Development of a MicH-specific immunoassay for MIC detection and diagnosis

Microbially-influenced corrosion (MIC) is a costly problem across several industries. The steadily rising use of advanced molecular biological methods to investigate MIC allowed ever deeper insights in the underlying microbial community structure and function. However, currently available technologies do not allow accurate detection and diagnosis of MIC in the field. Our team has recently developed a qPCR assay for a first MIC biomarker ( micH ) specific to corrosive methanogenic archaea. The micH gene encodes the large subunit of a special [NiFe] hydrogenase involved in MIC. Here we describe the development of recombinant antibody that enable the specific and sensitive detection of the MicH protein in western blot immunoassays. Using a recombinant MicH protein we determined the lower limit of detection per assay to be around ∼0.3 fg MicH (∼3·10 ³ protein molecules). The novel immunoassay was able to detect a strong signal for the MicH protein in a micH positive cultures of Methanobacterium sp. strain IM1 that was cultivated on iron granules, but the signal was 500 times lower in a micH negative Methanococcus maripaludis S2 culture. To further evaluate the ability to differentiate corrosive from non-corrosive microbial communities, we tested 10 oil field enrichment cultures that showed a wide range of corrosion rates (0.02 – 0.48 mm/yr). We detected the MicH protein in planktonic (2.2·10 ⁶ – 9.3·10 ⁷ MicH/mL) and carbon steel biofilm samples (1.7·10 ⁷ – 6.4·10 ⁸ MicH/cm ² ) from corrosive methanogenic enrichments (0.17 – 0.48 mm/yr) but did not detect MicH in any of the non-corrosive tests (<0.08 mm/yr) despite methanogenic activity in some. The results indicate that corrosion was likely caused by methanogenic archaea expressing a corrosive [NiFe] hydrogenase and that the newly developed MicH immunoassay can be used to detect and monitor their activity. Here we showed that an antibody can be applied to detect a MIC biomarker on the protein level and differentiate between corrosive and non-corrosive methanogenic communities. The development of a specific and sensitive immunoassays to detect MIC biomarkers added another technology to the toolbox of corrosion scientists to improve monitoring and detection of corrosive microorganisms and paves the way for development of rapid in-field testing.