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.
Effect of spray nozzle design on liquid-solid contact in fluidized beds
Abstract In industrial fluid cokers the feedstock, consisting of heavy bituminous hydrocarbons, is atomized with steam and injected into a hot fluidized bed of coke. Good and uniform contact of the liquid droplets with the solid particles is required to provide heat for the cracking reactions while minimizing mass transfer effects. Experiments in a pilot plant coker have suggested that the initial particle/liquid mixing, in the spray jet, is rather poor. Experiments in a X-ray scanner showed that liquid droplets and entrained particles accumulate just below the tip of the jet plume to form agglomerates. An experimental technique was used to quantitatively determine the quality of mixing with a variety of nozzle configurations including several novel designs. By improving spray stability, redistributing liquid droplets to the solids-rich region of the jet and increasing the surface area of the gas–liquid jet-fluidized bed interface, liquid/solid contact is improved.