title: Characterization of Cu(II) and Cd(II) resistance mechanisms in Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH and their potential application in the bioremediation of heavy metal-phenanthrene co-contaminated sites.
abstract: Soil that is co-contaminated with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) is difficult to bioremediate due to the ability of toxic metals to inhibit PAH degradation by bacteria. We demonstrated the resistance mechanisms to Cu(II) and Cd(II) of two newly isolated strains of Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH and further tested their potential application in the bioremediation of HM-phenanthrene (PhA) co-contaminated sites. The PHE-SPH and PHE-OCH strains tolerated 4.63 and 4.34 mM Cu(II) and also showed tolerance to 0.48 and 1.52 mM Cd(II), respectively. Diverse resistance patterns were detected between the two strains. In PHE-OCH cells, the maximum accumulation of Cu(II) occurred in the cell wall, while the maximum accumulation was in the cytoplasm of PHE-SPH cells. This resulted in a sudden suppression of growth in PHE-OCH and a gradual inhibition in PHE-SPH as the concentration of Cu(II) increased. Organic acid production was markedly higher in PHE-OCH than in PHE-SPH, which may also have a role in the resistance mechanisms, and contributes to the higher Cd(II) tolerance of PHE-OCH. The factors involved in the absorption of Cu(II) or Cd(II) in PHE-SPH and PHE-OCH were identified as proteins and carbohydrates by Fourier transform infrared (FT-IR) spectroscopy. Furthermore, both strains showed the ability to efficiently degrade PhA and maintained this high degradation efficiency under HM stress. The high tolerance to HMs and the PhA degradation capacity make Sphingobium sp. PHE-SPH and Ochrobactrum sp. PHE-OCH excellent candidate organisms for the bioremediation of HM-PhA co-contaminated sites.
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
authors.forename: Wenrui
authors.initials: W
authors.lastname: Lei
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
authors.forename: Min
authors.initials: M
authors.lastname: Lu
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
authors.forename: Jianan
authors.initials: J
authors.lastname: Zhang
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, People's Republic of China.
authors.forename: Chunling
authors.initials: C
authors.lastname: Luo
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
authors.forename: Yahua
authors.initials: Y
authors.lastname: Chen
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Hong
authors.affiliation: College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, People's Republic of China. zgsheng@njau.edu.cn.
authors.forename: Zhenguo
authors.initials: Z
authors.lastname: Shen
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001673:Biodegradation, Environmental; D002104:Cadmium / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D003300:Copper / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D007928:Lethal Dose 50; D008826:Microbial Sensitivity Tests; D042041:Ochrobactrum / Q000187:drug effects / Q000378:metabolism*; D010616:Phenanthrenes / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000737:chemistry / Q000494:pharmacology*; D045249:Sphingobacterium / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D010616:Phenanthrenes; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D003300:Copper
keywords: Bioremediation; Co-contamination; Heavy metals; Ochrobactrum; Phenanthrene; Sphingobium