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The effect of pH and counterions on the persistence of soil water repellency was examined. Repellency persistence increased at elevated pH in the presence of Ca 2+ but not Na + , increased at high cation concentrations, and decreased with increasing temperature. These results are explained by the behavior of monolayers of long-chain fatty acids on solid and liquid substrates. Other hydrophobic film-forming compounds, including long-chain alkanes, long-chain amines, and hydrophobins, cannot account for the observations. A conceptual model for repellency in soils was developed: (i) fatty acid headgroups are complexed with cations at positively charged surfaces and via divalent cation bridges at negatively charged surfaces, with chains facing outward, rendering the surface hydrophobic; (ii) these complexed fatty acid molecules have a relatively slow rate of reorientation when contacted by water; and (iii) there are relatively few easily hydrated hydrophilic moieties at the surface. The factors that determine whether a hydrophobic film will form at soil surfaces, and the stability and longevity of that film, include the abundance and nature of fatty acids and other components at particle surfaces, the mineralogy of the substrate, and the chemistry of the soil solution. This model explains many observed inconsistencies of repellent soils, including spatial and temporal variability, development on soils of differing acidities, changes in repellency upon heating, and more. In accordance with the model, we suggest that the molarity of ethanol droplet test is an indirect measure of the fatty acid abundance and strength of attachment at surfaces, and not of the initial contact angle.

The relationships between microorganisms and microfauna were studied in an evergreen oak ( Quercus ilex L.) forest floor located in a French Mediterranean region characterized by hot and dry summers. The soil was a brown fersialitic soil with an amphimull, i.e., a mull with a thick litter. A micromorphological study of both litter and organomineral layers was used to observe relationships between white-rot fungi and fauna, such as oribatids, millipedes, enchytraeids, and earthworms. Microbiological properties of the litter and physicochemical properties of the soil were analysed. Enchytraeids comminute the faeces of other animals, whereas earthworms form aggregates. These two opposite actions probably modify aeration and water movements in deeper layers. Brown leaves and animal faeces constitute a nutritional substrate for white-rot fungi and other animals. Inside degraded cells of rootlets and bleached leaves, fungi form calcium oxalate crystals because the absorbent complex is saturated by an excess of calcium. Enzymes such as laccases, manganese peroxidases, cellulases, or xylanases were detected in the litter at significant levels. The high activity values of phosphatases in the litter could reflect a deficiency in available phosphorus. This deficiency could partly explain a low rate of litter degradation and the presence of an OH sublayer.

Soil water repellency is usually unstable, as exemplified by the common method of quantifying repellency degree - the water drop penetration time (WDPT) test. Dynamic penetration and infiltration of water into repellent soils is generally attributed to either reduction of the solid-liquid interfacial energy (γ SL ) or reduction of the liquid-vapour interfacial energy (γ LV ), or both. The reduction of γ SL can result from conformation changes, hydration, or rearrangement of organic molecules coating soil particle surfaces as a result of contact with water, while the reduction of γ LV can result from dissolution of soil-borne surface active organic compounds into the water drop. The purpose of this study was to explicitly test the role of the second mechanism in dynamic wetting processes in unstably repellent soils, by examining the drop penetration time (DPT) of water extracts from repellent soils obtained after varying extraction times and at different soil: water ratios. It was indeed found that soil extracts had lower surface tensions (γ LV approx. 51-54 mN m -1 ) than distilled water. However, DPT of the soil extracts in water repellent soils was generally the same or greater than that of water. Salt solutions with the same electrical conductivity and monovalent/divalent cation ratio as the soil extracts, but lacking surface active organic substances, had the same DPT as did the extracts. In contrast, DPT of ethanol solutions prepared with the same γ LV , electrical conductivity, and monovalent/divalent cation ratio as the soil extracts, was much faster. Ethanol solutions are usually used as an agent to reduce γ LV and as such, to reduce DPT. It is concluded that the surface-active, soil-derived organic substances in aqueous soil extracts do not contribute to wetting dynamics, and as such, this mechanism for explaining kinetics of water penetration into water repellent soils is rejected. It is also concluded that the rapid penetration of ethanol solutions must be due not only to changes in γ LV , but to also to changes in either or both γ SL and the solid-vapour interfacial energy (γ SV ). These results stand in sharp contrast to well-accepted logical paradigms.

The study looked at anxiety and depression levels during the six weeks following admission to a medical rehabilitation ward and also at levels of physical ability. The Hospital Anxiety and Depression Scale (Zigmond & Snaith, 1983) was verbally administered to 48 patients on four occasions over a six-week period. Barthel Index Scores (Mahoney & Barthel, 1965) were obtained for all patients at admission and at the end of their contribution to the study. Results showed significant improvements in the level of physical ability from admission to the end. There were no overall group changes in anxiety and depression levels. However, there was a significant decrease in anxiety scores for patients with a high anxiety level at admission (N= 10). The study also compared anxiety and depression levels between patients who completed all four assessments and those who were discharged within six weeks of admission. No significant differences were found. The study concludes that ‘possible’ or ‘probable’ levels of anxiety on admission may indicate a reaction to the new environment rather than a clinical disorder.

This paper represents the third part of a larger study about the processes involved in litter biodegradation in an oak copse in France. It concerns the variations in activities of endoglucanases and of β-glycosidases over 13 months in forest litter. Evergreen oak ( Quercus ilex L.) litter was taken as a model because Q. ilex is the most abundant tree species in forests of the French Mediterranean area. The activities of several endoglucanases and β-glycosidases, and the concentrations of the proteins and reducing sugars were measured in the evergreen oak litter between October 1997 and October 1998. Several biotic and abiotic factors, potentially involved in the regulation of the activities of these hydrolyzing enzymes, were also measured: culturable heterotrophic bacteria, cellulolytic bacteria and cellulolytic fungi, moisture, temperature and pH of the litter. Under this Mediterranean climate, the moisture of the litter was strongly correlated with many factors and is likely to be important in regulating the temporal dynamics of various biological parameters. A multiple regression analysis showed that the annual dynamic of the culturable heterotrophic bacteria was primarily influenced by moisture but also by variations in concentration of reducing sugars in the litter. Moreover, these bacteria were correlated with the activities of several β-glycosidases, and specifically with the N -acetyl-glucosaminidases ( r =0.93). No relationships were established between the number of cellulolytic microorganisms (bacteria and fungi) and the activities of endoglucanases (i.e. cellulases and hemicellulases). The seasonal trends of certain biotic processes, and the influence of pH and of temperature on these processes are also discussed. Electrophoretic analyses were used to estimate the number of cellulase and xylanase isoenzymes in the litter, and to study their fluctuations over one year. The prevailing cellulase isoenzyme had a R f of 0.64, and there was no relationship between the abundance of cellulolytic microorganisms and the electrophoretic profiles of the cellulases. In the case of the xylanases, the electrophoretic profiles were homogenous throughout the year, and the prevailing xylanase had a R f of 0.75.

International audience; Two isozymes of laccase were obtained from an induced liquid culture of Marasmius quercophilus with p-hydroxybenzoic acid as the inducer. Both the constitutive and the induced isozyme have a molecular mass of 60 kDa as determined by polyacrylamide gel electrophoresis. Using isoelectric focusing, we found three isozymes with the constitutive enzyme (pI 4, 4.2, 4.4) and four of the induced form (pI 4.75, 4.85, 4.95, 5.1). We observed certain differences between these two isozymes; the specific activity of the induced isozyme was twice as high, and two optimum pH levels (5 and 6) were observed with the induced isozyme (only one, pH 5, for the constitutive isozyme). However, both of these enzymes have the same thermal stability and the same temperature for their highest activity (80°C). Furthermore, the reactivity of both these enzymes with aromatic compounds was similar. The use of mediators extended the oxidized substrate range of the laccases studied. Various products of degradation were observed, depending on the mediator used. When laccase was used alone, the decrease of the signal corresponding to the aromatic cycle, without any formations of other peaks at different wavelengths, suggested polymerisation of aromatic compounds; Deux isozymes de laccases ont été obtenues à partir d'une culture liquide induite de Marasmius quercophi-lus en utilisant l'acide p-hydroxybenzoïque comme inducteur. Les isozymes constitutives et induites ont toutes deux un poids moléculaire de 60 kDa mesuré en électrophorèse sur gel de polyacrylamide. En électrofocalisation, nous avons observé trois isozymes pour l'enzyme constitutive (pI 4, 4.2, 4.4) et quatre pour l'isozyme induite (pI 4.75, 4.85, 4.95, 5.1). Nous avons observé certaines différences entre ces deux isozymes; l'activité spécifique de l'isozyme induite était deux fois plus importante que celle de l'isozyme constitutive et deux pH optimum (5 et 6) ont été notés pour l'isozyme induite (seulement un, pH 5, pour l'isozyme constitutive). Les deux enzymes avaient la même stabilité ther-mique et la même température d'activité maximale (80°C). De plus, la réactivité de ces deux laccases vis-à-vis des composés aromatiques était semblable. L'utilisation de médiateurs a augmenté la gamme des substrats oxydés par les laccases étudiées. Différents produits de dégradation ont été observés selon le médiateur utilisé. Quand seule la laccase est utilisée, la diminution du signal correspondant au composé aromatique et l'absence d'autres pics à différentes lon-gueurs d'ondes, suggèrent une polymérisation des composés aromatiques.

The biodegradability of polyacrylic acid derivatives may be improved through introduction of some fragility points within the main carbon chains. These weakness points can be either hydrolizable bonds or oxidizable sites. Enzymatic hydrolysis and oxydative biomimetic degradation tests have been set up in order to quickly evaluate new polymeric structures, before their possible evaluation through microbial degradation by Candida tropicalis.

Laccases are blue-copper enzymatic proteins involved in the transformation of polyphenolic compounds, such as lignin, into forest litter. A method to measure their activity was developed using an evergreen oak litter as a model system. We considered factors that affect the extraction of these enzymes and the measurement of their activity. The factorsstudied included powdering of the leaves, adding polyvinylpolypyrrolidone or Tween 80, adsorption of enzymes on centrifugation pellets, concentration of the extracts, nature and molarity of the extraction solvent, amount of powdered leaves used for enzymatic extraction, extraction time, pH, and temperature during the measurement of the activity.

Marasmius quercophilus is a white-rot fungus producing laccase, a polyphenoloxidase involved in lignin degradation. The 17 strains under study were isolated from an evergreen oak litter (La Gardiole-de-Rians, Var, France). All the isolates synthesised the same constitutive laccase. Copper and various aromatic compounds in the medium enhanced laccase activity to different degrees. A copper concentration of 5 mg L 1 seemed to be the optimal tested. Coniferyl alcohol appeared to have the most extensive inducing potential. Each aromatic compound induced different new isoenzymatic forms in the electrophoretic patterns. These isoenzymes were similar for every strain.

A white-rot basidiomycete, Marasmius quercophilus , was isolated from an evergreen oak litter. This fungus, which very thoroughly bleaches the whole leaf area, produces laccases, a property which has not been studied before. Except on a ground leaf medium, we did not reveal phenoloxidases other than laccases. M. quercophilus is able to transform many aromatic compounds which are by-products of lignin and tannin metabolism. We observed, for example, that lignin monomers, namely p -coumaryl, coniferyl, and sinapyl alcohols are oxidized at different rates by the extracellular crude enzyme extract. The highest production of laccases is obtained with shaking cultures on malt extract supplemented with Tween 80 (0.1%) and CuSO 4 (0.5 mg l −1 ). These enzymes have an optimum activity at 80°C and a stable activity at 40°C for 18 h. The extracellular crude enzyme extract medium contains three isoenzymes with pI values of 3.8, 3.5, and 3.2. It is able to significantly reduce the kappa number (21.2%) of a kraft pulp without inclusion of any mediator.

The basidiomycete Marasmius quercophilus is commonly found during autumn on the decaying litter of the evergreen oak ( Quercus ilex L.), a plant characteristic of Mediterranean forest. This white-rot fungus colonizes the leaf surface with rhizomorphs, causing a total bleaching of the leaf. In synthetic liquid media, this white-rot fungus has strong laccase activity. From a three-step chromatographic procedure, we purified a major isoform to homogeneity. The gene encodes a monomeric glycoprotein of approximately 63 kDa, with a 3.6 isoelectric point, that contains 12% carbohydrate. Spectroscopic analysis of the purified enzyme (UV/visible and electron paramagnetic resonance, atomic absorption) confirmed that it belongs to the “blue copper oxidase” family. With syringaldazine as the substrate, the enzyme's pH optimum was 4.5, the optimal temperature was 75°C, and the K m was 7.1 μM. The structural gene, lac1 , was cloned and sequenced. This gene encodes a 517-amino-acid protein 99% identical to a laccase produced by PM1, an unidentified basidiomycete previously isolated from wastewater from a paper factory in Spain. This similarity may be explained by the ecological distribution of the evergreen oak in Mediterranean forest.

Two bacterial strains were isolated from a bacterial community formed of nine strains, selected from a marine sediment on a seawater medium with naphthalene as sole carbon source. The two strains studied in the present work were the only strains of this community able to grow in pure culture on naphthalene; therefore, they were called "primary" strains. The seven other strains were maintained in the community by using metabolic intermediates of the two primary strains; they were called "auxiliary" strains. Regulation of naphthalene metabolism was studied for the two primary strains. They oxidized naphthalene into catechol, which was degraded only by the meta pathway. For Pseudomonas Lav. 4, naphthalene oxygenase and salicylate hydroxylase were inducible; catechol 2,3-dioxygenase was constitutive. For Moraxella Lav. 7, naphthalene oxygenase was constitutive; salicylate hydroxylase and catechol 2,3-oxygenase were inducible. The Moraxella strain carries two cryptic plasmids, about 63-and 85-kb in molecular size. In the bacterial community culture medium, Moraxella Lav. 7 prevented accumulation of 2-hydroxymuconate semialdehyde formed by Pseudomonas Lav. 4. The auxiliary strains take up formic, acetic, pyruvic, propionic, and succinic acids released by the two primary strains. Key words: marine bacterial community, naphthalene metabolism.

The adding of a mixed culture of marine hydrocarbon-degrading bacteria to petroleum polluted seawater did not increase the hydrocarbon degradation capability of the water. All the strains of the mixed culture disappeared from the dominant microflora while the autochthonous bacteria showed a capacity for adaptation to petroleum degradation about four days after the oil spill. This confirms the advantage of natural bacterial communities. The oil spilled on the sea surface evolved very quickly under the influence of abiotic factors such as sunlight. Aromatic petroleum fractions were oxidized and polymerized. This chemical evolution causes a drastic decrease of the biodegradability of crude oil.

Resume L'etude de la biodegradation des produits petroliers rejetes en mer par une raffinerie a montre que la ‘concentration’ de l'effluent en hydrocarbures doit atteindre un seuil superieur a 50 mg/litre pour qu'un developpement important de microorganismes puisse se produire. Les differentes molecules d'hydrocarbures subissent alors l'action bacterienne. En general, le potentiel de degradation de la microflore presente dans l'eau de mer est plus eleve au debouche d'un tel effluent.

Resume Les effets des deversements en mer de l'effluent d'une raffinerie de petrole sur les caracteristiques physiques et chimiques des eaux, la production phytoplanctonique et les populations bacteriennes ont ete etudies. 1. (1) La temperature elevee des eaux de rejets entraine des variations thermiques importantes aux abords memes de la zone de deversement qui conduisent parfois a la realisation d'un milieu tres pauvre en oxygene. 2. (2) Les concentrations variables mais parfois tres elevees en PPO4 provoquent des perturbations importantes du rapport NNO3/PPO4. Une reduction, vraisemblablement d'origine bacterienne, du NNO3 accentue la desequilibre de ce rapport. 3. (3) La teneur moyenne en chlorophylle a des eaux voisines de la zone de rejets est a peu pres egale a celle des eaux situees plus au large mais l'evolution du rapport NNO3/PPO4 laisse supposer que les especes phytoplantoniques peuvent etre differentes. 4. (4) Les bacteries se developpant sur un gas-oil representent 10% des bacteries heterotrophes dans la zone de rejet et 4% dans une zone situee a l'ecart de toute contamination directe par les hydrocarbures. 5. (5) Les conditions physiques et chimiques au debouche de l'effluent en mer ne sont pas favorables a l'equilibre des populations phytoplanctoniques, mais elles peuvent l'etre a la degradation des hydrocarbures par les bacteries.

The hydrocarbon degradation potential of seawater appears higher in zones chronically polluted by these materials; they are characterized by an abundant bacterial development. The salinity of the effluent from a refinery and also its hydrocarbon content are factors affecting the speed of degradation.

Three bacterial strains, isolated on gas-oil from seawater, have a variously changed growth on hexadecane with supply of two organic substances. Acetate reduces growth of all tested strains and particularly the hexadecane degradation by Acinetobacter sp. On the contrary, trypticase-phytone promotes the degradation by the three strains.

In this work we tried to caractérisé biological activity of the formed litter into two QueAcut ilex ecosystems. The methods used showed that respiratory and alkaline phosphatase activities are different in the two ecosystems. The other enzymatic activities (acid phosphatases , ureases and catechol-oxygenases ) are very high in all ecosystems and do not allow to distinguish between them. No nitrogenasic activity could be revealed., Le but de ce travail a été de caractériser l 'activité biologique dans la litière de Chêne vert en deux stations. Les méthodes utilisées ont mis en évidence des différences dans les activités respiratoires et phosphatase alcalins. Les autres activités enzymatiques (phosphatases acides , uréases et catéchol-oxygénases) sont très élevées et ne permettent pas une distinction entre les stations. Aucune activité nitrogénasique n'a été décelée., Chabert Alain, Le Petit J., Loisel Roger, Matheron Robert, Tagger S. Dégradation biologique de la litière de chêne vert dans deux forêts de la région provençale (Var, France). In: Ecologia mediterranea, tome 10 n°1-2, 1984. pp. 171-181.

Using mineral media with gas oil as sole carbon source, 191 bacterial strains were isolated from the costal area of Marseille. These strains were attributed to Achromobacter, Alcaligenes, Pseudomonas, Acinetobacter and Arthrobacter genera. Amongst isolated strains there was a predominance of the Alcaligenes-Achromobacter group over others genera. Growth and respiratory activity of 5 strains were studied on hexadecane and acetate. Respiratory activity on hexadecane of 32 strains cultured on acetate has been measured. These strains could be placed in two groups. The group 1 shows an immediate respiratory activity which is not abolished by chloramphenicol. The group 2 presents either an immediate or a delayed respiratory activity which is always abolished by chloramphenicol. Maintenance or suppression of respiration by chloramphenicol is a character which is homogenously distributed amongst the species.