• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.2
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• pp.212-219
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• 2016

The bioavailability of dissolved organic nitrogen (DON) by dominant species Chaetoceros debilis and Leptocylindrus danicus under dissolved inorganic nitrogen (DIN)-limited condition in the southwestern East Sea was conducted to assess the quantitative evaluation using growth kinetic experiment. Nitrogen sources were nitrate and ammonium as DIN, glycine and urea, which is portion component of DON in East Sea. Maximum specific growth rate (${\mu}_{max}$) and half-saturation constant ($K_s$) of C. debilis calculated from Monod equations were estimated to be $1.50day^{-1}$ and $1.62{\mu}M$ in nitrate, $1.13day^{-1}$ and $6.97{\mu}M$ in ammonium, $1.46day^{-1}$ and $3.36{\mu}M$ in glycine, $0.93day^{-1}$ and $0.55{\mu}M$ in urea, respectively. Also, L. danics was estimated to be $1.55day^{-1}$ and $5.21{\mu}M$ in nitrate, $1.57day^{-1}$ and $4.57{\mu}M$ in ammonium, $1.47day^{-1}$ and $3.80{\mu}M$ in glycine, $1.42day^{-1}$ and $1.94{\mu}M$ in urea, respectively. Both C. debilis and L. dancius have higher affinity of urea than DIN. The high affinity of urea was indicated that the dominant species were able to growth using urea under DIN-limited conditions. Thus, DON utilization of phytoplankton may be one of the important dominant strategy under DIN-limited environments such as southwestern East Sea.

• Clinical and Experimental Reproductive Medicine
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• v.23 no.3
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• pp.379-384
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• 1996

This study was undertaken to investigate the sister chromatid exchange (SCE) frequency and embryonic development after exposure to cryoprotectants and vitrification of mouse zygotes. Mouse IVF zygotes were cryopreserved by vitrification using vitrification solution, EFS40 (40% ethylene glycol, 30% Ficoll and 0.3 M sucrose in phosphate buffer saline containing 10% FBS). After mouse zygotes were exposed to EFS40 at $25^{\circ}C$ for 30 sec., they were immediately plunged into $LN_2$ or cultured for cryoprotectant toxicity test without freezing. The results obtained in these experiments were summarized as follows: After thawing, survival rates to the 2-cell stage of zygotes exposed to or vitrified in EFS 40 (98.5%, 95.2%) were not significantly difference compared with that of control (100%). However, the developmental rates upto blastocyst and hatching blastocyst in vitrified groups (66.7, 50.0%) were lower than those of control (93.9, 81.8%) or exposed group (94.0, 78.8%) (p<0.05). When the influence of vitrification and exposure to cryoprotectant on the in vitro development of mouse zygotes was assessed by the SCE frequency, the SCE frequency in exposed ($20.2{\pm}2.1$) to or vitrified embryos ($21.4{\pm}3.2$) was higher than that in control embryos ($16.8{\pm}1.5$). These results suggest that the frequency of SCE was increased after cryoprotectant exposure or Vitrification although developmental rates of zygotes upto blastocysts and /or hatching blastocysts were not afected by cryoprotectant.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.5
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• pp.445-456
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• 2001

In the 1990s, Cochlodinium polykikoides red tide has been annually occurred in the southern coast of Korea and caused the mass damage to the fisheries with a huge amount of economic loss. The present study was done to establish the biological foundation for the elucidation of the mechanism of C. polykikoiaes red tide. The growth response of C. polykikoides to physico-chemical factors such as temperature, salinity, pH, and light intensity were examined using axenic cultures to evaluate the relative importance of these factors on the dynamics of natural populations, It was found that the highest growth conditions were $25^{\circ}C,\;40\%_{\circ}$, pH 7.5, and 7,500 lux, respectively. The tolerable salinity range of growth was relatively wide at an optimum temperature and was reduced to a much narrower range at a sub-optimum temperature. These findings indicate that C. polykikoides is an eurythermal and euryhaline organism. The organism demanded higher light intensity and oceanic pH narrow in its growth. C. polykikoides utilize inorganic nutrients, such as nitrate and ammonium as N, and phosphate as P. The nutritional requirements of C. polykikoides were $40{\mu}M$ for nitrate, $50{\mu}M$ for ammonium, and $5{\mu}M$ for phosphate. The half saturation constant (Ks) for growth was $2.10{\mu}M$ for nitrate, $1.03{\mu}M$ for ammonium, and $0.57{\mu}M$ for phosphate. These values were comparatively smaller than those of other dinoflagellates reported previously. We confirmed that the organism is characterized as an eutrophic species. However, ammonium Ks value is smaller than that of other eutrophic species, This result indicates that C. polykikoides red tide may outbreak in the waters which eutrophication is in progress rather than eutrophicated waters. C. polykikoides preferred ammonium better than nitrate as a nitrogen source when in a growth stage, Therefore, our results indicate that ammonium is more important nutrient on the growth of the organism in comparison with other inorganic nutrients and C. polykikoides red tide is related with the increased ammonium concentration in the coastal waters.

• Korean Journal of Microbiology
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• v.51 no.4
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• pp.355-363
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• 2015

The present work quantified the growth of young biofilm in a model distribution system that was fed with chlorinated drinking water at a hydraulic retention time of 2 h. Bacterial biofilms grew on the surface of polyvinyl chloride (PVC) slides at a specific growth rate of $0.14{\pm}0.09day^{-1}$ for total bacteria and $0.16{\pm}0.08day^{-1}$ for heterotrophic bacteria, reaching $3.1{\times}10^4cells/cm^2$ and $6.6{\times}10^3CFU/cm^2$ after 10 days, respectively. The specific growth rates of biofilm-forming bacteria were found to be much higher than those of bulk-phase bacteria, suggesting that biofilm bacteria account for a major part of the bacterial production in this model system. Biofilm isolates exhibited characteristic kinetic properties, as determined by ${\mu}_{max}$ and $K_S$ values using the Monod model, in a defined growth medium containing various amounts of acetate. The lowest ${\mu}_{max}$ value was observed in bacterial species belonging to the genus Methylobacterium, and their slow growth seemed to confer high resistance to chlorine treatment (0.5 mg/L for 10 min). $K_S$ values (inversely related to substrate affinity) of Sphingomonas were two orders of magnitude lower for acetate carbon than those of other isolates. The Sphingomonas isolates may have obligate-oligotrophic characteristics, since the lower $K_S$ values allow them to thrive under nutrient-deficient conditions. These results provide a better understanding and control of multi-species bacterial biofilms that develop within days in a drinking water distribution system.