Toxicity assessment of the herbicides sulcotrione and mesotrione toward two reference environmental microorganisms: Tetrahymena pyriformis and Vibrio fischeri.

The potential toxicity of sulcotrione (2-[2-chloro-4-(methylsulfonyl)benzoyl]-1,3-cyclohexanedione) and mesotrione (2-[4-(methylsulfonyl)-2-nitrobenzoyl]-1,3-cyclohexanedione), two selective triketonic herbicides, was assessed using representative environmental microorganisms frequently used in ecotoxicology: the eukaryote Tetrahymena pyriformis and the prokaryote Vibrio fischeri. The aims were also to evaluate the toxicity of different known degradation products, to compare the toxicity of these herbicides with that of atrazine, and to assess the toxicity of the commercial herbicidal products Mikado and Callisto. Toxicity assays involved the Microtox test, the T. pyriformis population growth impairment test, and the T. pyriformis nonspecific esterase activity test. For each compound, we report original data (IC(50) values) on nontarget cells frequently used in ecotoxicology. Analytical standards sulcotrione and mesotrione showed no toxic effect on T. pyriformis population growth but a toxic influence was observed on nonspecific esterase activities of this microorganism and on metabolism of V. fischeri. Most of the degradation products studied and the two commercial formulations showed a greater toxicity than the parent molecules. Compared with the effect of atrazine, the toxicity of these triketonic herbicides was less than in T. pyriformis and greater than or the same as in V. fischeri. Additional work is needed to obtain a more accurate picture of the environmental impact of these herbicides. It will be necessary in future experiments to study the ecosystemic levels (aquatic and soil compartments) and to assess the potential toxicity of the newly discovered degradation products and of the additives accompanying the active ingredient in the commercial herbicidal formulations.

Involvement of Tetrahymena pyriformis and selected fungi in the elimination of anthracene, and toxicity assessment of the biotransformation products.

Anthracene (AC) is a non-mutagenic and non-carcinogenic, low-molecular-weight polycyclic aromatic hydrocarbon present in the environment. Its toxicity can be dramatically increased after solar-light exposure. Biotransformation capacities of AC by Tetrahymena pyriformis and a selection of eight micromycetes were studied, and the ability of these microorganisms to detoxify the polluted ecosystems was assessed. We showed that T. pyriformis was able to accumulate high amounts of AC without any transformation. In contrast, the fungi Cunninghamella elegans, Absidia fusca, Absidia cylindrospora, Rhodotorula glutinis, and Aspergillus terreus were able to transform AC with a high efficiency. Cytotoxicity assays conducted on HeLa cells and T. pyriformis showed that crude extract from A. fusca culture medium obtained after AC biotransformation was not toxic. For A. fusca and A. cylindrospora, 1-4 dihydroxyanthraquinone was shown to be the major product during the biotransformation process. This compound seemed to be a dead-end metabolite at least for the Absidia strains. The cytotoxicity of 1-4 dihydroxyanthraquinone was higher than that of AC to T. pyriformis but lower to HeLa cells. On the whole our results showed that the microorganisms studied were all able to decontaminate an AC-polluted ecosystem, either by accumulating or transforming the compound. A possible detoxification process resulting from AC biotransformation can be considered only using the human cell model.

Assessment of the potential toxicity of herbicides and their degradation products to nontarget cells using two microorganisms, the bacteria Vibrio fischeri and the ciliate Tetrahymena pyriformis.

The potential toxicity of several herbicides-alachlor, diuron and its photo and biotransformation products, glyphosate and its metabolite aminomethyl phosphonic acid (AMPA)-to nontarget cells was assessed using two microorganisms frequently used in ecotoxicology, Vibrio fischeri and Tetrahymena pyriformis. Toxicity assays involved the Microtox test, the T. pyriformis population growth impairment test employing three different processes (flasks, tubes, microplates), and the T. pyriformis nonspecific esterase activities test. Several IC(50) or EC(50) values are reported for each molecule. Alachlor exerted a toxic effect on the two nontarget cells used. The results for diuron and its photo and biotransformation products indicated that most of the metabolites presented nontarget toxicity higher than that of diuron. Glyphosate and AMPA had a less negative effect on T. pyriformis than on V. fischeri. Nevertheless, in all cases, glyphosate was found to be more toxic than AMPA. Comparison analysis of the sensitivity of the different tests showed that, in general, tests using the eukaryotic cell (T. pyriformis) were more sensitive than test using the prokaryotic cell (V. fischeri), and that a population growth criterion is more sensitive than an enzymatic criterion. The three different processes that could be used to evaluate effects on population growth rate were equally sensitive for the herbicides tested. A significant correlation between toxicity data and the hydrophobicity of the chemicals could only be established with the growth population test. This study demonstrates that it is essential to assess the toxicity of the metabolites formed to complete a more comprehensive study of the environmental impact of a polluting agent.

Assessment of anthracene toxicity toward environmental eukaryotic microorganisms: Tetrahymena pyriformis and selected micromycetes.

The toxicity of anthracene, a nonmutagenic, noncarcinogenic, low-molecular-weight polycyclic aromatic hydrocarbon present in the environment, was assessed using a ciliated protozoan, Tetrahymena pyriformis, and a selection of 10 micromycetes from different taxonomic groups living in two environmental compartments, namely aquatic and soil ecosystems. With T. pyriformis, a concentration-dependent inhibitory effect was shown on the cell proliferation rate, IC(50) = 33.40+/-4.84 mg/L (kinetic method). Phagocytosis of nonsoluble anthracene was confirmed by the presence of digestive vacuoles with photon microscopy. In fungi, anthracene did not exhibit a fungicide effect but showed a fungistatic action. Except for Absidia fusca and Cladosporium herbarum, the micromycetes showed a concentration-dependent decrease in growth. From IC(50) values determined by endpoint or kinetic methods, Rhodotorula glutinis and all of the Ascomycotina (except for Penicillium chrysogenum) were the most sensitive species, while Phanerochaete chrysosporium, P. chrysogenum, and the two Deuteromycotina were more resistant to anthracene. Our discussion focuses on the evaluation of toxicity by the two methods used for the calculation of the IC(50) values (endpoint and kinetic), the advantages of studying growth by a kinetic method (the dynamic aspect), and a comparison of toxicity to T. pyriformis and the different micromycetes.

Purification and characterization of an anti-(A+B) specific lectin from the mushroom Hygrophorus hypothejus.

A lectin (HHL) was isolated from the fruiting body of the mushroom Hygrophorus hypothejus by a combination of affinity chromatography on stromas of group B erythrocytes embedded in polyacrylamide gel, and DEAE-trisacryl and gel filtration chromatography. Its molecular mass, as determined by gel filtration, is estimated to be 68000 kDa and its structure is tetrameric with four identical subunits assembled with non-covalent bonds. HHL agglutinates specifically A and B blood group erythrocytes and in hemagglutination inhibition assays, exhibits sugar-binding specificity toward lactose, the anomeric alpha form being more effective than the beta form.

Isolation and characterization of an N-acetyllactosamine-binding lectin from the mushroom Laetiporus sulfureus.

A hemagglutinating and hemolytic lectin (PSL) has been isolated from carpophores of the parasitic mushroom Laetiporus sulfureus by affinity chromatography on Sepharose. Its molecular weight, as determined both by gel filtration and by electrophoresis in non-denaturing conditions, is about 190,000 and its structure is tetrameric, with two distinct types of subunits (about 60,000 and 36,000). It appeared homogeneous on HPLC gel filtration but exhibited microheterogeneity on isoelectric focusing. Hapten inhibition assay indicated that the Laetiporus lectin is specific for N-acetyllactosamine residues and that hemagglutinating and hemolysis activities are supported by the same site.

Characterization of a Lectin from Lactarius deterrimus (Research on the Possible Involvement of the Fungal Lectin in Recognition between Mushroom and Spruce during the Early Stages of Mycorrhizae Formation).

A lectin (LDetL) was isolated from carpophores of the mushroom Lactarius deterrimus, a specific symbiont of the spruce, by a combination of affinity, hydroxylapatite, and gel-filtration chromatography. Its molecular mass, as determined by gel filtration, is about 37,000 D, and its structure is dimeric, with two identical subunits assembled by noncovalent bonds. It appeared homogeneous on high-performance liquid chromatography gel filtration, but isoelectric focusing revealed microheterogeneity, with a main band in the pH zone near 6.5. Amino acid analysis showed that LDetL contains a large proportion of glycine and especially methionine. Hapten inhibition assay indicated that LDetL is most specific for [beta]-D-galactosyl(1->3)-D-N-acetyl galactosamine residues. The lectin was formed in the in vitro-cultivated mycelium, and anti-lectin antibodies revealed by indirect immunofluorescence the presence of lectin in the cell wall. Receptor sites for LDetL were found on the roots, especially on the root hairs, of axenically grown spruce seedlings. The lectin LDL previously isolated by us from the taxonomically related mushroom Lactarius deliciosus, a symbiont of the pine, does not bind to the spruce radicle. This suggests a role of the fungal lectin in recognition and specificity during the early stages of mycorrhizae formation.

Piromyces rhizinflata nov. sp., a strictly anaerobic fungus from faeces of the Saharian ass: a morphological, metabolic and ultrastructural study.

A new species of strictly anaerobic chytridiomycete was isolated from dried faeces of the Saharian ass that had been stored for up to 150 days. Because of its monocentric thallus and uniflagellate zoospores it belongs to the genus Piromyces. It exhibits a high affinity for P. mae and P. dumbonica but differs from them in its morphological and ultrastructural characteristics. Its flagellar apparatus is similar to that of all previously reported fungi.

Isolation and characterization of a lectin from the mushroom, Lactarius deliciosus.

A lectin (LDL) has been isolated from carpophores of the edible mushroom, Lactarius deliciosus, using a combination of affinity chromatography on stromas of group O erythrocytes embedded in polyacrylamide gel and hydroxylapatite, and gel filtration chromatography. Its molecular weight, as determined by gel filtration, is about 37,000 and its structure is dimeric, with two distinct types of subunits (about 19,000 and 18,000). It appeared homogeneous on HPLC gel filtration, but exhibited microheterogeneity on isoelectric focusing. Amino acid analysis revealed that it contains a large amount of glycine. Hapten inhibition assaying indicated that the Lactarius lectin is most specific for D-Gal beta 1----3D-GalNAc. The lectin was found in the mycelium and its possible role in the fungus is discussed.

Anaeromyces mucronatus nov. gen., nov. sp. A new strictly anaerobic rumen fungus with polycentric thallus.

A new species of strictly anaerobic fungus was isolated from the cow rumen. It is characterized by a polycentric thallus, a polynuclear rhizomycelium, mucronate zoosporangia and uniflagellated zoospores. It is also singular in that the sporocysts do not react to the specific lectins of L-fucose, N-acetyl-D-galactosamine and diacetyl chitobiose. These characteristics justify the creation of a new genus.

[Study using lectins of the parietal polysaccharides of Sphaeromonas communis]. / Etude à l'aide de lectines des polysaccharides pariétaux de Sphaeromonas communis.

Using fluorescein isothiocyanate-labeled lectins of various specificities, differences in the cell wall polysaccharide composition among the different parts of the thallus and during the cycle of S communis were demonstrated.

Use of lectins for a comparative study of cell wall composition of different anaerobic rumen fungal strains.

The technique based on fluorescein-linked lectins used to determine the cell wall structure of anaerobic rumen fungi belonging to genera: Neocallimastix, Piromonas and Sphaeromonas, appears to be an interesting tool for distinguishing between strains. Furthermore this technique shows differences of cell wall composition between different parts of the thallus (spores, sporangia, rhizoïds).