Toxoplasma gondii (T. gondii) is a single-cell parasite, and the most successful parasite on the planet, infecting up to a third of the world’s human population. Inside a host T. gondii develops within a host-cell. How the parasite detects and interprets biological information (signals) within this cell is poorly understood. These signals can be transmitted by Reactive Oxygen Species (ROS) such as hydrogen peroxide. ROS are encountered by T. gondii during replication within a host cell, and when outside of this cell and visible to the host immune system. Though the parasite experiences ROS signals, how they are detected and how the parasite responds is not known and is one avenue of research we are pursuing.