Last Friday, on the last day of November, 2018, Mike Henson successfully defended his dissertation, entitled High-Throughput Cultivation of Bacterioplankton from the Gulf of Mexico and Genomics of the First Cultured LD12 Representative. It was a sunny, beautiful morning and Mike had a great turnout. His dissertation contains three data chapters, two of which have already been published (Henson et al. mSphere 2016; Henson et al. ISME J 2018), and a third that is nearing submission. These chapters describe improvements we made to the dilution-based cultivation protocol pioneered by Don Button and colleagues and enhanced to a high-throughput format by Steve Giovannoni and many of his former students and post-docs (including yours truly). It also quantifies the relative efficacy of our cultivation work by strain, explores why cultivation effectiveness might differ across taxa, and highlights the added cultivar diversity contributed by Mike’s efforts over the years. The dissertation also includes an in-depth exploration of the genomics of the first cultivated LD12 representative, which Mike has previously posted about below. Mike also has another first-author publication on the microbiome of the Mississippi River (Henson et al. L&O 2018) that is not included in the dissertation. So in short, Mike has three first authored publications after 4.5 years of graduate school, and has two in the pipe, combined with many other co-authorships. Mike was also able to secure two different grants during his time here at LSU. He will be coming with the lab to USC for a one year postdoc to finish his projects and help get us rolling there. We’re very happy we don’t have to say goodbye to Mike yet!
Emily Nall (far left in the photo), who has been an undergraduate researcher in the lab for her entire time at LSU, defended her Honors Thesis yesterday entitled Physiological and Genomic Characterization of a Novel Isolate from the OM252 Clade of Gammaproteobacteria. Emily has been working steadily on this project for a couple years. She has used comparative genomics to reconstruct the metabolism of strain LSUCC0096, tested a number of physiological parameters, some of which were predicted from the genome, and has examined the organism’s distribution throughout our coastal data as well as the Tara Oceans data. The next step will be getting the final pieces of this project together for publication. It’s important to note that Emily also funded part of this project herself through a Louisiana Sea Grant Undergraduate Research Opportunities Program (UROP) Fellowship. We’re very proud of you Emily and wish you all the best after graduation!
Our paper on the cultivation and genomics of the freshwater SAR11 strain LSUCC0530 has been published online in the ISME Journal (Here). The SAR11 LD12 lineage evolved to colonize freshwater ecosystems, and, like its marine cousins, occurs as one of the most abundant freshwater bacterioplankton worldwide. Strain LSUCC0530 represents the first cultivated representative of the LD12 clade and presented the Thrash lab with an unprecedented opportunity to provide new insights into the important evolutionary processes behind marine-freshwater transitions. Specifically, we demonstrated the capacity of strain LSUCC0530 to grow in salinities up to 5, provided evidence for LD12 ecotype differentiation based on temperature, and developed a hypothesis on how the loss of key genetic functions enabled the SAR11 clade to transition into fresh water. This work is only the beginning of our exploration into the SAR11 LD12 clade and its marine-freshwater transition, so be on the look out for more data soon!
If you have any questions or want to know more about LSUCC0530, please feel free to contact us! We are more than willing to answer any questions you may have.
Henson, Michael W., V. Celeste Lanclos, Brant C. Faircloth, and J. Cameron Thrash. (2018) Cultivation and genomics of the first freshwater SAR11 (LD12) isolate. The ISME Journal. AOP.
On Monday, January 15th, I got to join Celeste on a sampling trip to Calcasieu Jetties in Cameron, Louisiana. This was my first time going on a sampling trip since joining the Thrash Lab. While it was quite a cold morning, it was still a fun time. There were some beautiful views along the way of Louisiana’s marshes.
Once we got to the sampling site, Celeste had the joy of wading out into the cold water and collecting. At least it was a beautiful morning with the sun shining down and bright blue skies.
The purpose of this trip was to obtain a water sample for the mCURE sections of introductory biology lab. Using this sample, the students will learn high throughput cultivation protocols used in the Thrash Lab. I’m happy to have been able to help with the fieldwork and hope that the students enjoy learning about what our lab does.
Cameron and the lab got highlighted by LSU as a recent Featured Tiger. There are some great shots from near Lake Borgne included and solid cameos by Mike, Celeste, Emily, Anna, and of course the RV Schipperke.
By Paige Jarreau. LSU biological sciences graduate student Mike Henson recently conducted field research in the great big blue! Mike works in Dr. Cameron Thrash’s lab. We asked him to tell us more about his field experience at sea below. Enjoy!
Waves stretch far into the horizon. The sun’s rays pierce the crystal clear blue water. The ocean here gives no hints about its oxygen-less waters beneath its depths. Yet, about 100 miles west of Manzanillo, Mexico in the Eastern Northern Tropical Pacific is one of largest anoxic bodies of water, or oxygen minimum zones (OMZ), in Earth’s oceans.
OMZs form when nutrient rich bottom waters from the Pacific Ocean are brought up to the surface, causing large blooms or growth explosions of photosynthetic algae. As the algae begin to die, other microscopic organisms (or backterioplankton) in the water consume oxygen to metabolize organic matter produced by the algal cells. Once you reach 100 meters below the surface, oxygen levels begin to decrease. At 300 meters, the oxygen has been completely consumed. Any organisms such as fish passing through these areas that are incapable of living without oxygen will die unless they can escape to the more oxygenated surface waters.
This may sound familiar to many Louisianans. However, unlike the hypoxia (a.k.a. the “dead zone”) that occurs seasonally in the Gulf of Mexico from nutrient pollution, this naturally occurring oxygen minimum zone is present year-round.
In the Thrash lab, we study the microbiology of northern Gulf of Mexico hypoxia. We are also collaborating with Chief Scientist Dr. Frank Stewart of the Georgia Institute of Technology, who has National Science Foundation funding to study the oxygen minimum zone in the Eastern Northern Tropical Pacific. Scientists from eight different countries, including USA, Canada, Mexico, Iceland, Denmark, Austria, Spain, and Germany, myself included, recently spent three weeks aboard the R/V Oceanus collecting water and sediment to elucidate the organisms and processes involved in forming this peculiar area of the ocean….