April 28, 2016

Our recent collaborative paper with Ramin Golestanian and Gerard Wong received some press recently, in a nice piece written by the lead author of the paper, Rachel Bennett.

April 27, 2016

A recent paper in the Journal of Bacteriology by Amy Baker (shown here), a PhD student in the lab, reports the role of a PilZ domain protein called FlgZ in controlling swarming motility by P. aeruginosa.  Specifically, the paper shows that FlgZ binds to one of the stator complexes (MotCD) in a c-di-GMP-dependent fashion.  The MotCD stator is the "powering stator" that drives flagellar rotation during swarming, so we believe interaction with FlgZ when c-di-GMP is high may keep MotCD from the motor and thus shut-down swarming.  The localization of FlgZ to the pole is also enhanced when c-di-GMP levels are high, and also depends on the presence of MotCD.  Overall, our data support the following model: when c-di-GMP levels increase during early biofilm formation, FlgZ binds this second messenger and then can bind to MotCD.  FlgZ-bound MotCD is not available to serve its function in the flagellar motor so surface-associated swarming motility is reduced.  Amy's work has further enhanced our understanding of how P. aeruginosa transitions from a motile to sessile biofilm) lifestyle.  Importantly, this work was a collaborative effort with Sherry Kuchma, a senior scientist in the lab, as well as Andi Diepold and Judy Armitage at Oxford University, who did the terrific imaging studies.

April 21, 2016

April 19, 2016

Angeles Hueso-Gil is a visiting student from Victor de Lorenzo's lab at the Centro Nacional de Biotecnología, Madrid, Spain.  She'll be visiting the lab through August, and will be studying biofilm formation in Pseudomonas putida.  Welcome!

April 11, 2016

Two PhD students in the lab Giulia Orazi and Alan Colins, and Michelle Clay who is a first year student in the graduate program, taught 6th - 9th grade students about the plant pathogen called Pseudomonas syringae at Dartmouth Science Day this weekend. They explained how in nature the bacteria cause plant leaves to freeze, which results in injury to the plant and allows the bacteria to invade the damaged leaves and access nutrients. They also performed a hands-on demonstration to show how P. syringae is able to nucleate ice formation. The middle school students also had the chance to work with these (safe for humans) bacteria.

April 04, 2016

Kurt Dahlstrom, a PhD student in the lab recently just published his second first-author paper in JB.  He had shown previously in a paper in mBio that a diguanylate cyclase enzyme that makes cyclic-di-GMP (called GcbC) could interact with the cyclic-di-GMP receptor called LapD.  GcbC and LapD interact via surface-exposed alpha helices, and together control the localization of the large adhesin LapA to the cell surface.  Cell-surface LapA is absolutely critical for the ability of Pseudomonas fluorescens to make a biofilm.  In this most recent study, Kurt showed that a second feature of GcbC was required for interaction with LapD - that is, the regulatory I-site of GcbC.  This is an exciting finding because the I-site had traditionally been shown to serve as a negative allosteric regulator of diguanylate cyclase enzymes.  The figure shown here indicates that the active site of the enzyme (yellow circles) is formed in the active state of the enzyme, fostering cyclic-di-GMP synthesis.  The binding of cyclic-di-GMP to the I'site represses activity by re-organizing the active site.  Kurt's work shows that the I-site also plays a positive regulatory role by facilitating interaction of GcbC with the LapD receptor.  This work will force us to reconsider how we think about the function of I-site in cyclic-di-GMP regulatory networks.