Isolation And Characterization Of Cupriavidus Sp. SHE

Indole is an N-heterocyclic aromatic compound widely used in pharmaceutical and pesticide industries. Indole-containing wastewater may pose a threat if discharging into environmental matrices directly. Biological treatment has been successfully applied in the remediation of various pollutants due to the eco-friendly and economical merits. It has been proven that microbes harbor indole degradation ability, whereas various issues remain to be solved such as limited indole-degrading resources, low degradation rates, controversial degradation mechanisms and unclear functional genes. As such, isolation of superior indole degradation microbial resources, characterization of the degradation processes and exploration of degradation mechanisms using chemical and molecular methods should pave ways for practical applications.In the present study, a novel indole-degrading strain, named SHE, was isolated from Niujiaoshan (Dalian, China). It was identified as Cupriavidus sp. based on 16S rRNA gene sequence analysis with GenBank accession number KJ875863. Strain SHE could utilize indole as the sole carbon source and completely remove 100 mg/L indole within 48 h. It still harbored relatively high indole degradation capacity (over 85%) within pH 4-9 and temperature 25-35℃ . Experiments also showed that some heavy metals such as Mn2+, Pb2+ and Co2+(below 0.5 mmol/L) did not pose severe inhibition on indole degradation. Furthermore, strain SHE could also use phenol, catechol and benzoic acid as the sole carbon source for growth, indicating it obtained the aromatic metabolic versatilitv.During the process of indole degradation, yellow products could be observed and accumulated. Based on high performance liquid chromatography-mass spectrometry analysis, the yellow product was identified as C15H8N2O3 with molecular mass of 265.0605. Besides, isatin was detected as an intermediate while other common intermediates, such as anthranilic acid and gentisic acid, were not detected. The results suggested that a novel transformation pathway of indole exsited. To explore the potential genes responsible for indole degrading, the genome of strain SHE was sequenced. With the help of RAST (rapid annotation using subsystem technology), a rich set genes (158) were predicted to be related with aromatic degradation. Various oxidordeuctases such as P450, hydroxylase, monooxygenase and dioxygenase were also found in the genome, which should play significant roles in indole degradation. Moreover, we also found that SHE contained abundant toxics tolerant/reduction genes and transportation genes, indicting its potential ability in toxics tolerance and reduction. Experiment results showed strain SHE could effectively reduce Se(Ⅳ) and Au(Ⅲ) to form nanoparticles. The optimal conditions for Se(Ⅳ) reduction by strain SHE were pH 8, temperature 30℃ and Se(Ⅳ) 1.0 mmol/L, and the reduction rate could reach 100%. Based on the analyses of UV-Vis spectroscopy, microscopic morpgotogy, size distribution analysis and X-ray diffraction, Se nanoparticles were in hexagonal phase with a diameter of 130.2±27.0 nm. The gold-nanoparticle synthesis ability of strain SHE was also investigated, and it indicated that SHE could reduce chloroauric acid to form gold particles with different sizes.