Freeze-fracturing in normal vacuum reveals ringlike yeast plasmalemma structures

Area of Science:

• Cell Biology
• Microscopy Techniques
• Biophysics

Background:

• Saccharomyces cerevisiae, or baker's yeast, possesses regular arrays of subunits on its plasmalemma.
• Previous studies suggested specific conditions for visualizing these structures.

Purpose of the Study:

• To compare the fine structure of plasmalemma arrays in resting and starved yeast.
• To evaluate different freeze-fracture replication methods for high-resolution imaging.

Main Methods:

• Utilized various freeze-fracture replication techniques on Saccharomyces cerevisiae.
• Performed freeze-cleaving at different temperatures (173 K, 133 K, 108 K) under vacuum or liquid nitrogen.
• Investigated condensation contamination on fracture faces under controlled conditions.

Main Results:

• Observed significant morphological differences in plasmalemma subunits between resting and starved yeast.
• Identified a crater-like structure on the P face of starved yeast plasmalemma, visible under various conditions.
• Demonstrated that prolonged exposure did not cause contamination at 108 K with liquid nitrogen shrouds.

Conclusions:

• Preparation conditions, including temperature and atmosphere, do not obscure the distinct yeast plasmalemma structures.
• High-resolution freeze-etching is feasible without complex ultrahigh vacuum technology.
• The study reveals novel structural insights into yeast cell membranes under different metabolic states.