In situ p rotein‐ SIP highlights Burkholderiaceae as key players degrading toluene by para ring hydroxylation in a constructed wetland model

Abstract

Summary In constructed wetlands, organic pollutants are mainly degraded via microbial processes. Helophytes, plants that are commonly used in these systems, provide oxygen and root exudates to the rhizosphere, stimulating microbial degradation. While the treatment performance of constructed wetlands can be remarkable, a mechanistic understanding of microbial degradation processes in the rhizosphere is still limited. We investigated microbial toluene removal in a constructed wetland model system combining 16S rRNA gene sequencing, metaproteomics and 13 C ‐toluene in situ protein‐based stable isotope probing (protein‐ SIP ). The rhizospheric bacterial community was dominated by B urkholderiales and R hizobiales , each contributing about 20% to total taxon abundance. Protein‐ SIP data revealed that the members of B urkholderiaceae , the proteins of which showed about 73% of 13 C ‐incorporation, were the main degraders of toluene in the planted system, while the members of C omamonadaceae were involved to a lesser extent in degradation (about 64% 13 C ‐incorporation). Among the B urkholderiaceae , one of the key players of toluene degradation could be assigned to R alstonia pickettii . We observed that the main pathway of toluene degradation occurred via two subsequent monooxygenations of the aromatic ring. Our study provides a suitable approach to assess the key processes and microbes that are involved in the degradation of organic pollutants in complex rhizospheric ecosystems.

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