A proteomic analysis of bacterial strain<Emphasis Type="Italic">Sinorhizobium fredii</Emphasis> RT19 subjected to salt shock

Sinorhizobium fredii RT19, a strain of free- living bacteria, was subjected to salt shock and its protein expression profiles were analyzed by differential display proteome approaches. The results of separation by two-dimensional polyacrylamide gel electrophoresis (2D PAGE) showed that the number of resolved proteins was 481, 465 and 424, corresponding to salt-free control, 5 and 50 min 1 mol/L salt treatment, respectively. Among the resolved proteins, 82 in total had altered expression in response to salt-shock stress. 26 out of the 82 proteins were induced and 23 were completely inhibited, while 12 were up-regulated and 21 down-regulated in response to salt shock. In addition, the appearance of differentially displayed proteins responding to different salt shock periods is also reported. The identity of the 26 induced proteins was revealed by matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) followed by database searching. Among them, 20 were assigned to proteins with known functions. Their roles in response to salt shock stress are discussed.