Two kinds of surface specializations of chlamydiae have been described: hemispheric projections and spikelike rods. We undertook the present studies to demonstrate chlamydial ultrastructure in greater detail in conventional thin-sectioned specimens. Chlamydia trachomatis (LGV strain L2/434/Bu), cultured for 40 h in L929 mouse fibroblasts, was fixed in glutaraldehyde-acrolein, p-formaldehyde-glutaraldehyde, or glutaraldehyde-osmium tetroxide mixtures, postfixed in osmium tetroxide, stained in uranyl acetate, dehydrated in ethanols, and embedded in Epon. By the use of fixatives that penetrate and fix rapidly, chlatnydial outer and plasma membranes were clearly revealed. Our results indicate that the hemispheric projections are specializations of the plasma membrane of elementary bodies. The spikelike projections are found in interniediate forms, originate beneath depressions of the plasma membrane, and extend through the periplasmic space and outer membrane to end with pointed tips. Improved preservation of chlamydiae provides a new, informative view of their complex structure. Significant interactions between chlamydiae and host cells might be influenced by the surface structures shown in this study.
Seven isolates of an unusual Neisseria sp. were obtained from eye cultures of children in two rural Egyptian villages. These Neisseria utilized only glucose, they exhibited a positive reaction when tested with antisera to crude antigen from Neisseria meningitidis and N. gonorrhoeae, and they did not react with the fluorescent antibody tests for N. gonorrhoeae or with the monoclonal antibodies used to serotype gonococci. The Egyptian isolates had colony morphology more typical of meningococci than gonococci and showed opaque and transparent colony variants. On SDS-PAGE, the major outer-membrane proteins had different patterns than those noted for comparable proteins of meningococci and gonococci; heat-modifiable outer-membrane proteins were present. Four of the six isolates examined had cryptic plasmids of 2.8 megadaltons, which were slightly larger than the cryptic plasmid of N. gonorrhoeae. These plasmids were homologous to the gonococcal cryptic plasmid, but had different restriction enzyme fragment patterns. The DNA from the Egyptian isolates, like DNA from N. meningitidis but unlike DNA from N. gonorrhoeae, could be cut with the restriction enzyme HaeIII. The frequency of transformation into a temperature-sensitive mutant of N. gonorrhoeae was 0.2 for the Egyptian isolates and 0.1 for N. meningitidis, a frequency that was 5-10-fold lower than that for the N. gonorrhoeae control isolates. Whole-cell DNA from the Egyptian isolates showed 68%-73% homology with N. gonorrhoeae and 57%-63% with N. meningitidis. On the basis of our observations, the Egyptian isolates are distinct from N. meningitidis and may represent a variant of N. gonorrhoeae. We suggest that the isolates be called Neisseria gonorrhoeae ssp. kochii.
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