title: [Mechanism of heavy-metal tolerance in Pseudomonas aeruginosa ZGKD2].
abstract: The cadmium-resistant bacterium Pseudomonas aeruginosa strain ZGKD2 exhibiting tolerance to various heavy-metals was isolated from gangue pile of coal area in our laboratory. This bacterium could serve as an effective metal sequestering and growth-promoting bioinoculant for plants grown in metal-contaminated soil. However, the mechanism of heavy-metal tolerance is still unclear. When the beef extract-peptone medium was supplemented with 200-3 000 micromol x L(-1) Cd2+, Cu2+, Zn2+, Ni2+, Pb2+ or Mn2+, the maximum biomass of strain ZGKD2 decreased with the increase of heavy-metal concentrations, while different concentrations of heavy-metals had no significant effect on its alkaline production. Stationary-phase cells of strain ZGKD2 were exposed to 0, 200, 600 and 1 000 micromol x L(-1) of Cd2+ , Cu2+, Zn2+ and Ni2+ or 0, 1 000, 2 000 and 3 000 micromol x L(-1) of Pb2+ and Mn2+ for 2 h, respectively. The activity of SOD and CAT increased in a heavy-metal-concentration-dependent manner, especially in the Cd2+ and Cu2+ treatments. The siderophore production of strain ZGKD2 in modified sugar-aspartic acid medium was enhanced by 200- 1 000 micromol x L(-1) of various heavy-metals. Cd2+ and Zn2+ strongly induced the siderophore production of strain ZGKD2, Ni2+ and Mn2+ had little effect, whereas Cu2+ led to significant inhibition. The siderophore production of strain ZGKD2 was positively related with its metal tolerance. These results indicated that alkaline production, siderophore production, and the increase of antioxidant enzyme activities in strain ZGKD2 might be the main mechanisms of heavy-metal tolerance.
authors.affiliation: School of Chemical and Environmental Engineering, China University of Mining and Technology (Beijing), Beijng 100083, China. zhangyuxiu@cumtb.edu.cn
authors.forename: Yu-Xiu
authors.initials: YX
authors.lastname: Zhang
authors.forename: Jiao
authors.initials: J
authors.lastname: Wang
authors.forename: Tuan-Yao
authors.initials: TY
authors.lastname: Chai
authors.forename: Qian
authors.initials: Q
authors.lastname: Zhang
authors.forename: Jin-Guang
authors.initials: JG
authors.lastname: Liu
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.forename: Zhi-Qiang
authors.initials: ZQ
authors.lastname: Bai
authors.forename: Zeng-Jian
authors.initials: ZJ
authors.lastname: Su
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects* / Q000235:genetics; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000378:metabolism; D003031:Coal; D019216:Metals, Heavy / Q000378:metabolism*; D008906:Mining; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017262:Siderophores / Q000096:biosynthesis; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
chemical_list: D003031:Coal; D019216:Metals, Heavy; D017262:Siderophores; D012989:Soil Pollutants; D002104:Cadmium; D015032:Zinc