Yoo Kyung Lee

Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska

The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0–10 cm to 10–20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen ( and ). The community compositions of the two different depths showed that Alphaproteobacteria decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted unifrac distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska.

Loss of BubR1 acetylation causes defects in spindle assembly checkpoint signaling and promotes tumor formation

Failure of chromosome–spindle attachment and a weakened spindle assembly checkpoint lead to genetic instability and cancer in mice expressing acetylation-deficient BubR1.

Maribacter arcticus sp. nov., isolated from Arctic marine sediment.

A Gram-negative, non-motile, aerobic bacterium, designated strain KOPRI 20941(T), was isolated from a sample of marine sediment from Ny Alesund, Spitsbergen, Norway. A phylogenetic analysis based on 16S rRNA gene sequences revealed that the Arctic isolate nested within the genus Maribacter and showed the highest sequence similarity (98.1 %) with respect to Maribacter orientalis KMM 3947(T). Chemotaxonomic data (DNA G+C content of 36 mol%; MK-6 as the major respiratory quinone and iso-C(17 : 0) 3-OH, C(16 : 1)omega7c/iso-C(15 : 0) 2-OH and iso-C(15 : 0) as the major fatty acids) supported the affiliation of strain KOPRI 20941(T) to the genus Maribacter. The results of phylogenetic analyses, physiological and biochemical tests and a DNA-DNA reassociation test (<54 % relatedness) allowed genotypic and phenotypic differentiation of the strain from the recognized species of the genus Maribacter. Therefore strain KOPRI 20941(T) represents a novel species of the genus Maribacter, for which the name Maribacter arcticus sp. nov. is proposed. The type strain is KOPRI 20941(T) (=KCTC 22053(T)=JCM 14790(T)).

Sanguibacter antarcticus sp. nov., isolated from Antarctic sea sand

A Gram-positive, yellow-pigmented bacterium, strain KOPRI 21702(T), was isolated from sea sand on King George Island, Antarctica. Cells were irregular rods with peritrichous flagella; their optimum growth temperature was 23-26 degrees C. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the Antarctic isolate formed a distinct phyletic line in a clade of the genus Sanguibacter and showed highest sequence similarity (97.7%) to the type strain of Sanguibacter keddieii. The major isoprenoid quinone, predominant cellular fatty acids and DNA G+C content were consistent with placement of the Antarctic isolate in the genus Sanguibacter. Phylogenetic analysis and differences in physiological and biochemical characteristics between strain KOPRI 21702(T) and the four recognized Sanguibacter species indicate that the isolate represents a novel species of this genus. The name Sanguibacter antarcticus sp. nov. (type strain KOPRI 21702(T) =KCTC 13143(T) =JCM 14623(T) =DSM 18966(T)) is proposed for this isolate.

Antioxidant activity of Sanionia uncinata, a polar moss species from King George Island, Antarctica.

Antioxidant agents counter reactive oxygen species (ROS) and can be used in cosmetic and medicinal applications. The goal of this study was to evaluate the antioxidant activity of an Antarctic moss species from King George Island (Antarctica), tentatively designated as KSJ‐M5. On the basis of morphological characteristics, KSJ‐M5 was identified as Sanionia uncinata (Hedw.) Loeske (Amblystegiaceae). The identification was confirmed by comparing the partial sequence of the ITS (internal transcribed spacer) region with that in GenBank. The antioxidant activity of an ethanol extract of KSJ‐M5 was evaluated by analyzing its reducing power, superoxide scavenging activity, ABTS [2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid)] cation scavenging activity, and DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) free‐radical scavenging activity. The reducing power of 1 mg of KSJ‐M5 extract was equivalent to 31.9 ± 0.9 µg (Mean ± SD, n = 3) of the commercial standard, BHT (butylated hydroxytoluene). IC50 values of the KSJ‐M5 extract for DPPH free‐radical scavenging activity, superoxide scavenging activity, and ABTS cation scavenging activity were found as 356 ± 26.8 µg/mL, 466.2 ± 43.4 µg/mL, and 181.3 ± 12.2 µg/mL, respectively. The total phenolic content in 1 mg of KSJM5 extract was equivalent to 12.7 ± 2.7 µg of pyrocatechol. These results clearly showed that KSJ‐M5 could be an important source of natural antioxidant agents for improved medicinal and cosmetic applications. Copyright

Mutant selection of Hahella chejuensis KCTC 2396 and statistical optimization of medium components for prodigiosin yield-up

Prodigiosin is a natural red pigment with algicidal activity against Cochlodinium polykrikoides, a major harmful red-tide microalga. To increase the yield of prodigiosin, a mutant of Hahella chejuenesis KCTC 2396, assigned M3349, was developed by an antibiotic mutagenesis using chloramphenicol. When cultured in Sucrose-based Marine Broth medium (SMB), M3349 could produce prodigiosin at 1.628±0.06 g/L, while wild type producing at 0.658±0.12 g/L under the same conditions. To increase the yield of prodigiosin production by M3349, significant medium components were determined using a two-level Plackett-Burman statistical design technique. Among fourteen components included in SMB medium, NaCl, Na2SiO3, MgCl2, H3BO3, Na2HPO4, Na2SO4, and CaCl2 were determined to be important for prodigiosin production. The medium formulation was finally optimized using a Box-Behnken design as follows: sucrose 10.0, peptone 8.0, yeast extract 2.0, NaCl 10.0, Na2SO4 12.0, CaCl2 1.8, MgCl2 0.7 g/L; and H3BO3 22.0, Na2HPO4 20.0, Na2SiO3 8.0 mg/L. The predicted maximum yield of prodigiosin in the optimized medium was 2.43 g/L by the Box-Behnken design, while the practical production was 2.60±0.176 g/L, which was 3.9 times higher than wild type with SMB Medium (0.658 g/L).

Isolation of Protease-Producing Arctic Marine Bacteria

We isolated and identified three protease-producing bacteria that had inhabited the region around the Korean Arctic Research Station Dasan located at Ny-Alesund, Svalbard, Norway . Biofilms were collected from the surface of a floating pier and from dead brown algae in a tide pool near the seashore. The biofilm samples were transported to the Korea Polar Research Institute (KOPRI) under frozen conditions, diluted in sterilized seawater, and cultured on Zobell agar plates with 1% skim milk at . Three clear zone forming colonies were selected as protease-producing bacteria. Phylogenetic analysis based on 16S rDNA sequences showed that these three stains shared high sequence similarities with Pseudoalteromonas elyakovii, Exiguobacterium oxidotofewm Pseudomonas jessenii, respectively. We expect these Arctic bacteria may be used to develop new varieties of protease that are active at low temperatures.

SEXUAL DIFFERENTIATION OF GRIFFITHSIA (CERAMIALES, RHODOPHYTA): NUCLEAR PLOIDY LEVEL OF MIXED-PHASE PLANTS IN G. JAPONICA1

Mixed‐phase plants of Griffithsia japonica Okamura spontaneously occurred in a laboratory culture. Four female plants produced tetrasporangia and spermatangia in addition to their normal female reproductive structures (bisexual/mixed‐phase plants), and four male plants produced tetrasporangia as well as spermatangia (male/mixed‐phase plants). To determine the nuclear ploidy level of these mixed‐phase plants, relative nuclear sizes of male, female, tetrasporangial, and mixed‐phase plants were measured using a microscopic image analysis system. Haploid gametophytes could be distinguished from diploid tetrasporophytes by relative nuclear sizes, with the later having nuclei twice the size of the former. Relative nuclear sizes of the mixed‐phase plants were similar to those of the haploid plants. Thus, the mixed‐phase plants were determined to be haploid. Haploid mixed‐phase plants of G. japonica have a potential to produce male, female and tetrasporangial reproductive structures. Sex determination models are discussed to explain “haploid” mixed‐phase phenomena in red algae.

HEAT‐SHOCK PROTEIN 90 MAY BE INVOLVED IN DIFFERENTIATION OF THE FEMALE GAMETOPHYTES IN GRIFFITHSIA JAPONICA (CERAMIALES, RHODOPHYTA)

A cDNA library from a mixed population of female and male gametophytes of Griffithsia japonica Okamura was constructed, and a cDNA clone, designated GjFP‐1 (G. japonica female predominant‐1), was isolated by differential screening of the cDNA library. The transcript corresponding to GjFP‐1 was abundant in female gametophytes, but only basal levels of the transcript were detected in male and tetrasporangial thalli. Determination of the nucleotide sequence of GjFP‐1 identified a putative open reading frame encoding 313 amino acids and a 3′ untranslated region of 116 nucleotides. The deduced amino acid sequence of GjFP‐1 for the putative open reading frame shared high homology with the previously reported amino acid sequences of heat shock protein 90 (hsp90). RNA blot hybridization analysis for the transcripts of heat‐shocked G. japonica and DNA hybridization analysis for the genomic DNA of G. japonica with GjFP‐1 as a probe suggested that GjFP‐1 is a cDNA clone for the hsp90 gene in G. japonica.In situ hybridization for the GjFP‐1 transcript again showed a differential specificity of the transcript in female gametophytes. The data reported here suggest a possibility of hsp90 function linked to the development of the female gametophytes in G. japonica.

Removal of heavy metals by an enriched consortium

An enriched consortium obtained from lake-sediment was developed for the removal of heavy metals such as Cu, Pb, Cr, Ni, and Zn from heavy metal-contaminated water. The removal efficiency of heavy metals in a shaking condition was generally higher than that in the static state. After the fifteenth enrichment with assorted heavy metals, the removal efficiencies in the shaking and static condition at an average concentration of 100 mg/L of each heavy metal were approximately 99∼100% and 95∼100%, respectively, depending on the type of heavy metal. An aerobically grown, pure culture isolated from an enriched culture was analyzed by 16S rRNA sequencing and identified as Ralstonia sp. HM-1. This strain was found to remove various heavy metals with an efficiency of approximately 97∼100% at an average concentration of 200 mg/L of each heavy metal.