Bacteria encounter reactive nitrogen species (RNS) in different environments. For example, in the human body bacterial pathogens are attacked by RNS (and reactive oxygen species) derived from phagocytic cells. DNA and proteins are targets of RNS-induced cellular damage. Bacteria use various mechanisms to resist the actions of RNS (e.g. scavenging, enzymatic inactivation, general stress responses, and repair mechanisms). By using a combination of transcriptome and molecular genetic analyses we have provided a view of how Bacillus subtilis cells respond to and manage nitrosative stress. This part of our studies focuses on exploring bacterial NO-sensing and detoxification mechanisms.
Structure of flavohemoglobin, Hmp. The protein has three domains: a NAD-binding domain (yellow), a flavin-binding (FAD) domain (green) and a globin domain (red) containing heme. Many microorganisms employ Hmp to metabolize nitric oxide (NO) to nitrate (NO3-) according to the reaction 2NO + 2O2+ 2e- --> 2NO3-. In Bacillus subtilis and other bacteria Hmp forms the first line of defense against NO toxicity.