Member Highlight: Exploring The Microbiome Of An Ocean Bacteria

2018-02-12T12:29:20+00:00 February 12, 2018|
(Credit: State of the Planet)

(Credit: State of the Planet)

Adrift on a boat in the middle of the North Pacific Ocean, the most astounding sight is the utter absence of anything to see. The glassy calm water is undisturbed and gently undulating for miles in every direction.

(From By Kyle Frischkorn) —  Even if you peer over the edge of the deck into the crystalline blue water, the light of the sun penetrates to a depth of around 600 feet without anything to block its path. There appears to be nothing to see but water here, but looks can be deceiving. It’s the impossibly small organisms and their disproportionately large impact on the ecosystem who lured me and a team of scientists to brave the high seas, a curious shark, and an impending hurricane. We came to the middle of the ocean to tap into the secret lives of the microbes that call the open ocean home. We recently published our results in The ISME Journal.

In the summer of 2015, a team from Columbia’s Lamont-Doherty Earth Observatory–Sonya Dyhrman, Sheean Haley, and I–packed up the contents of our laboratory and shipped it to the other side of the planet. We followed close behind, thankfully with less baggage, and joined approximately 60 biological oceanographers from around the world in Honolulu, Hawaii. From there, we were destined for the North Pacific Subtropical Gyre aboard a fleet of two research vessels.

Our expedition was funded by the Simons Foundation and called the Simons Collaboration on Ocean Processes and Ecology, or SCOPE. The mission of SCOPE is to measure and model how marine microbes interact with and influence each other and the environment at large. These processes take place hundreds of miles away from dry land, but they have critical importance for all life on earth. After all, microscopic marine plants, or phytoplankton, are responsible for roughly half of the planet’s primary productivity. This means that for every other breath you take, you can thank a phytoplankton.

My own research focuses on a phytoplankton called Trichodesmium. It’s a keystone species out in the subtropical open ocean. In low nutrient, almost desert-like conditions, Trichodesmium is an oasis. It’s a photosynthetic bacterium, so it can use little more than sunlight and carbon dioxide to make its own sugar for food. It’s also a nitrogen fixer. Just like the bacteria that live in the roots of the leguminous plants like peas, Trichodesmium can take inert N2 gas from the atmosphere and turn it into a form that supports life. In a harsh environment where other organisms barely eke out a living on the low supply of bio-available nitrogen, Trichodesmium is a floating fertilizer factory. For this reason, it forms hotspots of biological activity—constellations of floating microbial cities that enable global biogeochemical cycles to keep on churning.

Comparing Trichodesmium to a city isn’t much of a stretch. The cells are large—for a bacterium that is. They’re around 20 micrometers wide, nearly 8 times the length of a typical bacterium. These cells form long chains, and those chains clump together to form puffball-like colonies that look like pea green bales of hay the size of a pinhead. If you were to zoom in on one of those puffballs, you’d find…

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