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Effect of growth temperatures on the protein levels in a psychrotrophic bacterium, Pseudomonas fragi
M Hebraud1, E Dubois, P Potier
1Station de Recherches sur la Viande, Institut National de la Recherche Agronomique de Theix, Saint-Genès-Champanelle, France.
Abstract:
Pseudomonas fragi has the ability to grow between 0 and 35 degrees C and grows optimally at 30 degrees C. Cellular proteins from mid-log-phase cells growing from 4 to 34 degrees C were labeled with L-[35S]methionine during 1 generation time and analyzed by two-dimensional gel electrophoresis. The electrophoretic patterns revealed differences in the patterns of protein synthesis over this temperature span. A qualitative comparison of cellular proteins led to their separation into five thermal classes. The first class contained proteins whose relative rates of synthesis were unaffected by the growth temperature. Three other classes included proteins with optimal expression at 4 to 10, 15 to 20, and 25 to 30 degrees C. A fifth class contained proteins which were more specifically synthesized at a supraoptimal growth temperature (34 degrees C). Two low-molecular-mass proteins, designated C7.0 and C8.0, were highly concentrated at 4 to 10 degrees C, and their relative rates of synthesis steadily increased with decreasing temperature. Polyclonal antibodies were separately raised against these two proteins. Immunological analyses revealed cross-reaction between these two proteins and between two additional low-molecular-mass proteins which were maximally produced at elevated temperatures. Antisera directed against C8.0 recognized the major cold shock protein of Escherichia coli, CspA, indicating the presence of similarities between these proteins.
Insights
Pseudomonas fragi exhibits distinct protein synthesis patterns across temperatures. Specific low-molecular-mass proteins (C7.0 and C8.0) are crucial for cold adaptation, showing similarities to E. coli cold shock proteins.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Pseudomonas fragi is a bacterium with a broad temperature growth range (0-35°C), optimal at 30°C.
- Understanding how bacteria adapt protein synthesis to varying temperatures is key to microbial physiology.
Purpose of the Study:
- To investigate temperature-dependent protein synthesis in Pseudomonas fragi.
- To identify and characterize proteins involved in thermal adaptation.
Main Methods:
- Two-dimensional gel electrophoresis of L-[35S]methionine-labeled cellular proteins from mid-log-phase cells grown at different temperatures (4-34°C).
- Qualitative analysis and classification of protein synthesis patterns into thermal classes.
- Generation of polyclonal antibodies against specific low-molecular-mass proteins (C7.0, C8.0).
- Immunological analysis including cross-reactivity and comparison with Escherichia coli cold shock protein CspA.
Main Results:
- Protein synthesis patterns varied significantly across the tested temperature range.
- Proteins were classified into five thermal expression groups, including those unaffected by temperature, optimally expressed at specific low, mid, or high ranges, and those synthesized at supraoptimal temperatures.
- Two low-molecular-mass proteins, C7.0 and C8.0, were highly synthesized at low temperatures (4-10°C), with synthesis increasing as temperature decreased.
- Antibodies against C8.0 cross-reacted with the major cold shock protein of E. coli (CspA), suggesting conserved structural or functional similarities.
Conclusions:
- Pseudomonas fragi differentially regulates protein synthesis in response to growth temperature.
- Specific low-molecular-mass proteins, C7.0 and C8.0, play a significant role in cold adaptation.
- The observed similarity between P. fragi C8.0 and E. coli CspA suggests conserved mechanisms for cold shock response in bacteria.