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Effect of heavy metals on nitrification activity as measured by RNA- and DNA-based function-specific assays
Citation:
Kapoor, V., M. Elk, X. Li, C. Impellitteri, AND K. Chandran. Effect of heavy metals on nitrification activity as measured by RNA- and DNA-based function-specific assays. Presented at ACS National Meeting, San Diego, CA, March 13 - 17, 2016.
Impact/Purpose:
Heavy metals can inhibit nitrification, a key process for nitrogen removal in wastewater treatment. The transcriptional responses of functional genes (amoA, hao, nirK and norB) were measured in conjunction with specific oxygen uptake rate (sOUR) for nitrifying enrichment cultures exposed to different metals (Ni(II), Zn(II), Cd(II) and Pb(II)). The results show that RNA-based function-specific assays can be used as potential surrogates for measuring nitrification activity, the degree of inhibition inferred from sOUR and gene transcription is different.
Description:
Heavy metals can inhibit nitrification, a key process for nitrogen removal in wastewater treatment. The transcriptional responses of functional genes (amoA, hao, nirK and norB) were measured in conjunction with specific oxygen uptake rate (sOUR) for nitrifying enrichment cultures exposed to different metals (Ni(II), Zn(II), Cd(II) and Pb(II)). There was significant decrease in sOUR with increasing concentrations for Ni(II) (0.03-3 mg/L), Zn(II) (0.1-10 mg/L) and Cd(II) (0.03-1 mg/L). However, no considerable changes in sOUR were observed with Pb(II) (1-100 mg/L), except at dosage of 1000 mg/L causing 84% inhibition. Based on RT-qPCR data, the transcript levels of amoA and hao decreased when exposed to Ni(II) dosages. Slight up-regulation of amoA, hao and nirK (0.5-1.5 fold) occurred after exposure to 0.3-3 mg/L Zn(II), although their expression decreased for 10 mg/L Zn(II). With the exception of 1000 mg/L Pb(II), stimulation of all genes occurred on Cd(II) and Pb(II) exposure. While overall the results show that RNA-based function-specific assays can be used as potential surrogates for measuring nitrification activity, the degree of inhibition inferred from sOUR and gene transcription is different.
