The beneficial bacteria in question reside inside the nodules of legumes such as peas, beans, alfalfa and clover, where they pluck molecules of nitrogen from air in the soil and turn it into ammonia, which feeds the plant. It sounds simple, but it is a complicated and poorly understood process. Only bacteria that contain a special enzyme are capable of this sort of "nitrogen fixing" using airborne nitrogen no other type of living organism can do it. All other plants have to get their nutrients from using already fixed nitrogen in the soil.
This special ability allows legumes to flourish in nitrogen-poor soils, whereas other plants require applications of manufactured nitrogen fertilizer to grow well. But even legumes can't flourish without the right symbiotic bacteria.
"When you deal with a natural soil, you are dealing with a lot of complexity. Everything we learn about what makes symbiosis work gives us a tool to understand why, sometimes, symbiosis fails," Long said. "Plant breeders who are trying to help develop better-adapted plants can now analyze traits such as this. We've given them a new tool."
The more efficient that legumes can be made and the wider the range of environments they can thrive in, the more they can help reduce the need for chemical nitrogen that runs off into water or sinks into the groundwater or decomposes into a gaseous form. Long said
The gene's the thing
The legume that Long's team worked with is called barrel medic, a forage plant similar to alfalfa. They tracked down the newly discovered gene by studying mutant plants that were failing to produce healthy nodules on their roots.
While bacteria inside normal nodules will thrive, in the defective nodules of this plant those bacteria can't provide the benefit they are wired to deliver. Long said that the mutant "contained perfectly good bacteria, but was making these lousy nodules."
Wang found that the mut
|Contact: Louis Bergeron|