Purification and biochemical characterization of manganesecontaining superoxide dismutase from deep-sea thermophile Geobacillus sp. EPT3

Thermostable SOD is a promising enzyme in biotechnological applications. In the present study, thermo-phileGeobacillussp.EPT3 was isolated from a deep-sea hydrothermal field in the East Pacific. A thermo-stable superoxide dismutase （SOD） from this strain was purified to homogeneity by steps of fractional am-monium sulfate precipitation, DEAE-Sepharose chromatography, and Phenyl-Sepharose chromatography. SOD was purified 13.4 fold to homogeneity with a specific activity of 3 354 U/mg and 11.1% recovery. SOD fromGeobacillussp. EPT3 was of the Mn-SOD type, judged by the insensitivity of the enzyme to both KCN and H2O2. SOD was determined to be a homodimer with monomeric molecular mass of 26.0 kDa. It had high thermostability at 50＆#176;C and 60＆#176;C. At tested conditions,SOD was relatively stable in the presence of some inhibitors and denaturants, such asβ-mercaptoethanol （β-ME）, dithiothreitol （DTT）, phenylmethylsulfonyl fluoride （PMSF）, urea, and guanidine hydrochloride.Geobacillussp. EPT3 SOD showed striking stability across a wide pH range from 5.0 to 11.0. It could withstand denaturants of extremely acidic and alkaline conditions, which makes it useful in the industrial applications.

A Minireview of Marine Algal Virus-Coccolithoviruses

Coccolithophorid is unicellular marine microalgae with a global distribution in temperate and sub-temperate oceanic regions and has the ability to produce ‘the coccoliths'. It is considered to be the second most productive calcifying organism on earth and becoming an important factor in the global carbonate cycle. Emiliania huxleyi is one of the only two bloom-forming coccolithophores and becomes a species crucial to the study of global biogeochemical cycles and climate modeling. Coccolithoviruse is a recently discovered group of viruses infecting the marine coccolithophorid E. huxleyi. They are a major cause of coccolithophore bloom termination, and DMSP concentration is increasing in the process of viral lysis. Phylogenetic evidences support that some genes are functional both in E. huxleyi and its virus(Eh V). Horizontal gene transfer(HGT) of multiple functionally coupled enzymes occurs in E. huxleyi and its DNA virus Eh V has been confirmed, which contributes to the diversification and adaptation of plankton in the oceans and also critically regulates virus-host infection by allowing viruses to control host metabolic pathways for their replication. Therefore, it is of particular interest to understand this host-virus interaction. On this issue, we have made a minireview of coccolithoviruses focusing on the basic characteristics, phylogenesis, horizontal gene transfer and the interaction between the host and its viruses, as well as its important role in global biogeochemical cycling.