Effect of heavy metals on acdS gene expression in Herbaspirillium sp GW103 isolated from rhizosphere soil

This study aimed to understand the influence of heavy metals on 1-aminocyclopropane-1-carboxylate deaminase activity (ACCD) and acdS gene expression in Herbaspirillium sp. GW103. The GW103 strain ACCD activity decreased in cells grown in a medium supplemented with Pb and As, whereas cells grown in medium supplemented with Cu showed increase in enzyme activity. The GW103 strain produced 262.2 +/- 6.17 Rmol of a-ketobutyrate per milligram of protein per hour during ACC deamination at 25 degrees C after 24 h incubation. Using a PCR approach, an acdS codinggene of 1.06 kbp was amplified in isolate GW103, showing 92% identity with Herbaspirillum seropedicae SmR1 acdS gene. Real time quantitative polymerase chain reaction results indicate that the acdS expression rate was increased (7.1-fold) in the presence of Cu, whereas it decreased (0.2- and 0.1-fold) in the presence of As and Pb.