ABSTRACT
A Comamonas testosterone bacterial strain, named as DB-7, capable of utilizing dimethyl phthalate (DMP) as sole carbon source and energy for growth was isolated from soil with plastic film mulching by an enrichment culture technique. This bacterium was identified as C. testosterone by 16S rRNA sequence analysis and phospholipid fatty acid profile. DB-7 could degrade more than 99% of 450 mg L-1 DMP within 14 hours, and degraded DMP of different concentrations rapidly. The optimal degradation temperature and pH were 30-35 °C and pH 9.0, respectively. The degradation rate of DMP was positively related to inoculum volume of the bacterium. The result of HPLC and LC/MS analysis of metabolic products indicated that the major degrading intermediates were mono-methyl phthalate (MMP) and phthalic acid (PA) during the degradation of DMP by DB-7. Partial sequences of three genes involved in PA metabolism were detected in DB-7, and the expression of phthalate 4, 5-dioxygenase was drastically induced in the presence of DMP and PA. DB-7 is promising to be applied to DMP bioremediation because of its high degrading efficiency.
Subject(s)
Biodegradation, Environmental , Comamonas testosteroni/isolation & purification , Comamonas testosteroni/metabolism , Phthalic Acids/metabolism , Soil Microbiology , Comamonas , Comamonas testosteroni/genetics , Comamonas testosteroni/growth & development , Fatty Acids , Genes, Bacterial/genetics , Hydrogen-Ion Concentration , Metabolism/genetics , Oxygenases/genetics , Oxygenases/metabolism , RNA, Ribosomal, 16S/genetics , Sequence Analysis , Temperature , Time FactorsABSTRACT
Cyanobacterial harmful algal blooms (CyanoHABs) cause severe environmental problems, economic losses and threaten human health seriously. In the present study, a Bacillus sp. strain, designated as AF-1, with strong antagonistic activity against plant pathogenic fungus Fusarium graminearum was isolated from purple soil. Bacillus sp. AF-1 selectively killed Microcystis aeruginosa at low cell density (1.6×103cfu/mL), and showed the strongest bactericidal activity against M. aeruginosa NIES-843 (Ae=93%, t=6d). The algicidal substances originated from strain AF-1 were stable in the temperature range of 35-100°C, and pH range of 3-11. Cell-free filtrate of AF-1 culture caused excessive accumulation of intracellular reactive oxygen species (ROS), cell death and the efflux of intracellular components of M. aeruginosa NIES-843 cells. The expression of genes recA, psbA1, psbD1, rbcL and mcyB, involved in DNA repair, photosynthesis and microcystin synthesis of NIES 843, were significantly influenced by the cell-free filtrate of AF-1 culture. Bacillus sp. AF-1 has the potential to be developed as a bifunctional biocontrol agent to control CyanoHABs and F. graminearum caused plant disease.
