The effect of cold stress on the proteome of the marine bacterium Pseudomonas fluorescens BA3SM1 and its ability to cope with metal excess

• P. fluorescens BA3SM1 acclimates to cold stress by a number of changes in protein regulation.
• Some resistance mechanisms developed under cold stress are similar to those developed in response to Cd, Zn and Cu.
• P. fluorescens BA3SM1 is able to biosorb high levels of metals even at low temperature.
• P. fluorescens BA3SM1 appears as a promising agent for bioremediation processes.

This study examined the effect of cold stress on the proteome and metal tolerance of Pseudomonas fluorescens BA3SM1, a marine strain isolated from tidal flat sediments. When cold stress (+10 °C for 36 h) was applied before moderate metal stress (0.4 mM Cd, 0.6 mM Cd, 1.5 mM Zn, and 1.5 mM Cu), growth disturbances induced by metal, in comparison with respective controls, were reduced for Cd and Zn while they were pronounced for Cu. This marine strain was able to respond to cold stress through a number of changes in protein regulation. Analysis of the predicted differentially expressed protein functions demonstrated that some mechanisms developed under cold stress were similar to those developed in response to Cd, Zn, and Cu. Therefore, pre-cold stress could help this strain to better counteract toxicity of moderate concentrations of some metals. P. fluorescens BA3SM1 was able to remove up to 404.3 mg Cd/g dry weight, 172.5 mg Zn/g dry weight, and 11.3 mg Cu/g dry weight and its metal biosorption ability seemed to be related to the bacterial growth phase. Thus, P. fluorescens BA3SM1 appears as a promising agent for bioremediation processes, even at low temperatures.