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Spinae are attached to protease-sensitive structural proteins in the external surface of the outer membrane. Agents and (or) treatments affecting ionic, hydrophobic, or hydorgen bonds are ineffective in releasing spinae from bacteria. As judged by thin-sectioning and freeze-fracturing techniques, the outer membrane is not modified at the attachment site to a detectable extent, and the other surface layers are not involved. The attachment of spinae is thus differentiated from that of flagella.

The iron-protein ferritin has been purified from mycelium, sporangiophores, and spores of the fungus Phycomyces blakesleeanus. It has a protein-to-iron ratio of 5, a sedimentation coefficient of 55S, a buoyant density in CsCI of 1 .82 g/cm3, and the characteristic morphology of ferritin in the electron microscope . Apoferritin prepared from Phycomyces ferritin has a sedimentation coefficient of 18S and consists of subunits of molecular weight 25,000 . In the cytoplasm of Phycomyces, ferritin is located on the surface of lipid droplets (0 .5-2 .0 y in diameter) where it forms crystalline monolayers which are conspicuous in electron micrographs of sporangiophore thin-sections . Ferritin is found in all developmental stages of Phycomyces but is concentrated in spores . The level of ferritin iron is regulated by the iron level in the growth medium, a 50-fold increase occurring on iron-supplemented medium .

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Two temperate bacteriophages of differing morphology and host range were isolated by screening 94 isolates of Clostridium difficile. Phage 41 had a 300-nm flexible tail, whereas phage 56 had a shorter tail with a contractile sheath. Electron microscopy of phage 56 lysates exposed to elevated magnesium concentrations showed small virus-like particles which were 21 nm in diameter. The addition of MgCl2 to semisolid agar overlays enhanced both the titer and plaque size of phage 56. Phage 56 was more temperature labile than phage 41 and demonstrated unusual lability in buffer at pH 7.0. One-step growth and adsorption experiments revealed that both phages had latent periods of about 60 min, but phage 56 adsorbed to its indicator strain more efficiently. Phage 56, which was obtained from a toxigenic strain of C. difficile, was used to lysogenize its