• Journal of Microbiology and Biotechnology
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• v.29 no.3
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• pp.465-472
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• 2019

Several reports describe antimicrobial-resistance transfer among children and the community in outbreak situations, but transfer between a child and a caregiver has not been examined in child care facilities under normal circumstances. We investigated the transfer of antimicrobial-resistance genes, resistant bacteria, or both among healthy children and teachers. From 2007 to 2009, 104 Escherichia coli isolates were obtained from four teachers and 38 children in a child care center. Twenty-six cephem-resistant isolates were obtained from children in 2007 and 2008. In 2009, cephem-resistant isolates were detected in children as well as a teacher. Nalidixic acid-resistant isolates from the same teacher for 3 years showed low similarity (<50%) to each other. However, an isolate from a teacher in 2007 and another from a child in 2008 showed high similarity (87%). Pulsed-field gel electrophoresis revealed 100% similarity for four isolates in 2007 and one isolate in 2008, and also similarity among seven isolates carrying the virulence gene (CNF1). This study yielded the following findings: (1) a gene for extended-spectrum ${\beta}$-lactamase was transferred from a child to other children and a teacher; (2) a nalidixic acid-resistant isolate was transferred from a teacher to a child; and (3) a virulent bacterium was transferred between children.

• Microbiology and Biotechnology Letters
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• v.50 no.2
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• pp.193-201
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• 2022

Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) are major causes of hospital- and community-acquired infections. The treatment of biofilm-related infections caused by these bacteria is a global healthcare challenge. Therefore, the development of alternative therapeutics is required. An essential oil extracted from Curcuma zedoaria (CZ) Rosc, also known as white turmeric, has been reported to possess various antimicrobial activities. In the present study, we evaluated the antibiofilm activities of an ethanolic extract of the CZ rhizome against MRSA and MSSA. The results showed that the CZ extract with the highest sub-minimum inhibitory concentration (sub-MIC), 1/2 MIC (0.312 mg/ml), significantly inhibited biofilm production by up to 80-90% in both tested strains. Subsequently, we evaluated the ability of the CZ extract to prevent cell-surface attachment to a 96-well plate and extracellular DNA (eDNA) release from the biofilm. The CZ extract demonstrated an inhibitory effect on bacterial attachment and eDNA release from the biofilm biomass. The CZ extract may inhibit biofilm formation by preventing eDNA release and cell-surface attachment. Therefore, this CZ extract is a potential candidate for the development of alternative treatments for biofilm-associated MRSA and MSSA infections.

• Journal of Korean Dental Science
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• v.16 no.1
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• pp.35-46
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• 2023

Purpose: Culture-based methods for microbiological diagnosis and antibiotic susceptibility tests have limitations in the management of orofacial infections. We aimed to profile pus microbiota and identify antibiotic resistance genes (ARGs) using a culture-independent approach. Materials and Methods: Genomic DNA samples extracted from the pus specimens of two patients with orofacial abscesses were subjected to shotgun sequencing on the NovaSeq system. Taxonomic profiling and prediction of ARGs were performed directly from the metagenomic raw reads. Result: Taxonomic profiling revealed obligate anaerobic polymicrobial communities associated with infections of odontogenic origins: the microbial community of Patient 1 consisted of one predominant species (Prevotella oris 74.6%) with 27 minor species, while the sample from Patient 2 contained 3 abundant species (Porphyromonas endodontalis 33.0%; P. oris 31.6%; and Prevotella koreensis 13.4%) with five minor species. A total of 150 and 136 putative ARGs were predicted in the metagenome of each pus sample. The coverage of most predicted ARGs was less than 10%, and only the CfxA2 gene identified in Patient 1 was covered 100%. ARG analysis of the seven assembled genome/metagenome datasets of P. oris revealed that strain C735 carried the CfxA2 gene. Conclusion: A metagenomics-based approach is useful to profile predominantly anaerobic polymicrobial communities but needs further verification for reliable ARG detection.

• Biomolecules & Therapeutics
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• v.32 no.4
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• pp.403-423
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• 2024

The human gastrointestinal (GI) tract houses a diverse microbial community, known as the gut microbiome comprising bacteria, viruses, fungi, and protozoa. The gut microbiome plays a crucial role in maintaining the body's equilibrium and has recently been discovered to influence the functioning of the central nervous system (CNS). The communication between the nervous system and the GI tract occurs through a two-way network called the gut-brain axis. The nervous system and the GI tract can modulate each other through activated neuronal cells, the immune system, and metabolites produced by the gut microbiome. Extensive research both in preclinical and clinical realms, has highlighted the complex relationship between the gut and diseases associated with the CNS, such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. This review aims to delineate receptor and target enzymes linked with gut microbiota metabolites and explore their specific roles within the brain, particularly their impact on CNS-related diseases.

• Korean Journal of Microbiology
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• v.47 no.3
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• pp.275-280
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• 2011

In order to evaluate the diversity and change of bacterial population during the manufacturing process of traditional soybean paste (doenjang), bacterial communities were analyzed using 16S rRNA gene-based pyrosequencing. In rice straw, the most important inoculum source for fermentation, the bacterial sequences with a relative abundance greater than 1% were assigned to four phyla, Proteobacteria (71%), Actinobacteria (20.6%), Bacteroidetes (4.2%), and Firmicutes (1.3%). Unlike bacterial community composition of rice straw, a different pattern of bacterial population in meju was observed with predominantly high abundance (99.1%) of Firmicutes. Phylum composition in young doenjang was almost same as that of meju. Major genera in young doenjang were Bacillus (81.3%), Clostridium (6.9%) and Enterococcus (6.3%) and the predominant species among bacterial population was B. amyloliquefaciens (63.6%). Abundance of the phylum Firmicutes in mature doenjang was 99.98%, which was even higher value than those in meju and young doenjang. Predominant species in mature doenjang were B. amyloliquefaciens (67.3%), B. atrophaeus (12.7%), B. methylotrophicus (6.5%), B. mojavensis (3.2%), and B. subtilis. (2.5%), which were also identified as major species of the microbial flora in meju. These results suggested that rice straw was a primary source for supplement of Bacillus species in manufacturing the traditional doenjang and that some species of Bacillus strains were mainly involved in the fermentation process of traditional doenjang.

• Journal of Applied Biological Chemistry
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• v.56 no.2
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• pp.95-100
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• 2013

Soil microbes are important integral components of soil ecosystem which have significant and diverse role in organic matter decomposition, nitrogen cycling, and nitrogen fixation. In this study an effective denaturing gradient gel electrophoresis (DGGE) method was employed for paddy soil microbial diversity survey. For optimum paddy soil microbial DNA extraction, different methods such as Lysis buffer, skim milk bead, sodium phosphate buffer, Epicentre Soil Master DNA extraction kit (Epicentre, USA) and Mo Bio Power Soil DNA kit (MO BIO, USA) methods were utilized. Among all the method, using Mo Bio Power Soil kit was most effective. DGGE analysis of Bacteria was carried out at 6% polyacylamide gel and 45-60% denaturing gradient in the optimal conditions. Whereas DGGE analysis of fungi was done at 6% polyacrylamide gel and 45-80% denaturing gradient in the optimal conditions. By applying the above assay, it was found that variation within the microbial community of paddy soil occurs by a factor of time. DGGE assay used in this study through for a variety of soil microbial analysis suggests the potential use of this method.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.752-756
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• 2006

The independent anoxic reactor was introduced in biological aerated filters as the regulation of water quality requirement, especially total nitrogen, had been strengthened. The process studied in this work was upflow $Biobead^{(R)}$ process which was used commercial invented for removal of organic materials and nitrification. For the purpose of evaluating the independent anoxic reactor, PCR-DGGE, of the molecular biological methods, was performed. Two types of nitrite reductase genes were selected. One is nirS represented cytocrome $cd_1$ nitrite reductase gene and the other is nirK represented Cu-containing nitrite reductase gene. Denitrifier community in the independent anoxic reactor was analyzed with PCR-DGGE using these two denitrifying functional genes. As the result of the PCR, only nirS gene was detected between nirS and nirK. With the result of the DGGE, specific bands became strong, as the operating days were longer, nitrate loading rate was increased. otherwise those of the initial activated sludge showed various bands. In the consequence of the sequence of DGGE bands, various denitrifiers were sequenced in the initial activated sludge, while specific denitrifiers like alcaligenes faecalis were predominant in the anoxic reactor. Consequently, introduction of the independent anoxic reactor made it possible to achieve 96% denitrification efficiency, and was proper for the modification of BAF process.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.3
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• pp.240-248
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• 2006

In this study, a retrofitting BNR process that was modified for the economical applicability was proposed and evaluated in the pilot plant($50m^3/d$). At the same time the bacterial community structure was investigated in the pilot plant by using FISH(fluorescent in situ hybridization) method. Economically 16% of the initial construction cost for the proposed process(introduction of a biological nutrient removal process of $60,000m^3/d$ scale basis) was reduced due to the absence of a bioreactor. Water treatment efficiencies and maintenance facilities of the modified process were satisfied with the strengthened discharge permits in Korea throughout a long term pilot plant operating including a winter season. Bacterial populations in the pilot plant and in the control plant(A2/O process, B SIP(Sewage Treatment Plant)) were remained uniformly during the test period, but bacterial structure in the bioreactor was changed drastically. Proportions of ${\beta}$-proteobacteria group including soil bacteria which play a important role in wastewater treatment increased $25{\sim}607%$ in population.

• Journal of Korean Society on Water Environment
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• v.39 no.1
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• pp.61-75
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• 2023

Denitrifying bacteria convert nitrate to nitrogen gas using an external carbon source as an electron donor. The external carbon source affects the denitrification performance and bacterial community structure. Although methanol is a cheap and effective external carbon source, the addition of diverse carbon sources may improve the total nitrogen removal rate and biomass characteristics, such as settleability. In this study, denitrifying reactions were performed using solely methanol and mixed carbon sources of methanol, glucose, and acetate in a sequencing batch reactor. The denitrifying reactor using methanol resulted in a total nitrogen removal rate of 0.39 ± 0.025 kg-N/m³-day while the suspended biomass transformed into dark brown granules. Methyloversatilis discipulorum had the highest predominance at 43.84%. The individual denitrifying biomasses, which were separately enriched with methanol, glucose, and acetate, showed the same total nitrogen removal performance of 0.39 ± 0.016 kg-N/m³-day. However, the addition of mixed carbon sources showed an improved total nitrogen removal rate of 0.42 ± 0.043 kg-N/m³-day, with the domination of Candidatus Saccaribacteria at 25.61%. The denitrifying granules turned pale yellow color. Influent COD/NO₃^--N ratios of 3.5, 5, and 7.5 exhibited COD/NO₃^--N consumptions of 4.3 ± 0.4, 4.4 ± 0.8, and 5.2 ± 0.7, and the consistent predominance of Candidatus Saccharibacteria.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.349-362
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• 1999

To understand the role of protozoa in the early formation of microbial fouling community, the studies on the formation of microbial film, the succession of microbial fouling communities, and the grazing pressure on bacteria population in microbial film were carried out in the laboratory, Inchon outer port and Inchon inner harbour. Bacteria and heterotrophic flagellates formed primary microbial film on the aluminum surface within 6 hours and oligotrich ciliates were observed 2 cells $mm^{-2}$ on the same surface at 9 hours in Inchon inner harbour which had physically stagnant condition. The larvaes of Balanus albicostatus which were dominant meiobenthos in Inchon coastal area attached on the glass surface at the first day of experiment. Heterotrophic flagellates showed maximum abundance of 465 cells $mm^{-2}$ at the 13rd day and ciliates showed maximum abundance of 63 cells $mm^{-2}$ at the 11st day in the Inchon inner harbour. In the Inchon outer port which opens to the outer sea, the maximum abundance of protozoa occurred at early phase, but not so many. The dominant heterotrophic flagellates were Metrornonas simplex and Bodonids. Dominant ciliates were small tintinnids and oligotrich ciliate Strombidium sp., Large Strombidium (oligotrich ciliate) and sessile Acineta turberosa (suctorian ciliate) occurred after 10 days. The attached larvae of Balanus occurred as biofouling organism on the early surface and showed maximum abundance of 18 indiv. $cm^{-2}$ at 7th day. At that time, adult barnacles were observed on the surface and dead barnacles were observed after two days. Except barnacles, the larvaes of Anthozoa sp., Oysters (Crassostrea gigas) and Polychaeta were observed on the surface from 3rd day. 3 benthic copepods including Harpacticus sp., I isopod, 1 polychaeta and 1 gastropoda were observed as predators of the microbial film on the surface after 7 days when microbial film developed very well. Although the ingestion rates of protozoa on the bactctia of the rnicrobi31 film were relatively low, the average grazing rate of protozoa on bacteria was high of 0.058 $h^{-1}$. This implied that the grazing pressure of protozoa influences the mortality of bacteria populations on the microbial film. but protozoa cannot get enough energy from only bacteria on the microbial film.