Hee-Mock Oh

Publications (98)220.92 Total impact

• Article: NOVEL APPROACH FOR THE DEVELOPMENT OF AXENIC MICROALGAL CULTURES FROM ENVIRONMENTAL SAMPLES

  Dae-Hyun Cho, Rishiram Ramanan, Byung-Hyuk Kim, Jimin Lee, So-Ra Kim, Chan Yoo, Gang-Guk Choi, Hee-Mock Oh, Hee-Sik Kim
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  ABSTRACT: We demonstrate a comprehensive approach for development of axenic cultures of microalgae from environmental samples. A combination of Ultrasonication, Fluorescence Activated Cell Sorting (FACS) and Micropicking was used in this study to isolate axenic cultures of Chlorella vulgaris and Chlorella sorokiniana from swine wastewater, and Scenedesmus sp. YC001 from an open pond respectively. Ultrasonication was employed to disperse microorganisms attached to microalgae, which reduced the bacterial population by 70% followed by cell sorting which yielded 99.5% pure microalgal strains. The strains were rendered axenic by Micropicking, which is described first in this study, and were tested for purity in both solid and liquid medium under different trophic states. Denaturing Gradient Gel Electrophoresis (DGGE) of 16S rRNA gene confirmed the absence of even unculturable bacteria whereas fluorescence microscopy and Scanning Electron Microscopy (SEM) further confirmed the axenicity. This is the most comprehensive approach developed till date for obtaining axenic microalgal strains and the use of antibiotics and repetitive sub-culturing, which have their own pitfalls, are not employed.
  Journal of Phycology 03/2013; · 2.07 Impact Factor
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  Available from: Long Jin

  Article: Aquihabitans daechungensis gen. nov., sp. nov., a novel actinobacterium isolated from Daechung Reservoir.

  Long Jin, Hangsak Huy, Kwang Kyu Kim, Hyung-Gwan Lee, Hee-Sik Kim, Chi-Yong Ahn, Hee-Mock Oh
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  ABSTRACT: A novel Gram-positive bacterium, strain CH22-21(T), was isolated from a water sample taken from Daechung Reservoir, Republic of Korea, during the late-blooming period of cyanobacteria. The cells of strain CH22-21(T) were short rods and non-motile with cilia, and formed creamy-white colonies on a half-strength modified R2A agar. The chemotaxonomic results showed menaquinone MK-9(H(6)) as the predominant respiratory menaquinone, diphosphatidylglycerol (DPG), phosphatidylinositol (PI), and phosphatidylinositolmannoside (PIM) as major polar lipids, 16 : 1 ω5c, 16 : 0, 17 : 1 ω8c, and 18 : 1 ω9c as the major fatty acids, and a DNA G+C content of 71.8 mol%. A phylogenetic analysis based on 16S rRNA gene sequencing indicated that the strain formed a separate lineage within the order Acidimicrobiales, showing similarity values under 92.3 % with their closest phylogenetic neighbours. The combined genotypic and phenotypic data showed that strain CH22-21(T) could be distinguished from all genera within the order Acidimicrobiales and represented a novel genus, Aquihabitans gen. nov., with the name Aquihabitans daechungensis sp. nov., in the family Iamiaceae. The type strain is CH22-21(T) (=KCTC 19849(T) =JCM 17787(T)).
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 02/2013; · 2.11 Impact Factor
• Article: Lipid droplet synthesis is limited by acetate availability in starchless mutant of Chlamydomonas reinhardtii.

  Rishiram Ramanan, Byung-Hyuk Kim, Dae-Hyun Cho, So-Ra Ko, Hee-Mock Oh, Hee-Sik Kim
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  ABSTRACT: Phenotypic and genotypic changes in Chlamydomonas reinhardtii BafJ5, a starchless mutant, with respect to lipid metabolism was studied in different trophic states under nitrogen (N) sufficient and limited conditions. Interestingly, cellular lipid content increased linearly with input acetate concentration with highest lipid content (∼42%) under nitrogen limitation and mixotrophic state. RT-qPCR studies indicate that key fatty acid biosynthesis genes are down-regulated under N limitation but not under mixotrophic state, whereas, ACS2, encoding Acetyl-CoA synthetase, and DGTT4, encoding Diacylglycerol O-acyltransferase, are up-regulated under all conditions. These results collectively indicate that acetate is the limiting factor and central molecule in lipid droplet synthesis. The study also provides further evidence of the presence of a chloroplast pathway for triacylglycerol synthesis in microalgae.
  FEBS letters 01/2013; · 3.54 Impact Factor
• Article: Increased microalgae growth and nutrient removal using balanced N:p ratio in wastewater.

  Seung-Hoon Lee, Chi-Yong Ahn, Beom-Ho Jo, Sang-Ah Lee, Ji-Yeon Park, Kwang-Guk An, Hee-Mock Oh
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  ABSTRACT: Microalgal cultivation using wastewater is now regarded as essential for biodiesel production, as two goals can be achieved simultaneously; that is, nutrient removal efficiency and biomass production. Therefore, this study examined the effects of carbon sources, the N:P ratio, and the hydraulic retention time (HRT) to identify the optimal conditions for nutrient removal efficiency and biomass production. The effluent from a 2nd lagoon was used to cultivate microalgae. Whereas the algal species diversity and lipid content increased with a longer HRT, the algal biomass productivity decreased. Different carbon sources also affected the algal species composition. Diatoms were dominant with an increased pH when bicarbonate was supplied. However, 2% CO2 gas led to a lower pH and the dominance of filamentous green algae with a much lower biomass productivity. Among the experiments, the highest chlorophyll-a concentration and lipid productivity were obtained with the addition of phosphate up to 0.5 mg/l P, since phosphorus was in short supply compared with nitrogen. The N and P removal efficiencies were also higher with a balanced N:P ratio, based on the addition of phosphate. Thus, optimizing the N:P ratio for the dominant algae could be critical in attaining higher algal growth, lipid productivity, and nutrient removal efficiency.
  Journal of Microbiology and Biotechnology 01/2013; 23(1):92-8. · 1.38 Impact Factor
• Article: Multi-level stressor analysis from the DNA/biochemical level to community levels in an urban stream and integrative health response (IHR) assessments.

  Jae Hoon Lee, Joon Ha Kim, Hee-Mock Oh, Kwang-Guk An
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  ABSTRACT: The objectives of this study were to identify multi-level stressors at the DNA/biochemical level to the community level in fish in an urban stream and to develop an integrative health response (IHR) model for ecological health diagnosis. A pristine control site (S (c) ) and an impacted site (S (i) ) were selected from among seven pre-screened sites studied over seven years. Various chemical analyses indicated that nutrient enrichment (Nitrogen, Phosphorus) and organic pollution were significantly greater (t > 8.783, p < 0.01) at the S (i) site compared to the S (c) site. Single-cell gel electrophoresis (comet assays) of DNA-level impairment indicated significantly (t = 5.678, p < 0.01) greater tail intensity, expressed as % tail-DNA, at the S (i) site and genotoxic responses were detected in the downstream reach. Ethoxyresorufin-O-deethylase (EROD) assays, as a physiological bioindicator, were 2.8-fold higher (p < 0.05, NK-test after ANOVA) at the S (i) site. Tissue analysis using a necropsy-based health assessment index (NHAI) showed distinct internal organ disorders in three tissues, i.e., liver, kidney, and gill, at the S (i) site. Population-level analysis using the sentinel species Zacco platypus showed that the regression coefficient (b) was 3.012 for the S (i) site and 2.915 for the S (c) site, indicating population skewness in the downstream reach. Community-level health was impaired at the S (i) site based on an index of biological integrity (IBI), and physical habitat modifications were identified by a qualitative habitat evaluation index (QHEI). Overall, the model values for the integrative health response (IHR), developed using the star plot approach, were 3.22 (80.5%) at the S (c) site and 0.74 (18.5%) at the S (i) site, indicating that, overall, ecological health impairments were evident in the urban reach. Our study was based on multi-level approaches using biological organization and the results suggest that there is a pivotal point of linkage between mechanistic understanding and real ecological consequences of environmental stressors.
  Journal of Environmental Science and Health Part A Toxic/Hazardous Substances & Environmental Engineering 01/2013; 48(2):211-22.
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  Available from: Long Jin

  Article: Geodermatophilus soli sp. nov. and Geodermatophilus terrae sp. nov., two novel actinobacteria isolated from grass soil.

  Long Jin, Hyung-Gwan Lee, Hee-Sik Kim, Chi-Yong Ahn, Hee-Mock Oh
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  ABSTRACT: Two strains, PB34(T) and PB261(T), were isolated from grass soil sampled in Daejeon, Republic of Korea. Comparative 16S rRNA gene sequence studies showed the two bacteria to be clearly affiliated with Actinobacteria and most closely related to the genus Geodermatophilus showing 16S rRNA gene sequence similarities to the type strains of Geodermatophilus species of 95.0% - 96.3% and sharing a 98.5% similarity value between the two strains. The two strains were Gram-positive, aerobic, motile, and rod-shaped bacteria. The peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. The predominant menaquinones were MK-9(H(4)) and MK-9(H(0)). The major fatty acids were C(15 : 0) iso, C(16 : 0) iso, C(17 : 0) iso, and summed feature 3 (C(16 : 1) ω7c and/or C(16 : 1) ω6c) for strain PB34(T), and C(14 : 0) iso, C(15 : 0) iso, C(16 : 0) iso, and C(16 : 0) for strain PB261(T). The G+C contents of the genomic DNA of strains PB34(T) and PB261(T) were 73.2 mol% and 74.1 mol%, respectively. Thus, based on the polyphasic evidence, it is proposed that strains PB34(T) and PB261(T) belong to two novel species, for which the names Geodermatophilus soli sp. nov. (type strain PB34(T) = KCTC 19880(T) = JCM 17785(T)) and Geodermatophilus terrae sp. nov. (type strain PB261(T) = KCTC 19881(T) = JCM 17786(T)) are proposed.
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 12/2012; · 2.11 Impact Factor
• Article: Lipid droplet synthesis is limited by acetate availability in starchless mutant of Chlamydomonas reinhardtii

  Rishiram Ramanan, Byung-Hyuk Kim, Dae-Hyun Cho, So-Ra Ko, Hee-Mock Oh, Hee-Sik Kim
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  ABSTRACT: Phenotypic and genotypic changes in Chlamydomonas reinhardtii BafJ5, a starchless mutant, with respect to lipid metabolism was studied in different trophic states under nitrogen (N) sufficient and limited conditions. Interestingly, cellular lipid content increased linearly with input acetate concentration with highest lipid content (~42%) under nitrogen limitation and mixotrophic state. RTqPCR studies indicate that key fatty acid biosynthesis genes are down-regulated under N limitation but not under mixotrophic state, whereas, ACS2, encoding Acetyl-CoA synthetase, and DGTT4, encoding Diacylglycerol O-acyltransferase, are up-regulated under all conditions. These results collectively indicate that acetate is the limiting factor and central molecule in lipid droplet synthesis. The study also provides further evidence of the presence of a chloroplast pathway for triacylglycerol synthesis in microalgae.
  FEBS Letters 12/2012; · 3.54 Impact Factor
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  Available from: Long Jin

  Article: Caulobacter daechungensis sp. nov., a stalked bacterium isolated from a eutrophic reservoir.

  Long Jin, Hyung-Gwan Lee, Hee-Sik Kim, Chi-Yong Ahn, Hee-Mock Oh
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  ABSTRACT: A Gram-negative, aerobic, nonspore-forming, motile with a single polar flagellum or non-motile (stalked one), and straight or rod-shaped bacterium, H-E3-2(T), was isolated from a water sample taken from Daechung Reservoir, Republic of Korea, during the late-blooming period of cyanobacteria. Comparative 16S rRNA gene sequence studies showed the isolate had a clear affiliation with Alphaproteobacteria and the closest relatedness to C. fusiformis ATCC 15257(T) and Caulobacter mirabilis LMG 24261(T) showing 97.6% and 97.3% 16S rRNA gene sequence similarity, respectively, and 95.3 - 96.3% to all other species of the genus Caulobacter. The predominant ubiquinone was Q-10. The major fatty acids were summed feature 8 (C(18:1) ω6c and/or C(18:1) ω7c) and C(16:0). The G+C content of the genomic DNA of strain H-E3-2(T) was 64.7 mol%. DNA-DNA hybridization values of strain H-E3-2(T) with C. fusiformis ATCC 15257(T) and Caulobacter mirabilis LMG 24261(T) were 21.2 and 19.7%, respectively. Thus, based on the polyphasic evidence, it is proposed that strain H-E3-2(T) is a novel species in the genus Caulobacter, for which the name Caulobacter daechungensis sp. nov. is proposed. The type strain is H-E3-2(T) (KCTC 32211(T) =JCM 18689(T)).
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 12/2012; · 2.11 Impact Factor
• Article: Microalgae-associated bacteria play a key role in the flocculation of Chlorella vulgaris.

  Jimin Lee, Dae-Hyun Cho, Rishiram Ramanan, Byung-Hyuk Kim, Hee-Mock Oh, Hee-Sik Kim
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  ABSTRACT: Flocculation is most preferred method for harvesting microalgae, however, the role of bacteria in microalgal flocculation process is still unknown. This study proves that bacteria play a profound role in flocculating by increasing the floc size resulting in sedimentation of microalgae. A flocculating activity of 94% was achieved with xenic Chlorella vulgaris culture as compared to 2% achieved with axenic culture. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene of xenic C. vulgaris culture revealed the presence of Flavobacterium sp., Terrimonas sp., Sphingobacterium sp., Rhizobium sp. and Hyphomonas sp. as microalgae-associated bacteria. However when Flavobacterium, Terrimonas, Sphingobacterium were eliminated by fluorescence activated cell sorter (FACS), flocculating activity reduced to 3%. Further studies with cell free extracts also suggest that bacterial extracellular substances might also have a role in enhancing flocculation. We conclude that the collective presence of certain bacteria is the determining factor in flocculation of C. vulgaris.
  Bioresource technology 12/2012; 131C:195-201. · 4.25 Impact Factor
• Article: Microalgae-associated bacteria play a key role in the flocculation of Chlorella vulgaris

  Jimin Lee, Dae-Hyun Cho, Rishiram Ramanan, Byung-Hyuk Kim, Hee-Mock Oh, Hee-Sik Kim
  Bioresource Technology 11/2012; · 4.98 Impact Factor
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  Article: Belnapia soli sp. nov., a novel proteobacterium isolated from grass soil.

  Long Jin, Hangsak Huy, Hyung-Gwan Lee, So-Ra Ko, Chi-Yong Ahn, Hee-Mock Oh
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  ABSTRACT: A Gram-negative, aerobic, non-motile, non-spore-forming, cocci-shaped, red-pigmented bacterium, designated strain PB-K8(T), was isolated from grass soil sampled in Daejeon, Republic of Korea. Comparative 16S rRNA gene sequence studies showed the isolate was clearly affiliated with the class Alphaproteobacteria, and most closely related to Belnapia moabensis DSM 16746(T) and Belnapia rosea DSM 23312(T), showing a 16S rRNA gene sequence similarity to the type strains of each species of 98.4 % and 97.2 %, respectively. The cells of strain PB-K8(T) formed red colonies on an R2A agar, contained Q-9 as the predominant ubiquinone, and included summed feature 3 (C(16 : 1) ω7c / C(16 : 1) ω6c), C(16 : 0), summed feature 8 (C(18 : 1) ω7c / C(18 : 1) ω6c), C(18 : 1) 2-OH and C(19 : 0) cyclo ω8c as the major fatty acids. The G+C content of the genomic DNA of strain PB-K8(T) was 72.1 mol%. Thus, the combined genotypic and phenotypic data supported the conclusion that strain PB-K8(T) represents a novel species of the genus Belnapia, for which the name Belnapia soli sp. nov. is proposed. The type strain is PB-K8(T) (=KCTC 23765(T) =JCM 18033(T)).
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 09/2012; · 2.11 Impact Factor
• Article: Ettlia sp. YC001 showing high growth rate and lipid content under high CO(2).

  Chan Yoo, Gang-Guk Choi, Sun-Chang Kim, Hee-Mock Oh
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  ABSTRACT: Over 100 green-colored colonies were isolated from environmental samples when cultivating on a BG11 agar medium, and 4 strains showing different morphologies were selected based on light microscopic observation. Among these strains, the microalgal species with the highest growth rate under 10% CO(2) was identified as Ettlia sp. YC001 using an 18S rDNA-based phylogenetic analysis and morphological comparison. The highest cell density of 3.10g/L (based on dry cell weight) and biomass productivity of 0.19g/L/d were obtained under 5% CO(2) after 16days. The lipid content and productivity were also up to 42% of the dry cell weight and 80.0mg/L/d, respectively. The color of the Ettlia sp. YC001 culture changed from green to red after a month due to the accumulation of certain carotenoids. Therefore, it would seem that Ettlia sp. YC001 is appropriate for mitigating CO(2) due to its high biomass productivity, and a suitable candidate for producing biodiesel and high-value products.
  Bioresource technology 09/2012; 127C:482-488. · 4.25 Impact Factor
• Article: Recent trends in development of biosensors for detection of microcystin.

  Shweta Singh, Ankita Srivastava, Hee-Mock Oh, Chi-Yong Ahn, Gang-Guk Choi, Ravi Kumar Asthana
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  ABSTRACT: Increased cyanobacterial blooms, a source of cyanotoxins are linked with climate change and eutrophication in aquatic bodies, a major concern worldwide. Microcystins are potently hepatotoxic, nephrotoxic as well as carcinogenic. Thus microcystins are threat to tourism, agriculture and animal's health. However, there is a still lacuna in the knowledge of regulation of microcystins production. Presence of toxic and non-toxic cyanobacterial strains together and occurrence of various microcystin variants in aquatic bodies compounded the problem. Although several analytical techniques for microcystin detection such as bioassay, ELISA, HPLC and LC-MS etc. have been already prevalent, the development of biosensors offered rapid and accurate detection, high reproducibility and portability. Sequencing of Microcystis spp., opened the new vistas towards the development of biosensor at molecular and genetic level. This review incorporates the current trends in the development of biosensors for microcystin detection in the light of state-of-the-art techniques.
  Toxicon 06/2012; 60(5):878-94. · 2.51 Impact Factor
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  Available from: Rishiram Ramanan

  Article: Simple, Rapid and Cost-Effective Method for High Quality Nucleic Acids Extraction from Different Strains of Botryococcus braunii

  Byung-Hyuk Kim, Rishiram Ramanan, Dae-Hyun Cho, Gang-Guk Choi, Hyun-Joon La, Chi-Yong Ahn, Hee-Mock Oh, Hee-Sik Kim
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  ABSTRACT: This study deals with an effective nucleic acids extraction method from various strains of Botryococcus braunii which possesses an extensive extracellular matrix. A method combining freeze/thaw and bead-beating with heterogeneous diameter of silica/zirconia beads was optimized to isolate DNA and RNA from microalgae, especially from B. braunii. Eukaryotic Microalgal Nucleic Acids Extraction (EMNE) method developed in this study showed at least 300 times higher DNA yield in all strains of B. braunii with high integrity and 50 times reduced working volume compared to commercially available DNA extraction kits. High quality RNA was also extracted using this method and more than two times the yield compared to existing methods. Real-time experiments confirmed the quality and quantity of the input DNA and RNA extracted using EMNE method. The method was also applied to other eukaryotic microalgae, such as diatoms, Chlamydomonas sp., Chlorella sp., and Scenedesmus sp. resulting in higher efficiencies. Cost-effectiveness analysis of DNA extraction by various methods revealed that EMNE method was superior to commercial kits and other reported methods by >15%. This method would immensely contribute to area of microalgal genomics.
  PLoS ONE 05/2012; 7(5-e37770):1-9. · 4.09 Impact Factor
• Article: Growth and amino acid contents ofSpirulina platensis with different nitrogen sources

  Aeran Choi, Song-Gun Kim, Byung-Dae Yoon, Hee-Mock Oh
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  ABSTRACT: The growth and amino acid contents of the cyanobacterium,Spirulina platensis strain NIES 46, were investigated using ammonium, nitrate, nitrite, or urea as the sole nitrogen source in a batch culture. Chlorophylla concentration was highest at 2,096 μg/L in the nitrate group after 10 days of cultivation, while the dry weight ofS. platensis was highest at 4.5 g/L in the ammonium group after 30 days of cultivation. The total amino acid content was highest at 174 mg/g dry weight ofS. platensis in the urea group at the end of the cultivation period, yet the amino acid patterns forS. platensis were similar for all the experimental groups. Therefore, it seemed that the growth and amino acid composition ofS. platensis varied depending on the type of nitrogen sources, while the amino acid patterns were not changed. Also, the most efficient harvesting time forS. platensis seemed to be approximately 10 days after cultivation.
  Biotechnology and Bioprocess Engineering 04/2012; 8(6):368-372. · 1.28 Impact Factor
• Article: Effect of nitrogen limitation on oleic acid biosynthesis in Botryococcus braunii

  Gang-Guk Choi, Byung-Hyuk Kim, Chi-Yong Ahn, Hee-Mock Oh
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  ABSTRACT: The influence of nitrogen (N) deficiency on the cell growth and intracellular lipid production of the alga Botryococcus braunii UTEX 572 was investigated. Biomass concentration and lipid content of B. braunii cultivated in modified Chu-13 medium containing 0.04, 0.37, and 3.66mM nitrate were 0.23–0.38g L−1 and 36–63% of dry cell weight, respectively. The specific growth rate of B. braunii reached a constant of 0.185day−1 during cultivation with an initial nitrate feed of 3.66mM. The maximum lipid content of B. braunii was 63% with 0.04mM nitrate. However, the maximum lipid productivity of 0.019g L−1day−1 was achieved with 0.37mM nitrate. The level of oleic acid, an important component of biodiesel, was higher at 86% of the total fatty acids under N-limited conditions (0.04mM nitrate) compared to 69% under N-sufficient conditions (3.66mM nitrate). Furthermore, expression of the stearoyl-ACP desaturase gene (sad) encoding a stearoyl-ACP desaturase involved in the synthesis of oleic acid was 2.6-fold higher under N-limited conditions than under N-sufficient conditions. KeywordsBiodiesel– Botryococcus braunii –Nitrogen limitation–Oleic acid– sad –Stearoyl-ACP desaturase
  Journal of Applied Phycology 04/2012; 23(6):1031-1037. · 2.41 Impact Factor
• Article: Adsorption of turbid materials by the cyanobacterium Phormidium parchydematicum

  Choong-Jae Kim, Yun-Ho Jung, Chi-Yong Ahn, Young-Ki Lee, Hee-Mock Oh
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  ABSTRACT: The present study investigated the adsorption of turbid materials such as clays, by microalgae. Among six tested microalgae, including Chlorophyceae and Cyanophyceae, a cyanobacterium, Phormidium parchydematicum strain KCTC 10851BP, and unicellular alga, Chlorella vulgaris strain UTEX 265, showed a higher turbidity-removal efficiency (TRE) of 99% and 93%, respectively, for clay-containing water after 24h, which was much higher than the 36% for the control. The TREs of all the treatments were >95% after 24h, except for the treatment with a lower algal density and optical density (OD) = 0.1. Phormidium parchydematicum demonstrated a slightly higher TRE than a polyaluminum chloride coagulant (Al13(OH)28Cl9SO4) for a turbid field water. Scanning electron microscope (SEM) observations revealed a dense adsorption of clay particles to the surface of P. parchydematicum. Thus, it would appear that P. parchydematicum and C. vulgaris can be used for clay removal in turbid water by sedimentation through microalgae–clay flocculation. Keywords Chlorella vulgaris -Clay-Cyanobacteria- Phormidium parchydematicum -Turbid material
  Journal of Applied Phycology 04/2012; 22(2):181-186. · 2.41 Impact Factor
• Article: Comparison of sampling and analytical methods for monitoring of cyanobacteria-dominated surface waters

  Chi-Yong Ahn, Seung-Hyun Joung, Chan-Sun Park, Hee-Sik Kim, Byung-Dae Yoon, Hee-Mock Oh
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  ABSTRACT: Different sampling methods can often produce different results when cyanobacterial blooms are intense and there are surface scums. Accordingly, five commonly used sampling methods and four sampling times were compared for monitoring of Oscillatoria and Microcystis populations. The different methods and times led to significantly different results for cyanobacterial biomass and its variance. Sampling methods that tended to be more specific to surface scums resulted in much higher and more variable measurements. Although sampling later in the day greatly reduced variances, the measured biomass was much lower than at earlier times of day, which was attributed to cyanobacterial downward migration in the afternoon. These trends were common for Oscillatoria and Microcystis. In order to overcome such problems, the median and median absolute deviation (MAD) were proposed, instead of the arithmetic mean and standard deviation (SD), for presenting a central tendency of measured values. Although the mean±SD has been widely used to express a central tendency, it is too sensitive to outlying values that are very common during cyanobacterial blooms. The large differences in the mean values between the sampling methods and times were reduced by using the median values. Furthermore, the median±MAD revealed the real data distribution more effectively.
  Hydrobiologia 04/2012; 596(1):413-421. · 1.78 Impact Factor
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  Article: Direct colorimetric assay of microcystin using protein phosphatase

  Hee-Mock Oh, Seog June Lee, Jee-Hwan Kim, Chan-Sun Park, Byung-Dae Yoon
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  ABSTRACT: A new direct colorimetric assay of microcystin in water and algal samples is proposed consisting of two procedures as follows: 1) the elimination of phosphorus in the sample and concentration of microcystin using a C18 cartridge, 2) the detection of the released phosphorus by the ascorbic acid method and determination of protein phosphatase (PP) inhibition by microcystin. The optimum amounts of phosphorylase α and PP-1 in 50 μL concentrated sample were 50 μg/50 μL buffer and 1.0 unit/50 μL buffer, respectively, for the best assay. The pH for the maximum activity of PP-1 was 8. The minimum detectable concentration for this method was about 0.02 μg/L, which is sufficient to meet the proposed guideline level of 1 μg microcystin/L in drinking water. Consequently, it would seem that the proposed direct colorimetric assay using PP is a rapid, easy, and convenient method for the detection of microcystin in water and algal samples.
  Biotechnology and Bioprocess Engineering 04/2012; 5(6):418-421. · 1.28 Impact Factor
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  Article: Arenimonas daechungensis sp. nov., isolated from the sediment of a eutrophic reservoir.

  Hangsak Huy, Long Jin, Young-Ki Lee, Keun Chul Lee, Jung-Sook Lee, Jung-Hoon Yoon, Chi-Yong Ahn, Hee-Mock Oh
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  ABSTRACT: A Gram-negative, motile, non-spore-forming, and rod-shaped bacterial strain, CH15-1(T), was isolated from a sediment sample taken from Daechung Reservoir, South Korea, during the late-blooming period of cyanobacteria. A phylogenetic analysis based on 16S rRNA gene sequences confirmed that strain CH15-1(T) belongs to the genus Arenimonas with the similarity range from 92.6-97.4 % and is closely related to Arenimonas oryziterrae YC6267(T) (97.4%), Arenimonas composti TR7-09(T) (95.4%),Arenimonas metalli CF5-1(T) (94.7 %), Arenimonas malthae CC-JY-1(T) (94.6%), and Arenimonas donghaensis HO3-R19(T) (92.6%). However, the DNA-DNA hybridization between strain CH15-1(T) and the closest strain, Arenimonas oryziterrae YC6267(T), was 8.9-12.9%. The DNA G+C content was 63.9 mol%. Strain CH15-1(T) included Q-8 as the major ubiquinone, and phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and phosphatidylmonomethylethanolamine as the major polar lipids. The major fatty acids were iso-C(15:0), iso-C(16:0), iso-C(14:0), iso-C(11:0) 3-OH, and iso-C(17:0) (>5%). Therefore, the combined genotypic and phenotypic data supported that strain CH15-1(T) represents a novel species in the genus Arenimonas, for which the name Arenimonas daechungensis sp. nov. is proposed. The type strain is CH15-1(T) (= KCTC 23553(T) = DMS 24763(T)).
  INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 04/2012; · 2.11 Impact Factor