• Journal of Microbiology and Biotechnology
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• v.27 no.6
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• pp.1078-1089
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• 2017

Biofilm formation of Staphylococcus aureus is one of its mechanisms of drug resistance. Anti-biofilm screening of 106 compounds from marine-derived fungi displayed that 12 compounds inhibited S. aureus biofilm formation by >50% at the concentration of $100{\mu}g/ml$, and only secalonic acid D (SAD) and B inhibited by >90% at $6.25{\mu}g/ml$ without inhibiting cell growth after 24-h incubation. Meanwhile, it was found that the double bond between C-1 and C-10 of citrinin derivatives and the C-C connection position of two chromone monomers may be important for their anti-biofilm activities. Moreover, SAD slightly facilitated biofilm eradication and influenced its architecture. Furthermore, SAD slowed the cell growth rate in the preceding 18-h incubation and differentially regulated transcriptional expression of several genes, such as agr, isaA, icaA, and icaD, associated with biofilm formation in planktonic and biofilm cells, which may be the reason for the anti-biofilm activity of SAD. Finally, SAD acted synergistically against S. aureus growth and biofilm formation with other antibiotics. These findings indicated that various natural products from marine-derived fungi, such as SAD, could be used as a potential biofilm inhibitor against S. aureus.

• Microbiology and Biotechnology Letters
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• v.44 no.4
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• pp.535-539
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• 2016

The prevalence of pathogenic bacteria such as Streptococcus parauberis (Sp), Streptococcus iniae (Si), and Edwardsiella tarda (Et) in flounder fish farms in Jeju Island and their management by gallium treatment was studied. Sp, Si, and Et were found to exhibit a low rate of cell growth and high biofilm formation. Hence, in the present study, cell growth and biofilm formation were measured spectrophotometrically 72 h after the addition of different concentrations of gallium (2, 4, or 8 mg/ml). In addition, cell death was measured by resazurin and propidium iodide staining assays. The results showed that bacterial cell death increased and biofilm formation decreased with an increasing concentration of gallium. Hence, the present study signifies that the use of gallium against bacterial pathogens could be useful for disease management in flounder farms.

• Membrane and Water Treatment
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• v.10 no.6
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• pp.395-404
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• 2019

The influence of chlorine on marine bacterial communities was examined in this study. A non-chlorine-adapted marine bacterial community (NCAM) and a chlorine-adapted bacterial community (CAM, bacterial community treated with $0.2mg-Cl_2/L$ chlorine) were cultivated for 1 month. A distinct difference was observed between the NCAM and CAM, which shared only eight operational taxonomic units (OTUs), corresponding to 13.1% of the total number of identified OTUs. This result suggested that chlorine was responsible for the changes in the marine bacterial communities. Kordiimonas aquimaris was found to be a chlorine-resistant marine bacterium. The effect of intermittent chlorination on the two marine biofilm communities formed on the reverse osmosis (RO) membrane surface was investigated using various chlorine concentrations (0, 0.2, 0.4, 0.6 and 0.8 mg $Cl_2/L$). Although the average number of adherent marine bacteria on the RO membrane over a period of 7 weeks decreased with increasing chlorine concentration, disinfection efficiencies showed substantial fluctuations throughout the experiment. This is due to chlorine depletion that occurs during intermittent chlorination. These results suggest that intermittent chlorination is not an effective disinfection strategy to control biofilm formation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.2
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• pp.129-136
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• 2024

Lactic acid bacteria (LAB) growth in processed meat products produces slime. In this study, 10 different biofilm-forming LAB, including Leuconostoc mesenteroides, Lacticaseibacillus paracasei, Levilactobacillus brevis, Lactiplantibacillus plantarum, Leuconostoc citreum, Weissella viridescens, and Latilactobacillus sakei, were isolated from various meat products and identified based on 16S rRNA gene analysis. To inhibit biofilm formation by LABs, Eisenia bicycles methanolic extract (EB) and ethyl acetate soluble fraction (EA) were used as antibacterial and antibiofilm agents, respectively. Furthermore, EA and EB were employed to synthesize gold nanoparticles (AuNPs) such as EB-AuNPs and EA-AuNPs, which could serve as antibiofilm agents against the isolated LAB. These findings demonstrate that EA, EB-AuNPs, and EA-AuNPs exhibit significant antibacterial activity against the isolated LAB. Furthermore, EB-AuNPs reduced L. citreum biofilm production, whereas EA-AuNPs inhibited L. mesenteroides and L. brevis biofilm formation. The current results suggest that EB-AuNPs and EA-AuNPs can be used as nanomaterials to inhibit LAB that form biofilms on meat products.

• Journal of Marine Bioscience and Biotechnology
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• v.1 no.2
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• pp.84-90
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• 2006

Various ${\Delta}opp$ mutants of Vibrio fluvialis were constructed by allelic exchange method. The mutants occurred in target genes were confirmed by PCR and Southern hybridization analyses. After the exact mutants were identified, cell growth and biofilm production were examined using the respective mutants. The growth of wild strain was more rapid than mutants within 4hr incubation. Thereafter, the growth of wild strain and mutants reached to same level. When the productivities of wild strain and mutants were examined, ${\Delta}oppA$ mutant showed the highest productivity. Though ${\Delta}oppC,D$ and F mutants produced the lower production than that of ${\Delta}oppA$ mutant, the productivities of those mutants were much higher than that of wild strain.

• Korean Journal of Microbiology
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• v.52 no.1
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• pp.49-58
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• 2016

Compared to planktonic bacterial populations, biofilms have distinct bacterial community structures and play important ecological roles in various aquatic environments. Despite their ecological importance in nature, bacterial community structure and its succession during biofilm development in the Antarctic marine environment have not been elucidated. In this study, the succession of bacterial community, particularly during the early stage of biofilm development, in the Antarctic marine environment was investigated by pyrosequencing of the 16S rRNA gene. Overall bacterial distribution in biofilms differed considerably from surrounding seawater. Relative abundance of Gammaproteobacteria and Bacteroidetes which accounted for 78.9-88.3% of bacterial community changed drastically during biofilm succession. Gammaproteobacteria became more abundant with proceeding succession (75.7% on day 4) and decreased to 46.1% on day 7. The relative abundance of Bacteroidetes showed opposite trend to Gammaproteobacteria, decreasing from the early days to the intermediate days and becoming more abundant in the later days. There were striking differences in the composition of major OTUs (${\geq}1%$) among samples during the early stages of biofilm formation. Gammaproteobacterial species increased until day 4, while members of Bacteroidetes, the most dominant group on day 1, decreased until day 4 and then increased again. Interestingly, Pseudoalteromonas prydzensis was predominant, accounting for up to 67.4% of the biofilm bacterial community and indicating its important roles in the biofilm development.

• Journal of Microbiology
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• v.40 no.4
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• pp.260-266
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• 2002

Bacterial strains were isolated from biofilms formed on glass slides submerged in seawater in Dae-Ho Dike. Eight strains showing fast attaching ability were selected and identified. Their exopolysaccharide (EPS)-producing ability and EPS properties were characterized. Based on Microlog System, 4 among the 8 strains were identified as Micrococcus luteus and the rest were Bacillus thuringiensis, Bacillus megaterium,, Staphylococcus saprophyticus and Agrobacterium vitis. A, vitis was reidentified as Sulfitobacter pontiacus based on 16S rDNA sequence data. The amount of water-soluble EPS produced by the 8 strains ranged from 0.114 to 1.329 g$.$l$\^$-1/ and the productivity was negatively correlated with the cell biomass. The molecular weight of the produced EPS ranged from 0.38 to 25.19$\times$10$\^$4/ Da. Glucose and galactose were ubiquitous sugar components. Mannose, ribose, and xylose were also major sugar components. The molecular weight and composition of the EPS showed strain-specific variation.

• Proceedings of the Korean Society for Applied Microbiology Conference
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• 2003.06a
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• pp.161-163
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• 2003

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.182.4-182
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• 2005

• Proceedings of the Microbiological Society of Korea Conference
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• 2008.05a
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• pp.42-44
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• 2008

Bacterial biofilms are analogous to multi-cellular organisms or to clonal communities of higher organisms. In this respect, it can be demonstrated that biofilms display the type of genetic variation associated with macroorganisms. The formation of genetic variants from biofilms is the result of internally produced and regulated signals and the appearance of these variants coincides with dispersal from the biofilm. Moreover, the generation of such variation, has similar outcomes for the bacterial community, where diversification of phenotypic traits ensures that the bacterial community optimizes its chances of success when dispersing or surviving when challenged with environmental stress. These observations increase the complexity with which we view bacteria and also suggest that microbial systems can serve as models for the testing of eukaryotic ecological theories.