L-forms of group A streptococci Size of viable particles and growth requirements
Filtrability is one of the characteristics of the L-phase of bacteria. The results of the filtration experiments reported in the literature indicate a diameter of the minimal reproductive unit of approximately 0.3t~. However, by measurements on photographs of slide cultures of the L-phase of several bacteria the diameter of the reproductive elements was found to be > 0.6/~ to 0.7t~ (Weibull and Lundin, 1962; Weibull, 1963). With the L-phase of two strains of group A streptococci the same discrepancy between the results of both techniques was obtained. Dependent on the expelimental conditions the filtration endpoint varied between 0.25/~ and 0.45u.. Slide cultures, observed by phasecontrast microscopy and photographed at regular intervals during incubation, showed that only elements having a diameter > 0.8~ developed into colonies. The possibility that the L-phase, due to its plasticity, is capable of passing through filters of smaller pore size than their diameter was investigated. Filtrates of 0.45~. filters were conceotrated by ultracentrifugation. Slide cultures inoculated with the sediment showed that the elements responsible for growth had a diameter ranging from 0.7tL-1.7tz. The results obtained indicate that the reproductive elements of the L-phase of the group A streptococci have a diameter > 0.8/~. Another property in which the L-phase differs from the parent strains is the need for special growth requirements (Sharp, 1954). However, results were obtained which indicate that these special conditions are not required during subculture. It proved to be possible to get luxuriant growth in a chemically defined medium of both the L-phase and the parent strains.
Size of Minimal Reproductive Units of Bacterial L Forms.
Summary L forms of Proteus mirabilis, a staphylococcus and a diphtheroid were grown in serum-free media. Slide culture experiments indicated that the diameter of the minimal reproductive units varied between 0.6 and 1.0 μ.
French film theory and criticism : a history/anthology, 1907-1939
These two volumes examine a significant but previously neglected moment in French cultural history: the emergence of French film theory and criticism before the essays of Andr Bazin. Richard Abel has devised an organizational scheme of six nearly symmetrical periods that serve to "bite into" the discursive flow of early French writing on the cinema. Each of the periods is discussed in a separate and extensive historical introduction, with convincing explications of the various concepts current at the time. In each instance, Abel goes on to provide a complementary anthology of selected texts in translation. Amounting to a portable archive, these anthologies make available a rich selection of nearly one hundred and fifty important texts, most of them never before published in English.