The Isolation, Characteristics And Molecular Identification Of A Dual-functional Bacterial Consortium Degrading Phenanthrene And Oxidizing Arsenite Simultaneously

Polycyclic aromatic hydrocarbons (PAHs) and heavy metals are two main categories of environmental pollutants. Thus far, many reports have focused on the microorganisms which can degrade one category of pollutants, and no microorganisms which can transfer two categories of pollutants were reported. In this study, a heterotrophic bacterial consortium, which can degrade phenanthrene (PHE) and oxidize arsenite (As (Ⅲ)) simultaneously was isolated from a disused cocking plant in Shanghai. On the basis of the characteristics study, we mainly focused on the structure, diversity and abundance of function genes in the consortium, with the main results as follows:(1) A dual-functional consortium was isolated and domesticated using PHE and As (Ⅲ) as the selection pressure. The consortium can grow well in mineral salt medium containing200mg·L-1PHE and60mg·L-1As (Ⅲ) under30℃,150r-min-1, and6days. Under this condition,71.4%PHE can be degraded and96.2%As (Ⅲ) can be oxidized within48hrs.(2) The clone library results indicated that the main genera were Pseudomonas, Pusillimonas, Alcaligenes and Achromobacter in the consortium.The16S rRNA PCR-DGGE analysis indicted that the community structure seldom changed when the initial concentration of PHE was200mg-L-1and As (Ⅲ) was60mg-L-1. On the other hand, the community structure varied remarkably when the ratio and composition of PHE and As (Ⅲ) were changed. The results also showed that Pseudomonas and Achromobacter sp. were possibly the dominant species for PHE degradation and Alcaligenes sp. was the dominant one for As (Ⅲ) oxidation.(3) The diversity of PAHs-degrading RHDa gene and arsenite-oxidizing aox B gene in the bacterial consortium was also studied using clone library approach. The results indicated that the RHDa gene shared the high similarity with those from Pseudomonas aeruginosa and Pseudomonas putida (≥99%), and aoxB gene shared the high similarity with those from Pseudomonas stutzeri and Alcaligenes faecalis (≥99%).(4) The abundance of above two functional genes were also studied using real time PCR. The results showed that the copies of the two genes increased with the increase of the incubation time. Within48hrs incubation, the copy number of the aox B genes was between 3.0×l08and1.48×1010, while the copy number of RHDa genes was between2.54×107and8.70×109.This study was the first one on molecular identification of dual-functional consortium which can degrade PHE and oxidize As (Ⅲ). The results will be useful in elucidating the bio remediation mechanism for the transfer of combined pollutants.