Robustness of Cell Disruption of Heavy Metal-Resistant Pseudomonas fluorescens BA3SM1 Isolates

A bacterial strain (BA3SM1) was isolated from the tidal flat sediments collected in west of Cherbourg seaport (France). The biochemical characteristics and the partial 16S rDNA gene sequencing of isolate, BA3SM1, have identified it as Pseudomonas fluorescens. When cultivated, this strain exhibits a very high tolerance to metal contamination [minimal inhibitory concentration = 10mM (650mg/L) for zinc (Zn), 9mM (560mg/L) for copper (Cu), and 3mM (350mg/L) for cadmium (Cd)]. To attempt to explain this high tolerance, future studies will be undertaken to analyze stress proteins produced by BA3SM1 in the presence of heavy metal excess. For this aim, several protein extraction procedures were tested, that is, biochemical, sonication, and high-pressure treatments. Our results show that BA3SM1 is very resistant to cell disruption, because an efficient protein release was only obtained with a drastic physical protocol: a treatment by a hypoosmotic shock followed by three passages through a French press at 159 MPa. This preliminary work is essential because it recommends a convenient protein extraction procedure to perform quality 2D-electrophoresis, from a tidal flat strain particularly resistant to heavy metals and to cell disruption. In further studies, proteomic analysis will allow understanding of the resistance mechanisms developed by this strain to counteract heavy metal stresses. A better knowledge of these mechanisms will give us more information about the abilities of BA3SM1 to be used for bioremediation applications.