• Journal of Microbiology and Biotechnology
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• v.29 no.9
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• pp.1424-1433
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• 2019

DDT is a hydrophobic organic pollutant, which can be bio-accumulated in nature and have adverse consequences on the physical condition of humans and animals. This study investigated the relationship between the white-rot fungus Pleurotus eryngii and biosurfactant-producing bacterium Ralstonia pickettii associated with the degradation of DDT. The effects of R. pickettii on fungal development were examined using in vitro confrontation assay on a potato dextrose agar (PDA) medium. R. pickettii culture was added to the P. eryngii culture at 1, 3, 5, 7, and 10 ml ($1ml{\approx}1.44{\times}10^{13}CFU$). After 7 d incubation, about 43% of the initial DDT ($12.5{\mu}M$) was degraded by the P. eryngii culture only. The augmentation of 7 ml of R. pickettii culture revealed a more highly optimized synergism with DDT degradation being approximately 78% and the ratio of optimization 1.06. According to the confrontational assay, R. pickettii promoted the growth of P. eryngii towards the bacterial colony, with no direct contact between the bacterial cells and mycelium (0.71 cm/day). DDD (1,1-dichloro-2,2-bis(4-chlorophenyl) ethane), DDE (1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene), and DDMU (1-chloro-2,2-bis(4-chlorophenyl) ethylene) were identified as metabolic products, indicating that the R. pickettii could enhance the DDT biodegradation by P. eryngii.

• Journal of Microbiology and Biotechnology
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• v.30 no.2
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• pp.244-247
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• 2020

We have expressed extracellular poly(3-hydroxybutyrate) (PHB) depolymerase of Ralstonia pickettii T1 on the Escherichia coli surface using Pseudomonas OprF protein as a fusion partner by C-terminal deletion-fusion strategy. Surface display of depolymerase was confirmed by flow cytometry, immunofluorescence microscopy and whole cell hydrolase activity. For the application, depolymerase was used as an immobilized catalyst of enantioselective hydrolysis reaction for the first time. After 48 h, (R)-methyl mandelate was completely hydrolyzed, and (S)-mandelic acid was produced with over 99% enantiomeric excess. Our findings suggest that surface displayed depolymerase on E. coli can be used as an enantioselective biocatalyst.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.7
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• pp.503-508
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• 2013

The aim of this study was to investigate the microbial communities in animal carcass disposal soils to examine the possible threat of pathogens from leachate. DNA extraction was performed for the soils in three carcass disposal sites located in Gyeonggi-do, Korea, and then 16S rRNA pyrosequencing was conducted to identify the microbial communities. Results indicate that, according to phylum classification, Proteobacteria (100%) was identified in soil A, Actinobacteria (66.4%) > Proteobacteria (31.1%) > Bacteriodetes (2.1%) > Acidobacteria (0.3%) in soil B, and Actinobacteria (63.1%) > Proteobacteria (36.9%) in soil C. According to genus classification, Pseudomonas was dominant in soil A (98%), Arthrobacter in soil B (68%) and C (61%). There were no detections of pathogens such as Salmonella, Campylobacter and Clostridium perfringens. However, high concentration of Ralstonia pickettii causing bacteremia was observed. Although carcass disposal soils examined in this study were not highly contaminated with pathogens, further monitoring is still needed to examine the potential threat of pathogens in leachate derived from carcass disposal sites.

• Korean Journal of Microbiology
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• v.40 no.4
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• pp.313-319
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• 2004

The distribution and characteristics of acidotolerant heterotrophic and naphthalene-degrading bacteria were investigated in two forest areas, one near Ulsan petrochemical industrial complex (Sunam) and the other in countryside (Daeam). Average values of soil pH at Sunam and Daeam were 3.8 and 4.6, respectively. When het­erotrophic and naphthalene-degrading bacteria were enumerated by most probable number (MPN) procedures at Sunam, the median values of heterotrophs growing at pH 7.0 and pH 4.0 were $5.3{\times}10^7\;and\;3.3{times}10^7$ MPN/g, whereas those of naphthalene-degraders were $5.6{\times}10^4\;and\;4.0{times}10^5$ MPN/g, respectively. While the medians of heterotrophs at Daeam were larger than those at Sunam, the concentrations of naphthalene-degraders were higher at Sunam compared to those at Daeam. From the MPN tubes and enrichment cultures, we obtained 17 isolates of naphthalene-degraders which were identified as Sphingomonas paucimobilis, Brevundimonas vesic­ularis, Burkholderia cepacia, Ralstonia pickettii, Pseudomanas fluorescens, and Chryseomonas luteola. Among them, 6 isolates showed higher naphthalene-degrading activity on minimal media of pH 4 compared to pH 7, whereas the extent of growth was not greater at pH 4 than at pH 7 when they were inoculated on nutrient-rich media. It is plausible that the pH may affect naphthalene-degrading activity of the isolates by changing fatty acid composition of bacterial membrane.

• Journal of Soil and Groundwater Environment
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• v.17 no.6
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• pp.23-32
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• 2012

This study was conducted to monitor microbial species dynamics within the aquifer due to long term operation of geothermal heat pump system. The species were identified by molecular biological methods of 16S rDNA. Groundwater sample was collected from both open (S region) and closed geothermal recovery system (J region) along with the control. J measured and control as well as S measured found Ralstonia pickettii as dominant species at year 2010. In contrast, Rhodoferax ferrireducens was dominantly observed for the control of S. In 2011, Sediminibacterium sp. was universely identified as the dominant species regardless of the monitoring places and type of sample, i.e., measured or control. The difference in the dynamics between the measured and the control was not critically observed, but annual variation was more strikingly found. It reveals that possible environmental changes (e.g. ORP and DO) due to the operation of geothermal heat recovery system in aquifer could be more exceedingly preceded to differentiate annual variation of microbial species rather than positional differences.

• Journal of Korean society of Dental Hygiene
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• v.18 no.5
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• pp.843-852
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• 2018

Objectives: The study aimed to isolate the abundant bacteria in dental caries in children and to investigate the bacterial species involved in addition to those that have been previously reported. Methods: The specimens were collected from the supragingival plaques of each dental caries area, pit and fissure caries, deep dentinal caries, smooth surface caries, and dental caries, and from healthy subjects in the control group. Bacteria were cultured from these specimens, DNA was extracted from the isolated bacteria, and the 16S rRNA gene sequences were analyzed and identified. Results: Based on the results of the 16S rRNA gene sequence analysis for the 90 strains of dominant bacteria from the 45 specimens, 5, 7, 8, 7, and 13 species were identified from the supragingival plaques from healthy teeth, pit and fissure caries, deep dentinal caries, smooth surface caries, and dental caries, respectively. In healthy teeth, Actinomyces naeslundii dominated. Corynebacterium durum, Ralstonia pickettii, and Streptococcus intermedius showed equal distribution. The dominant bacterial species in dental caries, S. sanguinis, showed the greatest difference in prevalence in pit and fissure caries. In deep dentinal caries, S. mutans and Lactobacillus rhamnosus were dominant; in smooth surface caries, S. mutans and S. sanguinis were dominant; and in the supragingival plaques of dental caries, S. sanguinis and S. mutans were dominant. Conclusions: The bacterial species isolated from dental caries encompassed four phyla, eight genera, and 22 species. In addition, the SS1-2 strain, belonging to the genus Neisseria, was identified as a new species from among the isolated strains.

• Journal of Microbiology and Biotechnology
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• v.32 no.10
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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.