Move over, cyanobacteria! A large-scale study of the Earth’s surface ocean indicates the microbes responsible for fixing nitrogen there—previously thought to be almost exclusively photosynthetic cyanobacteria–include an abundant and widely distributed suite of non-photosynthetic bacterial populations.
The international study, published this week in Nature Microbiology, was led by A. Murat Eren (Meren) of the University of Chicago and the Marine Biological Laboratory, Woods Hole, and Tom O. Delmont of the University of Chicago.
Nitrogen fixation is a critical ecological process in which atmospheric nitrogen is converted to ammonia, making nitrogen “bioavailable” to living organisms to use as a fundamental building block of DNA, RNA and proteins.
“Microbes that can fix nitrogen or carbon are at the center of the ecology of microbial communities in many environments, including the surface ocean,” Delmont said. “Prior to our study, it was thought that the marine microbes responsible for carbon fixation were also largely responsible for fixing nitrogen. It turns out not to be so simple.”
“The ability of microbes to fix nitrogen is vital to all life,” said David Mark Welch, MBL director of research. “This study expands our understanding of the biological diversity of nitrogen fixation by providing the first genomic evidence that non-photosynthetic bacteria on the ocean surface can carry out these reactions.”
—Prof. Jacqueline Stewart
