Phenol degradation by Fusarium oxysporum GJ4 is affected by toxic catalytic polymerization mediated by copper oxide

Genomic Insights into the Aquatic Fusarium spp. QHM and BWC1 and Their Application in Phenol Degradation

Fusarium species are widely distributed in ecosystems with wide pH ranges and play pivotal roles in aquatic communities through xenobiotic degradation. It is necessary to explore genomic insights for the application of Fusarium species. In this study, the aquatic Fusarium strains QHM and BWC1 were isolated from a coal mine and a subterranean river, respectively, cultured under acidic conditions and sequenced genomically. Phylogenetic analysis of the isolates was conducted based on the sequences of internal transcripts and sequences encoding β-microtubulin, translation elongation factors and the second large subunit of the RNA polymerase. Fusarium QHM demonstrates close relationships to the type strains of Fusarium ramigenum and Fusarium napiforme in Fusarium fujikuroi species complex. Fusarium BWC1 is predicted to be Fusarium subglutinans. A total of 479 and 2352 scaffolds, corresponding to 14,814 and 15,295 genes, were obtained for Fusarium spp. QHM and BWC1, respectively. Genomic analyses revealed that they harbored biodegradation pathways for aromatic compounds. Phenol stress experiments indicated that Fusarium spp. QHM and BWC1 exhibited optimal degradation at a density of 300 mg/L to achieve a phenol degradation rate of 39.91-43.65% at pH 3.5-4.0. Fusarium spp. QHM and BWC1 were applied to mock phenol-water, and an average phenol degradation rate of 51.71-65.55% indicated the feasibility of these species. The findings of this study have important implications for Fusarium spp. QHM and BWC1 applied to phenol wastewater in acidic or neutral pH environments.

A new Rhodococcus aetherivorans strain isolated from lubricant-contaminated soil as a prospective phenol-biodegrading agent

Microbe-based decontamination of phenol-polluted environments has significant advantages over physical and chemical approaches by being relatively cheaper and ensuring complete phenol degradation. There is a need to search for commercially prospective bacterial strains that are resistant to phenol and other co-pollutants, e.g. oil hydrocarbons, in contaminated environments, and able to carry out efficient phenol biodegradation at a variable range of concentrations. This research characterizes the phenol-biodegrading ability of a new actinobacteria strain isolated from a lubricant-contaminated soil environment. Phenotypic and phylogenetic analyses showed that the novel strain UCM Ac-603 belonged to the species Rhodococcus aetherivorans, and phenol degrading ability was quantitatively characterized for the first time. R. aetherivorans UCM Ac-603 tolerated and assimilated phenol (100% of supplied concentration) and various hydrocarbons (56.2–94.4%) as sole carbon sources. Additional nutrient supplementation was not required for degradation and this organism could grow at a phenol concentration of 500 mg L⁻¹ without inhibition. Complete phenol assimilation occurred after 4 days at an initial concentration of 1750 mg L⁻¹ for freely-suspended cells and at 2000 mg L⁻¹ for vermiculite-immobilized cells: 99.9% assimilation of phenol was possible from a total concentration of 3000 mg L⁻¹ supplied at daily fractional phenol additions of 750 mg L⁻¹ over 4 days. In terms of phenol degradation rates, R. aetherivorans UCM Ac-602 showed efficient phenol degradation over a wide range of initial concentrations with the rates (e.g. 35.7 mg L⁻¹ h⁻¹ at 500 mg L⁻¹ phenol, and 18.2 mg L⁻¹ h⁻¹ at 1750 mg L⁻¹ phenol) significantly exceeding (1.2–5 times) reported data for almost all other phenol-assimilating bacteria. Such efficient phenol degradation ability compared to currently known strains and other beneficial characteristics of R. aetherivorans UCM Ac-602 suggest it is a promising candidate for bioremediation of phenol-contaminated environments.

Trichoderma harzianum SQR-T037 rapidly degrades allelochemicals in rhizospheres of continuously cropped cucumbers

To alleviate the stress of continuous cropping for cucumber continuous cropping (CCC) system, a beneficial fungus Trichoderma harzianum SQR-T037 (SQR-T037) was isolated and applied to soil to degrade allelochemicals exuded from cucumber plants in a Rhizobox experiment. The following phenolic acids (PAs), classified as allelochemicals, were isolated and identified from cucumber rhizospheres: 4-hydroxybenzoic acid, vanillic acid, ferulic acid, benzoic acid, 3-phenylpropionic acid, and cinnamic acid. Mixed PAs added in potato dextrose broth, each with 0.2 gram per liter, were completely degraded by SQR-T037 after 170 h of incubation. In Rhizobox experiments, inoculation of SQR-T037 in the CCC soil also degraded the PAs exuded from cucumber plant roots. This degradation was 88.8% for 4-hydroxybenzoic acid, 90% for vanillic acid, 95% for benzoic acid, and 100% for ferulic acid, 3-phenylpropionic acid, and cinnamic acid at 45 days after plantation. Simultaneously, a significant (p ≥ 0.05) decrease in the disease index of Fusarium wilt and an increase in dry weights of cucumber plants were obtained in pot experiments by application of SQR-T037. This was mostly attributed to degradation of PAs exuded from cucumber roots in CCC soil by SQR-T037 and alleviation of the allelopathic stress. Application of beneficial microorganisms, such as SQR-T037 that biodegrades allelochemicals, is a highly efficient way to resolve the problems associated with continuous cropping system.