Abstract Benzo(a)pyrene (BaP) is one of the most common organic pollutants in the environment, and its microbial removal has great ecological and economic value. Here, using BaP (50 mg/L) as the sole carbon source, dynamic changes in camel rumen and gut bacterial communities were analyzed by high-throughput sequencing. Next, cultivable BaP-degrading isolates were obtained, and their degradation characteristics were explored. The relative abundance of most bacteria in the gut and rumen underwent apparent changes after BaP treatment. The rumen and gut bacteria have the ability to degrade BaP but fluctuated during iterative culturing from the first to the fifth generation of gut communities displaying the highest BaP degradation efficiency (BDE) (74.4 and 81.1%, respectively). Moreover, 37 isolates exhibiting BDE were identified. Among these isolates, CL9 ( Klebsiella sp.), CL16 ( Ochrobactrum sp.), CC6 ( Ochrobactrum sp.), and CC16 ( Bacillus sp.) showed BDEs of up to 70.8, 69.3, 68.4, and 76.2%, respectively. The enzyme catechol-2,3-dioxygenase was involved in BaP degradation in these four BaP-degrading isolates and represented the main BaP degradation pathway in isolates CL9 and CL16; however, the relative expression level of the gene phnAc was higher in isolates CC6 and CC16 than in isolates CL9 and CL16. Our results provided promising bacterial resources for the removal of BaP and laid the foundation for the application of animal gastrointestinal bacteria to degrade environmental pollutants.
Hongyun Nie,Maiqian Nie,Yongzhe Yang,Jing Zhao,Xinyi Zhang,Yutao Guo,Yi Wan,Jing Zi
Characterization of phenol metabolization by P. stutzeri N2 was proposed based on the identification of relevant metabolites and enzyme activities of catechol 1,2-oxygenase and catechol 2,3-dioxygenase. P. stutzeri N2 started to grow on 400 mg l−1 phenol with no obvious lag phase, and then phenol decomposition was rapidly completed within 32 h. Results of enzyme activities, UV spectrums of cultures, and the mass spectrum identification of cis, cis-muconic and 2-HMS, which showed that catechol C12O and C23O were acting simultaneously on the fission of the phenol ring. The existence of P-hydroxybenzoic acid and straight-chain saturated dicarboxylic acids in the culture medium showed that carboxylation and hydrogenation were involved during the phenol degradation. Metabolites containing five or four carbons indicated that catechol and its immediate ring-cleavage intermediates could be furthermore metabolized by P. Stutzeri N2. Therefore, P. stutzeri N2 which could degrade phenol with high efficiency and diverse pathways could have potential applications in the treatment of wastewater containing phenol.
In order to promote phenol tolerance and the carbon fixation rate of cells during CO 2 sequestration in coal chemical flue gas, γ-ray irradiation from cobalt-60 ( 60 Co) was used to mutate Arthrospira platensis to generate efficient strains. A phenol-tolerant strain Mutant 11k was obtained with 11,000 Gy of gamma irradiation. The phenol degradation efficiency of the mutant was 34.7 % higher than that of wild strain, attributing to the increased activity of phenol hydroxylase that catalyzed phenol to generate catechol. The catechol 1,2-dioxygenase activity in mutant cells was enhanced by 39.5 % while catechol 2,3-dioxygenase was weakened by 23.8 %, revealing that the β-ketoadipate pathway plays a more important role than 2-hydroxymuconic semialdehyde pathway in phenol degradation. The activity of superoxide dismutase and catalase increased by 6.1 % and 39.8 %, respectively, reducing peroxide damage and maintaining rapid cell growth. The contents of chlorophyll-a and maximum quantum yield of photosystem II in mutant cells were higher than those in wild strain. The biomass yield and carbon fixation rate of mutant were 20.8 % and 22.4 % higher, respectively, than those of the wild strain.
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