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

Abstract

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. Recent discovery of a special hydrogenase in certain corrosive methanogenic Archaea allowed for the development of a first ever MIC biomarker termed here micH. The micH gene encodes the large subunit of a special [NiFe] hydrogenase involved in MIC. Here we describe the development of a 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. The immunoassay was able to detect a strong signal for the MicH protein in micH-positive pure cultures of Methanobacterium-like. strain IM1 that was cultivated on iron granules, and the signal was over 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 ten 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 (36.5 - 1473.5 pg/mL) and carbon steel biofilm samples (41.0 - 7971.3 pg/cm2) 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. The results indicate that corrosion was likely caused by methanogenic Archaea expressing a corrosive [NiFe] hydrogenase and that the newly developed MicH-specific immunoassay can detect and monitor their activity. The development of a specific and sensitive immunoassays to detect a MIC biomarker allow corrosion scientists and field practitioners to detect and monitor the activity of corrosive methanogenic Archaea.