麻豆淫院

A microscopic enzyme could be the key to helping nitrogen fertilizers stick better to the soil and prevent runoff that causes harmful algal blooms, according to a new review article published by a Michigan State University research team.

Led by College of Natural Science Dean Eric Hegg, the paper compiles years of research on an enzyme known as NrfA that plays a key role in keeping nitrogen in soil. Krystina Hird, an MSU Ph.D. candidate and first author on the paper, said studying NrfA could help farmers not only avoid polluting nearby waterways but also save money by reducing their need for fertilizer. The findings are in the journal Applied and Environmental Microbiology.

"A significant amount of nitrogen fertilizer is lost because it's converted to a form that's easily leached away," Hird said. "If we can retain more of that nitrogen in the soil, it could have big, positive agricultural implications."

Nitrogen is an essential element for all living things, from humans down to the smallest bacteria. It's commonly added to farm fields in a variety of forms to boost crop yields. The problem is both soil and nitrites are negatively charged. Just as magnets of the same charge repel one another, nitrites are easily washed away from farm fields during heavy rains. When too much nitrogen ends up in lakes and rivers, the result can be harmful algal blooms that make waterways toxic to humans and animals.

One of the best forms of nitrogen for agriculture is ammonium. With its positive charge, it latches onto soil and is more easily taken up by plants. However, many microbes in the soil turn ammonium into nitrite.

That's where NrfA comes in. Not only does it help the bacteria turn nitrite into ammonium, but it does so while moving and storing electrons incredibly efficiently. Other enzymes can help produce ammonium, but not as quickly or efficiently as NrfA.

While many researchers have contributed to this field, the findings aren't centrally located. Hegg's team combed through primary research, collated it into a review paper and synthesized the findings to draw larger conclusions.

"I'm excited to help future students who were in my shoes, who are just getting into this field and are trying to understand this big project that they're agreeing to take on for the next five to six years," Hird said. "We decided to take all of this information and put it in one place as an introduction-level paper for those graduate students."

Farmers could use the review paper's conclusions to help them choose the best nitrogen-containing fertilizers for their fields. More research could also be done to determine how bacteria with NrfA could be strategically placed along the edges of fields where water is most likely to run downhill, Hird said. A step in between those options could be encouraging the growth of more soil microorganisms that can produce ammonium by balancing the carbon to nitrogen ratio in the soil.

Next, Hegg's team plans to dive deeper into the mechanism of how nitrate is converted into ammonium. They want to track how electrons move through NrfA and how it consistently produces ammonium, even when starting with different nitrogen compounds.

"We're trying to get really specific and nitty-gritty," Hird said. "The reaction goes so fast, and slowing down a very fast reaction can make it unstable. It's going to be like performing a delicate surgery."