STUDIES ON THE RELATIONSHIPS BETWEEN NEMATODES AND OTHER SOIL MICROORGANISMS. 3. LYTIC ACTION OF SOIL MYXOBACTERS ON CERTAIN SPECIES OF NEMATODES.
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Animals↗
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Differential effects of the herbicides bensulfuron and cinosulfuron on soil microorganisms.
Bensulfuron toxicity on soil microbes was evaluated by the methods used in a previous study on cinosulfuron; the effects of the two sulfonylureas were compared. Cinosulfuron and bensulfuron, at the normal field application rate and 100 times higher, had no effect on the total number of bacteria and nitrifiers, or on the respiration activity in the soil, but they did decrease the nitrification activity. In vitro toxicity tests carried out on representative soil microbial strains using bensulfuron at 50 mg l(-1) showed some inhibition of three of the 17 bacterial strains and strong inhibition of almost all the 12 fungal strains; cinosulfuron had had no effect on any of these strains in the previous study. It is concluded that, compared with cinosulfuron, bensulfuron is potentially more toxic on soil heterotrophic microorganisms, but only at very high concentrations that are nearly impossible to reach with the usual agricultural use of the herbicides. However, autotrophic nitrifiers were more sensitive to both sulfonylureas than the other microorganisms.
Bacteria↗
Isolation and Identification of Two l-Azetidine-2-carboxylic Acid-Degrading Soil Microorganisms, Enterobacter agglomerans and Enterobacter amnigenus
Soil samples collected at several times during the growing season and at different locations within Convallaria majalis beds in Ann Arbor, MI, were screened for their ability to grow with the cyclic amino acid, l-azetidine-2-carboxylic acid (l-A-2-C), as their sole nitrogen source (i.e., metabolize l-A-2-C). Two different soil microorganisms were isolated, characterized, and identified using fundamental selection methods, the standard battery of biochemical characterization tests, and scanning electron microscopy. The assignment of the identity of these organisms as Enterobacter agglomerans and Enterobacter amnigenus was further verified by comparison with authentic microbial samples obtained from ATCC that were able to utilize l-A-2-C as their sole nitrogen source.
Journal Article↗
[Research on mangrove soil microorganisms: past, present and future].
Special Mangrove soil niches possesses valuable microbial resources. Unfortunately, up to the present, so far there is very little knowledge on the mangrove soil microbial communities. It mainly due to the limitations of research methods. Cultureindependent approaches based on 16S rRNA, 18S rRNA gene analysis open the window to study microbial diversity in mangrove soil. The progress had achieved about studying on mangrove soil microbial species diversity, metabolic diversity and treating environmental pollutions was summarized in the paper. In addition, the bright future of mangrove soil microorganisms was described.
Biodegradation, Environmental↗
Rapid and cost-effective multiparameter toxicity tests for soil microorganisms.
Three biochemical parameters, DNA quantification in soil samples and two enzymatic activities, beta-galactosidase and dehydrogenase have been assessed as potential end-points for the use in cost-effective toxicity tests on soil microorganisms. The assessment included the development of a classical dose-response 24-h assay and the incorporation of measurements of the effects on microbial activities in soil column leaching studies and multispecies miniaturised terrestrial systems (MTS). Four different chemicals, copper, a new herbicide, thiabendazole and fenthion were studied. A rapid fluorescence DNA quantification technique did not produce adequate responses. The efforts to quantify DNA after extraction and clean-up procedures failed due to the presence of humic acids. From the protocol of the technique one could see that the technical procedure is time-consuming and expensive and, for this reason, not suitable for use as a parameter in rapid and cost-effective tests. However, the enzymatic activities showed their potential as toxicity end-points. Copper produced a concentration/response inhibition of beta-galactosidase and dehydrogenase with EC50 values of 78.39 and 24.77 mg Cu/kg soil, respectively. In the soil column study, these endpoints allowed the measurement of the microbial activities through the column. The effects of the new herbicide on beta-galactosidase and dehydrogenase activities were statistically significant for the highest application dose (40 g/ha). Thiabendazole affected the microbial activity when mixed within the soil, but no effects were observed when this fungicide was applied on the soil surface. Fenthion produced effects when applied either in the soil or on the soil surface. These results can be explained by the low mobility of thiabendazole. The results show the capabilities of these biochemical parameters to be included as endpoints in cost-effective bioassays.
Biological Assay↗
Effects of elevated atmospheric CO2 concentrations on soil microorganisms.
Effects of elevated CO(2) on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and synthesize results from studies assessing impacts of elevated CO(2) on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated CO(2) in atmosphere may enhance certain microbial processes such as CH(4) emission from wetlands due to enhanced carbon supply from plants. However, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of CO(2) fumigation systems are not fully understood.
Atmosphere↗
Interrelationships between soil microorganisms and polystyrene.
Transmission and scanning electron microscopy along with autoradiographic procedures were used for evaluating the interrelationship between soil microorganisms and polystyrene. Two hypotheses, allowing to explain the properties of polystyrene as a soil conditioner, were investigated: the first is concerned with a possible action of soil microorganisms on the compound; the second, reciprocally, with the polystyrene interference on microorganisms. Radioactivity translocation of 14C-Ecolyte-polystyrene along fungal hyphae and asexual fructification of strains, isolated from soil, as well as cytological modification at the cell wall level of the same microfungi, cultivated in the presence of polystyrene have been ascertained.
Cladosporium↗
Effects of Culture Conditions on Production of trans-Cinnamic Acid from Alkylbenzenes by Soil Microorganisms.
The production of trans-cinnamic acid from various alkylbenzenes by soil microorganisms was studied intensively by use of a co-oxidation technique. The microorganisms were grown on n-paraffins, and they did not use aromatic compounds as a carbon source when the preferred substrate was present in the medium. The effects of cell population, co-oxidation time, and type and mode of addition of the alkylbenzenes on the yield of trans-cinnamic acid were investigated. Yields (5 g/liter) of a product consisting of trans-cinnamic acid (88 to 100%) and 5-phenylvaleric acid (0 to 12%) were obtained when the proper conditions were chosen. Of a variety of microorganisms studied, a soil isolate closely related to Cellulomonas galba was found to be best for the production of trans-cinnamic acid.
Journal Article↗
[Degradation and utilization of 2,4-dioxohexahydro-1,3,5-triazine (DHT) by soil microorganisms].
The biodegradation and utilization of the antiphytoviral substance 2,4-dioxohexahydro-1,3,5-triazine (DHT) by soil microorganisms was investigated. Mixed cultures of microorganisms deriving from different soils diminish in nutrient broth the content of DHT with increasing duration of culture. Microorganisms from an Egyptian garden soil fully degrade 10(-3) mol/1 DHT in a culture without additional aeration within 28 days. Also in deficient media the mixed microorganisms reduce the amount of DHT, reaching in nitrogen free nutrient solution even a degradation rate up to 12 mg DHT per liter and day. Pure cultures of Rhizobium leguminosarum, Proteus vulgaris, Saccharomyces cerevisiae and especially Agrobacterium radiobacter diminish the content of DHT in nitrogen free media, too. No such effect was detectable in cultures of four other species of soil bacteria. The DHT degradation by the microorganisms is connected with significant cell multiplication, e.g. A. radiobacter in shaking cultures with DHT as sole source of nitrogen shows a typical growth cycle with a lag-phase of 24 hours. The short persistence time of DHT in soils is concluded to be mainly due to biodegradation by microorganisms.
Antiviral Agents↗
Stereoscan electron microscopy of soil microorganisms.
Details of the surface structure of microorganisms growing in soil and the complex topography of individual soil particles were observed with the Stereoscan electron microscope. Because it was not necessary to remove the microorganisms from the soil particles, it was possible to establish their occurrence in different microhabitats. This technique can provide useful ecological information about the soil microflora.
Ecology↗
Soil microorganisms of the McMurdo Sound area, Antarctica.
A study of soil microorganisms of Ross Island and the adjacent mainland was carried out during the brief austral summer of 1961-1962. In some cases, seasonal changes in microbial numbers were observed, although microorganisms could not be detected in some soils. Bacterial species common to temperate regions were isolated from a number of different samples. Thermophilic bacteria were present in some of the soils, and a significant portion of the bacterial population was capable of growth at 2 C. The soil microflora were capable of carrying out certain reactions of the nitrogen cycle at a very slow rate. In addition to temperature, other environmental factors which might influence growth and metabolic activity were discussed.
Antarctic Regions↗
Aerobic biodegradation of biphenyl and polychlorinated biphenyls by Arctic soil microorganisms.
We examined the degradation of biphenyl and the commercial polychlorinated biphenyl (PCB) mixture Aroclor 1221 by indigenous Arctic soil microorganisms to assess both the response of the soil microflora to PCB pollution and the potential of the microflora for bioremediation. In soil slurries, Arctic soil microflora and temperate-soil microflora had similar potentials to mineralize [14C]biphenyl. Mineralization began sooner and was more extensive in slurries of PCB-contaminated Arctic soils than in slurries of uncontaminated Arctic soils. The maximum mineralization rates at 30 and 7 degrees C were typically 1.2 to 1.4 and 0.52 to 1.0 mg of biphenyl g of dry soil-1 day-1, respectively. Slurries of PCB-contaminated Arctic soils degraded Aroclor 1221 more extensively at 30 degrees C (71 to 76% removal) than at 7 degrees C (14 to 40% removal). We isolated from Arctic soils organisms that were capable of psychrotolerant (growing at 7 to 30 degrees C) or psychrophilic (growing at 7 to 15 degrees C) growth on biphenyl. Two psychrotolerant isolates extensively degraded Aroclor 1221 at 7 degrees C (54 to 60% removal). The soil microflora and psychrotolerant isolates degraded all mono-, most di-, and some trichlorobiphenyl congeners. The results suggest that PCB pollution selected for biphenyl-mineralizing microorganisms in Arctic soils. While low temperatures severely limited Aroclor 1221 removal in slurries of Arctic soils, results with pure cultures suggest that more effective PCB biodegradation is possible under appropriate conditions.
Aerobiosis↗
Influence of ethylene produced by soil microorganisms on etiolated pea seedlings.
There is indirect evidence that soil microorganisms producing ethylene (C(2)H(4)) can influence plant growth and development, but unequivocal proof is lacking in the literature. A laboratory study was conducted to demonstrate the validity of this speculation. Four experiments were carried out to observe the characteristic "triple" response of etiolated pea seedlings to C(2)H(4) microbially derived from l-methionine as a substrate in the presence or absence of Ag(I), a potent inhibitor of C(2)H(4) action. In two experiments, the combination of l-methionine and Acremonium falciforme (as an inoculum) was used, while in another study the indigenous soil microflora was responsible for C(2)H(4) production. A standardized experiment was conducted with C(2)H(4) gas to compare the contribution of the microflora to plant growth. In all cases, etiolated pea seedlings exhibited the classical triple response, which includes reduction in elongation, swelling of the hypocotyl, and a change in the direction of growth (horizontal). The presence of Ag(I) afforded protection to the pea seedlings against the microbially derived C(2)H(4). This study demonstrates that microbially produced C(2)H(4) in soil can influence plant growth.
Journal Article↗
Autoradiographic method to screen for soil microorganisms which accumulate zinc.
An autoradiographic method was developed to screen for and isolate soil microorganisms which accumulate zinc (Zn). Diluted soil samples (Rubicon fine sand, Entic Haplorthods [pH 5.9]) were plated on soil extract-glucose agar containing radioactive 65Zn. After 7 days of incubation, individual colonies which accumulated sufficient 65Zn could be detected by autoradiography. These colonies were isolated and confirmed as Zn accumulators in pure culture by using the autoradiographic plate technique. Most Zn accumulators were filamentous fungi, identified as Penicillium janthinellum, Aspergillus fumigatus, and Paecilomyces sp. Isolates of Penicillium janthinellum were the most common Zn accumulators. The most abundant Zn-accumulating bacteria were Bacillus spp. The validity of the autoradiographic plate technique to differentiate soil microbes which accumulate Zn was examined independently by energy dispersive X-ray analysis in a scanning electron microscope. This method confirmed that fungal isolates which gave positive autoradiographic responses in the plate assay bioaccumulated more Zn in their biomass than fungal isolates from the same soil sample which gave negative autoradiographic responses. Thus, this technique can be applied to specifically screen for and isolate microbes from the environment which bioaccumulate Zn.
Aspergillus fumigatus↗
Degradation of the insecticide fensulfothion by a mixed culture of soil microorganisms.
Fensulfothion was incubated in nutrient media with a mixed culture of soil microorganisms obtained from sandy loam. The half life of fensulfothion in both inoculated samples and sterile controls was about 16 wk. There was some conversion to fensulfothion sulfone (16% at 6 wk) in inoculated samples, but not in the controls. Traces of fensulfothion sulfide were found in both inoculated samples (less than 3%) and controls (less than 2%). When 1% ethanol was added to the inoculated nutrient mixture the fensulfothion disappeared rapidly (t1/2 congruent to 1 1/2 wk) with 32% conversion at 20 wk to fensulfothion sulfide.
Biodegradation, Environmental↗
The potential of soil microorganisms to mineralize atrazine as predicted by MCH-PCR followed by nested PCR.
The potential of soil microorganisms to mineralize atrazine was studied in soil samples collected from fields with various histories of atrazine application. In contrast to many previous studies, which showed no atrazine mineralization activity, all the tested soils mineralized atrazine regardless of their atrazine application history. However, the delay before mineralization and the variation in the subsequent mineralization rate were in agreement with the initial copy number of the atrazine dechlorinaze gene, and the proliferation rate of the degraders. Soils from corn fields, which had up to 100 copies of the atzA gene per gram of soil, had a lag period of 4-5 days before atrazine mineralization started, and final mineralization percentages ranged from 40% to 54%. However, soils from fields that were never amended with atrazine had much longer lag periods (more than 17 days), which decreased after enrichment of the degrader population with high concentrations of atrazine for 15 days. Generally the mineralization rate and the atzA gene copy number increased after the enrichment period. The atrazine mineralization potential was measured by PCR of genes from the atrazine mineralization pathway. Magnetic capture hybridization was the most efficient of the two tested methods for purifying target DNA of PCR inhibitors, without reducing the copy number of the required fragment. Nested PCR proved to be the most effective method for predicting the exact potential of the soil to mineralize the pollutant even without enrichment of a small population with the target genes. This method can complement microcosm studies and eliminate futile efforts when the potential to mineralize the pollutant does not exist in the soil.
Atrazine↗
A screening technique for assessing effects of pesticides on population and activities of non-target soil microorganisms.
A simplified technique for assessing the effect of pesticides on non-target soil microorganisms was developed. Changes in microbial population determined by the dilution plate method, in nitrification by the soil perfusion technique, and in oxygen consumption using a differential respirometer are the only measurements required. A comparison of the effects observed for three pesticides, dieldrin, chlorpyrifos and Vorlex, in three soil types with those produced by an antibiotic, a fungicide, a nitrification inhibitor and steam pasteurization of the soil clearly demonstrate the effectiveness of the simple technique.
Chlorpyrifos↗
Degradation of [8,9,-14C]endosulfan by soil microorganisms.
Twenty-eight soil fungi, 49 soil bacteria, and 10 actinomycetes were tested as to their ability to degrade the insecticide endosulfan. Using 14C-labeled material, the qualitative as well as the quantitative formation of metabolities, as well as of 14CO2, could be followed. Sixteen fungi, 15 bacteria, and 3 actinomycetes were found capable of metabolizing more than 30% of the applied endosulfan. The major metabolities detected were endosulfate, formed by oxidation of the sulfite group, and endodiol, formed by hydrolysis of the ester bond. The majority of highly active fungi formed endosulfate as the major metabolite, whereas the majority of active bacteria formed endodiol. In addition to endosulfate and endodiol, individual cultures contained small quantities of endohydroxyether and two unidentified products. The very small quantities of 14CO2 evolved from cultures indicated that an extensive mineralization of the carbon skeleton of endosulfan did not occur.
Actinomycetales↗