Filterability of streptococcal L-forms

Quantitation of bacillus subtilis L-form growth parameters in batch culture

Several methods were used to monitor the growth of a stable L-form in batch culture. The end of the exponential growth phase was determined with greatest accuracy by the amounts of deoxyribonucleic acid per milliliter of culture. Optical density and viable count data were not as reliable because the L-forms began to lyse at the end of exponential growth. Lysis was detected visually, by phase-contrast observations of wet mounts, and by release of ultraviolet-absorbing material into culture supernatant fluids.

Identical nutritional requirements of Streptococcus faecium f24 and a derived stable L-phase variant

The nutritional requirements of Streptococcus faecium F24 and a lysozyme-produced stable L-phase variant of this strain appear to be identical. Thus, conversion of bacteria to the stable L-phase can occur without changes in nutritional requirements.

Morphology and viability of large bodies of streptococcal L-forms

A procedure is described for the massive formation and isolation of large bodies of group A and D streptococcal L-forms. Up to 90% individual bodies of 20 to 100 mum in diameter can be produced in pour plates of nutrient gelatin and subsequently harvested by simple micromanipulation. The growth of these giant bodies was followed by light microscopy and their ultrastructure and internal architecture was examined by transmission and scanning electron microscopy. Large bodies had a honeycomb structure of vacuoles. Numerous small units could be observed inside, protruding into, and between vacuoles. Intact large bodies (30 to 60 mum), when placed in small amounts of broth and incubated at 35 C, initiated turbid cultures, but when set on agar, they ruptured, releasing internal granules and producing typical L-form colonies. The number of internal colony-forming units (CFU) was correlated with the size of large bodies. Up to 200 CFU were detected in bodies of 40 to 60 mum in diameter, whereas corpuscles of 20 to 30 mum averaged only three CFU. The inefficiency of replication was apparent with the determination by light and electron microscopy that at least 100 times as many granules and elementary corpuscles as CFU were produced inside large bodies.

Isolation and characterization of cell wall-defective variants of Bacillus subtilis and Bacillus licheniformis

Quantitative mass conversion of intact bacterial cells of Bacillus subtilis and B. licheniformis to L-phase variants has been effected after lysozyme treatment. After subculture of the unstable L-phase variants for several months in the presence of methicillin, stable L-phase variants were obtained which grew in the absence of the antibiotic and were then unable to revert to the classical bacterial phase under conditions which gave rise to mass reversion of the protoplasts and unstable L-variants. These stable L-phase variants, which retained many of the physiological properties of the bacterium from which they were derived, were capable of growing exponentially and multiplying in liquid medium. Their morphology and apparent modes of reproduction were consistent with that described for other L-phase variants. The morphological events, as monitored by the electron microscope, of the reversion to the intact bacterial phase of an unstable L-phase variant of B. licheniformis are described.