title: Survival Strategies of the Plant-Associated Bacterium Enterobacter sp. Strain EG16 under Cadmium Stress.
abstract: Plant-associated bacteria are of great interest because of their potential use in phytoremediation. However, their ability to survive and promote plant growth in metal-polluted soils remains unclear. In this study, a soilborne Cd-resistant bacterium was isolated and identified as Enterobacter sp. strain EG16. It tolerates high external Cd concentrations (Cd(2+) MIC, >250 mg liter(-1)) and is able to produce siderophores and the plant hormone indole-3-acetic acid (IAA), both of which contribute to plant growth promotion. Surface biosorption in this strain accounted for 31% of the total Cd accumulated. The potential presence of cadmium sulfide, shown by energy-dispersive X-ray (EDX) analysis, suggested intracellular Cd binding as a Cd response mechanism of the isolate. Cd exposure resulted in global regulation at the transcriptomic level, with the bacterium switching to an energy-conserving mode by inhibiting energy-consuming processes while increasing the production of stress-related proteins. The stress response system included increased import of sulfur and iron, which become deficient under Cd stress, and the redirection of sulfur metabolism to the maintenance of intracellular glutathione levels in response to Cd toxicity. Increased production of siderophores, responding to Cd-induced Fe deficiency, not only is involved in the Cd stress response systems of EG16 but may also play an important role in promoting plant growth as well as alleviating the Cd-induced inhibition of IAA production. The newly isolated strain EG16 may be a suitable candidate for microbially assisted phytoremediation due to its high resistance to Cd and its Cd-induced siderophore production, which is likely to contribute to plant growth promotion.
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Chen
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China chaoyuanq@mail.sysu.edu.cn eesqrl@mail.sysu.edu.cn.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, People's Republic of China.
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Chao
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Yaying
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Qingqi
authors.initials: Q
authors.lastname: Lin
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Bai
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Tang
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, People's Republic of China.
authors.forename: Shizhong
authors.initials: S
authors.lastname: Wang
authors.affiliation: Nanjing Institute of Environmental Sciences, Ministry of Environmental Protection, Nanjing, People's Republic of China.
authors.forename: Rongrong
authors.initials: R
authors.lastname: Ying
authors.affiliation: School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, People's Republic of China chaoyuanq@mail.sysu.edu.cn eesqrl@mail.sysu.edu.cn.|Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Guangzhou, People's Republic of China.
authors.forename: Rongliang
authors.initials: R
authors.lastname: Qiu
mesh_terms: D002104:Cadmium / Q000378:metabolism* / Q000633:toxicity*; D004754:Enterobacter / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D007210:Indoleacetic Acids / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects*; D010937:Plant Growth Regulators / Q000378:metabolism; D017262:Siderophores / Q000378:metabolism; D012988:Soil Microbiology; D013312:Stress, Physiological
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D017262:Siderophores; D002104:Cadmium; C030737:indoleacetic acid