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Biomedical subjects

K Amako

Publications and source records attributed to K Amako.

At least 127 records · Page 7Linked to original sources
PubMed1980

Localization of bacteriophage receptor, clumping factor, and protein A on the cell surface of Staphylococcus aureus.

The surface of several laboratory strains of Staphylococcus aureus were observed with a scanning electron microscope, and the presence of two morphologically characteristic structures--a ridge separating cell surface into old and new surfaces and a concentric circular structure--are described. These two structures seemed to be present universally on the surfaces of cells of the genus Staphylococcus. The removal of the circular structures by a mild treatment of the cell with trichloroacetic acid suggested that this structure seemed to represent circularly arranged teichoic acid. With experiments using morphologically recognizable markers among three of the cell wall components, clumping factor, phage receptor, and protein A, the clumping factor was proven to be specifically localized on the old surface; and more phage receptors were detected on the old surface than on the new surface, but protein A was present all over the cell surface. This indicated that the clumping factor and most of the phage receptors appeared on the cell wall surface in a late stage of the cell growth cycle, but protein A was present in an early stage of the growth. The idea of aging of the cell wall is discussed.

Agglutinins↗
PubMed1979

Regular arrangement of wall polymers in staphylococci.

Concentric circular structures were observed on the newly exposed surface of the wall of Staphylococcus epidermidis and on its isolated cross-wall. These structures were removed by treatment with trichloroacetic acid. Chemical analysis revealed that after treatment with trichloroacetic acid most of the wall phosphorus was extracted but more than half of the N-acetylglucosamine remained associated with the wall. These observations suggest that polysaccharides are likely to be arranged circularly on the surface of the wall.

Carbohydrate Conformation↗
PubMed1979

Mode of cell separation and arrangement of Staphylococcus.

The process of cell separation and arrangement of Staphylococcus was investigated using a scanning electron microscope. After two cycles of cell division, the Staphylococcal cells cultured on an agar medium were generally observed to be arranged in three morphological types: linear, square, and crooked arrangements. Results of the examination of cell surface structure revealed that separations had occurred in these clustered cells following two patterns. One type of second separation occurred parallel to the transversal axis of the preceding pair of the parental cells (X-type) and the other occurred tangential to it (Y-type). In the former type, the four daughter cells were usually arranged tetragonally after the separations, and in the latter type they were arranged either linearly or crookedly depending on the direction of the second separation. The final pattern of the cell arrangement was thus determined by the type of septal wall formation and the direction of cell separation. After several cycles of cell divisions, the cells were finally arranged in an irregular grape-like cluster, even though the cross walls were formed regularly at the rectangular face of the preceding cross walls.

Cell Division↗
PubMed1978

Purification and the ultrastructure of a bacteriocin produced from Shigella sonnei strain 100052.

A bacteriocin produced by strain 100052 of Shigella sonnei (shigellacin 52) was purified about 80-fold from a mitomycin C-induced culture supernatant. The purified preparation gave a single band on sodium dodecyl sulfate-gel electrophoresis with an approximate molecular weight of 10,000. The negatively stained electron micrograph of the purified bacteriocin preparation revealed the existence of three different particles. They were a small cylindrical tube (4.2 by 6.0 nm), a ring-shaped particle and a filamentous structure. The molecular weight calculated from the shape of the small tube was approximately 50,000. The latter two particles appeared to be constructed from subunits which were morphologically similar to the cylindrical tube. These results suggested that the morphological subunit of shigellacin 52 consisted of five chemical subunits with molecular weights of 10,000 each, and it assembled into two types of polymers, a ring-shaped particle and a filamentous structure, which seemed to be the main components of the purified shigellacin 52 preparation.

Bacteriocins↗
PubMed1976

Size and structure of the cholera toxin molecule and its subunits.

Cholera toxin (choleragen) dissociated into two types of subunit with molecular weights estimated to be 28,000 daltons (A) and 11,000 daltons (B); this dissociation was effected by gel filtration at acid pH with or without urea. Subunit A could be separated into two fragments, A1 (23,000 daltons) and A2 (about 2,500 daltons), after reduction and alkylation. Choleragenoid (68,000 daltons) appeared to be a polymerized form of subunit B. A-specific antigen was found in choleragen as well as in A1 and A2, while B-specific antigen was found in both choleragen and choleragenoid. In electron micrographs, the toxin molecule appeared as a particle of uniform size consisting of subunits in V- or Y-shape and in ring form. The dimensions coincided with the values calculated from the molecular weights.

Antigens, Bacterial↗