From Bacterial Environmental Sensing Pathways to the Characterization and Design of a Gut Microbiota

The gut microbiota is a complex association of microorganisms which constitute an organ of vertebrate animals with multiple functions including food digestion, development of the organism, and protection from pathogens. Understanding how the bacterial building blocks of the gut microbiota function and how they interact with each other and with the host is crucial if we are ever to redesign the microbiota.

Here I will focus on two projects:

In the first we utilized a biosensor for a bacterial second messenger to identify molecules in the environment which are sensed by the gut pathogen Salmonella Typhimurium. Understanding what gut bacteria sense in the environment can enhance our understanding of environment, i.e. the gut, and how bacteria interact with it. We were able to identify multiple signals sensed and to characterize the molecular pathways involved including a novel pathway for the sensing of extracellular L-arginine. We are currently examining how environmental sensing by Salmonella impacts its interaction with host macrophages.

The aim of the second project is to develop probiotics for poultry. About 5% of chicks in commercial settings die in the first week of their lives because of gut infections. It is thought that the lack of a suitable microflora brought about by the separation of eggs from the laying hen is responsible. While this project is still in its infancy, I will discuss our plan which is to isolate bacteria from poultry, characterize them, characterize the interactions between them and then infect newly hatched chicks with single strains of bacteria to determine their ability to colonize the host over time as well as measure any changes in the host or its gut microbiota.