The aim of this study was to determine the physiological role of skin lectins of the Japanese bullhead shark (Heterodontus japonicus). A skin extract was subjected to affinity chromatography using seven different sugars as ligands. Molecular mass and N-terminal amino acid sequence analyses indicated elution of the same protein by each of the seven respective cognate ligands from sugar affinity columns. The predicted amino acid sequence encoded by the cDNA of this protein [designated as H. japonicus C-type-lectin (HjCL)] identified it as a novel fish subgroup VII C-type lectin evolutionarily related to snake venom lectins. HjCL was predicted to bind to mannose because of the presence of a Glu-Pro-Asn (EPN) motif; however, haemagglutination inhibition assays and glycoconjugate microarray analysis demonstrated its binding to numerous structurally diverse sugars. Competitive sugar-binding assays using affinity chromatography indicated that HjCL bound multiple sugars via a common carbohydrate-recognition domain. The mRNA encoding HjCL was specifically detected in the skin, and immunohistochemical analysis detected its expression in uncharacterized large cells in the epidermis. HjCL agglutinated the bacterial pathogen Edwardsiella tarda and promoted immediate clotting of shark blood, indicating that HjCL is involved in host defence on the skin surface especially when the shark is injured and bleeds.

Radioactive strontium ( 90 Sr) leaked into saline environments, including the ocean, from the Fukushima Daiichi Nuclear Power Plant after a nuclear accident. Since the removal of 90 Sr using general adsorbents (e.g., zeolite) is not efficient at high salinity, a suitable alternative immobilization method is necessary. Therefore, we incorporated soluble Sr into biogenic carbonate minerals generated by ureaseproducing microorganisms from a saline solution. An isolate, Bacillus sp. strain TK2d, from marine sediment removed Ͼ99% of Sr after contact for 4 days in a saline solution (1.0 ϫ 10 Ϫ3 mol liter Ϫ1 of Sr, 10% marine broth, and 3% [wt/vol] NaCl). Transmission electron microscopy and energy-dispersive X-ray spectroscopy showed that Sr and Ca accumulated as phosphate minerals inside the cells and adsorbed at the cell surface at 2 days of cultivation, and then carbonate minerals containing Sr and Ca developed outside the cells after 2 days. Energy-dispersive spectroscopy revealed that Sr, but not Mg, was present in the carbonate minerals even after 8 days. X-ray absorption fine-structure analyses showed that a portion of the soluble Sr changed its chemical state to strontianite (SrCO 3 ) in biogenic carbonate minerals. These results indicated that soluble Sr was selectively solidified into biogenic carbonate minerals by the TK2d strain in highly saline environments.IMPORTANCE Radioactive nuclides ( 134 Cs, 137 Cs, and 90 Sr) leaked into saline environments, including the ocean, from the Fukushima Daiichi Nuclear Power Plant accident. Since the removal of 90 Sr using general adsorbents, such as zeolite, is not efficient at high salinity, a suitable alternative immobilization method is necessary. Utilizing the known concept that radioactive 90 Sr is incorporated into bones by biomineralization, we got the idea of removing 90 Sr via incorporation into biominerals. In this study, we revealed the ability of the isolated ureolytic bacterium to remove Sr under high-salinity conditions and the mechanism of Sr incorporation into biogenic calcium carbonate over a longer duration. These findings indicated the mechanism of the biomineralization by the urease-producing bacterium and the possibility of the biomineralization application for a new purification method for 90 Sr in highly saline environments.KEYWORDS biomineralization, bioremediation, halophilic, marine environment, radionuclide, urease A t the Fukushima Daiichi Nuclear Power Plant (FDNPP), the nuclear reactors are cooled by the continuous treatment of contaminated water that contains radionuclides. Some of this contaminated water with high saline concentrations has leaked

Methanogens capable of accepting electrons from Fe0 cause severe corrosion in anoxic conditions. In previous studies, all iron-corrosive methanogenic isolates were obtained from marine environments. However, the presence of methanogens with corrosion ability using Fe0 as an electron donor and their contribution to corrosion in freshwater systems is unknown. Therefore, to understand the role of methanogens in corrosion under anoxic conditions in a freshwater environment, we investigated the corrosion activities of methanogens in samples collected from groundwater and rivers. We enriched microorganisms that can grow with CO2/NaHCO3 and Fe0 as the sole carbon source and electron donor, respectively, in ground freshwater. Methanobacterium sp. TO1, which induces iron corrosion, was isolated from freshwater. Electrochemical analysis revealed that strain TO1 can uptake electrons from the cathode at lower than −0.61 V vs SHE and has a redox-active component with electrochemical potential different from those of other previously reported methanogens with extracellular electron transfer ability. This study indicated the corrosion risk by methanogens capable of taking up electrons from Fe0 in anoxic freshwater environments and the necessity of understanding the corrosion mechanism to contribute to risk diagnosis.

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