Extraction of bacterial lipopolysaccharides from soil samples and their determination using the Limulus amebocyte lysate reaction

Lipopolysaccharides were extracted from soil using an aqueous phenol procedure and determined by using the Limulus amebocyte lysate coagulation reaction. When heat-killed Escherichia coli cells were added to soil at a concentration of organisms expected to occur in subsurface material, there was a 10% recovery of the added cellular lipopolysaccharides (LPS); because of the sensitivity of the Limulus amebocyte lysate (LAL) reaction this recovery is sufficient for the method to be a rapid (4 h) estimate of the Gram-negative bacteria present in soil samples. By using a kinetic assay LPS could be measured over a concentration range of five orders of magnitude, which is important with environmental samples.     

The potential application of the endophyte Phomopsis liquidambari to the ecological remediation of long-term cropping soil

A broad-spectrum endophyte, Phomopsis liquidambari, was used as a microbial agent to determine the effects of rapid litter decomposition on soil phenolic compounds dynamics, the soil microbial community balance and plant growth. The litter decomposition ratio was closely correlated with lignin degradation. The soil phenol concentration increased with the acceleration of litter decomposition after the first 30 days and later decreased to below the initial level. Based on denaturing gradient gel electrophoresis (DGGE) analysis, soil bacteria, especially gram-negative bacteria that have the potential to degrade aromatic compounds, were found in high abundance when the soil phenol concentration was high. When the phenolic concentration decreased, soil fungi increased in abundance. With fungal application, seed germination significantly increased to 69.87% and seedling growth was enhanced. Rapid litter decomposition by Pho. liquidambari initially led to higher releases of phenolic allelochemicals, which led to the enrichment of soil gram-negative bacteria. In addition, increased soil nutrients and temporarily higher concentrations of phenolics from litter decomposition strengthen seedling growth, suggesting that the endophytic fungus Pho. liquidambari is a suitable candidate for remediation of long-term cropping soil.     

Enhanced Phenol and Chlorinated Phenols Removal by Combining Ozonation and Biodegradation

Water treatment for wastewater containing phenols and their chlorinated variations has attracted important research efforts. Phenol??s high toxicity makes them a good model to test possible water treatment based on biological and/or chemical methods. High concentrations of phenols may be treated by pure biological schemes. However, chlorinated phenols are very toxic for many microorganisms. Therefore, mixed treatment trains can be proposed to solve the treatment of this class of organics. In this study, the ozonation was used as pretreatment to decompose chlorinated phenols. Besides, this study describes how the microbial consortiums were adapted to handle ozonation by-products. The biodegradation of different phenol concentrations from 50 to 1,500?mg/L was evaluated using preadapted microbial consortia in batch and in a trickling packed-bed reactor (TPBR). Under batch conditions, phenol was efficiently removed up to 500?mg/L. For every phenol concentration evaluated, higher degradation rates were obtained in TPBR. The chlorophenols were found to be poorly degraded by the pure biological treatment, 4-CPh was not degraded during the biological process and 2,4-DCPh was only 40?% degraded after 250?h of culture. By combining the chemical (as pretreatment) and the biological processes, 85?% of 4-CPh was removed, while the degradation of the 2,4-DCPh was enhanced from 40 to 87?%. The predominant bacteria found in the preadapted cultures were Xanthomonas sp., Ancylobacter sp., and Rhodopseudomonas. Total treatment period was reduced from several weeks to some days. This information reflects the benefits offered by the mixed water treatment train proposed in this paper.     

Food-derived peptides stimulate mucin secretion and gene expression in intestinal cells

In this study, the hypothesis that food-derived opioid peptides besides β-casomorphin 7 might modulate the production of mucin via a direct action on epithelial goblet cells was investigated in HT29-MTX cells used as a model of human colonic epithelium. Seven milk whey or casein peptides, a human milk peptide, and a wheat gluten-derived peptide with proved or probable ability to bind μ- or δ-opioid receptors were tested on the cell culture. Significantly increased secretion of mucins was found after exposure to six of the assayed peptides, besides the previously described β-casomorphin 7, as measured by an enzyme-linked lectin assay (ELLA). Human β-casomorphin 5 and α-lactorphin were selected to study the expression of mucin 5AC gene (MUC5AC), the HT29-MTX major secreted mucin gene. α-Lactorphin showed increased expression of MUC5AC from 4 to 24 h (up to 1.6-fold over basal level expression), although differences were statistically different only after 24 h of exposure. However, this increased expression of MUC5AC did not reach significance after cell treatment with human β-casomorphin 5. In conclusion, six food-derived peptides have been identifed with described or probable opioid activity that induce mucin secretion in HT29-MTX cells. Concretely, α-lactorphin is able to up-regulate the expression of the major secreted mucin gene encoded by these cells.     

Development of an enzyme-linked immunosorbent assay for bisphenol a using chicken immunoglobulins

Bisphenol A was coupled, after derivatization into a suitable hapten, to bovine serum albumin and ovalbumin in order to produce immunizing and coating antigens. The immunizing antigens were injected into chickens, which allowed the isolation of specific bisphenol A immunoglobulins from the egg yolk. These antibodies were used in an indirect competitive enzyme-linked immunosorbent assay for the determination of bisphenol A in aqueous solutions. Various parameters, influencing the assay sensitivity, were evaluated. The applicability of the assay for the determination of bisphenol A in milk was also studied. The assay was not as sensitive as other analytical techniques used in bisphenol A analysis, since typical I(50) levels of 2.5 microM were reached in aqueous solutions. This study nevertheless illustrates the usefulness and the potency of chicken antibodies in the analysis of migration residues from packaging materials using immunochemical techniques. In addition, the assay showed to be quite specific for bisphenol A as well. Only for bisphenol A analogues, cross reactivities of about 40% were reached, enabling the use of the antibodies for the screening of bisphenol A and alike compounds.     

Microbial and non-biological decomposition of chlorophenols and phenol in soil

The aerobic and anaerobic degradation of phenol and selected chlorophenols was examined in a clay loam soil containing no added nutrients. A simple, efficient procedure based on the high solubility of these compounds in 95% ethanol was developed for extracting phenol and chlorophenol residues from soil. Analysis of soil extracts with UV spectrophotometry showed that phenol,o-chlorophenol,p-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol and 2,4,6-trichlorophenol were rapidly degraded, whilem-chlorophenol, 3,4-dichlorophenol, 2,4,5-trichlorophenol and pentachlorophenol were degraded very slowly by microorganisms in aerobically-incubated soil at 23°C. Both 3,4,5-trichlorophenol and 2,3,4,5-tetra chlorophenol appeared to be more resistant to degradation by aerobic soil microorganisms at 23°C. None of the compounds examined were degraded by microorganisms in anaerobically-incubated soil at 23°C. Direct microscopic observation revealed that phenol and selected chlorophenols stimulated aerobic and to a lesser extent, anaerobic microbial growth in soil, and aerobic soil bacteria were responsible for the degradation of 2,4-dichlorophenol in aerobically-incubated soil at 23°C. Phenol,o-chlorophenol,m-chlorophenol,p-chlorophenol and 2,4-dichlorophenol underwent rapid non-biological degradation in sterile silica sand. Non-biological decomposition contributed, perhaps substantially, to the removal of some chlorophenols from sterile aerobically-incubated soil and both sterile and non-sterile anaerobically-incubated soil.     

Release of the recombinant Cry3Bb1 protein of Bt maize MON88017 into field soil and detection of effects on the diversity of rhizosphere bacteria

A three-year experimental field study with a genetically engineered Bt maize (event MON88017) and three conventionally bred cultivars was conducted to quantify the recombinant Cry3Bb1 protein released into soil and detect effects on the diversity of soil bacteria. Protein extraction and an enzyme-linked immunosorbent assay (ELISA) allowed a threshold detection of 0.01 ng Cry3Bb1 g^?1 soil. The maximum amount found in field plots with Bt maize was 1.0 ng Cry3Bb1 g^?1 rhizosphere soil. Average concentrations during the growing seasons varied between years from 0.07 to 0.29 ng g^?1. No accumulation of Cry3Bb1 in soil occurred over the three growing seasons. Four weeks after harvest, the major Cry3Bb1 reservoirs on the field were the remaining root stubbles, but their Cry3Bb1 concentration declined by 98.30–99.99% in the following seven months. During the three consecutive years of study there were never significant differences between the rhizosphere bacterial community structure of the Bt maize and the other cultivars, as detected by cultivation independent profiling of PCR-amplified 16S rRNA genes. The low concentrations of soil extractable Cry3Bb1, its degradation in decaying roots, and the lack of effects on rhizosphere bacteria give no indications of adverse effects of MON88017 cultivation on soil ecology.     

In‐situ remediation of contaminated farmland by horizontal transfer of degradative plasmids among rhizosphere bacteria

Horizontal transfer of catabolic genes for pollutant degradation among rhizobacteria plays an important role in environmental bioremediation, but lacks support from field trial data. To address this problem, Pseudomonas fluorescens strain TP13 was inoculated into the soils of a phenol‐contaminated farmland on which tomato seedlings were growing in April 2009, 2010, 2011 and 2012. Results consistently showed that introduction of TP13 strain significantly reduced phenol content and increased plant biomass after 20 days, compared with controls. Strain TP13 was able to colonize the plant rhizosphere and the number of rhizosphere bacteria which were grown on phenol and contained the plasmids containing the gene encoding for catechol 2, 3‐dioxygenase (C23O) increased gradually in the later stages of the experiment. The increase in magnitude of the plasmid‐containing rhizosphere bacteria correlated well with plant biomass, while the number of plasmid‐containing rhizosphere bacteria and phenol content was strongly negatively correlated. Furthermore, six strains (T1‐T6) of rhizosphere bacteria were isolated and found to possess large plasmids containing identical C23O genes and similar HindIII restriction patterns. Sequence alignment showed that the C23O genes from strains T1‐T6 contained almost identical sequences and the sequence of the C23O of strain T1 was the same as that of strain TP13. These data indicated that the plasmids were transferred from strain TP13 to these rhizosphere bacteria and that horizontal gene transfer stimulated phenol degradation and plant growth in the contaminated farmland. This is an important finding for in situ remediation of contaminated farmland.     

Analysis of the effects of heat treatment on gliadin immunochemical quantification using a panel of anti-prolamin antibodies.

Antigen-labeled capture enzyme-linked immunosorbent assay with four different anti-gliadin monoclonal antibodies and an anti-gliadin serum and two different sample systems (purified gliadin fractions heat-treated in soluble phase and a model of dough simulating a baking process) were employed to study the effects of heat treatment on gliadin quantification. The analysis of purified gliadins showed that there is no particularly heat stable fraction. Remarkably, omega-gliadin did not present a differential heat stability. Reactivity varied depending on the time-temperature conditions of the treatment, the antibody employed, and the fraction analyzed. Heated dough samples showed an impairment of protein extraction depending on the intensity of the treatment. Capillary electrophoresis analysis of extracts showed that each gliadin group is affected to a different extent; omega-gliadin is less modified. Immunochemical analysis of the heat-treated samples using either of the five antibodies showed a decrease in the quantified gliadin, in concordance to the loss in the extracted proteins. Among the different sources of error in gliadin immunochemical quantification, the impairment in extraction efficiency in heat-treated samples appears as a major drawback to be overcome.     

Influence of organic fertilization on the number of culturable diazotrophic endophytic bacteria isolated from sugarcane

The numbers of culturable diazotrophic endophytic bacteria (CDEB) from roots, stems and leaves of sugarcane submitted to organic, inorganic or no fertilization were compared. In order to determine the size of the N₂ fixing populations, the Most Probable Number technique (MPN) was used. The quantification of diazotrophic bacteria by using the acetylene reduction assay (ARA) was more accurate than observing the bacterial growth in the vials; to confirm N₂ fixing capability, the detection of gene nifH was performed on a sample of 105 isolated bacteria. The production of extracellular enzymes involved in the penetration of the plants by the bacteria was also studied. The results showed that organic fertilization enhances the number of CDEB when compared with conventional fertilization used throughout the growing season. The maximum number of bacteria was detected in the roots. Roots and stems presented the greatest number of CDEB in the middle of the cropping season and in leaves numbers varied according to the treatment. Using two pairs of primers and two different methods, the nifH gene was found in 104 of the 105 tested isolates. Larger amounts of pectinase were released by isolates from sugarcane treated with conventional fertilizers (66%), whereas larger amounts of cellulase were released by strains isolated from sugarcane treated with organic fertilizers (80%).     

Hydrological effects on the diversity of phenolic degrading bacteria in a peatland: implications for carbon cycling

Northern peatlands store ca. 1/3 of the world's soil organic carbon and this is attributed to low decomposition rates as a result of waterlogged, anaerobic conditions and high levels of phenolic substances. Climate change models predict both an increase in summer droughts and increased rainfall, depending on region, but information on the effect of these changes on the microbial population that mediate phenolic degradation is sparse. Temporal temperature gradient gel electrophoresis (TTGGE) was therefore used to assess the effect of simulated summer drought and increased rainfall on the diversity of phenolic degrading bacteria in a northern peatland using the gene XylE, encoding for the enzyme Catechol 2,3-dioxygenase (C23O), as an indicator. Under simulated drought, a greater diversity (129.4%, P<0.05) and abundance of phenolic catabolising bacterial species was found. Concurrent increased total phenol oxidase activities (83.3%) and β-glucosidase activities (157.6%, P<0.01) were found with consistently lower concentrations of phenolic compounds, DOC and increased CO₂ fluxes. This increased mineralisation is likely to lower carbon storage capacity and increase climate forcing. Conversely, the increased rainfall simulation suppressed diversity (62.2%, P<0.05), abundance and phenol oxidase activities (103.3%, P<0.001), giving increased phenolic compound (424.8%, P<0.1 only) and DOC concentrations (201.3%, P<0.001), along with increased anaerobic trace gas fluxes. These hugely increased aquatic carbon concentrations available for export are of serious concern due to their deleterious effect on drinking water quality.     

Promotion of plant growth and in situ degradation of phenol by an engineered Pseudomonas fluorescens strain in different contaminated environments

We show that Pseudomonas fluorescens strain P13, a plant growth-promoting bacterium, enhanced the growth of corn in uncontaminated soil but not in contaminated soil, perhaps because of its inability to reduce phytotoxicity. Another bacterial strain, Pseudomonas aeruginosa strain SZH16, showed in situ phenol-degrading activity and contained a plasmid loaded with a gene encoding for catechol 2, 3-dioxygenase, an important enzyme in the degradation pathway of aromatic compounds. We implanted this biodegradation ability into strain P13, using horizontal gene transfer techniques using strain SZH16 as the donor and P13 as the recipient, to generate a phenol-degrading transconjugant which obtained the effective plasmid from strain SZH16. Introduction of the transconjugant P13 strain into an artificially phenol-spiked soil promoted the growth of corn and in situ phenol degradation, and the increase in plant biomass correlated with the decrease in soil phenol content. Furthermore, the transconjugant P13 strain was also found to stimulate corn growth and reduce phenol concentration in water containing phenol and in historically contaminated field soils, indicating that the transconjugant strain could promote plant growth in both contaminated and uncontaminated environments. The transconjugant P13 strain was more efficient than either strain P13 or SZH16, and shows how plant growth-promoting bacteria which show no, or only limited, ability to degrade organic pollutants may be modified. This technique is attractive for many environmental remediation and agronomic applications.     

Detection of pH 4.6 insoluble beta-lactoglobulin in heat-treated milk and Mozzarella cheese

Different protein aggregates including beta-lactoglobulin (beta lg) were detected in the pH 4.6 insoluble fraction recovered from actual heat-treated milk samples by gel electrophoresis and immunoblotting. A competitive enzyme-linked immunosorbent assay (ELISA) using anti-beta lg polyclonal antibodies was developed to analyze the beta lg partition in the protein fractions obtained upon acidification of both milk and Mozzarella cheese at pH 4.6. According to ELISA determinations, nearly 90% of the pH 4.6 soluble beta lg included in raw milk was found in the pH 4.6 insoluble fraction of ultrahigh temperature (UHT)-treated milk. As concerns Mozzarella cheese analysis, ELISA results indicated that about 36% of the total beta lg milk content was transferred from pasteurized milk to Mozzarella cheese, whereas less than 0.5% was transferred from raw milk. The pH 4.6 insoluble beta lg proved to be a suitable indicator of the intensity of the heat treatment applied to milk. The ELISA-based detection of this parameter was suggested for quality control of both drinking milk and raw milk cheese.     

超高压和热灭菌对鲜榨菠萝汁品质影响的比较

对比分析了超高压（UHP,ultra-high pressure）及热处理在达到商业杀菌要求的基础上对菠萝原汁感官品质、营养成分及理化性质的影响。试验结果表明,随着压力值（300～500 MPa）的上升菌落总数逐渐减少,超高压处理（400 MPa,26℃,10 min）及热处理（85℃,5 min）条件下均可达商业无菌;上述2种处理条件处理后菠萝原汁pH值、总酸、总糖、可溶性固形物含量与对照样差异不显著（P＞0.05）;超高压处理样品能较好地保持体系的均匀稳定性;超高压处理样品与热处理样品的L*、a*、b*值与对照样相比变化均显著（P＜0.05）,但超高压处理样品更好地保持了原有色泽;超高压处理样品的还原型维生素C保留率达94.92%,远高于热处理;感官分析通过定量描述分析法对不同处理方式处理后的样品进行分析评定,结果表明,超高压处理样品在色、香、味等方面都接近对照样。因此,超高压技术不仅具有较好的杀菌效果,而且最大限度地保证了菠萝汁的品质。     

Anammox bacterial abundance and biodiversity in greenhouse vegetable soil are influenced by high nitrate content

The anaerobic ammonium oxidizing(anammox) process has been found to play an important role in terrestrial ecosystems in recent years. However,the diversity and abundance of anammox bacteria in nitrogen(N)-rich agricultural soils under high fertilizer greenhouse conditions are still unclear. Two greenhouse fields with different N fertilizer input levels were chosen, and their soil profiles were studied with molecular technologies, including quantitative polymerase chain reaction assay, a clone library, and phylogenetic analysis based on hzsB(encoding anammox hydrazine synthase β-subunit) gene. Molecular analyses suggested that anammox bacteria were at their highest density at 10–20 cm soil depth, and that the anammox bacterial abundance was significantly lower at high N than at low N. Candidatus Brocadia was the sole anammox bacterial genus throughout the soil depth profiles. The highest diversity of anammox bacteria was found at 30–40 cm soil depth, and different phylotypic clusters of Candidatus Brocadia were associated with specific soil environmental factors, such as nitrates, soil depth, and total N. Correlation analyses and redundancy analyses confirmed that high nitrate content associated with high N fertilizer input had a significant negative influence on the abundance and biodiversity of anammox bacteria. These results imply that excessive use of N fertilizer would affect arid land soil N loss to the atmosphere by the anammox pathway.     

Effect of heat treatment on the phenolic compounds and antioxidant capacity of citrus peel extract

This paper reports the effects of heat treatment on huyou (Citrus paradisi Changshanhuyou) peel in terms of phenolic compounds and antioxidant capacity. High-performance liquid chromatography (HPLC) coupled with a photodiode array (PDA) detector was used in this study for the analysis of phenolic acids (divided into four fractions: free, ester, glycoside, and ester-bound) and flavanone glycosides (FGs) in huyou peel (HP) before and after heat treatment. The results showed that after heat treatment, the free fraction of phenolic acids increased, whereas ester, glycoside, and ester-bound fractions decreased and the content of total FGs declined (P < 0.05). Furthermore, the antioxidant activity of methanol extract of HP increased (P < 0.05), which was evaluated by total phenolics contents (TPC) assay, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS*+) method, and ferric reducing antioxidant power (FRAP) assay. The correlation coefficients among TPC, ABTS, FRAP assay, and total cinnamics and benzoics (TCB) in the free fraction were significantly high (P < 0.05), which meant that the increase of total antioxidant capacity (TAC) of HP extract was due at least in part to the increase of TCB in free fraction. In addition, FGs may be destroyed when heated at higher temperature for a long time (for example, 120 degrees C for 90 min or 150 degrees C for 30 min). Therefore, it is suggested that a proper and reasonable heat treatment could be used to enhance the antioxidant capacity of citrus peel.     

Effects of panicles on infrared thermometer measurements of canopy temperature in wheat

A study was conducted in Phoenix, AZ on stressed and unstressed field plots of Anza wheat (Triticum aestivum L.) on an Avondale loam soil (a fine, loamy, mixed calcareous hyperthermic Anthropic Torrifluvent) to determine effects of panicles on the apparent canopy temperature and their consequent impact on the estimation of crop stress. The panicles were removed from a 1.5 × 4-m sample of each plot by extracting the peduncle from the upper sheath. For each treatment canopy radiative temperature measurements were made from vertical and oblique angles (30° from the horizontal), using an 8° field-of-view (FOV) infrared thermometer, at half-hour intervals from sunrise to sunset on 20, 22, and 30 April. Complementary measurements included leaf water potential and leaf diffusive resistance.Apparent canopy temperatures obtained from the oblique view of the canopy with panicles and under well-watered conditions were 2°C warmer than those of the unstressed canopy without panicles. In the stressed plot the canopy with panicles was 1°C cooler than that without panicles, but this effect was only noticed around 1200 MST. The temperature difference between viewing angles was apparently caused by different percentages of panicle area viewed by the radiometer. In the vertical view panicles contributed to 3% of the total viewed area while at the 30° oblique view panicles comprised 40% of the area. Since energy balance calculations of a non-transpiring cylinder with dimensions similar to a typical wheat panicle showed its temperature would remain very close to that of the surrounding air, canopy temperatures were adjusted for the proportion of panicles viewed assuming they were in equilibrium with air temperature. Results showed the corrected canopy temperatures of the canopy with panicles were the same as those measured in the canopy without panicles. Such a correction is necessary to avoid an overestimate of the stress level and an underestimate of differences between treatments. Crops with non-transpiring and/or well-ventilated morphological structures above the foliage will require this correction if radiative canopy temperatures are to be used in irrigation management programs or stress detection studies.     

Hydrodynamic Conditions Influence Bacterial Growth and Phenol Biodegradation of Strains with Different Morphology and Motility

Microorganisms are frequently exposed to flowing fluid, thus to investigate bacterial characteristics under different hydrodynamic conditions is of great importance in microbial ecology. This study characterized bacterial growth and phenol biodegradation of three strains, i.e., Microbacterium oxydans (rod-shaped, non-motile), Alcaligenes faecalis (rod-shaped, motile), and Staphylococcus haemolyticus (spherical, non-motile) in shake-flask cultures at various rotating speeds. For all the strains, a higher rotating speed always resulted in a shorter lag phase, indicating that the strains showed a superior adaptability under higher hydrodynamic conditions. The maximum specific growth rate of M. oxydans, A. faecalis, and S. haemolyticus increased rapidly with the increase of energy dissipation rate till the highest value of 0.386, 0.240, and 0.323 1/h and then decreased as the rotating speed further increased. The phenol biodegradation rate was also dependent on rotating speed, and the trends were consistent with the growth rate variations. A predictive model similar to Haldane model was proposed and was fitted well (R²?>?0.913) with bacterial growth under different hydrodynamic conditions. According to the predictive model, the optimum hydrodynamic conditions for the growth of M. oxydans, A. faecalis, and S. haemolyticus were 3.099, 2.197, and 2.289 m²/s³, respectively. The results suggested that non-motile and rod-shaped bacteria were more dependent on hydrodynamic conditions than motile and spherical ones, which could be attributed to the discrepancies in bacterial morphology and motility. The results provide a better understanding on bacterial responses to various hydrodynamic conditions and could be further applied in the bioremediation of contaminated water.     

Rhizosphere bacteria from sites with higher fungal densities exhibit greater levels of potential antifungal properties

A field study was performed to examine whether an increased density of saprotrophic fungi in the rhizosphere selects for bacteria with traits advantageous to living in a fungal-rich environment. Fast-growing bacteria were isolated from the rhizosphere of Carex arenaria (sand sedge) plants growing in fungal-poor (sand drifts) and fungal-rich (forest) sites in the Netherlands and screened for several potential antifungal properties, namely in vitro antagonism and the production of siderophores, cyanide and lytic enzymes. A higher incidence of putatively antifungal traits was generally found in bacteria isolated from fungal-rich soils, thus supporting the hypothesis that high fungal densities can impose a selection pressure on rhizosphere bacteria.     

Summer drought effects upon soil and litter extracellular phenol oxidase activity and soluble carbon release in an upland Calluna heathland

Extracellular phenol oxidases play an important role in the soil carbon cycle. The effects of a field-scale summer drought manipulation on extracellular litter and soil phenol oxidase activity, soluble phenolic compounds and dissolved organic carbon concentrations were examined for an upland Calluna heathland on a peaty podsol in North Wales. Litter and organic soil phenol oxidase activity was found to be positively correlated with moisture content. Thus in shallow organic soils, which are sensitive to drying during periods of low rainfall, drought may inhibit soil phenol oxidase activity as a result of water limitations. The release of soluble phenolic compounds and DOC from the droughted plots was found to be lowered during the drought period and elevated outside of the drought period. It is hypothesized that these changes may be a result of the reduced ability of extracellular phenol oxidases to process recalcitrant polyphenolic material under drought conditions. A drying incubation carried out with litter and soil cores from the same site suggests that extracellular phenol oxidase activity displays an optimal moisture level. This reconciled the observed water limitation of phenol oxidase activity at the heathland experimental site with previously observed stimulation of phenol oxidase activity by water table drawdown in deeper peats.