PNNL

This highlight is based on a PNNL news release issued January 30, 2017.

Vitamin B12 is produced by only a few organisms but is needed by nearly all. Scientists at the Pacific Northwest National Laboratory (PNNL) just published a paper recording further evidence that the water-soluble vitamin (synthesized in nature only by bacteria and archaea) wields great power in the microbial world.

The findings lend credence to the idea that B12 helps shape microbial communities - ubiquitous structures that affect energy and food production, the environment, human health, and much more.

"Vitamin B12 has an importance to microbial communities even greater than has been anticipated," said chemist Aaron Wright, corresponding author of the paper, which appeared January 30, 2017 in the Proceedings of the National Academy of Sciences. "We're exploring the functions it controls and its importance for the organization of microbial communities."

To do the study, Wright's team used a bacterium known as Halomonas sp. HL-48, a rare supplier of the vitamin in its microbial community. The sample was taken from a layered microbial community (a microbial mat) in northern Washington State's Hot Lake. The microbial mat, as with others, had dozens of community members that live together and trade nutrients like carbon and oxygen. These thermophilic microbes live in hot, salty water that is thick with algae and other micro-organisms.

In the microbes that build DNA and proteins, vitamin B12 controls crucial genes and enzymes. But research by Andrew Goodman at Yale University and Michiko Taga at the University of California at Berkeley indicates that B12 wields even broader influence in the microbial sphere.

In their study bacterium, Wright and his team found that B12 interacts with 41 different proteins and is central to the regulation of folate, ubiquinone, and methionine - substances crucial to the ability of microbial cells to create energy, build proteins, repair DNA, and to grow. Their findings about methionine show an expanded influence of B12 compared to what was known previously. The findings also show that vitamin B12 changes the instructions it sends to genes based on whether it's day or night - not a surprise in a community of organisms for which light is a central driver.

"B12 is very expensive for any organism to make," said Wright. "It takes a lot of energy for a microbe to synthesize, since there are more than 30 biochemical steps required. That's a signal that the substance is highly valuable and carries out important functions."

Wright's team created a chemical mimic of vitamin B12 that works just like the natural substance but can be tracked more closely in living cells. Through a system called "affinity-based protein profiling," the team tagged molecules to see precisely where they are active. Then the researchers used techniques like mass spectrometry to identify and measure the proteins of interest.

The work was funded by the Office of Science at the U.S. Department of Energy (DOE), with additional funding from the Russian Foundation for Basic Research and the Russian Academy of Sciences.

Measurements based on mass spectrometry were performed at the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility located on the PNNL campus.

Authors include scientists from the Sanford Burnham Prebys Medical Discovery Institute in La Jolla, Calif. and Polytech Nice-Sophia in France.

Reference:

Margaret Romine, Dmitry Rodionov, Yukari Maezato, Lindsey Anderson, Premchendar Nandhikonda, Irina Rodionova, Alexandre Carre, Xiaoqing Li, Chengdong Xu, Therese Clauss, Young-Mo Kim, Thomas Metz, Aaron T. Wright,  Elucidation of new roles for vitamin B12 in regulation of folate, ubiquinone, and methionine metabolism, Proceedings of the National Academy of Sciences,  (2017) doi: 10.1073/pnas.1612360114.