Related Experiment Videos
Evidence that Streptococcus mutans constructs its membrane with excess fluidity for survival at suboptimal
Abstract:
When cells from cultures of Streptococcus mutans strain FA-1 grown at 37 degrees C were exposed to incubation temperatures of 26 degrees C or less for 5 min or more, an extensive aggregation of particles was observed on the convex fracture faces of their freeze-cleaved membranes. Aggregation of particles was accompanied by a parallel increase in the activation energy for growth. By shifting the growth temperature from 37 to 24 degrees C for one doubling of culture mass, the transition temperature for membrane particle aggregation could be lowered from about 26 to 0 degrees C. Although membrane lipids became enriched with unsaturated fatty acids during this period of growth at 24 degrees C, this enrichment was not accompanied by an increased growth rate of the culture. However, the period of growth at 24 degrees C did result in bacteria that could grow more rapidly at 10 degrees C than could bacteria directly transferred from cultures grown at 37 degrees C. These observations suggest that the increase in membrane fluidity that occurs when bacteria are grown at 24 degrees C doses not allow bacteria to grow faster at 24 degrees C, but rather allows them to adapt more readily to further decreases in growth temperature.
Insights
Lowering growth temperatures for Streptococcus mutans causes membrane particle aggregation and alters lipid composition. This adaptation enhances bacterial survival at colder temperatures, improving cold adaptation rather than immediate growth rate.
Area of Science:
- Microbiology
- Cellular Biology
- Biochemistry
Background:
- Streptococcus mutans membrane structure and function are sensitive to temperature.
- Changes in membrane fluidity impact bacterial growth and survival.
Purpose of the Study:
- To investigate the effects of temperature shifts on Streptococcus mutans membrane particle aggregation.
- To understand how growth temperature adaptation influences lipid composition and cold tolerance.
Main Methods:
- Freeze-cleaving and electron microscopy to observe membrane particle aggregation.
- Measuring activation energy for growth at different temperatures.
- Analyzing changes in membrane lipid fatty acid composition.
Main Results:
- Incubation at 26°C or lower induced extensive membrane particle aggregation in Streptococcus mutans.
- Growth at a reduced temperature (24°C) lowered the transition temperature for membrane particle aggregation.
- While unsaturated fatty acids increased at 24°C, growth rate did not improve; however, cold tolerance at 10°C was enhanced.
Conclusions:
- Reduced growth temperatures induce significant changes in Streptococcus mutans membrane structure.
- Adaptation to lower temperatures enhances membrane fluidity, improving cold adaptation rather than immediate growth at moderately reduced temperatures.