Airborne Bacteria Detection

Virginia Tech researchers seek out mysterious blankets of biomaterials

By Danielle Lucey

A Rascal 110 UAV sits ready for a sampling mission at Virginia Tech’s Kentland Farm. All photos courtesy Schmale Laboratory at Virginia Tech.

S

omewhere, up in the air, live silent

passengers on a breeze. Kicked up

into the sky from as far away as other countries, these infinitesimally small microbes move in blanket-like waves. Not so silent is the havoc they can rain down on plant and animal life below, the results of which

Getting the project off the ground Ross has a background in dynamical systems and efficient space travel leveraged on gravity. By applying these concepts to the ways microbes move through the air, he can model and predict when these blankets

Farm, a campus-owned research farm about 10 miles west of Virginia Tech’s main Blacksburg, Va., campus. The facility has dedicated research areas and houses outreach and teaching space, where projects can bring in and educate stakeholders, members of the public and sometimes visit-

plague farmers, their crops, their animals

of microbes are on the move.

and even human health.

Schmale’s experience with unmanned aer-

functional and staffed in part through uni-

Called Lagrangian coherent structures by

ial vehicles puts the aircraft at the crux of

versity funding.

engineers, these dynamically distinct patches are typically talked about in terms of fluid

Schmale and Ross’ work, the tool that allows them to blend aerobiological monitor-

dynamics, relevant to ocean research. But

ing and plant pathology.

a project out of Virginia Tech hypothesizes

“We like to think about … microbial inva-

that similar structures occur in the air and waft between layers of the atmosphere.

It’s these invisible blankets that brought Virginia Tech researchers David Schmale and Shane Ross together for their interdisciplinary research. Their work aims to determine when and where these waves of microbial

sions,” says Schmale, an associate professor in Virginia Tech’s Department of Plant Pathology, Physiology and Weed Science.

He and Ross believe that pathogens move throughout the atmosphere and invade new territories. “We want to track them and find out where they’re coming from and where

invaders will happen and give farmers an

they’re going.”

early warning system to prepare for their

Virginia Tech is blessed with a large ag-

arrival.

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ricultural research facility in its Kentland

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ing school kids, says Schmale. The farm is

Most key for Schmale, however, is the facility’s 400-foot paved runway, perfect for the project’s fixed-wing unmanned systems.

“Having the facility has been instrumental to our success,” says Schmale. “I would say in terms of challenges, getting that facility up and running, it didn’t happen overnight.

We started all of our work basically on just a flat area of grass that the research farm gave us, and as we started to acquire resources, the administration started to respond with facilities.”

Going unmanned All this mysterious microbial movement falls under the umbrella of aerobiology, the study of the flow of life in the atmosphere, which is then broken down into three processes, says Schmale — release, horizontal transport and deposition. Fungi, for example, release their spores into the air, which are then swept up into turbulent currents. Then they’re transported over some distance and finally deposited onto another host crop.

Release and deposition happen at the Earth’s surface, and there are many tools — like spore vacuums and Petri plates on stakes — to measure these two easily accessible processes. Horizontal transport, however, requires a way to assess the atmosphere and, as a result, is much harder to understand.

There are a number of ways to do this, says Schmale, using full-size aircraft, balloons, even kites.

“With full-scale aircraft you’ve got issues of at least risking one human life,” says Schmale, echoing that a lot of these missions fall into the dull, dirty and dangerous categories, “as AUVSI likes to reflect on quite a bit. So putting an unmanned system in the kicker is an important part of fulfilling research obligations and being able to do things fairly inexpensively and without the risk of human life.

“It’s true, I mean a lot of the missions we do are very dull. I wouldn’t say they’re dangerous. They’re very dull and very dirty.”

When they sample, the team goes out for a week and flies all day long. And since

A ground-based sampling device to collect Fusarium.

they’re using an autopilot, “the plane’s doing the flying; we’re just sitting back watching.”

Sidestepping using a full-scale aircraft for this and using unmanned systems instead helps reduce pilot fatigue, says Schmale.

on Petri dishes containing a selective agar

Certificates of Authorization from the Fed-

medium.

eral Aviation Administration.

The team is using a SIG Rascal 110 for

The Penguin B comes with the largest price

their National Science Foundation-funded

For their research, Schmale, Ross and their

research, but they also fly a BlueBird Boo-

students use a series of four unmanned aer-

merang, a UAV Factory Penguin B and a

ial vehicles, all readily available as remote-

Senior Telemaster. All of the platforms are

controlled platforms, to gather pathogens

licensed to fly through their four separate

tag. It’s a fiberglass, “more professional, commercial body frame,” meanwhile the others are more hobby-based plywood platforms that aid in the project’s workload, says Schmale.

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Airspace Invaders — continued from Page 19 The Rascal 110 is the project’s “tried and

activity still occurs above the altitude where

true platform,” says Schmale. It can fly for

the team is allowed to fly.

45 minutes with their current configuration, “and she carries the wing loading of our plates really, really well, and so we’ve used her exclusively for all our NSF work.”

For

their

sensor-based

applications,

Schmale prefers the Penguin B, “because it’s a pusher, and of course we’re not disturbing airflow. We’re sort of in front of the plane, which allows us to channel things into the fuselage.”

The team has published data on hundreds of their flights, though a very literal ceiling limits the research the project can do.

While a lot of transport blankets occur in the operable airspace under Virginia Tech’s certificates of authorization, much of the

search on farms in the future.

“The idea of a consultant that wants to set

“The pathogens are flying considerably

up a business that’s based in part on our

higher than the FAA will let us actually fly

technology would have to get a COA in

for our COAs,” says Schmale.

“They’re

order to do this, and I don’t know how they

moving through the planetary boundary

would do it,” he says. “You’d have to know

layer and beyond.”

in advance where you’d be flying, and

However, the higher a microbe goes, the more it will be exposed to the elements, says Schmale, like UV radiation, which is hard on things like spores and can kill them.

The work at Kentland Farm is all restricted under the four COAs, which specify both altitude and operational restrictions.

you’d basically have to, more or less, say you’re going to fly anywhere in the contiguous U.S. Really, that’s the biggest restriction right now. There’s nothing more than that.”

Growers, however, are amenable to the idea of UAVs buzzing over their farms, says Schmale. If a plane were able to go up as a wave of microbes were coming and detect

Having the Kentland Farm facility makes

where they were coming from, it could help

it easier for the FAA to clear them, says

a farmer know when to spray a fungicide.

Schmale. The FAA’s current policies, however, could limit implementation of this re-

CropCam in Canada has the farming mar-

The Rascal 110 is outfitted with sampling arms, which open and close during flight.

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species,” he says.

One of the most important mycotoxins in the United States, according to Schmale, is deoxynivalenol, also known by the much more descriptive name vomitoxin.

“Symptoms that often occur from domestic animals consuming grain basically contaminated with this toxin will often exhibit symptoms of vomiting, even refuse to eat their feed, particularly in the case of swine, and death can ensue if levels are high enough,” warns Schmale.

Another type of mycotoxin — known as zearalenone — plagues animals like pigs and mimics the hormone estrogen, resulting in reproductive problems for the animals, Preparing sampling devices for unmanned aerial vehicles to collect Fusarium in the lower atmosphere.

like swollen teats and ovaries. “It’s a really big deal,” says Schmale.

Other kinds of Fusarium produce mycotoxins that lace common staple crops for humans, like wheat and corn. There are other species that cause skin diseases in humans and an eye disease called Fusari-

ket cornered in that country, says Schmale,

this group … causes a number of different,

because of its price and reliability. That

important diseases of relevance to plants,

model would also play well in the U.S., he

domestic animals and humans,” says

says.

Schmale.

“Those type of systems if you can get into

It can cause wilts, rots, cankers and blights

the few thousand dollar range, I think grow-

to many kinds of crops.

also creates pulmonary infections, with re-

“You’d be hard-pressed to find a crop that

zil, says Schmale.

ers would be really willing to entertain them, but then it’s the whole idea of actually being able to use it and make something of it in your business. And that’s where, if it’s not a hobby, it’s a business, and the FAA has to be involved.”

didn’t have some sort of Fusarium disease associated with it,” says Schmale. “It’s quite phenomenal.”

There are about 80 biological species of the genus around the globe, and that iden-

Fungus fatale The main culprit in all this pathogen research is the extremely prolific fungus in the genus Fusarium, the sole microbe of interest in the NSF study.

While not all species of Fusarium are dangerous — one is even approved for sale as food by the United Kingdom — many strains of the fungi cause widespread disease.

“Fusarium is one of the most important genera of fungi on the planet Earth, and

tified number likely falls far short of the actual number of species, which Schmale estimates as perhaps twice that number or

um keratitis that particularly affects contact lens wearers that don’t frequently wash their lenses in solution, where the fungus implants onto the cornea outer layer of the eye and grows through its layers. Fusarium cent localized outbreaks occurring in Bra-

Gathering samples To actually collect these microbial samples, the UAVs are outfitted with a series of Petri dishes that open and close at set points in flight.

“We have these sampling arms … that

more.

operated like a clam shell, that open and

Of the dangerous strains of Fusarium, some

Schmale.

produce dangerous toxins, called mycotoxins, commonly referred to as fungusproduced molds. These mycotoxins can

close remote control from the ground,” says

There are inner and outer sampling arms, and the configuration on the Rascal 110

contaminate food and feed, says Schmale.

can hold eight Petri plates. The plates con-

“We do a lot of analytical chemistry to

Fusarium.

detect these toxins in food and feed and ultimately attribute them to certain Fusarium

tain a specific medium that is selective for

“What’s neat about using these plates as a

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Airspace Invaders — continued from Page 21 sampling device is that with this medium we

Once they land, they’ll detach the used

can basically select just for Fusarium and

plates, put on new ones and repeat the

kind of ignore all the other stuff we’re not

flights. All the sample analysis happens on

trying to track.”

the ground in their lab.

The arms are closed during takeoff and

Types of sampling surfaces in the plates in-

SPR, that allows users to detect an agent in

landing, so there is no exposure to the

clude things like grease, sticky tape and, in

real time, so the team could identify biologi-

plates until the arms are opened, prevent-

the last couple years, filter papers coated

cal agents while the UAV is flying.

ing any sample contamination.

with glycerin that allow them to collect a

The sampling pattern is all autonomous; meanwhile, the researchers open one set of arms for 10 minutes, close them and repeat the process with the second set of arms.

“We have a sample that’s been collected over the period of 20 minutes, but it’s actually two independent samples, kind of like two separate flights, if you will,” says Schmale.

then inspected using DNA-based analyses back in the lab. The future of this research

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They are also exploring a device from a Washington company that makes a technology called surface plasmon resonance, or

Once identified, the researchers can hypothesize where a sample was flowing from based on the time of year.

is likely this type of multimicrobial analysis,

“That’s a big component of what we do,”

says Schmale.

says Schmale. “Some of the species are

Other sensors on the aircraft include an ionic spore sensor, which takes air funneled through the nose of a pusher platform. The air is charged as it passes through this device, and the particles then are deposited

Members of the Schmale lab conduct an aerial sampling mission.

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very varied sample of microbes, which are

on a surface of opposite charge.

exclusively localized to a certain region or certain crop type, so if you’re collecting a tropical species, for example, during the winter time here in Blacksburg, Va., then you might question, well, it’s likely coming from some warmer, tropical region.”

The team does back-trajectory analysis to

The students with no prior experience with

“What they might consider as a toy is a

test that hypothesis and looks for seasonal

unmanned systems tend to have a warm re-

tool for us,” says Schmale. “It sort of begs

trends in what they’re collecting. One of his

ception to the technology, he says.

the question of, what is the future of agri-

graduate students is focusing her research on these recurring trends from year to year.

“Everybody sort of gets excited … about things that fly. It’s just really cool,” says

Schmale says he’s very selective about

Schmale. “When you take something that

which grad students get to participate in his

can fly and then you turn it into a tool …

and Ross’ program, which blends students

that has some relevance to the system of

from many backgrounds and majors, some

agriculture, in general students get really

of which have never used unmanned sys-

excited.” Schmale says he’s impressed with

tems before.

how quickly young students take to the top-

“I have students who are trained solely through my department … and then we have students who also have a split role,

culture? And are these unmanned systems a part of it? Of course the answer coming from my side of the fence is yes.”

Danielle Lucey is managing editor of Mission Critical.

ic and the intelligent questions they have.

Schmale also has an RC simulator where high schoolers can try flying for themselves.

who are basically co-advised, but their de-

“Of course they crash and burn pretty

gree will come from an engineering depart-

quickly after they try, but it’s all on a video

ment or from my department, for example,”

game, which is really nice,” he says. “They

says Schmale.

can appreciate how tough it really is.

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