Magnetospirillum magnetotacticum possesses intracellular magnetite particles with a chain-like structure, termed magnetosomes. The bacterium expresses 22-kDa and 12-kDa magnetosome-associated proteins, termed Mam22 (MamA) and Mam12 (MamC), respectively. In this study, we investigated the structure of the purified magnetosomes with transmission electron microscopic techniques and found that the magnetosomes consisted of four compartments, i.e., magnetite crystal, magnetosomal membrane, interparticle connection, and magnetosomal matrix. Furthermore, we determined the precise localizations of Mam22 and Mam12 using immunogold staining of the purified magnetosomes and ultrathin sections of the bacterial cells. Interestingly, most Mam22 existed in the magnetosomal matrix, whereas Mam12 was strictly localized in the magnetosomal membrane. Moreover, the recombinant Mam22 was attached to the magnetosomal matrix of the Mam22-deficient magnetosomes prepared by alkaline treatment, such as 0.1 M Caps-NaOH buffer (pH 11.0). The spatial localization of the magnetosome-associated proteins in the magnetosomal chain provides useful information to elucidate the functional roles of these proteins.

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The recombinant actin-like protein MamK was purified from Escherichia coli and used as an antigen to generate the anti-MamK antibody. Immunostaining studies showed a linear distribution of MamK in Magnetospirillum magnetotacticum cells and of MamK in association with magnetosomes. Moreover, we demonstrated that MamK polymerizes into filamentous bundles in vitro.Magnetic bacteria synthesize a unique prokaryotic organelle called the magnetosome with which the organisms navigate along the geomagnetic field (1). Magnetosomes consist of membrane-enclosed magnetite crystal particles that are assembled into a straight chain with some structures, such as a magnetosomal matrix, and an interparticle connection (1,6,18). The magnetosome chain is positioned at the center of the cell, along the long axis of the cell in the Magnetospirillum species. A number of genes encoding magnetosome-associated proteins were identified within the unstable genetic island, referred to as the magnetosome island, in the genomes of the Magnetospirillum species and the Magnetococcus sp. MC-1 strain (16). This magnetosome island is essential for magnetosome formation and contains at least three operons (mamAB, mamDC, and mms) (15). MamK, which is encoded by the mamAB operon, is a new member of the bacterial actin homologue (3,6,7,12,17). Recently, networks of the cytoskeleton-like filamentous structures were observed along the magnetosome chains of Magnetospirillum gryphiswaldense, M. magneticum and M. magnetotacticum (6,7,9,14). Komeili et al. demonstrated that the ⌬mamK strain of M. magneticum AMB-1 abolishes the filamentous structure near the magnetosomes; hence, the filamentous structure may be composed of MamK (7). Furthermore, we reported that the green fluorescent protein-fused M. magneticum AMB-1 MamK protein forms a filamentous organization in the cells of Escherichia coli (12). To understand the structure and function of the MamK cytoskeletal filament as well as other bacterial actin homologues, such as MreB and ParM, preparation of the MamK filament in vitro and characterization of the features are required. However, there have been no reports about polymerization of MamK in vitro.In this study, first, we cloned, expressed, and purified M. magnetotacticum MamK from E. coli. Second, the localizations of MamK in the wild-type M. magnetotacticum cell and in the purified magnetosome chain were confirmed, using immunochemical techniques. Finally, we demonstrated for the first time that the recombinant MamK proteins polymerized into filamentous bundles in vitro.Localizations of MamK in the M. magnetotacticum cell and in the purified magnetosomes. The intracellular localization of MamK was examined and compared to that of MreB by using immunofluorescence microscopy (IFM) with the wild-type M. magnetotacticum cell. M. magnetotacticum MS-1 (ATCC 31632) was cultured in a chemically defined liquid medium (2) under microaerobic condition at 25°C in the dark and then harvested at the early stationary phase. The C-terminal Histagged recombinant M....

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The distribution of microorganisms in the subsurfaces of hydrothermal vents was investigated by using subvent rock core samples. Microbial cells and ATP were detected from cores taken at depths of less than 99.4 and 44.8 m below the seafloor (mbsf), respectively. Cores from various depths were incubated anaerobically with a heterotrophic medium. Growth at 60 and 90°C was ascribed to a Geobacillus sp. in the 448.6-to 99.4-mbsf cores and a Deinococcus sp. in the 64.8-to 128.9-mbsf cores, respectively, based on the 16S ribosomal DNA analysis.Since the discovery of deep-sea hydrothermal vents, a number of thermophiles and hyperthermophiles have been isolated from chimneys, sediments, and ambient water of the hydrothermal vent fields (reviewed by Reysenbach et al. [21]). In addition, non-culture-dependent 16S ribosomal DNA (rDNA) analysis has been applied to a variety of vent samples (see, e.g., references 11, 14, 15, 23, 29, and 30). However, most of the previous studies were limited to the surfaces of hydrothermal vent systems, while interest in the subsurface habitats of hydrothermal vents (subvents) has been increasing.Only a few subvent microbiological studies have been conducted with sediment, sedimentary rock layers, and igneous rocks from relatively shallow depths (less than 52 m below the seafloor [mbsf]) (4,5,22,26,27). Here, we report the first evidence for the occurrence of a deep-sea subvent biosphere (maximum depth, 128.9 mbsf), by using igneous rock core samples from a back-arc basin hydrothermal vent field.

Abstract-Rainwater collected during the period of February to April, 2003, at Kanazawa University, the Japan Sea Coast, was investigated by Ion chromatography for the dissolved ions. The filtered samples were evaluated by various kinds of 1 micro-techniques. The pH, Eh, electrical conductivity (EC), dissolved oxygen (DO), and depleted U (DU) of the rainwater were also measured. The results showed a rare case with low pH and high EC values of rainwater. The

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Clinoptilolite is investigated as a possible regenerable sorbent for acid rock drainage based on its adsorption capacity for Zn, adsorption kinetics, effect of pH, and regeneration performance. Adsorption of Zn ions depends on the initial concentration and pH. Adsorption/Desorption of Zn reached 75% of capacity after 1-2 h. Desorption depended on pH, with an optimum range of 2.5 to 4.0. The rank of desorption effectiveness was EDTA>NaCl>NaNO 3 > NaOAc>NaHCO 3 >Na 2 CO 3 >NaOH>Ca(OH) 2 . For cyclic absorption/desorption, adsorption remained satisfactory for six to nine regenerations with EDTA and NaCl, respectively. The crystallinity and morphology of clinoptilolite remained intact following 10 regeneration cycles. Clinoptilolite appears to be promising for ARD leachate treatment, with significant potential advantages relative to current treatment systems.