Former Projects | Hanson Lab @ University of Delaware

Chlorobiaceae physiology

TEM of Cba. tepidum cells. The dark objects at the cell edge are chlorosomes, the light harvesting antenna of the Chlorobiaceae.

This has been the long term interest of the lab and was what Prof. Hanson developed while a postdoctoral fellow with Dr. Bob Tabita at The Ohio State University. We've collaborated with Dr. George Luther and Dr. Clara Chan at UD and made significant progress in understanding how Chlorobaculum tepidum utilizes and prioritizes different sulfur compounds as electron donors. The project led to a couple of new strains from the Bahamas and the Chesapeake Bay. It has led to a number of open questions that we are continuing to pursue today. For example, why does Cba. tepidum have to synthesize S(0) to use it as an electron donor? Prof. Hanson is actively looking for additional funding to continue the work and does have one active project on metabolomics in the Chlorobiaceae listed here.

Graduate Students: Katie Kalis, Jake Hilzinger, Kevin Shuman, Brian Eddie, Jen Hiras, Leong-Keat Chan
Postdocs: Cassie Marnocha, Vidhya Raman, Lisa Waidner, Rachael Morgan-Kiss

Selected papers:
Properties of Cba. tepidum S(0)
Beginning to explore Cba. tepidum's energy landscape
Cba. tepidum requires its own biogenic S(0) for growth
Cba. tepidum S(0) interactions and (surprise!) motility
Sulfide as key regulatory signal in Cba. tepidum

Low molecular weight (LMW) thiols

Potential structures for Cba. tepidum's novel LMW thiol. It turned out to be the one on the right.

Prof. Hanson had been obsessed with the idea that a low molecular weight thiol (e.g. glutathione, cysteine, or methionine) was involved in S(0) metabolism by Cba. tepidum. While that didn't turn out to be the case, the group was able to show that Cba. tepidum does contain a novel LMW thiol whose structure was confirmed as N-methyl-bacillithiol in collaboration with Prof. Chris Hamilton. Using comparative genomics, we have shown that bacillithiol derivatives are likely the most widespread LMW thiols in prokaryotes and have worked with Dr. Javiera Norambuena while she was a student at Rutgers with Prof. Tamar Barkay and Prof. Jeff Boyd to examine the role of BSH in oxidative stress in Thermus thermophilus.

Graduate Students: Jen Hiras
Postdocs: Vidhya Raman

Selected Papers:
N-Me-BSH discovery and distribution
Oxidative stress enzymes protect BSH in T. thermophilus
Thiols, thioredoxins, and Hg(II) in T. thermophilus.

Nitrogen cycle microbes and physiology

We've collaborated with Prof. Barb Campbell, who led work on Nautilia profundicola, and Prof. Martin Klotz, who has wide ranging interests in nitrogen cycle microbiology, contributing genome sequencing, annotation, pathway prediction, and physiological measurements. The genomic and physiological data helped to establish that the Epsilonproteobacteria should be moved out of the Proteobacteria and into a separate phylum.

Graduate Students: Katie Kalis

Microbial Ecology

Looking north from Jade Mountain across Toolik Lake, AK over North Slope tundra.

Another set of collaborations with Prof. Barb Campbell led to investigating sulfur oxidizing microbes in sulfidic springs and caves along with a relatively early use of 454 sequencing to study microbial community structure in Arctic tundra soils in Toolik Lake, AK. The latter also involved Prof. Michelle Mack and Prof. Ted Schuur, ecosystem ecologists with long term interests in tundra soil organic matter.

Graduate Students: Karen Rossmassler

Selenium, Tellurium, and Polonium - oh my!

Salt marsh sediment bacteria plated on media without (L) or with (R) tellurite. The black color with tellurite is due to Te(0) precipitation.

These elements fall below sulfur in the periodic table and therefore should have somewhat related chemistry. Collaborating with Prof. Tom Church, we isolated a number of strains of microbes resistant to tellurite from Delaware salt marshes and examined how they interact with and transform these elements. This influences how these elements are distributed in the environment. Importantly, these organisms volatilize Po, which is a component of nuclear waste.

Graduate Students: Andrew Bahrou
Postdocs: Patrick Ollivier