Description:

Title:  Second Messenger Regulation of Foraging Behavior in Vibrio vulnificus

Speaker: Dean Rowe-Magnus, PhD / Indiana State University

Host: Karla Satchell, PhD

Topic:
Many free-swimming bacteria propel themselves through liquid using rotary flagella and mounting evidence suggests that the inhibition of flagellar rotation initiates biofilm formation, a sessile lifestyle that is a nearly universal surface colonization paradigm in bacteria. Vibrios produce a single polar flagella, and motility and biofilm formation are inversely regulated by the intracellular second messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). We identified a protein (PlzD) bearing a conserved c-di-GMP-sensing PilZ domain that localizes to the flagellar pole and alters the motility, biofilm formation and virulence of the opportunistic human pathogen, V. vulnificus. Our data suggests that PlzD interacts with components of the flagellar rotor to decrease bacterial swimming speed and turn frequency, and this activity is enhanced when cellular c-di-GMP levels are elevated. Moreover, PlzD recruits CheX, a conserved CheY~P phosphatase, to the flagellar pole. The decrease in local CheY~P levels alters the swimming pattern of individual cells from a hallmark “run-reverse-flick” pattern to long curvilinear traces indicative of mono-directional flagellar rotation, whereas deletion of CheX results in a striking alteration in foraging behavior to an unusual “ping-pong” pattern. These results reveal a new physical link between a second messenger (c-di-GMP), an effector (PlzD) and a regulator of flagellar rotational direction (CheX) that promotes transition from a motile to a sessile state.