• Mycobiology
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• v.28 no.4
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• pp.193-196
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• 2000

Thirty-eight species in addition to 2 varieties (3 unidentified) of zoosporic organisms belonging to 14 genera of Oomycetes and 3 genera of Chytridiomycetes were recovered from 50 soil samples randomly collected from different localities in the western region of Saudi Arabia. Allomyces and Dictyuchus have the highest frequency of occurrence while Achlya, Aqualinderella, Saproleginia and Phytophthora were of moderate occurrence, The remaining genera were less frequent. Seven species and two varieties were new records to Saudi Arabia, which are Achlya oblongata, Allomyces javancius var. allomorphus, Aphanomyces stellatus, Blastoccladia gracile, Dictyuchus magnusii, Olpidiopsis Saproleginia var. levis, Olpidium species, Phytophthora megasperma, and Saproleginia turfosa. Water and organic matter contents of soil samples are considered as major factors influencing the prevalence and occurrence of zoosporic organisms.

• Korean Journal of Environmental Agriculture
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• v.29 no.3
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• pp.287-292
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• 2010

We aimed to investigate the responses of soil organisms to cover plants and to provide information for the selection of proper plant species. We studied the effects of 7 cover plants, including rye, oat, rattail fescue, Chinese milk vetch, red clover, crimson clover, and hairy vetch, on soil organisms in an apple orchard. An increase in the microbial phospholipid fatty acids (PLFA) and in the number of nematodes and microarthropods in the soil under the cover plants reflects elevated activities of soil organisms. A decrease in the level of some marker PLFA, which is an indicator of environmental stress, suggests that cover plants provide favorable environments for soil organisms. The population of fungi and animals that feed on fungi increased in the soil surface under red clover. The population density of nematodes and mites increased in the soil surface under rattail fescue, and that of mites and omnivorous nematodes increased in the soil surface under Chinese milk vetch. The level of microbial PLFA in the soil surfaces under the tested cover plants was higher than that under clean culture system. These results suggest that proper selection of the cover plants can facilitate the creation of favorable environments for soil organisms.

• Applied Biological Chemistry
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• v.41 no.6
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• pp.457-464
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• 1998

For investigating the effect of amount of applied fertilizer with pig and chicken manures in the field, the number of soil bacteria were counted on the full strength conventional nutrient broth (NB) medium and its 100-fold dilution (DNB) medium. From the control soil samples without organic amendments, the number of bacteria on DNB medium was 5 to 10 times higher than that on NB medium. However, population density on NB medium was higher than on DNB medium from the treated soil with 60 and 120 Mg/㏊ for 3 years. Most of isolates from DNB plates did not grow on the NB plates. There were only grown on the 100-fold dilution medium, so it was called as DNB organisms. The DNB organisms were occupied as dominant group over 60% fo isolates in control soil. However, their occupation rates were rapidly decreased in the treatment soil with pig and chicken manures above 60 and 120 Mg per ha. These DNB organisms (oligotrophs) were significantly low population desities in the treatment soil with organic materials.

• Journal of Ecology and Environment
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• v.33 no.4
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• pp.317-323
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• 2010

Nutrient availability is a critical component of agroecosystems, and is relevant to both above- and below- ground interactions. The principal objective of this study was to determine how the cessation of fertilization affects the communities of weeds and soil organisms in a corn/wheat field. Changes in dominant weed species, substrate-induced respiration, and the population density of nematodes and microarthropods were evaluated. Microbial substrate-induced respiration (SIR) and the population density of microarthropods decreased following the cessation of fertilization and were partly correlated with the aboveground weed biomass. The cessation of organic fertilizer application but continuing application of inorganic fertilizer reduced the population density of nematodes. In response to the cessation of fertilization, weed communities were dominated by species with little dependency on fertilization. Amaranthus retroflexus was identified as the most dominant species in the corn field; however, it was replaced by Digitaria ciliaris after the cessation of fertilization. In the wheat field, the cessation of fertilization led to a rapid reduction in the biomass of most weeds, except for Vicia angustifolia, supposedly as the result of symbiotic nitrogen fixation. Additionally, the fact that weed biomass was partially correlated with SIR or the population density of microarthropods may reflect a mutual feedback between soil organisms and weeds. The results indicate that the cessation of fertilization alters communities of weeds and soil organisms through changes in weed biomass and interactions with symbiotic microorganisms.

• Environmental Analysis Health and Toxicology
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• v.25 no.1
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• pp.1-10
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• 2010

Monitoring toxicity levels in specific biological compartments is necessary to evaluate the ecotoxicological risk associated with soil environmental pollution. Gene expression, as potential biomarker, is increasingly used as rapid early warning systems in environmental monitoring and ecological risk assessment procedures. Various representative species are currently used for the purpose of assessing soil toxicity, however, investigations on toxicological assessments using endpoint based on gene-level have been limited. In this review, we will present the current trends in organisms and endpoints used in soil toxicity study and report gene expression related to toxicity using soil organism, and C. elegans as promising organisms for this approach.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2000.04a
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• pp.142-149
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• 2000

Recent molecular and polyphasic taxonomic approaches toward bacterial systematics have played a significant role in revolutionizing our insight in the taxonomy of bacterial organisms. This advance has also contributed greatly to delineation of new taxa from bacterial organisms isolated from a variety of natural sources of Korea. Recently, many bacterial organisms have isolated from soil, seawater, foods, wastewaters and humans of Korea and have been subjected to polyphasic taxonomic study. From the results of this study, some isolates have been found to be members of new genera and new species.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.471-478
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• 2018

The purpose of this study was to investigate effects of reusable organic wastes, on soil organisms and chemical properties. Bone meal, de-oiled cake, and oyster shell were applied and abundances of soil organisms were measured at 3 and 15 months, after treatment in soil under sawleaf zelkova cultivation. Soil organisms are affected, by the quality of applied organic wastes. Abundance of microorganisms was higher in oyster shell treated soils than in untreated soils, suggesting that soil pH is a driving force, altering abundance and structure of the microbial community. Increase in abundance of bacterivorous nematodes was observed under treatment with bone meal and de-oiled cake, but there was slight change in abundance of fungivorous and herbivorous nematodes. Abundance of herbivorous nematode was positively correlated with plant growth, at 15 months after treatment. Response of microarthropods in the Collembola and Oribatida was not apparent. Abundances of primary consumers were not significantly correlated with microorganisms. This study suggested that organic waste influences soil organisms primarily by altering soil chemical properties and bottom-up effects may not occur in trophic reactions.

• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.498-502
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• 2004

The current study was conducted to monitor the possibility of the gene transfer among soil bacteria, including the effect of drift due to rain and surface water, in relation to the release of genetically modified organisms into the environment. Four types of bacteria, each with a distinct antibiotic marker, kanamycin-resistant P. fluorescens, rifampicin-resistant P. putida, chloramphenicol-resistant B. subtilis, and spectinomycin-resistant B. subtilis, were plated using a small-scale soil-core device designed to track drifting microorganisms. After three weeks of culture in the device, no Pseudomonas colonies resistant to both kanamycin and rifampicin were found. Likewise, no Bacillus colonies resistant to both chloramphenicol and spectinomycin were found. The gene transfer from glyphosate-tolerant soybeans to soil bacteria, including Rhizobium spp. as a symbiotic bacteria, was examined by hybridization using the DNA extracted from soil taken from pots, in which glyphosate-tolerant soybeans had been growing for 6 months. The results showed that 35S, T-nos, and EPSPS were observed in the positive control, but not in the DNA extracted from the soilborne microorganisms. In addition, no transgenes, such as the 35S promoter, T-nos, and EPSPS introduced into the GMO soybeans were detected in soilborne bacteria, Rhizobium leguminosarum, thereby strongly rejecting the possibility of gene transfer from the GMO soybeans to the bacterium.

• Journal of People, Plants, and Environment
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• v.23 no.4
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• pp.399-410
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• 2020

The United Nations project the world population to reach 10 billion by the year 2057. To increase the food of the ever-increasing world population, agrochemicals are indispensable tools to the boon in agriculture production. These agrochemicals are a serious threat to the health of humans, plants, and animals. Agrochemicals are ultimately reached to the main reservoir/sink such as soil and contaminating the groundwater, disturb the soil health and in turn a serious threat to biogeochemical cycling and the entire biosphere. Among agrochemicals, quinalphosis one of the most repeatedly and widely used insecticides in the control of a wide range of pests that attack various crops. Quinalphos is shown to be primarily toxic in organisms by acetylcholinesterase enzyme action. Hydrolysis of quinalphos produces amajor metabolite 2-hydroxyquinoxaline (2-HQ), which has shown secondary toxicity in organisms. 2-HQ is reported to be mutagenic, carcinogenic, growth inhibition and induce oxidative stress in organisms. Quinoline is a heterocyclic compound and structural resemblance of 2-HQ with minor changes, but its degradation studies are enormous compared to the 2-HQ compound. Biotic factors in fate and behavior of 2-HQ in the environment are least studied. 2-HQ interactions with soil enzymes are vary from soil to soil. Based on the toxicity of 2-HQ in our stockpile we need to isolate a handful of microorganisms to treat this persistent metabolite and also other metabolites/compounds.This brief review will be significant from the point of biological and environmental safety.

• Journal of Plant Biology
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• v.13 no.1
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• pp.13-24
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• 1970

This investigation was one of the series of ecological studies on the plant communities of Quelpart Island which was held in 1969. It was aimed at studying the ground vegetation of Torreya nucifera and the soil properties of the ground in which it grows. Observaton of the flora in a place where wild growth of Crinum maritimum, soil properties and distribution of micro-organisms in a place where wild growth occurs, were also made. 1) A few kinds which have important values among the ground vegetation fo Torreya nucifera forest are Liniope graminifolia, Convallaria keiskei, Sasaquelpaertensis, Carex kingiana, Pteridium aquilinum, Pyrola japonica, Hedera tobleri, etc. 2) While the studies of 25 Quadrats were being held, 29 species in A plot, 30 species in B plot, and 26 species in C plot have been found. 3) The kind which has the highest important value among the species located in naked plot(outside of Torreya nucifera forest) is Zoysia japonica and 18 other kinds were found. 4) The soil fertility through all depths are found higher in the forest soil than in that of open places. 5) P2O5, K, and total exchangeable bases etc. have shown the difference of contents according to the depth and generally had lower value as much as it goes down. 6) The content of N was a lot higher than any other forest soil and P2O5, K and total exchangeable bases seemed to be a little lower. 7) The overall flora of Todo consists of 71 species (9 species of wood plant and 62 species of herbs) added 28 kinds of non-reported species. 8) Themineral contents are the highest at a place of wind growth of Crinum maritimum which has much organic matter. The subsoil of this place is more fertile than surface soil. 9) The soil of Todo which is sandy soil, consists of shellfish shell and quartz, and has low fertility and alkali. 10) In the total occurrences of micro-organisms, bacteria was the greatest in number followed by actinomycete and fungi, in that order. 11) A survey of the soil depth and the ecological distributional pattern of micro-organismsm revealed that the number of micro-organisms is the greatest on the surface, gradually decreasing in proportion to the depth. 12) It was found that a comparatively greater number of micro-organisms occurred when the soil showed an adequate increase in water content.