The Ryan lab studies mechanisms that regulate protein activity in bacteria. We have focused on the Gram-negative aquatic bacterium Caulobacter crescentus because it has a complex life cycle that is driven in large part by changes in the phosphorylation, proteolysis, localization, and interactions of proteins.
C. crescentus undergoes a developmental step during its division cycle from a motile cell unable to replicate its DNA to a nonmotile cell that is competent for chromosome replication. We use synchronized populations of motile G1-phase cells to study the events that occur during development. C. crescentus also divides asymmetrically, producing one motile and one nonmotile cell at each division. Proteins in the predivisional cell are segregated to opposite ends to mediate the differentiation of identity after division. We study the locations and movements of individual proteins using fluorescence microscopy.
Specific problems that we are investigating include the following: regulated degradation of a key transcription factor during the motile-sessile developmental step; the roles, locations, and interactions of enzymes that participate in cell wall biosynthesis; and the regulatory functions of protein phosphorylation on serine, threonine, or tyrosine residues.