• Korean Journal of Microbiology
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• v.49 no.4
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• pp.424-428
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• 2013

To identify risk factors for Legionella contamination, water quality variables routinely measured in examination of natural and city waters were meta-analyzed for significance of correlation to Legionella incidences. For evaluation of abundance of Escherichia coli as a risk factor, which is currently used as an indicator of Legionella contamination in an official guideline in Korea, odds ratio (OR) of above-cutoff total coliform counts for Legionella presence/absence was used as the effect size in the meta-analysis. The OR was estimated as 1.05 (0.36-3.12, 95% CI), and the probability of having identical odds reached 0.92. Also, ORs from individual studies showed significant heterogeneity (P=0.008), which contributed to 63% of total variance of the ORs. In the case of heterotrophic plate count (HPC), the OR for Legionella presence/absence was 2.72 (2.04-3.63) with highly significant deviation from identical odds (P<0.0001). ORs from different studies were seemingly homogeneous ($Q_{df=8}$=12.7, P=0.12). Turbidity and concentrations of chlorine, iron ion and cupper ion were other routine variables that could be considered as risk factors. However, statistical measures from different studies were not uniform enough to develop an appropriate effect size while the number of studies reporting the variables was also small (3-5). In conclusion, HPC appeared to be appropriate as indicator of Legionella contamination, rather than fecal bacteria contamination. HPC may imply abundance of habitats (amoebas and biofilms) of Legionella in water. This result warrants further studies for standardizing protocols and cutoff values to infer Legionella risks from HPC.

• Korean Journal of Microbiology
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• v.25 no.4
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• pp.318-327
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• 1987

Taxonomic composition and diversity were wxamined by statistical analysis for bacterial communities in surface waters of the Sudong Stream, a tributary of North Han River. For total 282 isolates, Flavobacterium, Aeromonas and Enterobacteriaceae was identified by the deterministic schemes as a major group above 50% of total isolates in all sampling sites. Morphological, biochemical and physiological characteristics were numerically analyzed for bacterial isolates from each site and clustered into 15-28 groups. Not all statistically clustered groups were identical to the groups derived from deterministic identification. Especially, consistent relationship was not found in dendrograms for the groups with each a single strain which gas peculiar sugar-degrading activity. At a level of 80% similarity, bacterial diversity (H) was ranged as 2.37-3.14, and it was suggested that the research area was oligotrophic-mesotrophic status. Regional distribution of bacterial community was most heterogeneous at the site where large input of allochthonous materials or bacteria were occurred. And that was the significant factor for the compositions of bacterial communities in the Sudong stream.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.751-760
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• 2021

This study investigated the changes in water quality parameters and microbial colonies when ozone was applied to a semi-recirculating aquaculture system (semi-RAS) for the olive flounder Paralichthys olivaceus (500 g in average weight). Concentrations of ozone-produced oxidants (OPO) in rearing tanks were maintained at 0, 0.014, 0.025 mg/L as Cl₂ for 26 days. Except total ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, phosphate phosphorus, chemical oxygen demand, and total suspended solids decreased significantly with increasing OPO concentration in daily and weekly monitoring (P<0.05). Colony forming unit (CFU) counts of heterotrophic marine bacteria decreased in an OPO concentration-dependent manner. Overall reduction rates of microbial colonies in the treatments were 80% higher than those of the control (P<0.05). During the experiment, the OPO concentration-driven ozonation was reliably practiced without any adverse effects on the animals cultured in semi-RAS. Considering the biohazard, operating cost, and stability of ozonation, an OPO concentration of 0.014 mg/L would be sufficient to control water quality parameters and microbial colonies in a semi-RAS.

• Korean Journal of Environmental Biology
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• v.17 no.4
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• pp.439-448
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• 1999

To investigate the population dynamics and survival of Genus Vibrio, population densities of aerobic saprophytic bacteria and Vibrio groups were measured 4 times in the intertidal waters of the Yellow Sea near Kunsan from November, 1997 to June, 1998. The distribution of heterotrophic bacteria during the survey periods by plate count and direct count method ranged from 1.2$\pm$0.6$\times$10$^3$~2.0$\pm$1.5$\times$10$^4$CFU ml­$^1$and from 6.0$\pm$4.0$\times$10$^{5}$ ~1.9$\pm$1.5$\times$10$^{7}$ cells ml­$^1$, respectively. Vibrio groups were distributed in the range of 1$\times$10 and 6$\pm$2.2$\times$10$^2$CFU ml­$^1$. The proportion of Vibrio groups to total heterotrophic bacteria was between 0.1 and 6% during the survey periods. A total of 51 isolates was obtained from TCBS agar plates and identified to species level by Biolog Identification System$^{TM}$. As a result, dominant genera were V, mediterranei, V aitguillarum, tr metschnikovii, and V. parahaemolyticus, and isolates were clustered into 26 groups based on the relatedness of average linkage clustering method at 70% level. As for the susceptibility of 51 isolates to 7 kinds of antibacterial agents (gentamicin, ampicillin, chlorarnphenicol, streptomycin, kanamycin, tetracycline, carbenicillin), 96% of isolates showed high resistance to more than one antibiotics and 65% of isolates contained a plasmid, of which size was observed greater than 12 kb, The number of cells of 3 tested strains (V. anguillarum, V. vulnificus, and V. metschnikovii) in filtered aged seawater decreased by approximately 1 to 5 orders of magnitude during 30-d incubation. In most cases, the numbers of cells decreased rapidly until day 3, then decreased slowly by day 30. The number of cells incubated at 15$^{\circ}C$ showed higher survival than those at 4$^{\circ}C$ and $25^{\circ}C$. These results may be considered for the basic supporting data in the risk assessment of vibriosis in summer.r.

• 한국해양학회지
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• v.30 no.5
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• pp.458-466
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• 1995

To clarify the role of protozooplankton in the microbial food web of Inchon coastal ecosystem, the grazing capacities and growth rates of heterotrophic flagellated (HFL) and ciliates were investigated. We measured the growth rates of bacteria, HFL, autotrophic flagellated (AFL) and ciliates using reverse flow (RF) filter set and obtained the clearance rates and ingestion rates of HFL and dilates by fluorescent labelled bacteria (FLB) method and isolation culture method from natural seawater of Inchon coastal area. The standing crops of bacteria, HFL, AFL and ciliates in this study area were 0.7∼1.5${\times}$10/SUP 6/ cells$.$ml/SUP -1/ 1,680∼2,180 cells$.$ml/SUP -1/, 1,090∼2,180 cells$.$ml, and 3,600∼5,700 cells$.$l/SUP -1/, respectively. The mean growth rates of bacteria, HFL, AFL and ciliates were 0.039 h/SUP -1/, 0.032∼0.033h/SUP -1/, 0.015∼ 0.025h/SUP -1/and 0.021h/SUP -1/, respectively. The growth rates of protozooplankton of Inchon coastal waters were relatively low. Mean grazing rate of HFL, AFL and ciliates were0.039 h/SUP -1/, 0.032∼0.033h/SUP -1/,0.015∼ 0.025h/SUP -1/and 0.021h/SUP -1/, respectively. The growth rates of protozooplankton of Inchon coastal waters were relatively low. Mean grazing rate of HFL on bacteria was 0.055h/SUP -1/. Mean grazing rates of ciliates on HFL was relatively high of 0.057 h/SUP -1/, while the grazing rate of ciliates on AFL was low of 0.019h/SUP -1/. The clearance rates and ingestion rates of HFL on bacteria were 3.6∼61.8nl$.$HFL$.$h/SUP -1/ and 6∼52 BAC. HFL$.$h/SUP -1/ respectively. FLB grazing experiment showed low values, while natural bacteria experiment showed high value meaning high grazing pressure on total bacteria. The clearance rates and ingestion rates of Tintinnopsis sp., dominant ciliates in Inchon coastal waters, were 3.2∼4.6 ul$.$CIL/SUP -1/$.$h/SUP -1/ and 5∼6 cells$.$CIL/SUP -1/$.$h/SUP -1/ respectively, showing higher values in the high tide than low tide. The ingestion rates of ciliates implies that ciliate took up 17∼20% of total nanoflagellates of Inchon coastal waters.

• Journal of Environmental Health Sciences
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• v.41 no.6
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• pp.397-404
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• 2015

Objectives: The aim of this study is to investigate microbial contamination in the school food service environment for the assessment of microbial food safety. Methods: We collected both swab samples from tables and desks and airborne bacterial samples from an elementary school (School A) and a high school (School B). Heterotrophic plate count, total coliform, Staphylococcus aureus, and Bacillus cereus were measured with selective media to quantify microbial concentration. PCR assay targeting 16S rRNA genes was performed to identify the strains of S. aureus and B. cereus isolated. In addition, we made a food service checklist for the locations to evaluate the food service environment. A Wilcoxon test was employed to examine the differences in microbial concentration between before lunchtime and afterwards. Results: Heterotrophic plate counts showed higher levels after-lunch compared to before-lunch at School B. However, levels of S. aureus were higher in the after-lunch period (p<0.05) in both classrooms and in the cafeteria in School A. B. cereus was only sparsely detected in School B. Several samples from food dining carts were found to be contaminated with bacteria, and facilities associated with food delivery were found to be vulnerable to bacterial contamination. Although microbial concentrations in the air showed little difference between before- and after-lunchtime in the cafeteria in School A, those in classrooms were greater after-lunchtime at both schools. Conclusion: Our results suggested that the microbial safety in schools after lunchtime of concern. Necessary preventive measures such as hygiene education for students and food handlers should be required to minimize microbial contamination during food service processes in schools.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.18 no.1
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• pp.57-62
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• 1985

The three tide pools of Kanagawagen Aburatsubo coast, Japan were studied for 5 months (June-October, 1991) to know the physicochemical factors and changes of the microflora, In the tide pools salinity was ${\simeq}35\%0$, temperature range was $14{\sim}32^{\circ}C$ and pH range was $7.4{\sim}8.9$. Particulate organic carbon (POC) was $255{\sim}3980\;{\mu}g-at/l$, and total phosphate-P was $1.0{\sim}27.0\;{\mu}g-at/l$. The numbers of suspended bacteria and heterotrophic bacteria on the algae were $10^4{\sim}10^7/ml$ and $10^6{\sim}10^8/g$, respectively. Bacterial flora isolated from the Samples were Acinetobacter spp., Moraxella spp., Flavobacterium spp. and Pseudomonas spp., While Acinetobacter spp. was predominant among them. T. japonicus occurred dominantly with densities of $2200{\sim}7000/l$ during $August{\sim}september$. During this period the sharp increases of the unicellular microalgae and the protozoans were observed. According to the experimental results (POC, total phosphate-P, numbers and composition of bacterial flora), T. japonicus seemed to inhabit the environment with high eutrophication and high variability.

• Ocean and Polar Research
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• v.34 no.2
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• pp.125-135
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• 2012

To evaluate the algicidal impact of a newly developed algicide thiazolidinedione derivative, TD49, on dinophyceae Akashiwo sanguinea in aquatic ecosystems, tentative culture experiments for the target species were conducted in small (SS), middle (MS), and large scale (LS) culture vessels. When TD49 was introduced at the final concentration of $2{\mu}M$ in SS and MS, as well as $1{\mu}M$ in LS, the abundance of A. sanguinea decreased significantly in all the treatments. On the other hand, total phytoplankton abundance, except A. sanguinea in the TD49 treatments, gradually increased with culture time, which implies that a cell destruction of A. sanguinea by TD49 is a major cause of the population growth by other phytoplankton species. Also, A. sanguinea was easily destroyed, which was likely to be a source of extracellular substances. In particular, a pH decrease was significant in the treatments than in the control, which indicates that the water in the treatments has been acidified, due to an increase in the heterotrophic metabolisms of bacteria and degradation of A. sanguinea cells. Our results indicate that the TD49 substance is the potential agents for the control of A. sanguinea in the enclosed and eutrophic water bodies.

• Korean Journal of Environmental Biology
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• v.18 no.3
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• pp.355-365
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• 2000

In order to study the relationship between water quality and phytoplankton standing crops, the authors investigated the physicochemical factors, phytoplankton standing crops and chlorophyll-a at two stations in the Daechung Reservoir during the period from May to November 1998. Nutrients (nitrite, nitrate, ammonia and phosphate) have gradually increased more than those of the previous reports. Concentrations of the total nitrogen, phosphorus, chlorophyll -a and transparency exceeded the standard value of eutrophication. It could be assumed that the eutrophication of the Daechung reservoir was caused by various pollutants. Chlorophyll-a concentration was under the influence of phytoplankton standing crops, but very tiny cell-sized blue-green algae were less important in regards to the chlorophyll-a. Except at station 1 from July to August, phytoplankton standing crops bloomed during the time of the survey. Spring phytoplankton blooms caused by nitrate and phosphate in the surface layer. High concentrations of the suspended solids in July and August were caused by an inflow of them due to heavy rains. Density of heterotrophic bacteria was high in August owing to the high water temperatures and the organic nutrients which were from the nearby reservoir.

• ALGAE
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• v.38 no.2
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• pp.111-126
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• 2023

Mixotrophic dinoflagellates act as primary producers, prey, and predators in marine planktonic food webs, whereas exclusively autotrophic dinoflagellates are primary producers and prey. Species of the dinoflagellate genus Scrippsiella are commonly found in marine ecosystems and sometimes cause harmful red tides. Among the 28 formally described Scrippsiella species, S. acuminata has been found to be mixotrophic and two unidentified species have been found to be mixotrophic. To determine whether the other species in this genus are similarly mixotrophic, the mixotrophic ability of S. donghaiensis SDGJ1703, S. lachrymosa SLBS1703, S. masanensis SSMS0908, S. plana SSSH1009A, and S. ramonii VGO1053 was explored using 15 potential prey items, including 2-㎛ fluorescently labeled microspheres (FLM) and heterotrophic bacteria (FLB), the cyanobacterium Synechococcus sp., and various microalgal prey species. The ability of S. acuminata to feed on FLM and FLB was also investigated. We found that S. donghaiensis, S. lachrymosa, S. masanensis, S. plana, and S. ramonii did not feed on any potential prey tested in this study, indicating a lack of mixotrophy. However, S. acuminata fed on both FLM and FLB, confirming its mixotrophic ability. These results lowered the proportion of mixotrophic species relative to the total number of tested Scrippsiella species for mixotrophy from 100% to 29-38%. Owing to its mixotrophic ability, S. acuminata occupies an ecological niche that is distinct from that of S. donghaiensis, S. lachrymosa, S. masanensis, S. plana, and S. ramonii.