Isolation And Characteristics Of Cadmium-resistant Phenanthrene-degrading Bacteria In Soil

The aim of this study is to isolate phenanthrene-degrading bacteria with strong cadmium resistance from soils co-contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metal in Northeast China. Three strains of such bacteria were isolated and studied in this thesis. Morphological appearance, Gram-straining, other physiological and biochemical characteristics and 16S rDNA were taken to identify isolates. The three strains were named as Alcaligenes faecalis strain J08, Brevundimonas sp. Strain X08 and Pseudomonas putida strain Q09. Acoording to 16S rDNA phylogenetic analysis, the three strains were belong toβ-proteobacteria,α-proteobacteria andγ-proteobacteria respectively.Yeast extraction can promote the growth and phenanthrene biodegradation of Alcaligenes faecalis strain J08 and Brevundimonas sp. Strain X08. Without Cd stress, Alcaligenes faecalis strain J08和Brevundimonas sp. Strain X08 can biodegrade 97.7% and 99.1% phenanthrene after 84h. And in the presence of 0.01 mM and 0.1 mM Cd, their growth and biodegradation showed no significant difference (p > 0.01) compared with Cd free treatments.In the stress of 0.5 mM Cd, there was no significant difference (p > 0.01) in the growth and biodegradation of Alcaligenes faecalis strain J08. Though this concentration of Cd can inhibit the growth of Brevundimonas sp. Strain X08, the biodegradation rate of Brevundimonas sp. Strain X08 was significant higher than other Cd treatments (p < 0.01).Pseudomonas putida strain Q09 can biodegrade 93.5% phenanthrene in 84h without yeast extraction and Cd. When the concentrations of Cd were 0.01 mM,0.1 mM and 0.2 mM, the lag phases of this strain were increased and the beginnings of biodegradation were delayed along with the increase of Cd concentrations. However, when it started to biodegrade phenanthrene, no significant difference was revealed in its biodegradation rates (p > 0.01) in different Cd treatments.Pseudomonas putida strain Q09 also presented its ability to remove Cd. After 84h of inoculation, 84.7% soluble Cd were removed in medium.With GC/MS, eight potential biodegradation products of phenanthrene of Pseudomonas putida strain Q09 were extracted and identified. And a possible biodegradation pathway was proposed.