January 30, 2014

Work over the past several years in the lab has identified a Pseudomonas aeruginosa secreted toxin called Cif.  This toxin is an epoxide hydrolase enzyme that alters the trafficking of CFTR, an apical membrane-localized chloride channel.  Thus, this toxin can generate a "cystic fibrosis" like disease, with increased susceptibility to bacterial infection.  In a recent collaborative project with Dean Madden's group here at Dartmouth, with contributions from a recently graduated PhD student Alicia Ballok (left), we studied a homolog of Cif from Acinetobacter, another important opportunistic pathogen that is highly resistant to antibiotics.  This report described the identification, purification and biochemical characterization of this protein, as well as determining its crystal structure and impact on host biology.

January 25, 2014

Chelsea Boyd, a PhD student in the lab, recently published a collaborative paper with Sofiane El-Kirat-Chatel and Yves Dufrene, two atomic force microscopy (AFM) experts are the Université catholique de Louvain in Belgium.  In this work, we used AFM to assess the bacterial adhesin "footprint" left behind by the bacterium Pseudomonas fluorescens after it detached from the surface in response to nutrient starvation (deficted on the left side of the figure).  In particular, single  molecule studies using an antibody-functionalized AFM tip could probe for the presence of the critical adhesion LapA on the cell surface, taking advantage of the HA epitope tagged engineered into LapA.  Thus, we could measure the biophysical properties of individual LapA moelcules on the left behind in the surface (right side of figure).  We could find LapA footprint on the surface that were in the shape of bacteria cells.  These are the first direct evidence that LapA does indeed bind to the surface, and thus mediates cell-to-surface adhesion in this microbe.

January 17, 2014

January 06, 2014

A project headed by Dr. Alex Gifford, a close collaborator, and funded by the Flatley Foundation of Boston and the NIH, was recently published in the Journal of Cystic Fibrosis.  The paper, entitled "Iron supplementation does not worsen respiratory health or alter the sputum microbiome in cystic fibrosis" addressed the question of whether CF patients, who are often anemic, should take iron supplements.  The bottom line is: iron supplements do not appear to harm or benefit this patient population.  While iron supplements did boost iron levels in the serum, these patients did not achieve higher levels of hemoglobin  (i.e., improvement in anemia).  On the other hand, these supplements did not increase levels of iron in the sputum - higher iron in the sputum is associated with higher Pseudomonas aeruginosa burden and worse patient outcomes - nor did these supplements appear to alter the structure of the microbiome associated with CF sputum.  This work, led by Dr. Gifford, addressed an important heretofore unaddressed clinical question for CF patients.

January 03, 2014

In a recent collaborative study with Eric Dane and Mark Grinstaff at Boston University, was published in Chemical Science.  Dane and Grinstaff synthesized a number of novel compounds (see figure) with surfactant-like activity. Some of these compounds showed the ability to block biofilm formation, and surprisingly, one of them also boosted biofilm formation (panel B).  Alicia Ballok, a recently graduated PhD student, is a co-author on the paper.  Our lab performed biofilm assays, swarming assays and electron microscopy studies as part of this work.  This work was funded in part by the NIH.