We study ion-translocating membrane transporters in bacterial cells are critical participants in the physiology of both pathogens and non-pathogenic bacteria of ecological interest.

1. Mrp-type monovalent cation/proton antiporter systems: basis and roles for the unusual complexity of this major bacterial antiporter system. In collaboration with Masahiro Ito's lab (Toyo University, Japan), we study the catalytic properties, physiological roles and structural features of Mrp systems from bacteria such as pathogenic Staphylococcus aureus and non-pathogenic Bacillus species. We are testing the hypothesis that Mrp proteins form a complex that is a "consortium" of transporters, including monovalent cation/proton antiporters, that function synergistically.
   
2. Role of monovalent cation/proton antiporters and additional ion-translocating membrane proteins in the early events of spore germination. Several diseases that are caused by Clostridium or Bacillus are initiated by the endospores that then germinate in the host. We study the transporters involved in early germination events in Bacillus subtilis and Bacillus anthracis, using expression in heterologous systems in which the transport events can be assayed and characterized.
   
3. Oxidative phosphorylation at high pH: a model system for probing the proton path during energization of ATP synthesis by the respiratory chain. Biochemical, molecular and biophysical studies of OXPHOS in membranes and purified systems test the hypothesis of sequestered proton transfer during OXPHOS.

Dr. Krulwich also leads an NIH-supported educational study on factors that enhance the successful post-baccalaureate intervention to promote research careers.