Abstract
The genus Arthrobacter is ubiquitously distributed in different natural environments. Many xenobiotic-degrading Arthrobacter strains have been isolated and described; however, few have been systematically characterized with regard to multiple interrelated metabolic pathways and the genes that encode them. In this study, the biodegradability of seven aromatic compounds by Arthrobacter sp. YC-RL1 was investigated. Strain YC-RL1 could efficiently degrade p-xylene (PX), naphthalene, phenanthrene, biphenyl, p-nitrophenol (PNP), and bisphenol A (BPA) under both separated and mixed conditions. Based on the detected metabolic intermediates, metabolic pathways of naphthalene, biphenyl, PNP, and BPA were proposed, which indicated that strain YC-RL1 harbors systematic metabolic pathways toward aromatic compounds. Further, genomic analysis uncovered part of genes involved in the proposed pathways. Both intradiol and extradiol ring-cleavage dioxygenase genes were identified in the genome of strain YC-RL1. Meanwhile, gene clusters predicted to encode the degradation of biphenyl (bph), para-substituted phenols (npd) and protocatechuate (pca) were identified, and bphA1A2BCD was proposed to be a novel biphenyl-degrading gene cluster. The complete metabolic pathway of biphenyl was deduced via intermediates and functional gene analysis (bph and pca gene clusters). One of the these genes encoding ring-cleavage dioxygenase in bph gene cluster, a predicted 2,3-dihydroxybiphenyl 1,2-dioxygenase (BphC) gene, was cloned and its activity was confirmed by heterologous expression. This work systematically illuminated the metabolic versatility of aromatic compounds in strain YC-RL1 via the combination of metabolites identification, genomics analysis and laboratory experiments. These results suggested that strain YC-RL1 might be a promising candidate for the bioremediation of aromatic compounds pollution sites.
Highlights
Widespread environmental pollution and tightening environmental regulations have increased demand for environmental remediation and driven research on pollutant degradation
Very little di 2-ethyl hexyl phthalate (DEHP) was degraded (12.7 ± 4.1% and 3.6 ± 2.5% under separated and mixed conditions, respectively) due to fortuitous hydrolysis by broadspectrum hydrolases. These results demonstrated that strain YCRL1 could utilize different kinds of aromatic compound for growth
DEHP hydrolase and mono(2-ethylhexyl) phthalate (MEHP) hydrolase, contributed to the first step (Latorre et al, 2012; Nahurira et al, 2017). These results indicated that strain YC-RL1 possess systematic metabolic pathways for aromatic compounds and related molecular mechanism
Summary
Widespread environmental pollution and tightening environmental regulations have increased demand for environmental remediation and driven research on pollutant degradation. Metabolic Versatility of Aromatic Compounds in Arthrobacter xenobiotics for detoxification or via fortuitous transformation by broad-spectrum enzymes, prokaryota typically metabolize them for assimilation as essential nutrients and energy (Copley, 2009; Fenner et al, 2013). Numerous bacteria have been isolated and characterized with respect to the molecular mechanisms underlying their metabolic potential for the degradation of environmental pollutants (Copley, 2009; Fenner et al, 2013). For example challenges remain regarding the degradation of pollutants present at low concentrations, present in extreme conditions (i.e., saline-alkali soil, deserts, etc.), present in mixtures with other compounds, and those that might be toxic or metabolized to toxic intermediates (Yagi et al, 2009; Laffin et al, 2010; Narancic et al, 2012)
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