Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 88

Efficiency of plating is defined as the infectious virus titer (in PFU/ml) divided by the total number of virus particles in the sample. The particle–to–plaque-forming-unit (PFU) ratio, a term more commonly used today, is the inverse value (Table 2.1). For many bacteriophages, the particle-to-PFU ratio approaches 1, the lowest value that can be obtained. However, for animal viruses, this value can be much higher, ranging from 1 to 10,000. These high values have complicated the study of animal viruses. For example, when the particle-to-PFU ratio is high, it may not be clear that properties measured biochemically are in fact those of the infectious particle or those of the noninfectious component.

Figure 2.9 Transformation assay. Chicken cells transformed by two different strains of Rous sarcoma virus are shown. Loss of contact inhibition causes cells to pile up rather than grow as a monolayer. One focus is seen in panel A and three foci are seen in panel B at the same magnification. Courtesy of H. Hanafusa, Osaka Bioscience Institute.