Authors : O. Meesungnoen, W. Nakbanpote, R. Thiwthong and K. Thumanu
Abstract: Pseudomonas aeruginosa PDMZnCd2003 is a Plant Growth Promoting Bacteria (PGPB) that was isolated from the rhizosphere of a Zn/Cd hyperaccumulative plant. This research aims to study the effect of Zn and/or Cd on the growth of P. aeruginosa PDMZnCd2003 and Zn and Cd tolerance mechanisms. The results showed that Zn and Cd treatments affected the growth of P. aeruginosa PDMZnCd2003 in Nutrient Broth (NB). Zn and Cd also induced the bacterium to secret yellow-green chemicals. Scanning Electron Microscopy (SEM) indicated that the bacterium produced large amounts of Extracellular Polymeric Substance (EPS) under the heavy metals treatments, especially Cd. The EPS were removed from native cells of P. aeruginosa PDMZnCd2003 by α-glucoamylase to become EPS-free cells. Statistical analyses of FT-IR spectra separated the native cells into control group and group with native cells treated with Zn and/or Cd by the shifts in α-helix and amide II. EPS-free cells were separated into three subgroups of control, EPS-free cells treated with Cd and EPS-free cells treated with Zn and Zn plus Cd. The α-helix and amide II peak shifts were found in the sub-groups of EPS-free cells treated with Zn and Zn plus Cd while the amount of α-helix was highest in EPS-free cells treated with Cd. In addition, there were shifts of sulfur groups and C-O bonds in both native cells and EPS-free cells after Zn and/or Cd treatments. Therefore, the biochemical structures involving in Zn and Cd accumulation were carbonyl, amine groups, protein containing thiol (-SH) groups and C-O bonds. Moreover, this study proposes P. aeruginosa PDMZnCd2003 has some specific mechanisms to tolerate Cd which are different from the mechanism responding to Zn and Zn plus Cd.
O. Meesungnoen, W. Nakbanpote, R. Thiwthong and K. Thumanu, 2012. Zinc and Cadmium Resistance Mechanism of Pseudomonas aeruginosa PDMZnCd2003. Research Journal of Biological Sciences, 7: 4-13.