Bacteriophages electron microscopy

Figure 5-13 Electron micrograph of a DNA molecule (from a bacterial virus bacteriophage T7) undergoing replication. The viral DNA is a long ( 14 pm) duplex rod containing about 40,000 base pairs. In this view of a replicating molecule an internal "eye" in which DNA has been duplicated is present. The DNA synthesis was initiated at a special site (origin) about 17% of the total length from one end of the duplex. The DNA was stained with uranyl acetate and viewed by dark field electron microscopy. Micrograph courtesy J. Wolfson and D. Dressier.

Both X-ray and neutron fiber diffraction (as well as electron microscopy) techniques have been applied to filamentous viruses, for which the prospect of three-dimensional crystals is poor. By combining neutron and X-ray fiber diffraction, NMR, circular dichroism, and Raman and infrared spectroscopies, an atomic model for the filamentous bacteriophage Pfl has been derived (Liu and Day, 1994). Other studies concerning Pfl have relied on purely X-ray fiber diffraction data, together with molecular modeling, to provide detailed filament structures (Pederson et at, 2001 Welsh et at, 1998a,b, 2000). Eiber diffraction was also used to solve the structure of the rodlike helical tobacco mosaic virus (TMV), where all of the coat protein and three genomic nucleotides... 

Earnshaw, W. C., King,J., and Eiserling, F. A. (1978a). The size of the bacteriophage T4 head in solution with comments about the dimension of virus particles as visualized by electron microscopy./. Mol Biol 122, 247-253. 

Lepault, J., Dubochet, J., Baschong, W., and Kellenberger, E. (1987). Organization of double-stranded DNA in bacteriophages A study by cryo-electron microscopy of vitrified samples. EMBO J. 6, 1507-1512. 

Fig. 13.1. The packaging motor of the bacteriophage

Wilrz M (1992) Bacteriophage structure. Electron Microscopy Reviews 5 283-310. 

Morphology and Dimensions of Bacteriophages as Determined by Electron Microscopy... 

Painstaking attempts to identify the size of the infectious unit have in the past been necessitated for plant viruses, and also for animal viruses for which hitherto no method of assay for single virus particles has materialized. These include chemical fractionation, physical fractionation by means of separation cells in the ultracentrifuge and electrophoresis apparatus, and inactivation of the virus (Lauffer, 181,182,184,299). Because of electron microscopy and the excellent linearity of the plaque count, these methods have not proved necessary with the bacteriophages. 

Eiserling, F. a., Romig, W. R. Studies of Bacillus suhtilis bacteriophages Structural characterization by electron microscopy, J. Ultrastruct. Res. 6, 540-546 (1962). Epstein, H. T. Transfection enhancement by ultraviolet light. Biochem. biophys. Res. Commun. 27, 258-262 (1967). 

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