Showing papers by "Korean Ocean Research and Development Institute published in 2005"

Genomic blueprint of Hahella chejuensis, a marine microbe producing an algicidal agent

Abstract: Harmful algal blooms, caused by rapid growth and accumulation of certain microalgae in the ocean, pose considerable impacts on marine environments, aquatic industries and even public health. Here, we present the 7.2-megabase genome of the marine bacterium Hahella chejuensis including genes responsible for the biosynthesis of a pigment which has the lytic activity against a red-tide dinoflagellate. H.chejuensis is the first sequenced species in the Oceanospiralles clade, and sequence analysis revealed its distant relationship to the Pseudomonas group. The genome was well equipped with genes for basic metabolic capabilities and contained a large number of genes involved in regulation or transport as well as with characteristics as a marine heterotroph. Sequence analysis also revealed a multitude of genes of functional equivalence or of possible foreign origin. Functions encoded in the genomic islands include biosynthesis of exopolysacchrides, toxins, polyketides or non-ribosomal peptides, iron utilization, motility, type III protein secretion and pigmentation. Molecular structure of the algicidal pigment, which was determined through LC-ESI-MS/MS and NMR analyses, indicated that it is prodigiosin. In conclusion, our work provides new insights into mitigating algal blooms in addition to genetic make-up, physiology, biotic interactions and biological roles in the community of a marine bacterium.

Snow chemistry across Antarctica

Abstract: An updated compilation of published and new data of major-ion (Ca, Cl, K, Mg, Na, NO3, SO4) and methylsulfonate (MS) concentrations in snow from 520 Antarctic sites is provided by the national ITASE (International Trans-Antarctic Scientific Expedition) programmes of Australia, Brazil, China, Germany, Italy, Japan, Korea, New Zealand, Norway, the United Kingdom, the United States and the national Antarctic programme of Finland. The comparison shows that snow chemistry concentrations vary by up to four orders of magnitude across Antarctica and exhibit distinct geographical patterns. The Antarctic-wide comparison of glaciochemical records provides a unique opportunity to improve our understanding of the fundamental factors that ultimately control the chemistry of snow or ice samples. This paper aims to initiate data compilation and administration in order to provide a framework for facilitation of Antarctic-wide snow chemistry discussions across all ITASE nations and other contributing groups. The data are made available through the ITASE web page (http://www2.umaine.edu/itase/content/syngroups/snowchem.html) and will be updated with new data as they are provided. In addition, recommendations for future research efforts are summarized.

Deep flow field in the Japan/East Sea as deduced from direct current measurements

Abstract: The mean flows and variability in the abyssal Japan/East Sea are investigated on the basis of direct current observation data. The distribution of the mean flow vectors indicates relatively strong cyclonic circulations along the basin periphery and sluggish flows in the interior region. Strong mean flows of faster than 6.0 cm s−1 are found at the western edge in the Yamato and Ulleung Basins, considered to be the western boundary currents in each basin. The similarity between the distributions of the mean flow vectors in the upper (400–1000 m) and lower layers (1000 m-bottom) indicates common circulation patterns throughout the water column of the Proper Water. Progressive vector diagrams show meandering curves with clockwise and anticlockwise turns due to the passing of mesoscale eddies. Since a dominant background flow is absent in the basin interior, the ratio of eddy kinetic energy to the mean-flow kinetic energy reaches more than 50 in the interior region. This indicates that the flows observed in the interior region are comparable to those in the basin periphery, even though the mean flow is generally weak. Spectral analysis has revealed that tidal fluctuations are prevailing in the Ulleung Basin, while they are absent in the Yamato and Japan Basins, though the inertial oscillation is dominant in all of the basins. This indicates that the tidal energy from the East China Sea is confined within the Ulleung Basin, suggesting the barrier effect of the Yamato Rise and the Oki Spur. Significant energy peaks are also found in the 2–5 and 5–10 day period bands in the Yamato Basin. The former variation represents the shelf-wave activity trapped on the basin edge and the latter is due to eddy migrations associated with the Tsushima Current.

Molecular Characterization of TEM-type β-Lactamases Identified in Cold-Seep Sediments of Edison Seamount (South of Lihir Island, Papua New Guinea)

Abstract: To determine the prevalence and genotypes of beta-lactamases among clones of a metagenomic library from the cold-seep sediments of Edison seamount (10,000 years old), we performed pulse-field gel electrophoresis, antibiotic susceptibility testing, pI determination, and DNA sequencing analysis. Among the 8,823 clones of the library, thirty clones produced beta-lactamases and had high levels of genetic diversity. Consistent with minimum inhibitory concentration patterns, we found that five (16.7%) of thirty clones produced an extended-spectrum beta-lactamase. 837- and 259-bp fragments specific to blaTEM genes were amplified, as determined by banding patterns of PCR amplification with designed primers. TEM-1 was the most prevalent beta-lactamase and conferred resistance to ampicillin, piperacillin, and cephalothin. TEM-116 had a spectrum that was extended to ceftazidime, cefotaxime, and aztreonam. The resistance levels conferred by the pre-antibiotic era alleles of TEM-type beta-lactamases were essentially the same as the resistance levels conferred by the TEM-type alleles which had been isolated from clinically resistant strains of bacteria of the antibiotic era. Our first report on TEM-type beta-lactamases of the pre-antibiotic era indicates that TEM-type beta-lactamases paint a picture in which most of the diversity of the enzymes may not be the result of recent evolution, but that of ancient evolution.

Levels of Persistent Organochlorine Contaminants in Fish from Korea and Their Potential Health Risk

Abstract: Organochlorine contaminants in the muscles of sport and market fish were determined to understand the potential risks to humans consuming fish originating in Korea's coastal waters. Polychlorinated biphenyls (PCBs; sum of 22 congeners) and DDTs were the dominant contaminants, and their concentrations were in the range of 2.96 to 96.6 and 0.84 to 27.0 ng/g (wet weight basis), respectively. The highest PCB concentrations were found in samples taken from an industrial complex. Hexachlorocyclohexanes, chlordane-related compounds, and hexachlorobenzene concentrations were relatively low and ranged from 0.64 to 5.6, 0.17 to 4.24, and 0.08 to 1.58, respectively. Sport fish had levels of PCBs and DDTs approximately two times higher than market fish, implying that sport fish posed high potential risk of contamination with OCs. Risk-based screening value (SV) based on U. S. Environmental Protection Agency (USEPA) method was calculated using the USEPA approach to identify the primary chemicals of concern. Total PCB concentrations in all sport and market fish exceeded the SV (5.04 ng/g based on total PCBs), but the other compounds were mostly below SV values. Based on the estimated SVs, PCB compounds were identified as potential chemicals of concern.

Photobacterium frigidiphilum sp. nov., a psychrophilic, lipolytic bacterium isolated from deep-sea sediments of Edison Seamount.

Abstract: A Gram-negative, motile, rod-shaped, psychrophilic and weakly halophilic bacterial strain, SL13(T), was isolated from deep-sea sediments (1450 m depth) of Edison Seamount in the western Pacific Ocean. Optimal growth of SL13(T) requires the presence of 1.5% (w/v) NaCl, a pH of 6.0 and a temperature of 14 degrees C. The whole-cell fatty acid profile of the isolate includes C16:1 and C16:0 as major fatty acids and contains C20:5omega3. This is consistent with corresponding data for Photobacterium profundum. The DNA G+C content of strain SL13(T) is 43.8 mol%. Phylogenetic analyses of 16S rRNA gene sequences place this bacterium in the 'Gammaproteobacteria', within the genus Photobacterium. Sequence similarity analysis indicates that the closest relatives of strain SL13(T) are Photobacterium indicum (99.3%), P. profundum (98.5%) and Photobacterium lipolyticum (98.2%). The DNA-DNA hybridization levels between the isolate and its closest known phylogenetic relatives, P. indicum, P. profundum and P. lipolyticum, are 27.1, 52.4 and 20.2%, respectively. Thus strain SL13(T) represents a novel species of the genus Photobacterium, for which the name Photobacterium frigidiphilum sp. nov. is proposed. The type strain is SL13(T) (=KCTC 12384(T)=JCM 12947(T)).

Drought-inducible-but ABA-independent-thaumatin-like protein from carrot (Daucus carota L.).

Abstract: Drought treatment induces the accumulation of dcTLP, which is similar in structure to the thaumatin- like proteins (TLPs) found in the embryogenic calli, seedlings, and mature plants of carrot (Daucus carota). We isolated a full-length dcTLP cDNA clone from carrot and characterized the 5 � upstream sequences. The coding region of dcTLP consisted of 645 nucleotides; the theoretical pI value was 4.9, and its molecular weight was approximately 22 kDa. The production of dcTLP transcripts in the seedlings increased dramatically with dehydration treatment but was not affected by abscisic acid (ABA), salicylic acid, or jasmonic acid. The expression patterns of dcTLP mRNA at different developmental stages and in response to a variety of signal molecules was analyzed using reverse transcriptase-PCR and promoter analysis with fused genes of 0.5-kb 5 � upstream sequences in which β-glucuronidase (GUS) reporter genes (gus) were established. The induction of dcTLP was found to be highly specific to drought stress in the embryogenic calli, seedlings, and mature plants. Our results suggest that this new isoform of TLP that has been isolated from carrot is

Patterns of recent sea level rise in the East/Japan Sea from satellite altimetry and in situ data

Abstract: [1] Patterns of recent sea level rise in the East/Japan Sea (EJS) are investigated through the analyses of TOPEX/Poseidon (T/P) sea level anomalies, thermosteric sea level (TSL), and long-term tide gauge data. The 9-year-long T/P analyses reveal average trends of 5.4 ± 0.3 mm yr−1 for all of EJS and 6.6 ± 0.4 mm yr−1 for the southern EJS. These are much larger than the global rates of 3.1 ± 0.4 mm yr−1 reported by Cabanes et al. (2001) and 2.8 ± 0.4 mm yr−1 by Cazenave and Nerem (2004). This T/P rate compares relatively well with those from TSL data and tidal sea level gauges, indicating that sea level rise in the EJS is mainly due to thermal expansion. The southern EJS shows a nonuniform sea level trend pattern, with the western part of the Ulleung and Yamato Basins having values of 10 mm yr−1 and larger. This nonuniform pattern is discussed in terms of variable thermal expansions arising from a recent decadal trend in the temperature anomaly in the upper layer of the two basins. The 40-year-long TSL time series also reveals a decadal oscillation in the Ulleung and Yamato Basins that can be explained by interannual to decadal variations in temperature in the upper ocean layers, with weaker anomalies at most of the other EJS locations. It is hypothesized that the long-term oscillation in the southern EJS may be related to the decadal variability of heat content anomaly in the upper 300 m of the Pacific Ocean, as reported by Levitus et al. (2000), and to the north-south migration of the Warm Tsushima Current and eddies in the southern EJS.

Observed deep circulation in the Ulleung Basin

Abstract: Records from 16 current meters and 23 pressure gauges moored near the sea floor in the Ulleung Basin of the southwestern Japan/East Sea (JES) characterized the deep circulation between June 1999 and July 2001. Mean currents range from 1 to 4 cm/s and deep pressure anomalies range from 3 to 10 mbar, with horizontal correlation scales of about 40 km, and with integral time scales that range from about 5 to 20 days. Focusing here on the 90-day to interannual variability, synoptic maps of the deep currents and dynamic pressure fields determine that the deep circulation in the Ulleung Basin is cyclonic, with additional multiple cyclonic and anticyclonic cells that occur on sub-basin spatial scales. Over the Korea Plateau a northward deep outflow is observed that suggests an anticyclonic circulation pattern to the north. The annual average deep currents are remarkably similar for the 2 years, only slightly weaker in the second year. No seasonal pattern is discernable, except weakly at one or two sites.

Photobacterium aplysiae sp. nov., a lipolytic marine bacterium isolated from eggs of the sea hare Aplysia kurodai.

Abstract: A bacterium, named GMD509T, showing lipolytic activity was isolated from the eggs of the sea hare Aplysia kurodai collected at Mogiyeo (depth, 12 m), an uninhabited small island in the South Sea of Korea. The strain is Gram-negative, motile, facultatively anaerobic, mesophilic and weakly halophilic. Optimal growth of strain GMD509T occurs in the presence of 3.0 % (w/v) NaCl and at pH 8 and 25 degrees C. The whole-cell fatty acid profile of the isolate includes C16 : 1, C16 : 0 and C18 : 1 as major fatty acids and its DNA G+C content is 45 mol%. Phylogenetic analyses of 16S rRNA gene sequences place this bacterium in the gamma-Proteobacteria, within the genus Photobacterium. The 16S rRNA gene sequence of strain GMD509T is most similar to those of Photobacterium frigidiphilum (97.8 %), Photobacterium profundum (97.5 %) and Photobacterium indicum (97.4 %). DNA-DNA relatedness levels between the isolate and its closest known phylogenetic relatives, P. frigidiphilum and P. indicum, are 25.3 and 13.7 %, respectively. Strain GMD509T therefore represents a novel species, for which the name Photobacterium aplysiae sp. nov. is proposed, with the type strain GMD509T (=KCTC 12383T=JCM 12948T).

Effects of methanol on the catalytic properties of porcine pancreatic lipase

Abstract: The effect of aqueous methanol on the catalytic properties of porcine pancreatic lipase has been investigated. The k cat values for the hydrolysis of N α -benzyloxycarbonyl-L-lysine p-nitrophenyl ester at 0C increased in a linear manner with increasing methanol concentration. However, the K M values were not influenced at methanol concentrations lower than 30% and then began to increase at higher concentrations in an exponential fashion. Based on product analysis, the increase in k cat with increasing methanol concentration can be accounted for by nucleophilic competition of methanol for the acyl enzyme intermediate, indicating that the rate-limiting step of the porcine pancreatic lipase-catalyzed reaction is deacylation under current experimental conditions. The exponential increase in K M at methanol concentrations higher than 30% is attributed to the hydrophobic partitioning effect on substrate binding. There was no loss of lipase activity over a 4h period in 60% methanol concentration at pH'5.5 and 0C. By monitoring the intrinsic fluorescence and absorbance, no evidence for structural changes by methanol was observed.

Remotely controlled apparatus for recovering liquid in sunken ship and method performed by the same

Abstract: A remotely controlled apparatus for transporting liquid, such as oil, toxic chemicals, or the like, in a tank of a sunken ship to a floating body, without leakage and a method performed by the apparatus are disclosed. An underwater recovery device ( 100 ) of the apparatus includes a supporting frame ( 10 ), to which a plurality of devices including a linkage ( 111 ) are fixed, chucking devices ( 20 ) for fixing the underwater recovery device ( 100 ) to the sunken ship ( 500 ), a grabber ( 30 ) for attaching the base plate ( 80 ) to the supporting frame ( 10 ), DTB systems 40 for attaching the base plate ( 80 ) to the sunken ship ( 500 ), thrusters ( 50 ) for providing a propulsive force so as to attach the supporting frame ( 10 ) to the sunken ship ( 500 ), a hole cutter ( 60 ) for drilling a hole for the recovery of the liquid, and a liquid recovery device ( 70 ) for recovering the liquid through the hole drilled in the sunken ship ( 500 ).

Simulations of Annual Cycle of Phytoplankton Production and the Utilization of Nitrogen in the Yellow Sea

Abstract: A nutrient dynamic model coupled with a 3D physical model has been developed to study the annual cycle of phytoplankton production in the Yellow Sea. The biological model involves interactions between inorganic nitrogen (nitrate and ammonium), phosphate and phytoplankton biomass. The model successfully reproduces the main features of phytoplankton-nutrient variation and dynamics of production. 1. The well-mixed coastal water is characterized by high primary production, as well as high new production. 2. In summer, the convergence of tidal front is an important hydrodynamic process, which contributes to high biomass at frontal areas. 3. The evolution of phytoplankton blooms and thermocline in the central region demonstrate that mixing is a dominant factor to the production in the Yellow Sea. In this simulation, nitrate- and ammonium-based productions are estimated regionally and temporally. The northern Yellow Sea is one of the highly ranked regions in the Yellow Sea for the capability of fixing carbon and nitrogen. The annual averaged f-ratio of 0.37 indicates that regenerated production prevails over the Yellow Sea. The result also shows that phosphate is the major nutrient, limiting phytoplankton growth throughout the year and it can be an indicator to predict the bloom magnitude. Finally, the relative roles of external nutrient sources have been evaluated, and benthic fluxes might play a significant role in compensating 54.6% of new nitrogen for new production consumption.

Numerical Modeling of Nonlinear SurfaceWaves Caused By Surface Effect Ships Dynamics And Kinematics

Abstract: We model fully nonlinear free surface waves caused by a translating disturbance made of a pressure patch and/or a surface-piercing body (ship), within the framework of potential flow theory. The three-dimensional higher-order Boundary Element Model by Grilli et al. (2001) and Fochesato et al. (2004) is utilized with some recent extensions. In addition to the regular Eulerian-Lagrangian updating of the free surface geometry and potential, based on higher-order explicit Taylor series expansions, a pseudo-Lagrangian updating algorithm is developed to express and solve the problem in a coordinate system traveling at the instantaneous speed of the moving disturbance. This paper presents theoretical developments and applications illustrating both the accuracy and efficiency of the present method for a traveling pressure patch and an advancing Wigley hull. Based on numerical results, it is concluded that the present numerical approach, with a pseudo-Lagrangian updating and a higher-order BEM provides accurate and efficient results.

Effects of temperature changes on the endogenous rhythm of oxygen consumption in the Japanese flounder Paralichthys olivaceus

Abstract: The effects of temperature changes on the endogenous rhythm of oxygen consumption in the Japanese flounder Paralichthys olivaceus which were acclimated to 3, 14 or 20°C in advance were investigated. The oxygen consumption rate (OCR) of individuals (total length >28 cm) that were acclimated to 3°C, maintained a relatively low value of 6.9±2.3 mL (mean±SD) O2/kg ww (wet weight)/h till 5.8°C, which is considered a ‘minimum’ rate. Thereafter, the OCR gradually increased up to 18.7 mL O2/kg ww/h at the temperature of 10.6°C. The OCR of individuals acclimated to 14°C stabilized with 124.2±24.1 mL O2/kg ww/h, when tested at the relatively constant temperature of 14.4±0.17°C. Maximum entropy spectral analysis revealed that the peak OCR occurred at 23.9 h intervals, which could be a circadian rhythm. The mean OCR showed a peak at 06.00–08.00 hours. For the temperature above 25°C in which the fish were acclimated to 20°C, the rhythmic patterns of OCR were observed until the experimental temperature reached 26.4°C. For the temperature above 28.4°C, the metabolic activity rhythm of the OCR was dampened and then the OCR abruptly rose again. It is assumed that the oscillator of the endogenous rhythm lost the governing of normal metabolic activity in Japanese flounders above 28.4°C. These results suggest that the temperatures of around 5.8, 26.4 and 28.4°C are the ‘lower limit, temperature’, ‘upper incipient lethal temperature’, and the ‘critical thermal maximum’, respectively, for the endogenous rhythm of oxygen consumption in the Japanese flounder.

Diatom assemblages in the surface water of the Indian Sector of the Antarctic Surface Water in summer of 1999/2000

Abstract: Abundance and species composition of diatom assemblages in surface water of the Indian Sector of the Antarctic Surface Water of the Southern Ocean were examined using samples gathered during the JARE-41 Cruise of the icebreaker Shirase in the summer of 1999/2000. On the westward leg (Leg 1), abundance of the diatom assemblage was geographically rather uniform, while species composition was different geographically in mosaic manner. Dominant species on Leg 1 were the pennate Pseudo-nitzschia spp. and the centric Dactyliosolen tenuijunctus, Chaetoceros sp. cf. dichaeta and Chaetoceros neglectus. On the eastward leg (Leg 2), abundance and species composition were different east and west of 60 ̊E. The community to the west was large in abundance and dominated by D. tenuijunctus, while that to the east was small and dominated by the pennate Fragilariopsis species. These diatom assemblages were grouped into four clusters on Leg 1 and three on Leg 2. Mosaic distribution of the clusters was again evident on Leg 1, while rather simple east-west difference was the case on Leg 2. These geographical variations seem to be affected by local sea ice

A reconnaissance on the use of the speleothems in Korean limestone caves to retrospective study on the regional climate change for the recent and geologic past

Abstract: More than 1,000 limestone caves are extensively developed in Gangwon-do and Chungcheongbuk-do, Korea. A variety of numerous speleothems are actively growing in these caves today. A potential to use speleothems as regional paleoclimate proxy was explored by analyzing soda straw, stalactite and stalagmite. These proxy recorders that have grown during the past several decades were investigated using the presence of excess210Pb. Most specimens collected from six limestone caves were found to have an excess210Pb, indicating that they are less than about 100 yrs old. This excess210Pb was employed to estimate the growth rate for a tubular “soda straw” that yielded a longitudinal growth rate of 1.7 mm/yr past 60 years. Coeval decrease in δ13C values of the soda straw, spanning the time period of about 1930–1995 AD, may reflect the carbon isotope ratio of about 1930–1995 AD, may reflect the carbon isotope ratio of atmospheric CO2 for the same period. Studies on fine scale variations in the isotopic composition of recent speleothems along with age control using210Pb excess method from the speleothems in Korean limestone caves promise a great potential for the reconstruction of climate and environmental changes during the past hundred years or so.

Production of Novel Exopolysaccharide with Emulsifying Ability from Marine Microorganism, Alteromonas sp. Strain 00SS11568

Abstract: To find a novel exopolysaccharide, marine bacterial strains were isolated from coastal regions of Korea Strain 00SS11568 was then selected as it produced a mucous exopolysaccharide during the stationary phase in a batch culture The isolate was identified as Alteromonas sp based on its 16S rDNA sequence, morphological, and biochemical properties The exopolysaccharide, designated as p-11568, exhibited an emulsifying ability The Emulsification Index (E24) of 01% p- 11568 was 774% with an emulsified kerosene content, and was higher than those of commercial polysaccharides, such as xanthan gum (261%), gellan gum (13%), and sodium alginate (20%) p- 11568 was found to be composed of glucose and galactose as the main natural sugars in a molar ratio of 13:1, along with uronic acid (189%, w/w) and sulfate groups (12% w/w) The average molecular mass was 44 x 105 daltons by gel filtration chromatography The effects of pH, temperature, inorganic compounds, and C and N sources were tested to obtain the optimal medium composition for the production of p-11568 Under optimal growth conditions with the M-11568 medium, 149 g of crude p-11568 per liter was obtained

Isolation and Identification of Bacteria from Marine Biofilms

Abstract: In the marine environment, biofilms cover most of the subtidal and intertidal solid surfaces. Culturable bacteria forming marine biofilms were isolated on artificial substrate called acrylic coupons. The bacterial isolates were identified through a comparison of 16S rDNA sequences. A total of 115 strains were cultured and identified, 45 of which showed the same sequences with other strains. Therefore, 70 strains were finally identified. The bacterial isolates belonged to a–Proteobacteria (32 isolates), g–Proteobacteria (12 isolates), CFB group bacteria (4 isolates), high GC Gram-positive bacteria (9 isolates), and low GC Gram-positive bacteria (13 isolates). The bacterial isolates may be used as standard bacteria to test new antifouling agent. They may also be utilized as useful bacteria to enhance the settlement of commercial algae and invertebrate larvae for aquaculture.

Relationship Between Enhancement of Electrostriction and Decrease of Activation Energy in Porcine Pancreatic Lipase Catalysis

Abstract: The contribution of electrostriction of water molecules to the stabilization of the negatively charged tetrahedral transition state of a lipase-catalyzed reaction was examined by means of kinetic studies involving high-pressure and solvent dielectric constant. A good correlation was observed between the increased catalytic efficiency of lipase and the decreased solvent dielectric constant. When the dielectric constant of solvents was lowered by 5.00 units, the losses of activation energy and free energy of activation were 7.92 kJ/mol and 11.24 kJ/mol, respectively. The activation volume for k cat decreased significantly as the dielectric constant of solvent decreased, indicating that the degree of electrostriction of water molecules around the charged tetrahedral transition state has been enhanced. These observations demonstrate that the increase in the catalytic efficiency of the lipase reaction with decreasing dielectric constant resulted from the stabilization of electrostatic energy for the formation of an oxyanion hole, and that this stabilization was caused by the increase of electrostricted water around the charged tetrahedral transition state. Therefore, we conclude that the control of solvent dielectric constant can stabilize the tetrahedral transition state, thus lowering the activation energy.

Driving Forces of Interleaving in the Baroclinic Front at the Equator

Abstract: The different types of instability in the equatorial β-plane approximation are analyzed by means of a 2D linear stability problem. The double-diffusive (DD) and diffusive/baroclinic (2D baroclinic and McIntyre) instabilities are shown not to develop if contours of the mean salinity/density have a parabolic, symmetrical-relative-to-the-equator shape. Using modeling results, an illustrative scheme of Equatorial Undercurrent (EUC) regions where different types of instability can develop is presented and subsequently applied to understand the driving forces of the intrusions observed in a closed spaced CTD section, located between the equator and 1°N. Long coherence intrusions are situated within two isopycnal layers, aligned to 25 (layer 1) and 26.3 (layer 2) σT, where the vertical shear is low. It was shown from the model that the layer-1 intrusions being observed in the midlayer of the EUC where the mean horizontal gradient of salinity is approximately constant are likely generated by a combined e...

Genomic DNA Extracted from Ancient Antarctic Glacier Ice for Molecular Analyses on the Indigenous Microbial Communities

Abstract: From ancient Antarctic glacier ice, we extracted total genomic DNA that was suitable for prokaryotic 16S rDNA gene cloning and sequencing, and bacterial artificial chromosome (BAC) library and end-sequencing. The ice samples were from the Dry Valley region. Age dating by analysis on the volcanic ashes deposited in situ indicated the ice samples are minimum 100,000-300,000 yr (sample DLE) and 8 million years (sample EME) old. Further assay proved the ice survived freeze-thaw cycles or other re-working processes. EME, which was from a small lobe of the basal Taylor glacier, is the oldest known ice on Earth. Microorganisms, preserved frozen in glacier ice and isolated from the rest of the world over a geological time scale, can provide valuable data or insight for the diversity, distribution, survival strategy, and evolutionary relationships to the extant relatives. From the 16S gene cloning study, we detected no PCR amplicons with Archaea-specific primers, however we found many phylotypes belonging to Bacteria divisions, such as Actinobacteria, Acidobacteria, Proteobacteria , Firmicutes, and Cytophaga-Flavobacterium-Bacteroid$. BAC cloning and sequencing revealed protein codings highly identical to phenylacetic acid degradation protein paaA, chromosome segregation ATPases, or cold shock protein B of present day bacteria. Throughput sequencing of the BAC clones is underway. Viable and culturable cells were recovered from the DLE sample, and characterized by their 16S rDNA sequences. Further investigation on the survivorship and functional genes from the past should help unveil the evolution of life on Earth, or elsewhere, if any.