What is the substrate of the sMMO-like genes of Mycobacterium strain NBB4?
Monooxygenase (MO) enzymes are important for biogeochemistry, biocatalysis and bioremediation. In microbes, MOs are best known as the catalysts for methane oxidation, which is a process of immense importance for the global carbon cycle and for influencing climate change. Mycobacterium strain NBB4, an ethene-oxidising isolate from estuarine sediment, contains a diverse array of MO genes, including homologs of the particulate and soluble methane MOs (pMMO/sMMO), cytochrome p450's, and an ethene MO. We have previously shown that NBB4 can biodegrade several chlorinated pollutants, and that the pMMO homolog is actually an ethane/propane/butane MO. The function of the sMMO homolog in NBB4 (genes designated smoXYBCZ) is currently unknown. This gene cluster has only low identity to sMMO, and methane is not a substrate for growth of NBB4. The aim of this Honours project is to identify the substrate of this novel MO via knockout and heterologous expression experiments. Our hypothesis is that smoXYBCZ acts in the second step of the butane oxidation pathway to convert butanol to butanediol.