No abstract

CARRASCO, A., SCHWENCKE, J., and CARU, M. 1992. Isolation of Frankia from nodules of Trevoa trinervis: ultrastructural characterization. Can. J. Microbiol. 38: 174-180. Root nodules obtained from Trevoa trinervis and its actinomycete Frankia were studied by electron microscopy. The microsymbiont was found in the cortical cells and it exhibits the typical actinomycetal structures: septate hyphae and symbiotic vesicles. Using the double-layer technique, two Frankia strains were isolated from the nodules. In vitro these strains exhibit morphological characteristics considered specific to the genus Frankia, i.e., hyphae, Frankia vesicles, and polymorphic sporangia. CARRASCO, A., SCHWENCKE, J., et CARU, M. 1992. Isolation of Frankia from nodules of Trevoa trinervis: ultrastructural characterization. Can. J. Microbiol. 38 : 174-1 80. Les nodules radiculaires obtenu de Trevoa trinervis et son actinomycete Frankia ont Ct C CtudiCes par microscopie Clectronique. Le microsymbiote Ctait trouvC dans les cellules corticales et on exhibe le plus typique actinomycetal structures : des hyphes et des vesicules symbiotiques. En utilisant la technique de double-plaque, on a is016 deux souches d'actinomyckte a partir des nodules. Des souches sont considerkes comme appartenant au genre Frankia puisqu'elles posskdent les caractkres morphologiques propres a ce genre : des Frankia hyphes, des vCsicules et des sporanges polymorphes.

A particulate fraction derived from bacterial cells stimulates septation in irradiated Escherichia coli lon mutants when added to postirradiation plating media. It was established that the particles are derived from the cytoplasmic membrane and that they have been partially purified by sucrose density gradient centrifugation. These particles also contain the cytochrome-based respiratory activity of the cell. A variety of experiments established a correlation between the septation-promoting activity of the particles and their ability to remove oxygen from the postirradiation plating medium. It was suggested that the efficient removal of oxygen from the medium allowed the lon cells to repair radiation-induced damage to the septation mechanism.

The Frankia strains TtI 11 and TtI 12 isolated from T. trinervis Miers were characterized regarding their carbon source utilization, intrinsic antibiotic resistance, infectivity, and effectivity on the original host. Both strains grew on BAP medium supplemented with glucose, maltose, and sucrose, but differed in their ability to use other carbon sources such as propionate, pyruvate, acetate, succinate, citrate, and mannitol.The isolates were sensitive to five of the twelve antibiotics tested at 1 #g mL-1 concentration: chloramphenicol, tobramycin, eritromycin, streptomycin, and rifampicin. They exhibited a variable degree of resistance at 1 /zg mL-1 concentraction to penicillin G, 4-fluorouracil, oleandomycin, and lincomycin.Both isolates were able to infect and nodulate the original host plant, and thus represent the first reported infective and effective microsymbionts for T. trinervis Miers, a rhamnaceous actinorhizal host.

Fusion of Bacillus subtllis plasma membrane vesicles with planar lipid bilayers ind uced the appearance of discrete current fluctuations characteristic oi" ion channels. These channels showed a wide range ofconductances and kinetic behaviors. In 300 mM KCI, their condueumces ranged from a Few hundreds of pS to more than l aS, and most of them exhibited several sub.states. The channels poorly discriminated between small univalent onions and cations. Some of them showed voltage dependence and most of them presented a complex gating kinetics. "File results are consiste~tt with the hypothesis of the presence in the B. st~brilis plasma membrane of pores composed of subunits that l'unction cooperatively.