• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.585-595
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• 2021

Even though most of aquatic animal pathogens are considered opportunistic and many pose a low direct risk to personnel, all personnel working with aquatic pathogens and facilities using these organisms must comply with the regulation to prevent the release of the pathogen into the environment and causing disease in aquatic animals. First of all, in order to establish a biosafety system for aquatic pathogen, the list of microorganisms that can infect aquatic animals and humans should be drawn up according to the microorganisms encountered within national boundaries. Second, risk assessment guideline for diseases of livestock and aquatic environment is desperately needed. Third, microorganisms should be classified into risk group based on their potential impact on human and aquatic environment. Fourth, facilities handling aquatic pathogens should ensure that these pathogens are securely contained and safely handled for experimental or commercial development purposes. In conclusion, classification is based on the pathogenicity, mode of transmission and host range of the aquatic microorganisms, availability of effective preventative measures and treatments. Furthermore, risk group of aquatic pathogens should be correlated with physical containment facility requirements according to domestic characteristics.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.661-668
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• 2003

Performance of an airlift bioreactor (ABR) containing the immobilized microorganisms was evaluated in an integrated pilot scale recirculating aquaculture system stocked with Nile tilapia (Oreochromis niloticus) at an initial rearing density of $5\%$ and compared to a rotating biological contactor (RBC) for 40 days. The TAN concentration of rearing tank for ABR and RBC were maintained at $0.4\;g/m^3$ and $0.5\;g/m^3,$ respectively, The nitrite nitrogen was completely removed by the ABR. The ABR's aeration was more stable than the RBC's. On the whole, the feasibility of ABR as an aquacultural water treatment unit was recognized.

• Korean Journal of Environmental Biology
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• v.20 no.3
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• pp.189-196
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• 2002

The direct detection of intestinal pathogens and viruses often requires costly, tedious, and time-consuming procedures. These requirements developed a test to show that the water was contaminated with sewage-borne pathogens by assessing the hygienic quality of water based on indicator microorganisms whose presence indicates that pathogenic microorganisms may also be present. Various groups of microorganisms have been suggested and used as indicator microorganisms. Proposed and commonly used microbial indicators are total coliforms, fecal coliforms, fecal streptococci, Clostridium perfringens, heterotrophic plate count, bacteriophage, and so on. Unfortunately, most, if not all, of these indicators are not ideal because of the sensitivity and resistance to environment stresses and disinfection. However, the development of gene probes and PCR technology may give hope for the discovery of rapid and simple methods toy detecting small number of fecal pathogens in various environments.

• Applied Microscopy
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• v.34 no.2
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• pp.103-111
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• 2004

Fresh specimens of the aquatic macrophyte, Spirodela polyrhiza, have been examined employing scanning and transmission electron microscopy. Observations revealed the occurrence of microbial colonization during development. Submerged parts of the small, free-floating S. polyrhiza body exhibited a variety of microorganisms such as bacteria, cyanobacteria, and diatoms throughout their development. However, immature and/or young plants normally demonstrated much less microbial colonization compared to mature plants. During the study, heavy colonization by the microorganisms was routinely encountered at maturity, especially in the fully developed abaxial fronds and root caps. The mucilaginous layer was shown along the root caps, and the microorganisms appeared to be either clustered or attached to this layer. In contrast, only moderate degrees of colonization were observed in the root, and little to no colonization was observable in the adaxial frond surface. Transmission electron microscopy clearly demonstrated the microbial colonization to be external in the S. polyrhiza specimen examined in the current study. The association between the microorganisms and S. polyrhiza has been considered non-harmful, as no frond senescence and almost no mechanical penetration of the plant by the microorganisms were noticed during the study.

• Fisheries and Aquatic Sciences
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• v.6 no.3
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• pp.135-139
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• 2003

During routine survey of Pacific oyster (Crassostrea gigas) collected from Tongyoung area in southern coast of Korea, histological examination revealed that a intracellular microorganisms infected the digestive gland of the oyster. They infected hepatopancreatic cells extensively. The size of intracellular microorganism was of 45 to 86nm in diameter and 200nm to more thar 500nm in length. They were pleomorphic. The morphological characteristic of intracellular microorganisms lacked cell wall and was bounded by the plasma membrane. They contained typical prokaryotic ribosomes and fibrillar DNA-like strands. No additional internal structure has been observed. Based on the lack of cell wall and the cellular localization, the intracellular microorganism is considered as a Mycoplasma-like organism.

• 한국생물공학회:학술대회논문집
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• 2005.10a
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• pp.445-445
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• 2005

• Journal of fish pathology
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• v.20 no.2
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• pp.169-178
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• 2007

• Journal of fish pathology
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• v.25 no.2
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• pp.77-84
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• 2012

Various antibiotics, that could induce the appearance of resistant microorganisms, have been used for treatment or prevention of bacterial diseases in marine and ornamental fish. We determined and characterized the level of antibiotic-resistant bacteria and proportion of multi-drug resistant bacteria in intestinal microflora of both marine fish cultured in Korea and imported ornamental freshwater fish. For this the bacterial species and resistance to antibiotics were investigated in intestine of rock bream Oplegnathus fasciatus cultured in Korea and pearl gourami Trichogaster leeri imported from Singapore to characterise. Although the bacterial species were different, proportions of resistant bacteria to single antibiotics or multi-drug were higher in intestinal microflora of pearl gourami Trichogaster leeri imported from Singapore than in rock bream Oplegnathus fasciatus cultured in Korea. These results indicate that various antibiotics have been being used before trading without measures in the market of asian ornamental fishes, providing high risks for the emergence of multi-drug resistant bacteria.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.52 no.2
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• pp.180-184
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• 2019

Aerobic bacteria, coliforms, Escherichia coli, and pathogenic bacteria were investigated in laver Porphyra sp. samples from various regions of Korea. The mean bacterial counts were $6.9{\pm}0.87log\;CFU/g$ (range 4.0 to 7.7) log CFU/g in dried laver, $2.83{\pm}4.36log\;CFU/g$ in roasted laver, and $4.93{\pm}1.43log\;CFU/g$ in seasoned laver. Coliforms were most abundant (mean count: $2.1{\pm}1.01log\;CFU/g$) in dried laver. No pathogenic bacteria, including Staphylococcus aureus, Salmonella spp. Vibrio parahaemolyticus, or Listeria monocytogenes, were detected in any of the samples. Aerobic microorganisms were the most diverse microorganisms in dried laver. Staphylococcus spp. were predominant, but S. aureus was not detected. Standardization of laver production is necessary to ensure a hygienic product because laver products are often ingested without heating or cooking, and the production process is simple.

• Journal of fish pathology
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• v.31 no.1
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• pp.41-48
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• 2018

The utility of Bacillus spp. organisms for reduction of dissolved hydrogen sulfide ($H_2S$) in white leg shrimp (Litopenaeus vannamei) culture was tested with different combinations of Bacillus spp. microorganisms: combination A (B. subtilis + B. licheniformis); combination B (B. licheniformis + B. amyloliquefaciens); combination C (B. subtilis + B. licheniformis + B. amyloliquefaciens). Of these 3 combinations, C was effective in few hours after addition whereas B needed longer time to be effective. The $H_2S-reducing$ effect of combination C was dependent on the amount of microorganisms added to $H_2S-containing$ test solution. Exposure of white leg shrimp to $H_2S$ at 8 mg/L for 7 days led to survival of 80% and 1 mg/L for 14 days it was 82.5%. The survival rate was 97.5% when combination C was simultaneously added to shrimp tanks during $H_2S$ exposure at 1 mg/L for 14 days. It was demonstrated that combination C microorganisms (B. subtilis + B. licheniformis + B. amyloliquefaciens) can reduce dissolved $H_2S$ concentrations, and this effect can be utilized to protect white leg shrimp from $H_2S$ toxicity.