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.

The unique ability of magnetotactic bacteria to navigate along a geomagnetic field is accomplished with the help of prokaryotic organelles, magnetosomes. The magnetosomes have well-ordered chain-like structures, comprising membrane-enveloped, nanosized magnetic crystals, and various types of specifically associated proteins. In this study, we applied atomic force microscopy (AFM) to investigate the spatial configuration of isolated magnetosomes from Magnetospirillum magneticum AMB-1 in near-native buffer conditions. AFM observation revealed organic material with a ∼7-nm thickness surrounding a magnetite crystal. Small globular proteins, identified as magnetosome-associated protein MamA, were distributed on the mica surface around the magnetosome. Immuno-labeling with AFM showed that MamA is located on the magnetosome surface. In vitro experiments showed that MamA proteins interact with each other and form a high molecular mass complex. These findings suggest that magnetosomes are covered with MamA oligomers in near-native environments. Furthermore, nanodissection revealed that magnetosomes are built with heterogeneous structures that comprise the organic layer. This study provides important clues to the supramolecular architecture of the bacterial organelle, the magnetosome, and insight into the function of the proteins localized in the organelle. magnetotactic bacteria | scanning probe microscopy | nanoparticle | TPR protein | protein localization

Plasticity in sex differentiation is known to be common in teleost fishes. Anemonefishes are protandrous; females are the largest and dominant members of social groups, displaying frequent aggressive behavior towards other members of groups. The second-ranked individuals become males and others remain as non-reproductive individuals. Here we examine the influence of social interaction in-group on sex differentiation in the false clown anemonefish, Amphiprion ocellaris, under laboratory conditions. Three juvenile anemonefish were kept in a tank for 180 days and their behaviors observed once a month. The social rank of individuals was distinguishable by their interactions in a group, with rank order clearly correlated with aggressive and appeasing behaviors. The dominant individuals occupied the shelter in the tank from the start to completion of the observation period. The body mass of dominant individuals increased compared to group-housed control fish, while third-ranked individuals showed growth suppression. The ratio of testicular tissue in gonads increased in dominant and second-ranked individuals but decreased in the third-ranked individuals. Differences in the plasma concentrations of estradiol, testosterone, and cortisol were not significant, but the concentration of 11-ketotestosterone was significantly higher in dominant individuals. These results suggest that, in false clown anemonefish, reproductive suppression of lower-ranked individuals becomes apparent in the first stage of group formation, and sex differentiation of upper-ranked individuals is gradually determined by long-term social interactions.

No abstract

The drying characteristics of a single coarse lignite particle in superheated steam are investigated. Spherical particles of Loy Yang lignite 30 mm in diameter were used. The particles were dried with superheated steam at temperatures ranging from 110 to 170°C under atmospheric pressure, and their weights and temperatures were measured with electronic balance, thermocouples and infrared thermograph. Condensation of water droplets on the surface was observed initially, then constant drying rate period (CDRP) and decreasing drying rate period (DDRP) were observed successively. A numerical model of the drying process was developed based on the results, taking into account transfer of free water inside the particle, equilibrium moisture content and shrinkage of the lignite particle itself.

We investigated the diversity of epibiotic bacteria possessing antimicrobial activity isolated from nine species of red algae, and identified their phylogenetic position. For the isolation of epibiotic bacteria, nine species of red algae, Pachymeniopsis lauceolata, Plocamium telfairiae, Gelidium amansii, Chondrus oncellatus, Grateloupia filicina, Ceramium kondoi, Lomentaria catenata, Schizymenia dubyi and Porphyra yezoensis, were collected from the intertidal zone of Awaji Island, Japan. In total 92 bacteria were collected from the above red algal species. Primary screening results using disc diffusion assay revealed that 33% of bacteria possess antibacterial activity. Ten bacteria that showed high antibacterial activity were further studied for their ability to inhibit a set of fouling bacteria, some luminescent Vibrio and Photobacterium species and a panel of pathogenic bacteria. In general, the inhibitory activities were high against fouling and luminescent bacteria, while low against various pathogenic bacteria tested. These results suggest that some epibiotic bacteria have adapted to defend their position in their surface environment through the production of antibacterial metabolites giving defense against a broad spectrum of bacterial competitors. The phylogenetic analysis using 16 S rRNA sequences identified 7 of the 10 strains as belonging to the genus Bacillus, and other strains each 1 belonging to genus Microbacterium, Psychrobacter, and Vibrio species.

No abstract

This study proposes a numerical analysis for predicting fiber motion during injection molding of short-fiber-reinforced composites using the moving particle semi-implicit (MPS) method. Its meshless and Lagrangian nature enables us to track individual fibers and to easily represent free surfaces. In this study, the mechanism of fiber orientation in a T-shaped bifurcation was investigated experimentally and numerically. The fiber orientation of injection-molded glass-fiber/polypropylene composite was observed by X-ray CT. Despite the symmetric mold shape, there was asymmetric fiber orientation due to the mold filling process.Fiber motion in the bifurcation was then analyzed by the proposed simulation, and the fiber orientation was quantitatively evaluated in each small region. The prediction agreed well with the experiment, and the associated mechanism of fiber orientation is discussed. Furthermore, this approach explicitly demonstrates the interaction between fibers, which is an advantage of the proposed approach.