• 미생물학회지
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• 제50권3호
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• pp.191-200
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• 2014

가스 하이드레이트는 높은 지구 온난화 잠재력을 가지고 있는 메탄가스를 해수 또는 대기 중으로 유입시킬 수 있어 전 지구적 탄소순환과정과 기후 변화에 중요한 역할을 한다. 따라서 해양 또는 대기로 방출되는 메탄의 90% 이상을 미생물 반응을 통해 산화시킬 수 있는 혐기적 메탄산화 과정이 매우 중요하다. 본 연구에서는 동해 울릉분지내 메탄 가스 하이드레이트 퇴적토에 서식하는 미생물 군집의 mcrA 유전자와 16S rRNA 유전자를 분석하였다. 혐기적 메탄산화 고세균(Anaerobic methane oxidizer: ANME) 군집의 수직적 분포를 조사한 결과, 표층과 황산염 메탄전이대(Sulfate methane transition zone: SMTZ)에서는 ANME-1 그룹이, high methane 층에서는 ANME-2c 그룹이 우점하였다. 16S rRNA 유전자를 이용한 고세균의 군집분석 결과, 혐기적 메탄산화가 일어나는 지역에서 주로 발견되는 marine benthic group-B가 50% 이상의 비율로 우점하였다. 세균의 경우 질산염을 환원시킬 수 있는 세균이 SMTZ (Halomonas 속: 56.5%)와 high methane 층(Achromobacter 속: 52.6%)에서 우점하였으며 황산염 환원 세균 군집은 확인되지 않았다. 동해 울릉분지 메탄가스 하이드레이트의 혐기적 메탄산화과정은 일반적으로 해양 퇴적토에서 알려진 혐기적 메탄산화 고세균과 황산염 환원 세균과의 공생에 의한 반응이 아닌 혐기적 메탄산화 고세균과 질산염 환원세균에 의한 반응이 주도할 것이라 생각된다.

• Journal of Microbiology and Biotechnology
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• 제17권2호
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• pp.253-261
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• 2007

Molecular and cultivation techniques were used to characterize the bacterial communities of biobead reactor biofilms in a sewage treatment plant to which an Aerated Up-Flow Biobead process was applied. With this biobead process, the monthly average values of various chemical parameters in the effluent were generally kept under the regulation limits of the effluent quality of the sewage treatment plant during the operation period. Most probable number (MPN) analysis revealed that the population of denitrifying bacteria was abundant in the biobead #1 reactor, denitrifying and nitrifying bacteria coexisted in the biobead #2 reactor, and nitrifying bacteria prevailed over denitrifying bacteria in the biobead #3 reactor. The results of the MPN test suggested that the biobead #2 reactor was a transition zone leading to acclimated nitrifying biofilms in the biobead #3 reactor. Phylogenetic analysis of 16S rDNA sequences cloned from biofilms showed that the biobead #1 reactor, which received a high organic loading rate, had much diverse microorganisms, whereas the biobead #2 and #3 reactors were dominated by the members of Proteobacteria. DGGE analysis with the ammonia monooxygenase (amoA) gene supported the observation from the MPN test that the biofilms of September were fully developed and specialized for nitrification in the biobead reactor #3. All of the DNA sequences of the amoA DGGE bands were very similar to the sequence of the amoA gene of Nitrosomonas species, the presence of which is typical in the biological aerated filters. The results of this study showed that organic and inorganic nutrients were efficiently removed by both denitrifying microbial populations in the anaerobic tank and heterotrophic and nitrifying bacterial biofilms well-formed in the three functional biobead reactors in the Aerated Up-Flow Biobead process.

• 한국미생물·생명공학회지
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• 제38권2호
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• pp.207-215
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• 2010

미생물 군집의 차이를 이용한 한국산 및 중국산 김치의 판별 가능성을 평가하기 위해 pH 5 이상의 발효초기 김치에 존재하는 bacteria의 다양성을 검토하였다. marine medium, nutrient medium, succinate minimal medium(SMM), leuconostocs selective medium(LUSM)의 한천배지를 이용하여 한국산 26종, 중국산 22종의 김치시료로부터 각각 45 속의 1017 균주, 54 속의 842 균주가 분리동정되었다. 한국산 김치에서는 Bacillus, Weissella, Leuconostoc, Pseudomonas, Lactobacillus 속 순으로, 중국산 김치에서는 Bacillus, Weissella, Lactobacillus, Pseudomonas, Serratia, Enterobacter 속의 순으로 우점하는 것으로 나타났다. 유산균의 경우, LUSM의 이용으로 한국산, 중국산 모두에서 Weissella 속이 편중되어 검출되었지만, 한국산은 Leuconostoc속이, 중국산은 Lactobacillus 속이 Weissella 속 다음으로 우점하는 것으로 나타났다. Weissella confusa는 한국산 김치에서 특이적으로 검출되었고, W. soli, Serratia proteamculans는 중국산 김치에서 특이적으로 검출되어 향후 김치의 원산지 판별을 위한 지표미생물로 사용될 가능성을 가지고 있다.

• Journal of Microbiology and Biotechnology
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• 제32권3호
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• pp.294-301
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• 2022

In our greenhouse experiment, soil heat treatment groups (50, 80, and 121℃) significantly promoted growth and disease suppression of Panax notoginseng in consecutively cultivated soil (CCS) samples (p < 0.01), and 80℃ worked better than 50℃ and 121℃ (p < 0.01). Furthermore, we found that heat treatment at 80℃ changes the microbial diversity in CCS, and the inhibition ratios of culturable microorganisms, such as fungi and actinomycetes, were nearly 100%. However, the heat-tolerant bacterial community was preserved. The 16S rRNA gene and internal transcribed spacer (ITS) sequencing analyses indicated that the soil heat treatment had a greater effect on the Chao1 index and Shannon's diversity index of bacteria than fungi, and the relative abundances of Firmicutes and Proteobacteria were significantly higher than without heating (80 and 121℃, p < 0.05). Soil probiotic bacteria, such as Bacillus (67%), Sporosarcina (9%), Paenibacillus (6%), Paenisporosarcina (6%), and Cohnella (4%), remained in the soil after the 80℃ and 121℃ heat treatments. Although steam increased the relative abundances of most of the heat-tolerant microbes before sowing, richness and diversity gradually recovered to the level of CCS, regardless of fungi or bacteria, after replanting. Thus, we added heat-tolerant microbes (such as Bacillus) after steaming, which reduced the relative abundance of pathogens, recruited antagonistic bacteria, and provided a long-term protective effect compared to the steaming and Bacillus alone (p < 0.05). Taken together, the current study provides novel insight into sustainable agriculture in a consecutively cultivated system.

• Journal of Microbiology
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• 제42권4호
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• pp.267-277
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• 2004

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.

• Journal of Microbiology and Biotechnology
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• 제26권1호
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• pp.99-109
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• 2016

We investigated the relation between the presence of geosmin in water and the bacterial community structure within the granular activated carbon (GAC) system of water treatment plants in South Korea. GAC samples were collected in May and August of 2014 at three water treatment plants (Sungnam, Koyang, and Yeoncho in Korea). Dissolved organic carbon and geosmin were analyzed before and after GAC treatment. Geosmin was found in raw water from Sungnam and Koyang water treatment plants but not in that from Yeoncho water treatment plant. Interestingly, but not surprisingly, the 16S rRNA clone library indicated that the bacterial communities from the Sungnam and Koyang GAC systems were closely related to geosmin-degrading bacteria. Based on the phylogenetic tree and multidimensional scaling plot, bacterial clones from GAC under the influence of geosmin were clustered with Variovorax paradoxus strain DB 9b and Comamonas sp. DB mg. In other words, the presence of geosmin in water might have inevitably contributed to the growth of geosmin degraders within the respective GAC system.

• Environmental Engineering Research
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• 제14권1호
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• pp.3-9
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• 2009

Microorganisms play an important role in the geochemical cycles, industry, environmental cleanup, and biotechnology among other fields. Given the high microbial diversity, identification of the microorganism is essential in understanding and managing the processes. One of the most popular and powerful method for microbial identification is comparative 16S rRNA gene analysis. Due to the highly conserved nature of this essential gene, sequencing and later comparison of it against known rRNA databases can provide assignment of the bacteria into the taxonomy, and the identity of its closest relatives. Isolation and sequencing of 16S rRNA genes directly from natural environments (either from DNA or RNA) can also be used to study the structure of the whole microbial community. Nowadays, novel sequencing technologies with massive outputs are giving researchers worldwide the chance to study the microbial world with a depth that was previously too expensive to achieve. In this article we describe commonly used research approaches for the study of individual microorganisms and microbial communities using the tools provided by Ribosomal Database Project website.

• Journal of Microbiology and Biotechnology
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• 제19권7호
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• pp.698-708
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• 2009

High rate sulfate reduction under acidic conditions opens possibilities for new process flow sheets that allow the selective recovery of metals from mining and metallurgical waste and process water. However, knowledge about high-rate sulfate reduction under acidic conditions is limited. This paper investigates sulfate reduction in a membrane bioreactor at a controlled pH of 5. Sulfate and formate were dosed using a pH-auxostat system while formate was converted into hydrogen, which was used for sulfate reduction. Sulfide was removed from the gas phase to prevent sulfide inhibition. This study shows a high-rate sulfate-reducing bioreactor system for the frrst time at pH 5, with a volumetric activity of 188 mmol $SO_4^{2-}$/I/d and a specific activity of 81 mmol $SO_4^{2-}$volatile suspended solids/d. The microbial community at the end of the reactor run consisted of a diverse mixed population including sulfate-reducing bacteria.

• Journal of Microbiology and Biotechnology
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• 제19권7호
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• pp.651-657
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• 2009

Shifts in the activity and diversity of microbes involved in aliphatic and aromatic hydrocarbon degradation in contaminated soil were investigated. Subsurface soil was collected from a gas station that had been abandoned since 1995 owing to ground subsidence. The total petroleum hydrocarbon content of the sample was approximately 2,100 mg/kg, and that of the soil below a gas pump was over 23,000 mg/kg. Enrichment cultures were grown in mineral medium that contained hexadecane (H) or naphthalene (N) at a concentration of 200 mg/l. In the Henrichment culture, a real-time PCR assay revealed that the 16S rRNA gene copy number increased from $1.2{\times}10^5$to $8.6{\times}10^6$with no lag phase, representing an approximately 70-fold increase. In the N-enrichment culture, the 16S rRNA copy number increased about 13-fold after 48 h, from $6.3{\times}10^4$to $8.3{\times}10^5$. Microbial communities in the enrichment cultures were studied by denaturing gradient gel electrophoresis and by analysis of 16S rRNA gene libraries. Before the addition of hydrocarbons, the gas station soil contained primarily Alpha- and Gammaproteobacteria. During growth in the H-enrichment culture, the contribution of Bacteriodetes to the microbial community increased significantly. On the other hand, during N-enrichment, the Betaproteobacteria population increased conspicuously. These results suggest that specific phylotypes of bacteria were associated with the degradation of each hydrocarbon.

• Journal of Microbiology and Biotechnology
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• 제29권1호
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• pp.91-104
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• 2019

The taxonomic and functional characteristics of bacterial communities in the pre-chlorinated rapid filters and ozonated biological activated carbon (BAC) filters were compared using Illumina MiSeq sequencing of the 16S rRNA gene and community-level physiological profiling (CLPP) based on sole-carbon-source utilization patterns. Both the rapid filters and BAC filters were dominated by Rhizobiales within ${\alpha}-proteobacteria$, but other abundant orders and genera were significantly different in both types of filter. Firmicutes were abundant only in the intermediate chlorinated rapid filter, while Acidobacteria were abundant only in the BAC filters. Bacterial communities in the rapid filter showed high utilization of carbohydrates, while those in the BAC filters showed high utilization of polymers and carboxylic acids. These different characteristics of the bacterial communities could be related to the different substrates in the influents, filling materials, and residual disinfectants. Chlorination and ozonation inactivated the existing bacteria in the influent and formed different bacterial communities, which could be resistant to the oxidants and effectively utilize different substrates produced by the oxidant, including Phreatobacter in the rapid filters and Hyphomicrobium in the BAC filters. Bradyrhizobium and Leptothrix, which could utilize compounds adsorbed on the GAC, were abundant in the BAC filters. Ozonation increased taxonomic diversity but decreased functional diversity of the bacterial communities in the BAC filters. This study provides some new insights into the effects of oxidation processes and filling materials on the bacterial community structure in the biological filters of drinking water treatment plants.