Treponema pallidum (Nichols strain) in tissue cultures: cellular attachment, entry, and survival

T J Fitzgerald, J N Miller, J A Sykes
1975 Infection and Immunity  
The existence of plasmids in all four types of colony morphology of Neisseria gonorrhoeae has been established by electron microscopy of the plasmid deoxyribonucleic acid (DNA) fractions separated by density equilibrium centrifugation on ethidium bromide-cesium chloride solutions. Cells of each colony type (Ti, T2, T3, and T4) were lysed with detergent, and most of the chromosomal DNA was removed by centrifugation and alkali denaturation. A simplified procedure avoiding the latter has also been
more » ... developed for N. gonorrhoeae plasmid isolation. The heavier bands containing the covalently closed, circular DNA plasmid molecules were collected and converted to the open circular form for electron microscopy. Contour lengths of the plasmid DNA isolated from all four colony types measured 1.5 Am, with a calculated molecular weight of 2.9 x 106. An internal standard of colicin El DNA was used in our determinations. All four isolates used were further characterized for the presence of pili (found only in Ti and T2) and for their sensitivities to several antibiotics. The functions of these gonococcal plasmids are unknown at the present time.
doi:10.1128/iai.11.5.1141-1146.1975 fatcat:qvh7miwpu5fdzmimutqquinny4