Reduction In Dehydrogenase Activity Research Articles

Effect of Herbicide Clopyralid and Imazamox on Dehydrogenase Enzyme in Soil of Regenerated Pedunculate Oak Forests

Clopyralid and imazamox are successfully used for weed control during the first years of regeneration of pedunculate oak forests. Hence, the question that arises is how these herbicides affect microorganisms, especially the activity of dehydrogenase enzyme, when they reach the soil. Two study sites were selected in regenerated pedunculate oak forests, and the two herbicides were applied in two doses that are used for weed control (clopyralid, 100 g a.i. ha−1 and 120 g a.i. ha−1; imazamox, 40 g a.i. ha−1 and 48 g a.i. ha−1). The effect of the herbicides was evaluated 7, 14, 21, 30, and 60 days after application. A significant reduction in dehydrogenase activity was found on days 7 and 14 at both sites. However, after 14 days there was a recovery of dehydrogenase activity for all treatments such that the values obtained on day 21 did not differ from the control values. The effect of clopyralid and imazamox on dehydrogenase activity was not dose-dependent. Dehydrogenase activity also depended on soil properties, soil sampling time and climatic conditions during the investigation years. The results show that clopyralid and imazamox can reduce soil dehydrogenase activity, but this effect is transient. This can be attributed to the ability of microorganisms to overcome the stress caused by the herbicide by developing the capability to utilize herbicides as a nutrient source and proliferating in such an environment.

Potential application of Pseudomonas stutzeri W228 for removal of copper and lead from marine environments.

High concentrations of metals in the environment alter bacterial diversity, selecting resistant and tolerant species. The study evaluated the selection of a potential bacterial strain from Sepetiba Bay-Rio de Janeiro, Brazil marine sediments to remove Cu and Pb. The bacterial strain isolated from the sediments was used in three different bioassays: (1) Cu at concentrations of 0 (control), 6 and 50 μg.mL-1; (2) Pb at concentrations of 0 (control), 6 and 50 μg.mL-1; (3) Cu + Pb in concentrations of 3 μg.mL-1 Cu + 3 μg.mL-1 Pb (6 μg.mL-1) and 25 μg.mL-1 Cu + 25 μg.mL-1 Pb (50 μg.mL-1). The number of cells and the enzymatic activities of dehydrogenases and esterases were quantified. Results of taxonomic identification indicated the selection of the Pseudomonas stutzeri W228 strain, showing a greater degree of similarity (±73%) with the database used. There was no significant variation in the number of cells, 108 cells.mL-1, which represents a high biomass production in the presence of stressors. However, we observed a reduction in dehydrogenase activity at all tested concentrations of Cu, Pb and Cu + Pb. The activity of esterase increased, indicating a higher energy demand to complete the bacterial life cycle. The study showed significant results for the absorption of Pb by the extracellular polymeric substances (EPS) and the efflux of Cu. The capacity of Pb absorption by EPS can be considered a resistance mechanism, as well as the efflux of Cu, so that the available EPS sites could be occupied by the most toxic ions demonstrating that Pseudomonas stutzeri is resistant to Pb and Cu.

Copper and lead removal from aqueous solutions by bacterial consortia acting as biosorbents

A bacterial consortium was selected in the presence of Cu from sediment samples taken from Sepetiba Bay, Brazil, which is a site historically contaminated by metals. Bacteria were exposed to 0, 1, 6, 12.5, 25 and 50μg·mL−1 Cu, Pb and Cu+Pb for 11days of bioassay. Results showed Alcanivorax dominance (81%) and cell counts of 108cells·mL−1. However, a reduction in dehydrogenase activity was observed from the fifth day of exposure for all Cu, Pb, and Cu+Pb concentrations tested. Esterase activity tended to increase, indicating higher energy demand to complete the bacterial lifecycle. Pb concentrations in the filtered culture medium (0.2μm) were below the detection limit, indicating biosorption, whereas concentrations of Cu were close to the tested concentrations, indicative of efflux. Results suggest the need for biomarkers, such as esterase and dehydrogenase enzymatic activity, in the assessment of resistance and tolerance of communities previously exposed to stressors.

Effect of solarization on nutrient availability, enzyme activity and growth of pomegranate (Punica granatum) air-layered on various potting mixtures

Pomegranate air layers are generally raised on potting mixture consisting of soil, sand and FYM/vermicompost in the nursery. Increasing concern over the impact of chemical fertilizers and pesticides on the environment for raising disease- free vigorous planting materials necessitate the exploitation of renewable solar energy for disinfecting growth medium and at the same time its enrichment with respect to plant nutrients. Solarization of components in the potting mixture (soil: sand: farmyard manure, 1:1:1, soil: sand: vermicompost, 1:1:1 and soil: sand, 1:1) and their use in various combinations [soil (nonsolarized, NS):sand (nonsolarized, NS):FYM (nonsolarized, NS); soil (solarized, S):sand (solarized, S):FYM (solarized, S); soil (S):sand (S):FYM (NS); soil (NS):sand (NS):vermicompost (NS); soil (S):sand (S):vermicompost (S); soil (S):sand (S):vermicompost (NS); soil (NS):sand (NS); soil (S):sand (S)] was evaluated for production of vigorous air- layer planting materials of pomegranate. Mixing of farmyard manure to solarized soil-sand media significantly increased available nutrient status (particularly P and K), alkaline and acid phosphatase activity and plant growth and vigour as indicated by chlorophyll content (SPAD value), photosynthetic and transpiration rate. Weed population also got reduced significantly. On the contrary, mixing of vermicompost to solarized soil-sand media did not result in any positive impact on plant growth over non-solarized and solarized soil-sand-vermicompost mixtures. With only soil-sand as potting media, non-solarized media recorded higher plant growth, nutrient availability (P and K) and enzyme activity (alkaline phosphatase and acid phosphatase) over solarized one but reduction in dehydrogenase activity and weed population were noted upon solarization of the said medium.

Effect of non-aqueous drilling fluid and its synthetic base oil on soil health as indicated by its dehydrogenase activity

Drilling fluids are used for drilling natural gas, oil and water wells. These spill over into the surrounding soil at the point of drilling, which may impair soil health. A laboratory investigation was carried out to determine the effect of non aqueous drilling fluid (NADF) and synthetic base oil used with it on soil health as indicated by the dehydrogenase activity. A non-sterile sandy loam soil was treated with different amounts of NADF and base oil at a rate of 800, 8,000 and 16,000 mg kg−1. Initially, reduction in dehydrogenase activity was observed, but it increased with the incubation time. On the 60th day of incubation dehydrogenase activity in untreated control was 1.04 mg TPF g−1 h−1 whereas in the soil samples treated with NADF and the base oil (16,000 mg kg−1), the activity was 1.53 mg TPF h−1 and 1.90 mg TPF h−1, respectively, which was 72 and 82% more than in untreated control. Base oil-treated soil showed more dehydrogenase activity than that observed with NADF. Both NADF and base oil stimulated the soil dehydrogenase activity.

Effect of organic amendments on microbial activity in chlorpyrifos contaminated soil

The aim of this research was to study the inhibitory effect of chlorpyrifos (CPF) on soil microbial activity and to evaluate the efficacy of different organic amendments as a biostimulation agent for sustaining the microbial activity and thereby assisting in the remediation of CPF (10 ppm) contaminated soil. Experiments were carried out under controlled conditions (37 °C) up to 74 days; CPF was analyzed by GC-ECD while dehydrogenase activity (DHA) was measured as one of the indices of soil microbial activity. Throughout the experiment, there was higher microbial activity in uncontaminated soil (S) as compared to CPF contaminated soil (SP) and overall a considerably high reduction (63.51%) in average DHA was noticed in CPF contaminated soil. Organic amendments enhanced the microbial activity over unamended CPF contaminated soil. The trend of DHA on 24th day was MS (SP + 1% Mushroom Spent) >VC (SP + 1% Vermicompost) >BS (SP + 1% Biogas Slurry) >SP (Soil spiked with 10 ppm CPF) >FM (SP + 1% Farmyard Manure). The enhancement in pesticide dissipation over the unamended soil showed the following trend VC (37%)>MS (24%) >FM (1.9%). In spite of sufficient DHA, BS could not enhance pesticide dissipation over the unamended soil (SP). These results indicate the potential of vermicompost and mushroom spent compost as suitable biostimulation agents to sustain the microbial activity in CPF contaminated soil.

Transgenic Bt‐Cotton Affects Enzyme Activity and Nutrient Availability in a Sub‐Tropical Inceptisol

AbstractWe investigated the dynamics of N and P availability in the rhizosphere of Bt and non‐Bt cotton crops during their growth. In a net‐house pot culture experiment at the Indian Agricultural Research Institute, New Delhi, Bt‐cotton (cv. MRC‐6301Bt) and its non‐transgenic near‐isoline (MRC‐6301) were grown on a sandy loam soil until maturity. A control (no‐crop) treatment was also included. Rhizosphere soil and root samples were collected at 60, 90, and 120 days after sowing (DAS). Soil samples were analysed for dehydrogenase activity, soil respiration, mineral‐N and Olsen‐P. Results have revealed a significant reduction in dehydrogenase activity (−17 %) and soil respiration (−3.5 %) in the rhizosphere of Bt‐cotton over non‐Bt isoline. Total mineral‐N (NH4+‐N + ‐N) in soil was reduced by 14 %, whereas Olsen‐P was increased by 8 % because of Bt‐cotton. Root biomass yields were not different (P > 0.05), but root volume was significantly higher in Bt than non‐Bt isoline. Time of sampling strongly (P < 0.05) affected the above parameters, showing their highest values at 60 or 90 DAS. A significant interactive effect of sampling time and treatments was also indicated. Our results suggest that Bt‐cotton may constrain the availability of N, but enhances P‐availability in these soils.

Inhibitory effects of the total and water-soluble concentrations of nine different metals on the dehydrogenase activity of a loess soil

This study focuses on a comparison of the microbial toxicity of nine metals, including As as a metalloid and two species of Cr. A loess soil [Ap horizon, clay 15.2%, organic C 1.12%, pH(CaCl2) 7.02] was spiked with 8–12 geometrically increasing doses of the metals. The dehydrogenase assay (2-p-iodophenyl-3-p-nitrophenyl-5-phenyltetrazoliumchloride method) was combined with sorption and solubility experiments. The resulting dose-response curves and sorption isotherms were used to derive total doses that caused definite percentage inhibitions [i.e. effective doses (ED) causing a 10–90% reduction in dehydrogenase activity (dha)] as well as the corresponding toxic solution concentrations causing the same reductions in dha (i.e. effective concentrations; EC10–EC90). Based on total doses, the toxicity decreased in the following order with ED50 values (mg kg–1) given in brackets: Hg (2.0)>Cu (35)>Cr(VI) (71)>Cr(III) (75)>Cd (90)>Ni (100)>Zn (115)>As (168)>Co (582)>Pb (652). With regard to solution concentrations, toxicity decreased in the order (EC50 in mg l–1): Hg (0.003)>Pb (0.04)>Cu (0.05)>Cd (0.14)>Zn (0.19)>Cr(III) (0.62)>Ni (0.69)>Co (30.6)>As (55.5)>Cr(VI) (78.1). The retention of the metals by the soil differed strongly. Pb, Cu, and Hg exhibited the highest and Ni, As, and Cr(VI) the lowest sorption constants (Freundlich K values: 2455, 724, 348, 93, 13, and 0.06 mg kg–1, respectively). The sorptivity of the metals and their microbial toxicity in the aqueous phase were characteristically related: metals with a strong toxic action in the soil solution were adsorbed by the soil to a high degree and vice versa. Therefore, especially for metals with a high inherent toxicity, sorption is an effective way of immobilizing them and temporarily detoxifying soil.

Effects of topoclimatic gradient on soil dehydrogenase activity in a Judean desert ecosystem

In this study, dehydrogenase activity assays were used to monitor microbial activity in Israel's Judean Desert, a rain shadow desert along a topoclimatic transect. Four locations at this gradient were studied: the pair Givat Yaarim, Maale Adumim and the pair Mishor Adumim, Kalia. These locations range from semidesert in the west 650 ni above sea level with a 620 mm average annual rainfall to the most eastern station (Kalia) 60 m below sea level with less than 100 mm average annual rainfall. Monthly soil samples were collected between January 1994 and July 1996. The soils, which differ mainly in slope location, were analyzed for dehydrogenase activity in the laboratory using the triphenylformazan extraction method. Although both enzyme activity and soil moisture content were found to be significantly different at each location, no significant correlation between them was obtained. However, drying of the soil during the long summer period resulted in a reduction in dehydrogenase activity, while increased soil moisture resulted in a marked increase in dehydrogenase activity.

Novel biotransformations to produce aromatic and heterocyclic aldehydes

Aromatic aldehydes may be produced by Pseudomonas putida ATCC 12633 via biotransformation of benzoylformate and substrate analogues using the mandelic acid pathway. A reduction in pH to 5.4 causes the partial inactivation of the benzaldehyde dehydrogenase isoenzymes within this pathway, thereby allowing the accumulation of the aldehyde. The reduction in dehydrogenase activity with pH is a general phenomenon affecting all dehydrogenases within the cell and is not restricted to the benzaldehyde dehydrogenases of the mandelate pathway. Both benzaldehyde and thiophene-2-carboxaldehyde have been produced with yields of over 85%.

Soil dehydrogenase activity adjacent to remedially treated timber, weathered in a physical field model

Three physical field models were constructed to assess the effects on soil of a chromated fluoride wood preservative treatment used at the groundline of creosoted electricity distribution poles. One model contained an untreated aged creosoted pole section in sandy loam soil, the second contained a remedially treated aged creosoted pole section in sandy loam soil and the third a similarly treated section in sand-amended sandy loam soil. The models were subjected to the equivalent of 6 months simulated rainfall exposure, and soil samples recovered from each model soilbed were used for the determination of soil dehydrogenase activity, fluoride and total chromium concentrations. Soil dehydrogenase activity was measured on both rye meal-supplemented and unsupplemented soil samples. Irrespective of supplementation, significant reductions in dehydrogenase activity were associated with increased soil concentrations of leached preservative constituents which were found within 5 cm of the treated pole sections. These reductions were enhanced by the lower organic matter content of the sand-amended soil. Supplementation with rye meal resulted in raised levels of dehydrogenase activity in all soil samples, which highlighted the negative effects of preservative soil contamination on microbial activity.

Ameliorative influence of organic matter on biological activity of salt‐affected soils

Salt‐affected soils have low biological activity both because of osmotic and ionic effects of salts and owing to ¡imitation of carbonaceous substrates. Alkali soils and artificially salinized soils were incubated at 28°C for 3 months with or without organic (1% Sesbania cannabina green manure) amendment, at 60% water‐holding capacity. CO2 evolution was measured by absorption in alkali, microbial biomass by chloroform fumigation‐incubation, dehydrogenase activity by tetrazolium reduction, and urease activity by measuring ammonia release titrimetrically. CO2 evolution and microbial biomass were reduced at pH 8.7 in unamended alkali soils by 18% and 35%, respectively; at pH 10.3 the reduction was by 83% and 35%, respectively. Organic matter (OM) amendment stimulated CO2 evolution, and the biological activity in soils up to pH 10.0 was restored to that of amended normal soil (pH 8.1). The activity of pH 10.3 soil was 78% of normal. Extent of added carbon decomposed was ∼38% throughout the pH range studied. CO2 evolution and microbial biomass were reduced at ECe 16 in unamended saline soils by 33% and 40%, respectively; at ECe 97 it was reduced by 62% and 63%, respectively. OM amendment improved activity only at salinities ECe ≤ 26. Dehydrogenase activity (DHA) showed a similar trend; OM stimulated activity in alkali soils up to pH 10.0, whereas in saline soils it could not fully restore the activity even at ECe 16.0. In saline soils there was an immediate reduction in DHA on salt addition followed by a further reduction on incubation. DHA increased immediately on salt removal by leaching. There was a reduction in pH and ESP values and increases in soil C and N contents of alkali soils, and an increase in urease activity of saline and alkali soils following the addition of organic amendment. Results supported our hypothesis that microbial growth is depressed in alkali soils owing, at least in part, to carbon stress and in saline soils owing to salt stress. Results reinforce the need to apply organic amendments during alkali soil reclamation, whereas in saline soils, organic amendments must follow leaching.

Effects of lead pollution on different soil enzyme activities

We studied the effects of Pb pollution on soil dehydrogenase and phosphatase activity. Samples of four soils (Saxe, Podesta, Porto Teulada, and Sa Xia Manna) were collected from various locations in southwestern Sardinia, Italy. The soils, which differ mainly in heavy metal contents of pedologic origin (Cu, Zn, Cd, and Pb), were treated with Pb (0, 100, 500, 1000, and 5000 μg Pb g-1 soil) and incubated in the laboratory. Samples of the incubated soils were collected periodically (0, 1, 2, 4, 8, and 16 weeks) and the enzymes were measured. Soil dehydrogenase activity was influenced by both the Pb additions and variations in soil moisture content. Only the addition of 5000 μg Pb g-1 soil led to a significant decrease in dehydrogenase activity compared to the controls, while the other doses of Pb did not always result in a clear reduction in enzyme activity. Drying the soil led to a considerable reduction in dehydrogenase activity, sometimes so far as to render the differences found between the various treatments not statistically significant. Soil phosphate activity was also influenced by the Pb additions, but the effect of the variation in soil moisture content was less than that found for the dehydrogenase. After the 2nd week of incubation, the phosphate activity in the Podesta and Saxe soils had decreased proportionally to the increase in Pb content. At the end of the incubation period, in the Porto Teulada and Sa Xia Manna soils, a net reduction in phosphatase activity versus controls was found only at the highest Pb concentration. Although both enzyme activities were influenced by the Pb additions, the phosphate activity was less sensitive to variations in the soil moisture content and may thus be a more suitable indicator for soil pollution by Pb.

Evaluation of dehydrogenase as a suitable indicator of soil microflora activity

Dehydrogenase activity was determined in a variety of soil samples to assess the assay's suitability as an indicator of soil microorganism activity. This technique, like others in soil ecology, has shortcomings. The work outlined below demonstrates that the dehydrogenase assay can provide a valid indication of soil microorganism activity. Although dehydrogenase activity can be correlated with the numbers of microorganisms isolated, the application of herbicides, which are not greatly toxic to microorganisms, results in a reduction in dehydrogenase activity but little alteration in the number of microorganisms isolated. As this reduction can be accounted for, the use of the assay could be advocated in determining soil microbial activity in ecological investigations.