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Dibutyl phthalate (DBP) is well known as a high-priority pollutant. This study explored the impacts of DBP on the metabolic pathways of microbes in black soils in the short term (20 days). The results showed that the microbial communities were changed in black soils with DBP. In nitrogen cycling, the abundances of the genes were elevated by DBP. DBP contamination facilitated 3′-phosphoadenosine-5′-phosphosulfate (PAPS) formation, and the gene flux of sulfate metabolism was increased. The total abundances of ABC transporters and the gene abundances of the monosaccharide-transporting ATPases MalK and MsmK were increased by DBP. The total abundance of two-component system (TCS) genes and the gene abundances of malate dehydrogenase, histidine kinase and citryl-CoA lyase were increased after DBP contamination. The total abundance of phosphotransferase system (PTS) genes and the gene abundances of phosphotransferase, Crr and BglF were raised by DBP. The increased gene abundances of ABC transporters, TCS and PTS could be the reasons for the acceleration of nitrogen, carbon and sulfate metabolism. The degrading-genes of DBP were increased markedly in soil exposed to DBP. In summary, DBP contamination altered the microbial community and enhanced the gene abundances of the carbon, nitrogen and sulfur metabolism in black soils in the short term.

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Summary Dimethyl phthalate (DMP), a member of the phthalate esters (PAEs), is a common contaminant and frequently detected in soil. In this study, metagenomics revealed that DMP contamination in a Mollisol led to alterations in biological genomes and pathways identified using the Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. The results of functional annotation with pathway information demonstrated that genes involved in metabolism and signal regulatory pathways were changed in soil contaminated with DMP. Genes involved in nitrogen metabolism, carbon metabolism (glycolysis, the citrate cycle and pentose phosphate pathway) and signal regulatory pathways (apoptosis pathway, adipocytokine signalling pathway and glutamatergic synapse signal pathways) were more abundant under DMP contamination in the Mollisol. Quantitative PCR (QPCR) assays also showed that copies of genes associated with DMP degradation, pcmA, pehA, phtAb, phtB and phtC, correlated positively with the concentration of DMP. The results also suggested that the acceleration of nitrogen and carbon metabolism in the Mollisol by DMP contamination arose from altering the signal regulatory pathways. This is one of the most damaging mechanisms for microorganisms; therefore, DMP contamination will adversely affect the ecosystem in the Mollisol. Highlights How can DMP contamination alter the metabolic pathways of microorganisms in a Mollisol? Changes in microbial metabolism under DMP contamination were estimated by metagenomics. DMP accelerated N and C metabolism by altering the signal pathways. DMP could disrupt the ecological balance by altering metabolism in a Mollisol.

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