOM) storage through multiple mechanisms. Microbial community responses to long-term N deposition were investigated in a sugar maple-dominated forest in northern Michigan during the 1998-2000 growing seasons. Litter and soil were collected from three fertilized plots (30 kg N ha 21 y 21 ) and three control plots. The activities of 10 extracellular enzymes (EEA) were assayed. ANOVA and meta-analysis techniques were used to compare treatment responses. EEA responses to N amendment were greater in litter than in soil (litter mean effect size [d ] ¼ 0.534 std. dev.; soil d ¼ 0:308). Urease, acid phosphatase and glycosidase (b-glucosidase, a-glucosidase, cellobiohydrolase, b-xylosidase) activities increased in both soil and litter; mean responses ranged from 7 to 56%. N-Acetylglucosaminidase activity increased 14% in soil but decreased 4% in litter. Phenol oxidase activity dropped 40% in soil, but increased 63% in litter. These responses suggest that N deposition has increased litter decomposition rate and depressed SOM decomposition. In previous studies, loss of phenol oxidase activity in response to N deposition has been attributed to suppression of lignin-degrading basidiomycetes. However, the decline of this activity in bacterially-dominated soil suggest that N inhibition of recalcitrant organic matter decomposition may be a more general phenomenon.