USDA scientists manage pathogen 'hot zone' in suburban Md. lab

FREDERICK, Md. -- A sign inside the locker room in Building 374 on the U.S. Army's Fort Detrick campus is framed by thick yellow and black striped tape.


Across the same military complex where scientists in space suits test the world's most deadly diseases, Department of Agriculture researchers are working with rare plant pathogens that have the power to wipe out food crops that feed billions of people, or if harnessed and applied precisely, could control noxious weeds that have infested millions of acres of land.

Many of the microbes do not otherwise exist in the United States, so pathologists must study them here in the Plant Disease Containment Facility, a high-security lab and greenhouse designed to ensure not a single microscopic spore escapes.

Before entering the facility, scientists with the Agricultural Research Service and all visitors must change from street clothes into scrubs. They pass from the locker rooms through double-door shower stalls into the lab's "hot side."

Nicknamed for its address on the Fort Detrick campus roughly an hour's drive from Washington, D.C., "374" looks like most any other government lab and greenhouse. Microscopes sit on black-top counters. Long tables are filled with potted plants. Natural light filters through glass walls and ceilings.

However, this is a "biosafety level 3" lab -- only diseases like anthrax and ebola require stricter security measures.

While there are several such high-security labs throughout the continental U.S., this is the only one focusing on foreign fungi, viruses and bacteria that attack crops and invasive weeds.

Built in the 1950s for the government's now-defunct biological warfare program, the greenhouse is constructed with specially treated glass strong enough to walk on and withstand severe storms that have flattened other greenhouses on the base.


"It's old, but still very functional," William Bruckart, a plant pathologist with ARS, said of the five-room greenhouse.

The facility is under negative air pressure, so air flows inward and runs through filters that trap any particles before making its way outside. Any liquid substances running to a drain are sterilized before entering the sewer.

Equipment and tools like pots are steamed at 250 degrees Fahrenheit in autoclaves to kill any organisms living on them. More sensitive items like paper or cameras must be fumigated for 15 hours.

When researchers are done for the day, they must leave their scrubs in the small changing area on the "hot" side, step into a shower stall and thoroughly wash before returning to the "cold side."

Deadly fungus

Arguably the most dangerous microbe being studied at the lab is wheat blast, a foreign fungus that cuts off nutrients to wheat heads so they turn white and don't produce grain.

First detected in Brazil in 1985, wheat blast started spreading in the past decade, wiping out up to 60 percent of the 2009 harvest in some parts of Brazil. Gary Peterson, an ARS plant pathologist, visited the South American country last year to collect samples and walked through fields with 100 percent infection rates.

"I've never seen a disease do that much damage," Peterson said.

The fungus has spread to Bolivia, Paraguay and Argentina, but it hasn't arrived in the United States -- yet.

The work done inside 374 helps scientists, farmers and regulators learn about the threats they face if wheat blast does make it to North America.

Though in today's globalized economy, it's often not a matter of if, but when, Bruckart said.

Peterson has infected 450 winter wheat strains native to the United States with wheat blast to see if any are resistant to the fungus. Only 12 strains showed signs of resistance, and they have been sent to Bolivia for further testing in the field.

Various spring wheat strains are now growing in pots in the greenhouse. Red, blue and white tape mark when wheat heads of the 2-foot-tall plants have been sprayed with the deadly fungus. The wheat heads in the group are all white -- the tell-tale sign of infection.

Peterson is also running experiments to understand how the fungus survives seasons when wheat crops are dormant. Specifically, he is trying to determine whether the pathogen exists in the soil or is bound up in weeds. He also wants to compare the original strain of the fungus to current samples to see if it has mutated or if environmental factors like climate change are fueling its rapid spread.

While such research will help USDA better prepare for the threat of wheat blast, it also benefits other governments that are combating the disease in their crop fields. Peterson shudders at the thought of the pathogen jumping from continent to continent.

"If it moved to Africa or Asia, you can imagine what that could do to the world in terms of starvation," Peterson said.

Biological controls

But not all the destructive organisms in the lab are considered threats.

Some foreign pathogens can actually help control invasive weeds that have taken a huge toll on natural ecosystems.

Invasive species remain a top priority for federal plant scientists because the invaders can outcompete native plants and alter entire landscapes, rendering them environmentally and economically defunct. ARS scientists search for the weeds' natural predators that keep their growth in check in their home countries, and investigate how to use them as biological control agents in the U.S.

These agents must undergo rigorous testing inside 374's containment barrier to prove they won't attack other endangered or economically important plants, because once such agents are released into the environment, there's no pulling them back.

"They are guilty until proven innocent," said Bruckart, who is currently studying pathogens for invasive blackberries and Japanese knotweed, including a potentially new disease discovered in Oregon.

It's a time-consuming process to learn about the pathogen and complete extensive risk assessment tests on non-target plants. Plants grow for two months before they are exposed to the pathogen, and then it usually takes up to two weeks to see symptoms.

"We test under optimal conditions for disease," Bruckart said. "We really make it favorable for the pathogen, so if it doesn't get sick here, it's not going to."

Once the tests are complete, the researchers submit an application for release to the Animal and Plant Health Inspection Service. Because there is no specific level of acceptable risk, the scientists are put in the unique position of advocating for a pathogen's release, Bruckart said.

The lab has overseen the three pathogens released in the United States since 1970 -- different fungi called "rusts" that attack invasive skeleton weed, musk thistle and yellow star thistle. While rust fungi don't kill the invasive plants outright, they debilitate their targets by sucking away energy and nutrients for the production of their own spores.

While the skeleton weed and musk thistle rusts have shown signs of success, the yellow star thistle rust, which was found in Iran, did not thrive in the warm, dry climate of California where it was released in 2003.

"We have a very high level of confidence of safety of agents," Bruckart said. "But we can't predict how well they are going to do outside of the lab."

Given the vast territory susceptible to invasion by foreign species, biological controls are the only economically feasible solution to combat invasives, said Dana Berner, another ARS plant pathologist. He said he is frustrated the Animal and Plant Health Inspection Service maintains such an extremely conservative stance towards biological control agents; hence, the release of only three beneficial pathogens in more than 30 years.

"APHIS, they are a tough bunch," Berner said. "They are not using science."

While there have been controversies over insect biological control agents, 26 fungal pathogens released in numerous countries have had a clean track record with no unintended consequences, according to researchers. And the Fort Detrick research team is hoping to release several new biological control agents in the coming years.

After more than a decade of work, they identified two agents that attack Russian thistle, or tumbleweed, and two others to control common crupina, a weed widespread in the West. One petition is currently under review by APHIS and the team is in the process of preparing the others.

Berner also thinks he's cracked the century-old question of how to control Canada thistle, which has plagued the United States since the 1600s. He said he figured out how the fungus infects the weed's extensive root system and researchers in other countries are testing his methodology. So far the results are looking very positive.

"If it keeps on working," Berner said, rapping his knuckles on his desk, "it's gone."

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