BACTERIAL NITRATE REDUCTION CONTRIBUTES TO THE GEOCHEMICAL OXIDATION OF IRON AND SUBSEQUENT REMEDIATION OF ACIDIC ABANDONED MINE DRAINAGE

Abandoned mine drainage (AMD) in Pennsylvania pollutes 5,000 km of streams. Passive systems that remediate AMD can include settling ponds, vertical flow ponds, limestone beds, and wetlands that are designed to increase the pH and precipitate metals onsite, preventing metals from entering the watershed. High levels of iron (Fe) present in AMD cause staining, damage water infrastructure, can be toxic, is associated with an increased infection risk, and may lead to cancer. Passive remediation systems are naturally colonized by native microbes that can impact the remediation within these systems. In acidic AMD, iron oxidation from soluble Fe(II) to precipitated Fe(III) is mainly mediated by microbes. Within the acidic Boyce Park passive remediation system, we have isolated Paraburkholderia sp. AV18 that reduces nitrate to nitrite, followed by geochemical iron oxidation. Paraburkholderia sp. AV18 encodes periplasmic nitrate reductase, napA, in its genome that was used to develop novel primers to detect the expression of napA during nitrate reduction through reverse transcriptase PCR (RT-PCR). Understanding the microbial mechanism and genes involved in nitrate reduction coupled with indirect iron oxidation will allow us to determine the extent that nitrate reduction contributes to iron remediation by determining the abundance and expression of these microbes and their metabolic genes within the system.