A MARTÍNEZ, HOST:
We're going to zoom in on this next story. Actually, zoom way in. A team of scientists looking at a microscopic mystery recently won a top prize from the publisher of the journal Science. Reporter Ari Daniel has more on their discovery and how it might revolutionize farming.
ARI DANIEL, BYLINE: Starting in the late '90s, Jon Zehr, a now retired microbial ecologist from UC Santa Cruz, was confronted with a puzzle. On research cruises, while testing seawater, he and his colleagues kept finding the same fragment of DNA in the ocean. But when they went to look for the organism it came from, no one ever managed to see it.
JON ZEHR: Every time we would get these samples, we looked through the microscope and there's nothing there.
DANIEL: And yet the DNA was everywhere - in the open ocean, along the coast, in the tropics, the Arctic. It also appeared to have a special and rare function of taking nitrogen from the surroundings, which living things need to survive, and turning it into a form that could then be fashioned into proteins and DNA. Usable nitrogen like this is pretty scarce.
ZEHR: That's why we add it as fertilizer in agriculture. Same is true in the oceans. It's in short supply over wide regions of the ocean.
DANIEL: Up until now, the ability to transform nitrogen was a feat scientists thought only certain kinds of bacteria and other simple microbes could pull off. But here's what this puzzle wound up revealing. Some 140 million years ago, a free-living bacteria that could grab all the nitrogen it wanted out of the water it was swimming in, fused with an ancient algal cell, says Tyler Cole, a biologist with UC Santa Cruz.
TYLER COLE: One cell engulfs another and then doesn't digest it, but rather incorporates it into its own body.
DANIEL: Over time, the bacteria jettisoned some of its genes. The algae became dependent on the nitrogen it was receiving until eventually, each one could no longer live without the other.
COLE: So the process of two species becoming one.
DANIEL: This is a lot like what gave rise to the mitochondria and chloroplast, but in this case, it led to a cellular structure that could transform nitrogen into something useful. The researchers called it the nitroplast, and it's responsible for pumping significant amounts of nitrogen into the global ocean. Solving this microscopic riddle took years. The first clue was that whatever had produced this fragment of DNA was missing all sorts of genes. To survive, Zehr figured it had to be getting help from another life form.
ZEHR: Because it lives with somebody else who can provide those things.
DANIEL: He was right. That somebody else turned out to be a kind of single-celled algae that looks like a teensy soccer ball. The team partnered with the Lawrence Berkeley National Laboratory to use x-rays to peer inside that soccer ball. Structural biologist Valentina Loconte was struck by what she saw.
VALENTINA LOCONTE: Side the alga, I found the little cell.
DANIEL: This little entity, what appeared at the time to be a little cell, was the oddball source of all that DNA in the ocean.
LOCONTE: It means that the two organisms are really living together.
DANIEL: Tyler Cole poured over the inner workings of both. He found the little guy's missing genes were housed in the big cell and the big cell received nitrogen from the little guy. That is, the two needed one another.
COLE: And at that point, it makes it very difficult to call these two different organisms if their genomes are so intermingled.
DANIEL: Instead, this was a single organism. The little guy was actually the nitroplast, a component of the bigger algal cell. This nitroplast allowed the more complex organism - so not a simple microbe - it had a nucleus - to capture its own nitrogen.
DOUG CAPONE: It's been in plain sight, but to get the details that finally made the leap of faith, wow, that's really cool.
DANIEL: Doug Capone is a biological oceanographer at the University of Southern California, who wasn't involved with the discovery. He says the nitroplast could be introduced someday to crops to allow them to convert their own nitrogen without relying on external fertilizer.
CAPONE: This provides a model system for how one might integrate the nitroplast into an agriculturally important crop.
ZEHR: It's one of the holy grails of biotechnology, says Jon Zehr, the ability to engineer plants that could snatch nitrogen out of the air and use it to grow without any of the pollution, energy, or expense that current fertilizers require. For NPR News, I'm Ari Daniel. Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.
