Abstract
BackgroundTemperature is an important environmental factor which can dramatically affect biochemical processes in bacteria. Temperatures above optimal cause heat shock, while low temperatures induce cold shock. Since the physiological response of the bacterium Escherichia coli to slow temperature fluctuation is not well known, we investigated the effect of periodic temperature cycling between 37° and 8°C with a period of 2 h on proteome profile, cold shock CspA and CspB protein and gene production.ResultsSeveral proteins (i.e. succinyl-CoA synthetase subunit alpha, periplasmic oligopeptide-binding protein, maltose-binding periplasmic protein, outer membrane porin protein, flavodoxin-1, phosphoserine aminotransferase) were up or down regulated during temperature cycling, in addition to CspA and CspB production. The results indicate that transcription of cspA and cspB increased during each temperature downshift and consistently decreased after each temperature upshift. In sharp contrast CspA-FLAG and CspB-FLAG protein concentrations in the cell increased during the first temperature down-shift and remained unresponsive to further temperature fluctuations. The proteins CspA-FLAG and CspB-FLAG were not significantly degraded during the temperature cycling.ConclusionThe study demonstrated that slow periodic temperature cycling affected protein production compared to cells constantly incubated at 37°C or during classical cold shock. Bacterial cspA and cspB mRNA transcript levels fluctuated in synchrony with the temperature fluctuations. There was no corresponding pattern of CspA and CspB protein production during temperature cycling.
Highlights
Temperature is an important environmental factor which can dramatically affect biochemical processes in bacteria
Bacterial strains and plasmids Proteins CspA and CspB were FLAG tagged as previously described using the plasmids pKD46 and pSUB11 [23] and the C-term FLAG was confirmed by PCR
Bacterial growth decreased during each temperature downshift, when the temperature of the bacterial growth medium dropped to 15°C or lower
Summary
Temperature is an important environmental factor which can dramatically affect biochemical processes in bacteria. Since the physiological response of the bacterium Escherichia coli to slow temperature fluctuation is not well known, we investigated the effect of periodic temperature cycling between 37° and 8°C with a period of 2 h on proteome profile, cold shock CspA and CspB protein and gene production. An educated guess based on the cold shock behaviour and growth at optimal temperature of E. coli can be made, the effect of temperature fluctuation on CspA and CspB has not been experimentally verified. In the natural microbial environment, temperature changes are usually gradual This is different from the classical cold shock experiment where the temperature is rapidly changed and cells do not experience a gradual change of temperature. There are, no systematic studies to show the effect of periodic slowly changing temperature on transcription and translation of CspA and CspB cold shock proteins
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