The sequestration and storage of metals, and the maturation and roles of metal-containing enzymes by bacterial pathogens are of keen interest. The bacterial pathogens under study include the persistent gastric pathogen Helicobacter pylori, other Helicobacters that colonize liver and colon environments, and some enteric diarrheal pathogens (e.g. Salmonella/Shigella). For example, all these bacteria sequester the metal nickel for use in nickel-containing enzymes, yet the mechanism of nickel storage and subsequent nickel allocation and insertion into the nickel enzyme sinks (hydrogenases and ureases) is not understood. Mutant analysis combined with pure protein studies and animal infection models are all used to study metal containing proteins in these pathogens. A key growth substrate used by all these pathogens in animals is molecular hydrogen produced by the host flora; the pathogens ability to use this small but highly energetic substrate is due to a nickel-containing H2-splitting enzyme. The nickel-dependent expression and maturation of this enzyme is studied, as well as unique ways (i.e. nickel chelation) to inhibit its activity. Another related area of research involves stress-combating proteins used by Helicobacter pylori to colonize the gastric mucosa of humans. Such colonization leads to a variety of inflammatory gastric diseases. The persistence of the pathogen in withstanding host defense mechanisms over a period of years or decades results in the most severe gastric diseases, including even gastric carcinomas. Growth of the bacterium in animals is partially inhibited by a battery of host-produced reactive oxygen species. Our goal is to identify and then characterize the expression of oxidative stress resistance proteins that enable the gastric pathogen to persistently survive the harsh host environment.
