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.
NEW GRID-REPLICA FOR PRECISE LOCALIZATION IN SLIDE CULTURES
This report describes a simple technique for the production and use of Formvar film replicas of rulings, such as counting grids, etched on glass slides. The resulting thin, transparent films, when dried on cover slips, are an excellent tool for counting and for orientation in slide cultures (Taubeneck, 1957). The method is similar to that of Powell (1956) who employs a lattice-like ruled area on cellophane, obtained by engraving type of matrix is manufactured by Feinoptische Werkstatten, Jena. Type II also bears four ruled areas each consisting of ten thousand numbered 60-, squares (figure 3). This type of matrix has been produced with the aid of photographic techniques, and is manufactured by the Zeiss Works, Jena. Using the above-mentioned types of matrices, the following technique has proved particularly efficient in the preparation