Ultrastructure of bacteriophages used for typing of Staphylococcus aureus

This paper reports the results of a study on the morphology, size and homogeneity of the bacteriophages used for typing Staphylococcus aureus. Fifty-five bacteriophages were studied. Preparations for the electron microscope were made directly from lysates or from purified and concentrated bacteriophages, and were contrasted with neutralized phosphotungstic acid (KPT) and examined under an electron microscope at x 40 000 microscopic magnification. The studied bacteriophages differed with regard to size and shape. The bacteriophages were classified into two morphological groups: BI and BIII. In the BI group, there morphological types were distinguished: B14, B15 and B16. Only one morphological type was distinguished in the BIII group, designated by the symbol BIII2. Only lysates of 42C, 70 and D bacteriophages contained virions of two morphological types: BI6 an BIII2. Until now, it is not clear whether the bacteriophages are a mixture of two different virions, or whether they represent variation in the size of their heads. Of the 55 bacteriophages studied, 25 were examined by other investigators. The results showed that of the 25 bacteriophages 5 belonged to different morphological types. It was concluded that the sets of standard bacteriophages should be checked by means of the electron microscope.