• 한국토양환경학회지
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• 제3권2호
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• pp.71-78
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• 1998

Pyrene은 보통 석유류로서 오염된 지역에서 쉽게 발견된다. 이 화합물은 생물학적으로 난분해성물질이므로 오염지역에서 장시간 존재한다. 세 종류의 토양(rhizosphere soil, non-rhizosphere soil, sterilized soil)에서 pyrene의 분해속도를 조사하기 위하여 microcosm실험을 수행하였다. Pyrene 농도감소속도는 rhizosphere soil)non-rhizosphere soil>sterilized soil 순서로 증가하였다. 또한 뿌리 유출물을 모사한 유기산의 첨가는 pyrene의 농도감소에 큰영향을 미치지 않았으나 pyrene농도감소 속도와 토양미생물의 증가는 좋은 상관관계를 보여주었다. 따라서 본 연구에서는 미생물의 밀도가 높은 rhizosphere 토양에서 pyrene의 생물학적 분해가 효과적으로 진행되는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제32권10호
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• pp.1292-1298
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• 2022

Soil autotrophic bacterial communities play a significant role in the soil carbon (C) cycle in paddy fields, but little is known about how rhizosphere soil microorganisms respond to different long-term (35 years) fertilization practices under double rice cropping ecosystems in southern China. Here, we investigated the variation characteristics of rhizosphere soil RubisCO gene cbbL in the double rice ecosystems of in southern China where such fertilization practices are used. For this experiment we set up the following fertilizer regime: without any fertilizer input as a control (CK), inorganic fertilizer (MF), straw returning (RF), and organic and inorganic fertilizer (OM). We found that abundances of cbbL, 16S rRNA genes and RubisCO activity in rhizosphere soil with OM, RF and MF treatments were significantly higher than that of CK treatment. The abundances of cbbL and 16S rRNA genes in rhizosphere soil with OM treatment were 5.46 and 3.64 times higher than that of CK treatment, respectively. Rhizosphere soil RubisCO activity with OM and RF treatments increased by 50.56 and 45.22%, compared to CK treatment. Shannon and Chao1 indices for rhizosphere soil cbbL libraries with RF and OM treatments increased by 44.28, 28.56, 29.60, and 23.13% compared to CK treatment. Rhizosphere soil cbbL sequences with MF, RF and OM treatments mainly belonged to Variovorax paradoxus, uncultured proteobacterium, Ralstonia pickettii, Thermononospora curvata, and Azoarcus sp.KH33C. Meanwhile, cbbL-carrying bacterial composition was obviously influenced by soil bulk density, rhizosphere soil dissolved organic C, soil organic C, and microbial biomass C contents. Fertilizer practices were the principal factor influencing rhizosphere soil cbbL-carrying bacterial communities. These results showed that rhizosphere soil autotrophic bacterial communities were significantly changed under conditions of different long-term fertilization practices Therefore, increasing rhizosphere soil autotrophic bacteria community with crop residue and organic manure practices was found to be beneficial for management of double rice ecosystems in southern China.

• 미생물학회지
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• 제12권1호
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• pp.15-24
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• 1974

This experiment has been carried out with a view to elucidating the distribution of Azotobacter and their population size in rhizosphere and sea and designed ro compare the results with some environmental factors. Results of the experiment are summarized as follows: 1) It was observed that the population sizes of Azotobacter were decided upon the moisture content of soil and that the soil pH was one of the most impertant factors influencing the distribution of Azotobacter. 2)Population sizes of Azotobacter in rhizosphere were changed in accordance with the kinds of vegetation on soil: The rhizosphere where bamboo, corn, legume, and oak inhabit showed the largest population size of Azotobacter. On the other hand, rhizosphere of ginseng revealed no Azotobacter. However, the largest population of general fungi were measured at the rhizosphere. 3)Comparing the population sizes of general microbes in rhizosphere with those of non-rhizosphere, the population sizes of microbes in rhizosphere are larger than those of non-rhizosphere. 4)In coastal environments, population sizes of Azotobacter in surface water of sea are similar to those of the soil(mud) of tidal land. But the sizes are generally smaller than those of terrestrial soils.

• The Plant Pathology Journal
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• 제38권3호
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• pp.203-211
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• 2022

Bacterial wilt, which is a major soil-borne disease with widespread occurrence, poses a severe danger in the field of tobacco production. However, there is very limited knowledge on bacterial wilt-induced microecological changes in the tobacco root system and on the interaction between Ralstonia solanacearum and fungal communities in the rhizosphere soil. Thus, in this study, changes in fungal communities in the rhizosphere soil of tobaccos with bacterial wilt were studied by 18S rRNA gene sequencing. The community composition of fungi in bacterial wilt-infected soil and healthy soil in two tobacco areas (Gengma and Boshang, Lincang City, Yunnan Province, China) was studied through the paired comparison method in July 2019. The results showed that there were significant differences in fungal community composition between the rhizosphere soil of diseased plants and healthy plants. The changes in the composition and diversity of fungal communities in the rhizosphere soil of tobaccos are vital characteristics of tobaccos with bacterial wilt, and the imbalance in the rhizosphere microecosystem of tobacco plants may further aggravate the disease.

• Environmental Engineering Research
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• 제12권2호
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• pp.37-45
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• 2007

Phytoremediation has been used effectively for the biodegradation of oil-based contaminants, including diesel, by the stimulation of soil microbes near plant roots (rhizosphere). However, the technique has rarely been assessed for itsinfluence on soil microbial properties such as population, community structure, and diversity. In this study, the removal efficiency and characteristics of rhizobacteria for phytoremediation of diesel-contaminated soils were assessed using barnyard grass (Echinochloa crusgalli). The concentration of spiked diesel for treatments was around $6000\;mg\;kg^{-1}$. Diesel removal efficiencies reached 100% in rhizosphere soils, 76% in planted bulk soils, and 62% in unplanted bulk soils after 3weeks stabilization and 2 months growth(control, no microbial activity: 32%). The highest populations of culturable soil bacteria ($5.89{\times}10^8$ per g soil) and culturable hydrocarbon-degraders($5.65{\times}10^6$ per g soil) were found in diesel-contaminated rhizosphere soil, also yielding the highest microbial dehydrogenase. This suggests that the populations of soil bacteria, including hydrocarbon-degraders, were significantly increased by a synergistic rhizosphere + diesel effect. The diesel treatment alone resulted in negative population growth. In addition, we investigated the bacterial community structures of each soil sample based on DGGE (Denaturing Gel Gradient Electrophoresis) band patterns. Bacterial community structure was most influenced by the presence of diesel contamination (76.92% dissimilarity to the control) and by a diesel + rhizosphere treatment (65.62% dissimilarity), and least influenced by the rhizosphere treatment alone (48.15% dissimilarity). Based on the number of distinct DGGE bands, the bacterial diversity decreased with diesel treatment, but kept constant in the rhizosphere treatment. The rhizosphere thus positively influenced bacterial population density in diesel-contaminated soil, resulting in high removal efficiency of diesel.

• The Korean Journal of Ecology
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• 제22권1호
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• pp.7-11
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• 1999

환경오염과 관련하여 제안된 미국자리공의 분포확대가 토양의 산성화와 나아가서는 사막화를 가져온다는 가설을 실험적으로 확인하여 그 실체를 밝히고자 울산과 청주를 대상으로 미국자리공 군락에서의 근권 토양산성도를 측정하였다. 측정한 장소 중에서 청주의 부모산을 제외한 울산의 신선산, 돗질산 그리고 봉대산은 pH가 5.0 이하로 5.25와 5.33의 범위에서 변화한 청주의 부모산의 근권토양보다 강한 산성을 나타내었다. 그러나 봉대산을 제외하고는 식물체의 축을 중심으로 수평적으로나 수직적으로나 근권산성도에 유의차가 보여지지 않았다. 반면, 울산의 봉대산에서는 뿌리를 중심으로 수평적으로는 근권산성도가 변하지 않았지만 지표면 토양이 그 아래 토양보다 높은 산성도를 나타내었다. 이것은 일반적인 토양산성도의 패턴과 반대 현상으로, 지표면이 더욱 산성이라는 것은 지상환경의 오염, 즉 대기오염과 관련이 있다는 것을 나타내 주고 있다. 또한 이러한 사실은 미국자리공의 생장과정에서도 근권 토양산성도가 거의 변하지 않았던 모델실험 결과와도 잘 부합되었다. 따라서 미국자리공이 토양을 산성화시킨다는 가설은 다시 한번 고려되어야 할 것이다.

• Mycobiology
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• 제49권4호
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• pp.346-354
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• 2021

The genus Aspergillus is commonly isolated from various marine and terrestrial environments; however, only a few species have been studied in rhizosphere soil. As part of the Korean indigenous fungal excavation project, we investigated fungal diversity from rhizosphere soil, focusing on Aspergillus species. A total of 13 strains were isolated from the rhizosphere soil of three different plants. Based on phylogenetic analysis of β-tubulin and calmodulin and morphological characteristics, we identified five Aspergillus species. A. calidoustus and A. pseudodeflectus were commonly isolated from the rhizosphere soil. Four species were confirmed as unrecorded species in Korea: A. calidoustus, A. dimorphicus, A. germanicus, and A. pseudodeflecuts. The detailed morphological descriptions of these unrecorded species are provided.

• Mycobiology
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• 제48권6호
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• pp.431-442
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• 2020

Penicillium, the most common genus plays an important ecological role in various terrestrial and marine environments. However, only a few species have been reported from rhizosphere soil. As part of a project to excavate Korean indigenous fungi, we investigated rhizosphere soil of six plants in the forest (terrestrial habitat) and sand dunes (coastal habitat) and focused on discovering Penicillium species. A total of 64 strains were isolated and identified as 26 Penicillium species in nine sections based on morphological characteristics and the sequence analysis of β-tubulin and calmodulin. Although this is a small-scale study in a limited rhizosphere soil, eight unrecorded species and four potential new species have been identified. In addition, most Penicillium species from rhizosphere soil were unique to each plant. Penicillium halotolerans, P. scabrosum, P. samsonianum, P. jejuense, and P. janczewskii were commonly isolated from rhizosphere soil. Eight Penicillium species, P. aurantioviolaceum, P. bissettii, P. cairnsense, P. halotolerans, P. kananaskense, P. ortum, P. radiatolobatum, and P. verhagenii were recorded for the first time in Korea. Here, we provide the detailed morphological description of these unrecorded species.

• 한국토양비료학회지
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• 제45권5호
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• pp.798-804
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• 2012

Although siderophores are induced primarily in response to iron deficiency, soil and other ecological factors can affect on this process. This study was to evaluate the production of siderophores by different fungal species isolated from heavy metal contaminated and uncontaminated soils. More than thirty fungal strains were isolated from heavy metal contaminated and rhizosphere uncontaminated soils. Chrome azurol sulfonate (CAS) was used for both quantitative and qualitative evaluation of siderophores production. No significant correlations were observed between the tested variables such as ultraviolet (UV) irradiation method and CAS-agar plate and heavy metal concentration in both soils. The production of siderophores in rhizosphere fungi was higher than those isolated from the contaminated soil; however, the difference was not significant. The siderophore production (%) by fungi isolated from heavy metal contaminated soil using UV irradiation method was positively correlated with the qualitative values using CAS-plate method (P<0.05). Pearson correlation test indicated a positive correlation between the quantitative and qualitative methods of detection for fungi isolated from rhizosphere and also those isolated from heavy metal contaminated soil.

• Journal of Microbiology and Biotechnology
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• 제13권2호
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• pp.236-242
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• 2003

A culture-independent and -dependent survey of the bacterial community structure in the rhizosphere and soil samples from hot pepper plants was conducted using 16S rDNA clone library and FAME analyses. Out of the 78 clones sequenced, 56% belonged to Proteobacteria, 4% to high G+C Gram- positive group, 3% to Cytophyga-Flexibacter-Bacreroides, and 32% could not be grouped with any known taxonomic division. Among the 127 FAME isolates identified, 66% belonged to low G+C Gram-positive bacteria (Baciilus spp.) and 26% to high G+C Gram-positive bacteria. In a cluster analysis, the results for both methods were found to be strikingly dissimilar. The current study is the first comparative study of FAME and 165 rDNA clonal analyses performed on the same set of soil, rhizosphere soil, and root samples.