Balanced macromolecular biosynthesis in "protoplasts" of Streptococcus faecalis

Area of Science:

• Microbiology
• Cell Biology

Background:

• Streptococcus faecalis 9790 can form osmotically fragile cells under specific growth conditions.
• Understanding the behavior of these fragile forms is crucial for studying bacterial cell wall synthesis and integrity.

Purpose of the Study:

• To characterize the growth and macromolecular biosynthesis of osmotically fragile Streptococcus faecalis 9790.
• To investigate the release of cellular components, particularly RNA, from these fragile forms upon osmotic stress.

Main Methods:

• Growth of Streptococcus faecalis 9790 in osmotically stabilized media (0.5 m sucrose or NH(4)Cl).
• Measurement of growth rate constants, turbidity, protein, RNA, and DNA content.
• Induction of osmotic shock and analysis of released RNA sedimentation properties.

Main Results:

• Protoplast cultures exhibited balanced macromolecular biosynthesis with growth rate constants between 0.66-0.94 mass doublings/hr.
• No evidence of cell division was observed in the protoplast cultures.
• Osmotic shock released 93-94% of RNA from protoplasts, compared to only 7% from intact streptococci.

Conclusions:

• Osmotically fragile Streptococcus faecalis 9790 cells undergo balanced growth without division.
• These fragile forms exhibit a significantly higher propensity for RNA release under osmotic stress than their intact counterparts.
• This suggests alterations in cell envelope structure or permeability in the osmotically fragile state.