February 25, 2010: BYU microbiologist helped discover a cellular machine some plants use to get food from bacteria
This article originally appeared in BYU News
See also Deseret
Farmers buy 88 million tons of nitrogen fertilizer annually to grow
staple crops such as corn, wheat and rice. And it takes 3 to 5 percent
of the world’s natural gas to make all that fertilizer. That’s
frustrating because three-fourths of the Earth’s atmosphere is nitrogen,
but it’s in a form that most crops can’t use.
But a few plants,
such as alfalfa, soybeans and peanuts, can fertilize themselves, in a
way, thanks to a friendly bacterial infection. These legumes recruit
bacteria that “inhale” naturally occurring nitrogen from the atmosphere
and convert it into the useful form that plants use for
A Brigham Young University professor was part of a Stanford
team that discovered an unexpected piece of cellular machinery these
plants use to send molecules into the microbes to help them get
established in their new home in the plants’ roots. The researchers report their results in this week’s edition of Science,
the top American scientific journal.
findings are fundamental to this important process, so the hope is that
someday researchers can help the legumes and bacteria work even better
together. A dream scenario would be to take an improved understanding of
this process of “fixing” natural nitrogen and genetically program other
crops – corn, wheat and rice – to welcome these bacteria into their
roots, so they too, can fertilize themselves.
“Think how much
energy consumption could be offset if we could rely more on biological
nitrogen fixation, which is solar-powered,” said Joel
Griffitts, BYU assistant professor of microbiology and co-author on
the Science paper.
Griffitts worked on the project when
he was a postdoctoral researcher in the lab of Stanford’s Sharon
Long, who is also an author. Dong Wang, a postdoctoral scholar in
Long’s lab, is the lead author.
Nitrogen is essential to life on
earth. Humans need 11 grams per day, for example, compared to 20
milligrams of iron per day. Too bad all that nitrogen in the air and
soil is in a form that is chemically useless to most living things.
what makes this alliance between legumes and bacteria so special.
a system in legumes that pulls nitrogen right out of thin air and
converts it into fertilizer,” Griffitts said. “I can give you one plant
with these bacteria and one without them, and if I don’t feed the second
one nitrogen fertilizer, then the plants with the bacteria will be much
larger and greener after just a few weeks.”
begins when a lucky bacterium of this type – called rhizobia –
encounters the root of a legume in soil and gets invited inside. The
plant creates a nodule on its root – a “high-density residence hall for
bacteria,” Griffitts says. There the plant protects the microbes and
sends them energy generated by photosynthesis in return for the
bacteria-generated useful nitrogen.
“The plants nurture these
bacteria – sort of like farming them – and they have to do it very
carefully,” Griffitts said. “We’ve found a pathway by which the plants
deliver the right molecules to the bacteria to facilitate nitrogen
Although the research looks only at the fundamentals of
this important process, possible future applications include:
the process in legumes so they are more efficient at producing useful
nitrogen and therefore grow better.
- Someday transferring this
nitrogen fixation process to important crops outside the legume family.
more about how diseases progress, because many of the genes involved in
the relationship between the bacteria and plants are also required for
the development of bacterial disease.
“This type of study brings us that much closer to understanding all
of the steps that are required to get this special arrangement right,”