Breathless: Mike’s Journey to Find Elusive Bacteria in the Oxygen-less Ocean

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!

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Port is now behind us! The R/V Oceanus and crew is headed to sea. Credit: Mike Henson.

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….

See the full interview with Mike and Paige Jarreau, including some epic photos, at The Pursuit LSU College of Science Blog HERE.

Thrash lab presentations at #ASMicrobe

Mike, Celeste, and Emily will all be presenting at the 2017 ASM Microbe conference in New Orleans this coming weekend. Here is the info to find them:

Saturday (6/3)
Poster Session: AES11 – Freshwater and Marine Microbiology I
Time: 12:15 PM – 2:15 PM

Cultivation and Ecology of Novel SAR11 Taxa from Coastal Louisiana Waters (#700), V. Celeste Lanclos

Metabolic and Physiological Flexibility in a Coastal Isolate from the OM252 Clade of Gammaproteobacteria (#712), Emily Nall

Sunday (6/4)
Symposium: 425 – Culturing the Unculturable in a Sequencing Age (Room 352)
Time: 2:30 PM – 5:00 PM

Fresh and Salty: Cultivating Bacteria from the Coast of Louisiana, Michael W. Henson

Cultivating members of the microbial majority

It is with great excitement that I get to post that our manuscript on cultivating members of the microbial majority using an artificial seawater medium is finally out! This manuscript represents the hard work of not just myself, but Dr. Thrash, our undergraduates (past and present), and Austen Webber. Over the last two years, I have traveled to sites along the Gulf of Mexico collecting water for cultivation experiments (> 2000 miles traveled, > 4500 well inoculated). From the sites along the coasts of Louisiana, we have cultivated organisms from the Gulf of Mexico representing many important marine clades: SAR11, SAR116, OM43, OM252, Roseobacter, and many more. While isolating these organisms is important, it is also important to isolate organisms that represent abundant taxa within your source water. We compared OTUs from community sequencing of the source water  to our  isolate sequences to demonstrate that our method frequently captured some of the most abundant organisms in the system.

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This work also represents the first instance where many of these clades were isolated from the Gulf of Mexico, and importantly, on an artificial seawater medium. While high throughput, dilution-to-extinction culturing using natural seawater has been highly successful, we hope that this new approach using artificial seawater media will help more researchers cultivate important microorganisms without the hassle of collecting large volumes of natural seawater and needing a boat.

If you have any questions, please feel free to contact us! We are more than willing to answer any questions you may have. You can check out our list of organisms isolated so far HERE!

Henson, Michael W., David M. Pitre, Jessica Lee Weckhorst, V. Celeste Lanclos, Austen T. Webber, and J. Cameron Thrash. (2016). Artificial seawater media facilitates cultivating members of the microbial majority from the Gulf of Mexico. mSphere 1(2). doi: 10.1128/mSphere.00028-16. (Undergraduate authors) Supplementary Information.

Some associated press became available on May 1st. Check out Becoming Acculturated, by Jeffrey M. Perkel.

Emily and Celeste present at LSU Discover Day

IMG_7074Emily presented her LA Sea Grant-funded work to characterize one of our coastal isolates from the OM252 clade, LSUCC0096. She showed this organism has remarkable salinity tolerance, and can grow under chemolithoautotrophic conditions, a feature that was predicted from genome analysis.

 

 

 

 

IMG_7071Celeste presented results of her experiment to enrich for microorganisms that could utilize fulvic acids as their sole carbon source. She compared her work to that of former lab member Jessica Weckhorst who performed a similar experiment with humic acids. These are both extremely important fractions of the marine DOC pool.

Sampling Lake Borgne

Last week David and I got up early enough to duck a series of storms coming through the region for some sunny sampling on Lake Borgne. This also saw the maiden voyage of a new Thrash Lab capital acquisition, the R/V Schipperke. We put in at Campo’s Marina, toodled out to a site past the old fort (these are commonplace in this region), and took measurements and water collections. The water was almost fresh, with a salinity ~5. David used these to inoculate the latest high throughput cultivation experiment since Mike Henson is currently at the C-MORE summer course. Here are some photos.

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On the way through the cut
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David taking YSI readings

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