The use of Artemia salina for developmental studies: preparation of embryos, tRNA, ribosomes and initiation factor 2.
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Animals↗
Biomedical subjects
T H MacRae
Publications and source records attributed to T H MacRae.
The function of fimbriae in Myxococcus xanthus. II. The role of fimbriae in cell-cell interactions.
Anti-fimbriae antiserum specifically inhibited swarming but no gliding motility per se in Myxococcus xanthus. However, formation of motile aggregates on agar and clumps in liquid media correlated with the presence of fimbriae. Ethylenediaminetetraacetic acid which inhibited swarming also inhibited fimbriae formation. Direct electron-microscopic observations revealed that fimbriae establish contact with apposing cell surfaces. Intact but not depolymerized fimbriae exhibited hemagglutination activity against guinea pig erythrocytes. This activity was inhibited by mannose, N-acetyl-D-galactosamine, and to a lesser degree by fructose, raffinose, melibiose, and alpha-methyl-D-mannoside. It is concluded that fimbriae are organelles which function to establish and maintain intercellular contacts, perhaps by a lectin-like function, during the coordinated movement of cell aggregates' (swarming) in myxobacteria. This hypothesis is supported by the observations of other workers that genes determining movement of cells in groups also control fimbriation in M. xanthus.
Acetylglucosamine↗
Fimbriation in gliding bacteria.
Of twenty-two strains of gliding prokaryotes examined, all but three were found to possess polar fimbriae. Fimbriae were not observed on two gliders, while Chloroflexus aurantiacus bore abundant peritrichous fimbriae. In some gliding bacteria, fimbriae were associated with 'holes' surrounded by an electron-transparent collar bearing 12 spike-like projections.
Bacteroidetes↗
The isolation and characterization of gliding motility mutants of Myxococcus xanthus.
Nonmotile and motility-altered mutants of Myxococcus xanthus have been obtained by the use of chemical mutagens, ultraviolet irradiation, and a procedure for selective spontaneous mutants. As judged by their behaviour on a variety of growth media, in both plate and slide culture, the mutants were divided into four groups. One group contains mutants which are truly nonmotile. Myxococcus xanthus NM, previously described as a nonmotile mutant, may be similar to type 3 mutants (described in text).
Hycanthone↗
Evidence for motility-related fimbriae in the gliding microorganism Myxococcus xanthus.
An electron-microscopic examination of negatively stained preparations from cell lysates of Myxococcus xanthus and in situ samples of Myxococcus xanthus, Myxococcus virescens, and Myxococcus fulvus has demonstrated the presence of polar fimbriae, about 8.5 nm in diameter, on motile but not nonmotile cells.
Cell Wall↗
Ultrastructural studies of Chondromyces crocatus vegetative cells.
Electron microscopy of sectioned, chemically fixed Chondromyces crocatus revealed a microorganism with a typical gram-negative cell envelope. The cytoplasm contained, in addition to tubules and two types of granules, a membrane-associated structure (MAS) that, although less extensive, bears some resemblance to polar membranes observed in flagellated bacteria. Examination of swarming cells negatively stained in situ, as well as thin sections, established that cell division occurs by septum formation and that well-defined mesosomes are associated with the process. Polar pili and a compact, amorphous slime layer surrounding the cells were evident in shadowed preparations of in situ cells. The slime layer and pili, by providing cell-to-cell interconnections, may influence the organized gliding movement characteristic of C. crocatus and other myxobacteria.
Cell Division↗