Monitoring\nthe Biochemical Activity of Single Anammox\nGranules with Microbarometers

Granule-based\nanaerobic ammonium oxidation (Anammox) is a promising\nbiotechnology for wastewater treatments with extraordinary performance\nin nitrogen removal. However, traditional analytical methods often\ndelivered an average activity of a bulk sample consisting of millions\nand even billions of Anammox granules with distinct sizes and components.\nHere, we developed a novel technique to monitor the biochemical activity\nof individual Anammox granules in real-time by recording the production\nrate of nitrogen gas with a microbarometer in a sealed chamber containing\nonly one granule. It was found that the specific activity of a single\nAnammox granule not only varied by tens of folds among different individuals\nwith similar sizes (activity heterogeneity) but also revealed significant\nbreath-like dynamics over time (temporal fluctuation). Statistical\nanalysis on tens of individuals further revealed two subpopulations\nwith distinct color and specific activity, which were subsequently\nattributed to the different expression levels of heme c content and\nhydrazine dehydrogenase activity. This study not only provides a general\nmethodology for various kinds of gas-producing microbial processes\nbut also establishes a bottom-up strategy for exploring the structural-activity\nrelationship at a single sludge granule level, with implications for\ndeveloping a better Anammox process.