• Journal of Microbiology and Biotechnology
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• v.22 no.3
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• pp.283-291
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• 2012

Bioremediation efforts often rely on the application of surfactants to enhance hydrocarbon bioavailability. However, synthetic surfactants can sometimes be toxic to degrading microorganisms, thus reducing the clearance rate of the pollutant. Therefore, surfactant-resistant bacteria can be an important tool for bioremediation efforts of hydrophobic pollutants, circumventing the toxicity of synthetic surfactants that often delay microbial bioremediation of these contaminants. In this study, we screened a natural surfactant-rich compartment, the estuarine surface microlayer (SML), for cultivable surfactant-resistant bacteria using selective cultures of sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB). Resistance to surfactants was evaluated by colony counts in solid media amended with critical micelle concentrations (CMC) of either surfactants, in comparison with non-amended controls. Selective cultures for surfactant-resistant bacteria were prepared in mineral medium also containing CMC concentrations of either CTAB or SDS. The surfactantresistant isolates obtained were tested by PCR for the Pseudomonas genus marker gacA gene and for the naphthalene-dioxygenase-encoding gene ndo. Isolates were also screened for biosurfactant production by the atomized oil assay. A high proportion of culturable bacterioneuston was tolerant to CMC concentrations of SDS or CTAB. The gacA-targeted PCR revealed that 64% of the isolates were Pseudomonads. Biosurfactant production in solid medium was detected in 9.4% of tested isolates, all affiliated with genus Pseudomonas. This study shows that the SML is a potential source of surfactant-resistant and biosurfactant-producing bacteria in which Pseudomonads emerge as a relevant group.

• Journal of Microbiology and Biotechnology
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• v.30 no.11
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• pp.1680-1687
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• 2020

Fungal endophytes are symbiotic microorganisms that are often found in asymptomatic plants. This study describes the genetic diversity of the fungal endophytes isolated from the roots of plants sampled from the west coast of Korea. Five halophytic plant species, Limonium tetragonum, Suaeda australis, Suaeda maritima, Suaeda glauca Bunge, and Phragmites australis, were collected from a salt marsh in Gochang and used to isolate and identify culturable, root-associated endophytic fungi. The fungal internal transcribed spacer (ITS) region ITS1-5.8S-ITS2 was used as the DNA barcode for the classification of these specimens. In total, 156 isolates of the fungal strains were identified and categorized into 23 genera and two phyla (Ascomycota and Basidiomycota), with Dothideomycetes and Sordariomycetes as the predominant classes. The genus Alternaria accounted for the largest number of strains, followed by Cladosporium and Fusarium. The highest diversity index was obtained from the endophytic fungal group associated with the plant P. australis. Waito-C rice seedlings were treated with the fungal culture filtrates to analyze their plant growth-promoting capacity. A bioassay of the Sm-3-7-5 fungal strain isolated from S. maritima confirmed that it had the highest plant growth-promoting capacity. Molecular identification of the Sm-3-7-5 strain revealed that it belongs to Alternaria alternata and is a producer of gibberellins. These findings provided a fundamental basis for understanding the symbiotic interactions between plants and fungi.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.6
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• pp.885-892
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• 2006

In order to investigate whether or not Total Coliforms (T.C.) and Fecal Coliforms (F.C.) are compatible as indicator microorganisms of waterbome enteric viruses, a total of 192 surface water samples from 24 locations in Korea were tested for T.C., F.C., and human enteric viruses from July 2003 to January 2006. Altogether, the number of T.C. in each samples was ranged from $0{\sim}5.3{\times}10^4$ colony forming unit(CFU)/100mL, and the number of F.C. ranged from $0{\sim}5.0{\times}10^3CFU/100mL$ per sample. Thirty-three percent of the samples tested positive for human enteric viruses after the total culturable virus assay. The results of the statistical analysis showed that T.C. and F.C. had a significant correlation with turbidity and temperature, but the waterbome enteric viruses did not. When compared to the number of T.C. or F.C. per sample, the concentration of waterbome enteric viruses was not found to be correlated. In conclusion, it is suggested that T.C. and F.C. may not be sufficient microbial indicators of waterbome enteric viruses in the samples analyzed in this study. However, further research is needed to find other microbial indicators of waterbome enteric viruses and to develop more advanced and sensitive methods to detect waterborne enteric viruses.

• Korean Journal of Microbiology
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• v.51 no.4
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• pp.440-443
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• 2015

The widespread emergence of antibiotic resistant microorganisms in clinics and natural environments has attracted public concern. Especially, microorganisms inhabiting natural environment is considered as a source responsible for increasing the abundance of antibiotic resistant genes in ecosystem. In this study, the diversity of culturable bacteria resistant to ampicillin was investigated with water samples collected from seven locations in Korea. The genera belonging to Aeromonas and Acidovorax were dominant among the isolated 498 strains. The 66% of isolates showed multi-drug resistance against more than six antibiotics among tested fourteen ones and isolates resistant to seven antibiotics were the most prevalent with 19.7% abundance. Using the antibiotics susceptibility results, the intrinsic resistance profile was suggested for the most dominant genera, Aeromonas, Acidovorax, Pseudomonas, and Elizabethkingia.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.305-311
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• 1993

Marine organisms were investigated to identify the marine actinomycetes that produced noble bioactive compounds. Microorganism counts range from $2.1{\times}10^3\;to\;1.2{\times}10\;CFU/g$ of marine organisms. Actinomycetes constituted 0.01 to $0.5\%$ of culturable microbial community. We identified the marine actinomycetes that produced novel bioactive compounds. During the course of screening for bioactives from the marine microorganisms, we found that the strain in sponge had antimicrobial activities. From the morphological, cultural and various physiological characteristics, this strain was identified for Actinomycetes No. 101. The optimal compositions of culture medium for Actinomycetes No. 101 were starch 30g/l as carbon source, casamino acid 10g/l as nitrogen source. The optimal pH of medium and fermentation temperature were $6.5{\sim}7.0$ and $30^{\circ}C$, respectively. Fermentation has been conducted in the marine broth at $30^{\circ}C$ for 72 hour. The yield of fermentation got about 3g as dry weight(per liter of broth). The distribution of antimicrobial activity of Actinomycetes No. 101 was screened by paper disc. The extract of cultured cell and broth inhibited the growth of Staphylococcus aureus and Bacillus subtilis, but the inhibition action was week against yeast and mold.

• Journal of Life Science
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• v.17 no.9 s.89
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• pp.1284-1289
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• 2007

The Biological Activated Carbon (BAC) process in the water treatments represents a kind of biofiltration process which capabilities of bacteria to remove organic matters are maximized. It enables to eliminate organic matters and effectively reduce microbial regrowth potentials. As attached bacteria employ natural organic matter as a substrate, they are significantly dependent on indigenous microorganisms. In this study, characteristics of bacterial community by culturable and unculturable Methods have been conducted in a pilot plant using SAC in water treatment process at the downstream of the Nakdong River. Based on the results, HPC and bacterial- production for coal-based activated carbon material were $1.20{\sim}56.2{\times}l0^7$ cfu/g and $1.2{\sim}3.7\;mgC/m^{3}h$, respectively, in the SAC process. The highest level of attached bacteria biomass and organic carbon removal efficiency was found in the coal-based activated carbon. The genera Pseudomonas, Flavobacterium, Alcaligenes, Acilzetobacter, and Spingomonas were identified for each activated carbon material. Pseudomonas vesicularis was the dominant species in the coconut- and coal-based materials, where as Pseudomonas cepacia was the dominant species in the wood-based material. The Scanning Electron Microscope (SEM) observation of the activated carbon surface also found the widespread distribution of rod form and coccus. The community of attached bacteria was investigated by performing Fluorescent in situ hybridization (FISH) analysis. a group was dominant in coal, wood and coccunt-based materials, ${\alpha},\;{\beta}\;and\;{\gamma}$ group ranged from 27.0 ${\sim}$ 43.0%, 7.1 ${\sim}$ 22.0%, 11.3 ${\sim}$ 28.6%, respectively. These results suggest that a group bacterial community appears to be regulated removal efficiency of organic material in water treatment process.

• Korean Journal of Microbiology
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• v.48 no.1
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• pp.8-15
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• 2012

Bioaerosols generated from composting facilities and landfills may create health risks for workers and nearby residents. To determine the levels of culturable airborne bacteria and fungi in bioaerosols, samples were seasonally collected at a composting facility and a landfill in Ulsan, Korea with an impaction-type sampler. Concentrations of heterotrophic bacteria averaged (in $MPN/m^3$) $6.5{\times}10^3$ (range $1.5{\times}10^2-1.5{\times}10^4$) in the composting facility and $3.9{\times}10^3$ (range $6.0{\times}10^1-9.3{\times}10^3$) at the entrance of the facility. These concentrations were 460 and 280 times higher than those of reference sites. Coliform bacteria were detected both inside and entrance of the facility. On the landfill, heterotrophic bacterial concentrations averaged (in $MPN/m^3$) $4.9{\times}10^2$ (range $1.7{\times}10^2-1.0{\times}10^3$), while they averaged $3.7{\times}10^2$ (range $4.8{\times}10^1-1.3{\times}10^3$) at the parking lot of the landfill. These concentrations were 35 and 26 times higher than those of reference sites. When we isolated and tentatively identified heterotrophic bacteria, Pseudomonas luteola was the most dominant species in bioaerosols from the composting facility, whereas the most abundant one in reference samples was Micrococcus sp. Average concentrations of airborne fungi were measured between $4.8{\times}10^2$ and $7.9{\times}10^2\;MPN/m^3$ depending on sites, which were 2.1-3.4 times higher compared to those of reference sites. While Cladosporium, Alternaria, and Penicillium were commonly identified fungal genera, genus Aspergillus was identified only in bioaerosols from the composting facility.

• Korean Journal of Microbiology
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• v.43 no.3
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• pp.193-200
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• 2007

Indoor airborne bacterial and fungal concentrations were examined at classrooms and corridors of 3 elementary schools in Ulsan. Airborne microorganisms were collected with an impaction-type air sampler using plate count agar and dichloran rose bengal chloramphenicol agar. During the semester, concentrations of bacteria ranged $168{\sim}3,887 MPN/m^3$ at classrooms and $168{\sim}6,339 MPN/m^3$ at corridors, while those of fungi ranged $34{\sim}389 MPN/m^3$ at classrooms and $91{\sim}507 MPN/m^3$ at corridors. The bacterial concentrations showed larger variations between situations and schools compared to those of fungi. When airborne bacteria were isolated and identified, 84% were observed as Gram-positive, and Micrococcus spp. was the most abundant group with 61% of tested isolates, followed by genus Staphylococcus with 10%. The Micrococcus spp. isolates, of which 75% were identified as M. luteus, appeared to be from human origins. The protective pigments and substantial cell wall of Micrococcus may provide selective advantage for their survival in the air. We also isolated and identified 15 genera of filamentous fungi. The most common culturable fungi were Cladosporium, Aspergillus and Penicillium, and these 3 genera were 69% of fungal isolates. Genus Stachybotrys, of which S. chartarum is a well known producer of many potent mycotoxins, was also detected from one of the schools. further systematic studies are necessary with an emphasis on species identification and mycotoxin production of isolated fungal genera, including Aspergillus, Penicillium, and Stachybotrys.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.5
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• pp.415-420
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• 2010

In Korea, oysters are used as an ingredient of Kimchi (Korean pickled cabbage) in early winter. Although viral contamination of oysters, including contamination by norovirus, can provoke gastroenteric illness, little is known of the epidemiological relationship to outbreaks. We postulated that Kimchi ripening can reduce the infectivity of norovirus, in order to test this hypothesis, we carried out a model experiment. Since norovirus is currently regarded as non-culturable, feline calicivirus (FCV) was used as a surrogate to examine the activation of norovirus with Kimchi ripening. In commercial well-prepared Kimchi, the infectivity ($TCID_{50}$) of FCV decreased by 2 log every 12 hours and reached the limit of detection after 48 hours during over-aging at $25^{\circ}C$. During storage at $4^{\circ}C$, the infectivity ($TCID_{50}$) of FCV decreased slowly and reached 5.00 $TCID_{50}$ after 48 hours. The low pH appears to affect the infectivity of FCV directly via organic acids produced by ripening during over-aging and storage. In neutralized lab-prepared Kimchi (pH 7.0), the infectivity ($TCID_{50}$) of FCV also decreased and reached the limit of detection after 72 hours at $4^{\circ}C$. This indicates that there are substances beside organic acids in Kimchi that originate from the raw materials and are produced during ripening. Among the raw materials, salt-fermented anchovies and garlic showed high direct antiviral activity. The main factor decreasing the infectivity of FCV in Kimchi was the high acidity caused by organic acids, regardless of the type, produced by ripening. Furthermore, unknown secondary products of microorganisms associated with Kimchi ripening and antiviral materials originating from raw material might contribute to the decreased infectivity of FCV, the surrogate of norovirus.

• Journal of fish pathology
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• v.26 no.3
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• pp.193-206
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• 2013

The ark shell, Scapharca broughtonii is a marine bivalve mollusks belonging to the family Arcidae and important seafood for Korean and Japanese, and southern coast is brisk bays for the ark shell aquaculture. However, productivity of ark shell from these regions were rapidly reduced during the last decade due to mass mortality. The reason of this great damage has not yet been identified. To overcome this economic loss, diverse investigations were focused on environmental factors that affects in the physiology of S. broughtonii, but microbiological researches were performed insufficiently. Hemoglobin is one of the major blood component of ark shell and is damaged by some species of bacterial toxins. We concentrated on this red pigment because hemolysis could be the cause of ark shell mortality. In this study, we analyzed microbial diversity of underwater sediments in coastal regions and also existences in the body of S. broughtonii. We investigate about 4,200 isolates collected from June to September for microbial diversity of sediments and ark shell. We screened all of culturable microorganisms, and identified 25 genera 118 species, 24 genera 89 species, 30 genera 109 species and 39 genera 141 species, and selected 140 unique colonies for identification and challenge assay.