Effect of the herbicide bentanex on soil microorganisms and their activity

The effect of the herbicide Bentanex, especially of its effective component bentazone, on selected soil bacteria and fungi, on their growth and reproduction and on some important physiological activities ensuring a regular nutrient cycle in nature was investigated. Bentazone affected growth and reproduction of soil bacteria and micromycetes in dependence on the concentration and species of the microorganism. Physiological and biochemical activities of bacteria with respect to nitrogen fixation, nitrification and CO₂ production were negatively influenced by high concentrations of the herbicide. These concentrations were used to observe the effect on selected activities of soil microorganisms and were much higher than those actually used in agriculture. Translated by Č. Novotny     

Metabolomic Profiling and Lipid Composition of Arctic and Antarctic Strains of Micromycetes Geomyces pannorum and Thelebolus microsporus Grown at Different Temperatures

Microbiology - Adaptive reactions of Arctic and Antarctic strains of psychrophilic micromycetes Geomyces pannorum and Thelebolus microsporus to growth within a broad temperature range were studied....     

Effect of industrial SO2 immissions on the epiphytic microflora of spruce

In regions highly influenced by immissions the concentrations of serobic and ammonifying bacteria and yeasts on the surface of apical shoots of spruce were 10–30 times higher in summer than in regions that were relatively less influenced; concentrations of micromycetes were almost two-fold. Deterioration by immissions eliminated the autotrophic oxidizers of sulphur and decreased the number of asymbiotic nitrogen-fixing bacteria to zero. Counts of proteolytic bacteria decreased pronoucedly. On the other hand, the number of bacteria capable of multiplication at pH 4.0 in the presence of 10 mM sulphite increased. The proportion of lipolytic bacteria, micromycetes and mainly of yeasts increased considerably. A similar trend was observed in the case of amylolytic bacteria. Heterotrophic sulphur oxidizers could not be detected. The possible significance of this phenomenon for senescence of conifer needle is discussed.     

Rhizosphere micro-organisms in relation to the apple replant problem

Summary One of the factors giving rise to soil sickness in apple orchards is the rhizosphere microflora. The composition of the microbial coenosis in the rhizosphere changes with increasing age of the apple trees. An increase in the counts of micromycetes and actinomycetes and a decrease in bacterial counts was found in agreement with the decreasing pH of the rhizosphere soil. The presence of fluorescent pseudomonads in the rhizosphere of old apple trees was rare, but the planting of apple seedling into sick soil induced their proliferation. The relative proportion of individual genera of micromycetes changed according to the tree age; fungi of the genus Mucor were more often found in the rhizosphere of younger trees than in that of older ones while fungi of the genus Penicillium had an opposite trend. Biological tests showed that Penicillium fungi form the majority of the phytotoxic microflora. The amount of phytotoxic micromycetes was higher in ‘sick’ soil as compared with control soil in which apple trees had not been grown for at least 15 years. Higher numbers of phytotoxic micromycetes were isolated also from the rhizosphere of apple seedlings grown in ‘sick’ soil as compared with those growing in control soil. An increase in the amount of phytotoxic micromycetes in apple tree rhizosphere could be induced by mere addition of 5% (w/w) ‘sick’ soil to the soil in which apple trees were grown for the first time. By adding sterilized ‘sick’ soil, the amount of phytotoxic micromycetes in the apple seedling rhizosphere was not affected. Increased numbers of phytotoxic micromycetes affected negatively the growth of apple trees and the morphology of apple tree roots. This demonstrated the possibility of transfer of a factor participating in the etiology of soil sickness in apple orchards.     

Aspergillus ochraceus micromycetes—producers of extracellular proteinases—protein C activators of blood plasma

Natural isolates of Aspergillus ochraceus micromycetes from soil and plant remains from various regions have been screened. The isolated strains were characterized by similar cultural and morphological features and an identical nucleotide sequence in the ITS1-5,8S-ITS2 region of rDNA. The ability of the extracellular proteinases of A. ochraceus micromycetes to activate protein C of blood plasma has been established. Differences are revealed in the accumulation of proteinases activating protein C and proteinases with thrombinand plasmin-like activities in the growth dynamics of producers.     

Long-run monitoring of bacteria,yeasts and other micromycetes in the air of an industrial conurbation

Three different methods were used for the monitoring of airborne microorganisms: (1). Cultivation of microbes trapped in a single-stage biological impactor directly on a solid agar nutrient medium (meat-pepton agar, Sabouraud's agar, blood agar) in Petri dishes. The repeated yearly course of concentrations of cultivable organisms, or colony-forming units (CFU), was obtained by long-run measurements. (2) Aeresol was trapped by impact on membrane filters, and the microorganisms were cultivated by placing the filters on the agar media as above. (3) Direct microorganism counting in a fluorescence microscope; air was sampled in a four-stage impactor where the aerosol was trapped on microscope slides, and the microorganisms were subsequently stained with fluorescent dyes (fluorescein diacctate, 4;6-diamidino-2-phenylindole and, particular, ethidium bromide).

The highest microorganism counts were obtained by using the fluorescence method, the direct cultivation method gave counts an order of magnitude lower, and the method of cultivation on filters gave values approximately 10 times lower than the conventional cultivation.

High variations in the airborne CFU concentrations over the year were observed in Prague. Over the winter season the variations in the amounts of airborne bacteria and other micromycetes as well as the amounts themselves were lower than in the remaining seasons. In the spring and in the summer, the concentrations of yeasts and other micromycetes were highest, whereas in the autumn the concentrations of the microorganisms decreased. Among the bacteria cultivated form the airborne aerosol, the genera Micrococcus, Bacillus, Neisseria and Corynebacterium predominated. The prevailing genera of micromycetes were Penicillium, Aspergillus and Cladosporium.

The concentrations of microorganisms in free air were also affected by the local weather conditions, temperature in particular, the overall air pollution by aerosols was of minor importance in this respect.     

5-Hydroxylation of benzimidazole by micromycetes I. Strains selection

Summary The ability of 610 strains of micromycetes to introduce a hydroxy-group into benzimidazole substrate has been investigated. Among them, 232 micromycetes have been selected and cultivated in a liquid synthetic medium. Convenient hydroxylation of benzimidazole was obtained with 78 fungi. Finally, 8 strains of micromycetes have been chosen for further investigation and optimization of this bioconversion.     

The role of chitinase in antifungal activity of Bacillus sp. 739]

Investigation of the crude extracellular chitinase of Bacillus sp. 739, an antagonist of phytopathogenic fungi, discerned a relationship between the chitinase and antifungal activities of this bacterium. Purified chitinase lost its ability to inhibit the growth of micromycetes. The antagonistic (antifungal) activity of crude chitinase was found to be located in a low-molecular-weight fraction of the enzyme, which does not possess chitinase activity. Both crude and purified chitinase were able to lyse the cell walls of intact mycelium. Accordingly, it may be inferred that the antagonistic activity of Bacillus sp. 739 against micromycetes is largely determined by low-molecular-weight nonenzymatic substances whereas the role of chitinase is to utilize chitin, which is ubiquitously present in soil.     

The Role of Chitinase in the Antifungal Activity of Bacillussp. 739

Investigation of the crude extracellular chitinase of Bacillussp. 739, an antagonist of phytopathogenic fungi, discerned a relationship between the chitinase and antifungal activities of this bacterium. Purified chitinase lost its ability to inhibit the growth of micromycetes. The antagonistic (antifungal) activity of crude chitinase was found to be located in a low-molecular-weight fraction of the enzyme, which does not possess chitinase activity. Both crude and purified chitinase were able to lyse the cell walls of intact mycelium. Accordingly, it may be inferred that the antagonistic activity of Bacillussp. 739 against micromycetes is largely determined by low-molecular-weight nonenzymatic substances, whereas the role of chitinase is to utilize chitin, which is ubiquitously present in soil.     

不加权组平均法在云南山地小型真菌生物多样性研究中的应用

采用香农指数(Shannon-VienerIndex)分别对中国云南省热带及亚热带七个山地系统分布的34属小型真菌的生态位宽度和48个样点的生物多样性进行了计算、并用不加权组平均法对七个山地系统的48个样点及其中分布的34属小型真菌之间的关系进行了聚类分析。结果表明不加权组平均法适用于生境的生物多样性和小型真菌的生态位分析,并能定量地反映它们之间的生态学关系。     

Antioxidant features of fungal melanin pigments

Fungal melanin pigments were shown to display a high antioxidant activity. An increase in the number of methyl substituents in benzidine molecules of melanins obtained from micromycetes and macromycetes was accompanied by a decrease in the efficiency of inhibition of peroxidase-catalyzed oxidation. Melanins were found to have considerable gene-protecting properties. Pigments isolated from macromycetes and applied at a much lower concentration than those obtained from micromycetes prevented damage to bacteriophage-lambda DNA induced by products of peroxidase-catalyzed degradation of aminobiphenyls.     

Microbiological degradation of asymmetrical dimethylhydrazine--a toxic component of rocket fuel

A possibility of microbiological cleaning of water and soil polluted with asymmetric dimethylhydrazine (ADMH), a highly toxic rocket fuel ingredient (RFI), was studied. Several isolates (bacteria, yeast, and micromycetes) capable of utilizing ADMH as the only source of nitrogen, carbon, and energy were isolated from RFI-polluted tundra soil. Acceleration of RFI biodegradation was achieved using a biosorbent that involved cells of the degrader strain immobilized on granulated activated carbon. Biological testing in Escherichia coli and cereals (wheat and barley) demonstrated that biodegradation significantly decreased the integral toxicity of solutions containing ADMH, suggesting its utility for microbiological cleaning of polluted territories.     

Filamentous micromycetes in working environment

We investigated quantitative and qualitative representation of the germs of filamentous micromycetes in the samples of plant origin which were taken in connection with objective and subjective changes of health state of employees' respiratory tract from various factories. On the basis of the received results it is required to deal with questions on the determination of certain acceptable amount of micromycetes in the environment, and the like. It is necessary to objectivize the degree of risk in workers at the professional exposition of micromycetes or their toxins.     

Toxigenesis of Aspergillus flavus isolated from groundnut fields

In experiments conducted with A.flavus strains isolated from groundnut fields at different periods of the year, it was possible for us to show significant differences in the intensity of the toxigenesis of these micromycetes. These differences appear to be dependent on the evolution of the mycoflora during the growth of the plant.     

Artificial induction of the apple replant problem byPenicillium claviforme inoculation

Inoculation of apple seedling roots withPenicillium claviforme reduced plant growth and resulted in morphological changes of roots resembling those found in seedlings growing in ‘apple replant problem’ soil (apple-sick soil). The introduced fungus persisted in the rhizosphere throughout the 30-month test period. The numbers of colony-forming units (CFU) ofPenicillium claviforme, as well as the ‘total’ number of CFU of micromycetes, were higher in the rhizoplane of the inoculated seedling in comparison with uninoculated plants. The numbers of CFU of phytotoxic micromycetes in the rhizosphere soil of inoculated seedlings were also proportionally higher. Apple tree growth was also reduced when seedlings were inoculated with the flucrescent bacteriumPseudomonas putida; however, no morphological changes were observed in the roots. Both micro-organisms introduced into the apple seedling rhizosphere caused changes in the microbial community. Inoculation withPenicillium claviforme andPseudomonas putida caused a decrease in the number of mycolytic bacteria in the rhizoplane of apple seedlings.     

The use of some fluorescent stains for studying morphogenesis of micromycetes

The use of some classical fluorochromes and optical brighteners in the fluorescence microscopy of micromycetes was investigated. Of the 16 compounds tested on slide cultures of Trichoderma viride 3 were too toxic, whereas the other stained primarily hyphae with various intensity. Reproductive structures did not stain or stained only weakly. With respect to vital staining the optical brightener Blankophor RKH exhibited most favorable properties. It did not inhibit either the growth or sporulation and stained intensively hyphae, septa and growth apices in particular. It also induced intensive fluorescence of a growing yeast culture.     

Analysis of the Ca2+ response of mycelial fungi to external effects by the recombinant aequorin method

Using the mutant strain Aspergillus awamori 66A producing a recombinant Ca2+-dependent photosensitive protein aequorin, the dynamics of Ca2+ was studied for the first time in the cytosol of the micromycetes exposed to stressful factors, such as an increase in extracellular Ca2+ to 50 mM, hypoosmotic shock, and mechanical shock. Cell response to stress proved to involve an increase in the Ca2+ concentration in the cytosol, which was determined from the amplitude of aequorin luminescence and the time of the amplitude enhancement and relaxation. The level of Ca2+ response depended on the physiological stimulus. Inhibitory analysis with various agents that block Ca2+ channels and with agonists that specifically enhance the activity of the channels suggested that (1) the level of Ca2+ in the cytosol of micromycetes increases in response to stress because of the ion influx from both the growth medium and intracellular reservoirs and (2) the potential-dependent transport systems play the major role in the Ca2+ influx into the cytosol of the micromycete cells.     

Microbiological Degradation of Asymmetric Dimethylhydrazine,a Toxic Rocket Fuel Ingredient

The possibility of microbiological cleaning of water and soil polluted with asymmetric dimethylhydrazine (ADMH), a highly toxic ingredient of rocket fuel (IRF), was studied. Several isolates (bacteria, yeast, and micromycetes) capable of utilizing ADMH as the only source of nitrogen, carbon, and energy were isolated from IRF-polluted tundra soil. Acceleration of IRF biodegradation was achieved using a biosorbent that involved cells of the degrader strain immobilized on granulated activated charcoal. Biological testing in Escherichia coli and cereals (wheat and barley) demonstrated that biodegradation significantly decreased the integral toxicity of solutions containing ADMH, suggesting its utility for microbiological cleaning of polluted territories.     

Interrelationships between vesicular-arbuscular mycorrhiza and rhizosphere microflora in apple replant disease

Phytotoxic micromycetes appear to be responsible for the apple replant disease (ARD). This was suppressed by the inoculation of apple-tree seedlings with some species of vesicular-arbuscular mycorrhizal (VAM) fungi—Glomus fasciculatum andG. macrocarpum. After the inoculation, growth of apple-tree seedlings improved in dependence on the type of soil, on VAM fungus species and on the ARD appearance. After 12-month cultivation, plant biomass (height, shoot and root dry masses) was markedly increased by inoculation withG. fasciculatum. Similarly, the numbers of colony forming units per unit soil (CFU) of phytotoxic micromycetes and of diazotroph bacteria (associative dinitrogen-fixing bacteria) in the rhizosphere was affected; CFU of phytotoxic micromycetes decreased, whereas CFU of the genusAzospirillum was higher. These bacteria could also serve as antagonists against phytotoxic micromycetes. It is also suggested that the ratio of CFU of diazotroph bacteria to CFU of phytotoxic micromycetes can be used as an indicator of the degree of ARD. It may be assumed that the use of some VAM fungi can replace the chemcial treatment of the soil with ARD.     

Nitrate levels affect the development of the black locust-Rhizobium symbiosis

Summary Experiments with black locust (Robinia pseudoacacia L.) seedlings grown under strictly controlled laboratory conditions indicated that the availability of nitrate has a marked impact on nitrogen fixation. When nitrate concentrations were very low, both nodulation and seedling growth were impaired, whereas nitrate concentrations high enough to promote plant growth strongly inhibited symbiotic nitrogen fixation. When nitrate was added to the growth medium after infection, nodulation and nitrogen fixation of the seedlings decreased. This effect was even more marked when nitrate was applied before infection with rhizobia. Higher nitrogen concentrations also reduced nodule number and nodule mass when applied simultaneously with the infecting bacteria. The contribution of symbiotic nitrogen fixation to black locust shoot mass by far exceeded its effects on shoot length and root mass. When nitrate availability was very low, specific nitrogen fixation (i. e. nitrogenase activity per nodule wet weight) was improved with increasing nitrogen supply, but rapidly decreased with higher nitrogen concentrations.