Growth of complete ammonia oxidizers on guanidine

Guanidine is a chemically stable nitrogen compound that is excreted in human urine, widely used in manufacturing of plastics, as flame retardant, component of propellants, and well known as a protein denaturant in biochemistry. It occurs widely in nature and is used by several microbes as a nitrogen source, but microorganisms growing on guanidine as the only substrate have not yet been discovered. In this project we examine if the complete ammonia oxidizer (comammox) Nitrospira inopinata and likely most other comammox microbes can grow on guanidine as the sole source of energy, reductant, and nitrogen.