Formation of protoplasts from resting spores

Area of Science:

• Microbiology
• Cell Biology
• Biochemistry

Background:

• Bacterial endospores possess a complex multi-layered structure, including a cortex and germ cell wall, providing resistance.
• Conversion of spores to protoplasts is a key technique for studying spore structure and function, but requires efficient cell wall digestion.
• The role of cations in stabilizing spore structures during enzymatic digestion is not fully understood.

Purpose of the Study:

• To investigate the essential cations required for the lysozyme-induced conversion of bacterial spores into viable protoplasts.
• To elucidate the specific roles of calcium and magnesium ions in spore membrane stabilization and core hydration.
• To identify optimal conditions for protoplast formation using coatless Bacillus megaterium spores.

Main Methods:

• Lysozyme digestion of Bacillus megaterium KM spores, pre-treated to remove the outer coat.
• Suspension of spores in hypertonic solutions with controlled addition of specific cations (Ca2+, Mg2+, Sr2+, Mn2+).
• Observation of spore core changes, membrane integrity, and hydration using microscopy and biochemical assays.

Main Results:

• Calcium ions are essential for preventing membrane rupture during lysozyme digestion.
• Magnesium ions are critical for core hydration and nuclear mass changes indicative of germination.
• Strontium ions can substitute for calcium, but manganese cannot substitute for magnesium; dipicolinic acid competes with calcium for membrane stabilization.

Conclusions:

• The conversion of bacterial spores to protoplasts by lysozyme requires specific cation cofactors.
• Calcium stabilizes the spore's inner membrane, while magnesium facilitates core hydration and germination-related changes.
• These findings provide insights into the structural and ionic requirements for spore germination and protoplast formation.