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Balanced Macromolecular Biosynthesis in "Protoplasts" of Streptococcus faecalis

^a Department of Microbiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140

ABSTRACT

Osmotically fragile forms of Streptococcus faecalis 9790 were grown in 0.5 M sucrose- or 0.5 M NH₄Cl-stabilized medium. The "protoplast" cultures exhibit an average growth rate constant of 0.66 to 0.94 mass doublings/hr. In a variety of experiments, turbidity and the net content of protein, ribonucleic acid (RNA) and deoxyribonucleic acid increase at the same rate, indicating balanced macromolecular biosynthesis. A total of two to three mass doublings was obtained, with no evidence of cell division. After osmotic shock, "protoplast" cultures released 93 to 94% of their RNA content in a form not sedimentable at 12,800 x g for 15 min, in contrast to streptococci, which released 7% of their RNA content after the same treatment.