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The Groisman Lab seeks answers to a fundamental biological question: How does an organism know when, where and for long to turn a gene on or off? We address this question by investigating bacterial species that establish intimate interactions with animal hosts.

All organisms respond to a change in their environment by modifying their behavior. We are interested in identifying the specific signals that denote a given environment, the nature of the sensors that detect such signals, and how the sensors transmit this information to the regulators implementing a response that enables the organism to survive and prosper in the new condition.

We investigate the gastroenteritis- and typhoid fever-causing Salmonella enterica and the gut symbiotic bacteria Escherichia coli and Bacteroides thetaiotaomicron.

We have been examining protein sensors that detect extracellular signals and RNA sensors that monitor cellular metabolites and ions. These investigations led both to the discovery of the first signal transduction systems that sense extracytoplasmic magnesium and ferric iron and to the first mRNAs that respond to cytoplasmic magnesium and ATP.

Our research focuses on understanding:

  • how bacteria integrate multiple signals into a cellular response,
  • the mechanisms by which a given signal elicits distinct responses from co-regulated targets,
  • how bacteria from the gut microbiome compete for resources,
  • the genetic basis for phenotypic differences that distinguish closely related bacterial species, such as a pathogen and a symbiont,
  • the biochemical function of novel proteins and
  • the genetic control of virulence factors.