Morphology of meningopneumonitis virus exposed to penicillin as observed with the electron microscope.

In a previous communication, Tajima et al. (1957) described how viruses of the psittacosislymphogranuloma group seem to have two different modes of multiplication in their developmental cycle. One is analogous to the intracellular development of pox viruses described by Morgan et al. (1954) and Tajima and Kubota (1956). In this mode, a pre-existing component of viral structure, the matrix, appears first in the cytoplasm of host cells; in the next stage, incomplete limiting membranes develop in the periphery of the matrix by condensation of fine, granular material to transform into the incomplete forms; the limiting membranes begin to enclose some portions of the matrix progressively, and finally the large forms are produced. The other mode of multiplication is one in which smaller forms increase in number as the result of segmentation of larger forms caused by constriction of the limiting membrane. Since the interesting observation made by Gardner (1940), it has been noted by many others (Smith and Hay, 1942; Weiss, 1943; Alture-Werber et al., 1945; Fisher, 1946; Shanahan et al., 1947; Nitzschke and Strauch, 1957; Zapf, 1957) that penicillin, in certain concentrations, arrests normal division of bacteria without necessarily interfering with their growth. This leads to the production of giant forms in the inhibited cells, and finally the bacteria undergo lysis. With regard to the viruses belonging to the psittacosis-lymphogranuloma group, Weiss (1950), in his histological investigation, made an interesting observation. The virus particles of feline and murine pneumonitis in the presence of penicillin did not divide, but rather developed large, irregularly shaped, vacuolated plaques. Hurst et al. (1953) obtained similar results with lymphogranuloma venereum virus.