Thesis (M.Sc.) - Asian Institute of Technology - Chulabhorn Research Institute - Mahidol University, 2007

Metals contaminated in the environnment have become important environmental pollutants and effect in soil, water and ground water. Acinetohacter sp. ADP1 was chosen in this study because it is common in soil and water. This study can be applied for the bio-indicator or as decomposer(s) when other microbes can not survive. Acinetohacter sp. ADP 1 has adaptive and cross protection responses when induced with 1OOuM zinc chloride and 25M cadmium chloride, indicating that ADPI contain genes responsible for zinc and cadmium resistance. However, no adaptive occurred when induce with 75M cobalt chloride. The cross protection response toward cobalt was also not occurred with zinc and cadmium induced cells. The czcA gene is the largest part of CzcCBA efflux pump system, which was proposed to be the cation efflux system that response to zinc, cobalt and cadmium. The czcA mutant strain was constructed and the result showed that the czcA mutant strain showed highly sensitive phenotype when cell were exposed to lethal concentrations of zinc, cobalt and also cadmium. This result strongly suggested that czcA gene plays a major role in the heavy metals resistance in Acinetobacter sp. ADP 1. Supporting the role of czcA in metal resistance, its transcription was up-regulated in the presence of zinc and cadmium. However, the czcA mutant remained most of adaptive and cross protection responses found in wild type, but at low level. This result provides an evidence for additional metal resistance determination in Acinetobacter sp. ADP 1.

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering and Management Inter-University Program on Environmental Toxicology, Technology and Management.