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Effect of growth temperature on several exported enzyme activities in the psychrotrophic bacterium Pseudomonas
Abstract:
In accordance with previous results, the activity of extracellular proteases from Pseudomonas fluorescens MF0 is maximal at a growth temperature of 17.5 degrees C, well below the optimal growth temperature. In addition, the activities of three periplasmic phosphatases display the same growth temperature optimum. Chemostat experiments have shown that it is the growth temperature itself and not the value of the growth rate that regulates these activities. In contrast, a foreign periplasmic phosphatase, expressed under the control of its own promoter, displays a different sensitivity toward temperature. We conclude that in the psychrotrophic strain P. fluorescens MF0, growth temperature exerts a specific control upon the activity of certain enzymes. The critical temperature (17.5 degrees C) is within the range of normal growth, suggesting that this control is probably different from a cold shock or heat shock response.
Insights
Pseudomonas fluorescens MF0 exhibits maximal extracellular protease and periplasmic phosphatase activity at 17.5°C, a specific growth temperature regulating enzyme activity independent of growth rate. This psychrotrophic strain shows unique temperature-dependent enzyme control.
Area of Science:
- Microbiology
- Enzymology
- Molecular Biology
Background:
- Pseudomonas fluorescens MF0 is a psychrotrophic bacterium.
- Enzyme activity in bacteria is often influenced by growth conditions.
- Previous studies indicated specific temperature optima for certain enzymes.
Purpose of the Study:
- To investigate the effect of growth temperature on extracellular protease and periplasmic phosphatase activity in Pseudomonas fluorescens MF0.
- To determine if growth temperature or growth rate is the primary regulator of these enzyme activities.
- To compare the temperature sensitivity of native enzymes with a foreign phosphatase expressed in P. fluorescens MF0.
Main Methods:
- Culturing Pseudomonas fluorescens MF0 at various temperatures using chemostat experiments.
- Measuring the activity of extracellular proteases and periplasmic phosphatases.
- Expressing a foreign periplasmic phosphatase under its own promoter to assess temperature sensitivity.
Main Results:
- Extracellular protease activity was maximal at 17.5°C, below the optimal growth temperature.
- Three periplasmic phosphatases also showed maximal activity at 17.5°C.
- Chemostat experiments confirmed that growth temperature, not growth rate, regulates these enzyme activities.
- A foreign phosphatase exhibited different temperature sensitivity, indicating specific regulation of native enzymes.
Conclusions:
- Growth temperature specifically controls the activity of certain enzymes in the psychrotrophic strain P. fluorescens MF0.
- The critical temperature of 17.5°C is within the normal growth range, suggesting a regulatory mechanism distinct from cold or heat shock responses.
- This specific temperature-dependent regulation of enzyme activity is a key characteristic of P. fluorescens MF0's adaptation to its environment.