All organisms on Earth require certain types of trace metal co-factors like Fe, Mn and Cu for key enzymes in their metabolisms. Aerobic ammonia oxidation is one of the most important biological metabolic pathways of the nitrogen cycle on Earth and involves oxidation of ammonia to nitrite. Until 2005 it was believed that only bacteria contributed to this pathway. However, since 2005 it is now recognized that AOA are the main microorganisms controlling ammonia in terrestrial and aquatic systems. Ammonia oxidizing archaea (AOA) require copper (Cu) to carry out ammonia oxidation because it is a co-factor to many of the enzymes involved in this pathway. In contrast to bacteria, where various models of Cu acquisition and incorporation of Cu into enzymes exist, it is currently unknown how AOA acquire Cu in the environment. One hypothesis is that similar to bacteria, AOA secrete chalkophores—biological molecules that capture Cu and transport it back into the AOA cell. AOA might also take up Cu into the cell by an active transport mechanism or a cell pore that binds trace-metals. The key aim of project CORA was to determine how archaea take up Cu from the environment. This study was innovative because it is among the first to address this problem and will provide fundamental understanding to a key process that is of economic importance in agriculture and wastewater remediation. AOA provide crops with nitrogen for growth in soils and are used in remediating wastewater containing high levels of ammonia contamination. Results from this study will contribute to the fundamental understanding of Cu acquisition by archaea and will also be the first step to understanding an important factor that likely controls ammonia oxidation by AOA in terrestrial and aquatic environments.
