- I can add these bacteria to rice, and corn, and tomatoes,
and bell peppers, and even Douglas fir
to increase plant growth and health, without having
to use chemical fertilizers, pesticides, even water.
My dream, is that we can drastically reduce the amount
of nitrogen fertilizer we use.
It's causing so many environmental problems.
- When you see an area like this, you see mostly trees.
But it's a complex, inter-related community
of many organisms.
- Some of the most important processes are driven
by microbes, and therefore hidden from our views.
- Imagine if we could use these microbes to grow plants
in arid regions, marginal soils,
and even contaminated soils.
- And that's why we're here, just outside of Seattle to meet
Dr. Sharon Doty, who is using genomic technologies
to make this dream a reality.
- Why are you collecting samples at this location?
- If you look below you, you're standing
in rocks and sand, and yet these trees are flourishing here.
What led me here originally was I was doing
poplar tissue culture.
And there's always this contaminant in the way
that was a slimy bacteria.
I found out it was a Rhizobium!
- You usually think of these things as growing in nodules.
- Right, yeah.
Only in root nodules of legumes or in Frankia
like alder trees.
And so then I thought well, if there's Rhizobium in
the poplar tree, maybe it's getting nitrogen
from the bacteria.
I made cuttings.
Just stuck them in nitrogen-free medium, and sure enough,
the trees were totally healthy,
- Is Rhizobium in these trees as well?
- There's some Rhizobium, but it's mostly other species.
There's lots of Berkleberia, Erbesprelum, Sudonomus,
and a lot of the bacteria can fix nitrogen.
- During nitrogen fixation oxygen inhibits the process.
How do the plants manage it, because we always thought
the root nodules were critical to that whole process.
- That's a dogma I've been battling against
for many, many years.
It's true that nitrogenase enzyme is inhibited by oxygen,
but there are free living bacteria that can fix nitrogen.
They are not waiting around for a plant to make a nodule
for them to use this enzyme.
It's really not a problem.
It's only a problem with the dogma.
- I am taking the branch samples that we collected
at the Snoqualmie River site.
I cut it into little pieces, then I surface sterilize it
and then grind it up using the pestle.
We can't do it using liquid nitrogen because
that will harm the microbes.
I just grind it up till we have this nice green juice
we call it a poplar smoothie.
We purify the strains and we characterize them,
then have the full genome sequenced.
And then we can expose the poplar roots to this solution
usually for a day and then we put the plant
on selective medium.
Usually we are making a whole consortia of different strains
having a lot of potentially symbiotic properties
including nitrogen fixation.
We can fluorescently tag these microbes, and follow them.
- It is so weird to see the microbes inside the plants.
How do the microbes actually manage to get into the plants?
- We've shown that they can enter into the plant
through these lateral root junctions.
It's called crack entry.
The defense responses go up, initially,
but then that response goes down.
- And do the microbes stay?
- Three years later, I was able to re-isolate
that same bacteria from those trees.
- And this colonization is it even or is it kinda clustered?
- We found that the microbes form these microbe colonies
within the plant, and we think that that might
be where they're fixing nitrogen.
- Can you take this technology and move it to other plants?
- We've shown again and again, in so many different plant
species, that we can add these microbes, and then they have
the ability now to grow with limited fertilizer.
We've also found that the microbes have all sorts of other
benefits to the plant.
It's overall plant health and stress tolerance.
- Are there certain strains that work better,
or is it something they need to breed back in again?
- I think you're right, that they've been breeding all
of these agricultural crops for the response to chemical
fertilizer, and now we need to start breeding for
the ability to interact well with these beneficial microbes.
- There are a few key processes.
For example photosynthesis, transpiration, or respiration.
All these impact the plant physiological functions
and therefore the crop production.
First I inoculate the plant.
About four to five days after they're germinated I measure
the photosynthesis using some hand held instruments.
We hope to see these symbiotic technology impact producing
agriculture crops in a better way using less resources
to grow the plant in the agriculture ecosystem.
- A strong area of research in my lab
is called phytoremediation.
That's using trees to clean up environmental pollutants.
- In Tacoma there was a smelter that operated
for about 100 years.
And it's polluted large areas, about 1,000 square miles
of Puget Sound with arsenic, cadmium, and lead.
The challenge with heavy metals, or metaloids like arsenic,
is that they don't break down and they don't degrade
in the environment.
The Asarco site itself fell under an EPA Superfund site
and so it was remediated using conventional
remediation technologies.
Outside of the Asarco site are thousands of houses
that have arsenic contamination and so we think that using
phytoremediation is something that could extend the reach
of the conventional remediation activities.
We want to have plants that move the arsenic from the soil
into the roots and then into their above ground tissues.
We're looking at woody plant species like willow and poplar,
which can be coppiced, which means just cutting them off
at the base, and then removing the plant tissues
from the site.
And then they'll regenerate, or regrow, off of their roots,
and so it's an annual product you can just harvest
the above ground tissues and remove the arsenic off site.
- What was the biggest surprise that you got
from the work you've done?
- Just finding out how many different ways that these
microbes are impacting the plant growth and plant health.
- How is that going to impact the future?
- I think it has huge implications for every time that we
grow plants, whether it be for agriculture or forestry
or bio-energy, that now we have the means to make it more
not only environmentally sustainable
but also economically sustainable