Speaker
Description
Hosts and pathogens frequently engage in physiological and evolutionary 'battles for iron', as each adapts to sequester this essential nutrient. We focus on the battle for iron between the intracellular bacterium Legionella pneumophila and its natural hosts, free-living amoebae. Amoebae restrict Legionella replication by pumping iron out of the Legionella-containing vacuole. In turn, the bacteria are able to counteract this activity by inserting their own iron transporter, MavN, into the host membrane, thereby returning iron to the vacuole. MavN's iron-binding loop shows signatures of accelerated evolution, suggesting that it may be evolving as part of an arms race with its amoeba hosts. But unlike other examples of host-microbe arms races, no direct host binding partners of MavN are known. We here investigate whether MavN engages in indirect antagonism with the host by altering its iron binding affinity vs. whether undiscovered host binding partners are driving the rapid evolution of this protein. We leverage natural variants of MavN as a ready-made allelic series to identify the specific evolved genetic changes responsible for success or failure in the battle for iron with the host.
