QUANTITATIVE CONVERSION OF CELLS AND PROTOPLASTS OF PROTEUS MIRABILIS AND ESCHERICHIA COLI TO THE L-FORM

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Abstract
Media and methods were developed which allow the development of a 3B type L-colony from every cell in strains of P. mirabilis and E. coli strain K12. One medium for Proteus consists entirely of mineral nutrients plus a carbon source and penicillin; the medium for E. coli is also chemically defined, except for a requirement for a high concentration of vitamin-free acid-hydrolyzed casein. Success in the development of these media can be partly attributed to the working hypothesis that a protoplast stage is intermediate between bacillary form and L-colony: medium characteristics such as high solute and magnesium levels which are crucial to protoplats stabilization proved to be equally critical to L-colony development. In addition, penicillin concentration, agar concentration, and use of the pour-plate method of decisive importance to L-colony growth.