popular science

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MY EUREKA MOMENT

Dust-Mite Queen

Spore Power

RUBABA HAMID SHAFIQUE, RESEARCH ASSOCIATE AT INSTITUTE OF
BIOMEDICAL AND GENETIC ENGINEERING IN ISLAMABAD, PAKISTAN

OZGUR SAHIN,

BIOPHYSICIST AT COLUMBIA UNIVERSITY

Dust mites are microscopic creatures that live
in rugs, blankets, and cushions, triggering skin
rashes and asthma in millions of people world-
wide. In Pakistan, physicians started diagnosing
people with dust allergies, in the mid-1990s. But no one knew
if these allergy-inducing bugs actually lived there! Knowing
which species—if any—lived in Pakistani homes could help
doctors make more accurate diagnoses.
So in spring 2011, I collected dust from 300 homes in urban
areas of Pothwar. People aren’t accustomed to strangers show-
ing up at the door with a vacuum cleaner! I used my network of
friends to reach as many subjects as possible.
But I didn’t find any mites. I thought the entire project was
a failure. Then I remembered the pests like humid air, and
spring in Pothwar is dry. So I tried collecting again during the
rainy weather that summer—and this time I saw loads. They
belonged to two fairly common strains, which confirmed that
doctors could diagnose allergies with Western kits. I learned
so much about the mites that people now call me for advice
about infestations. I’m regarded as the “dust-mite queen.”

When a bacterium gets

stressed out, it stashes some

of its DNA in a hardy structure

called a spore, which can stay

dormant for years before reactivating. Back

in 2006, I started studying the spores made

by Bacillus subtilis because a colleague

told me they expand significantly in size

when they come into contact with moisture.

I wanted to harness that mechanical power.

First, to see how much the subtilis

grew with water in the air, I put some spores

in a special microscope that can measure

minuscule movements. Before I added mois-

ture, I leaned in to look. Immediately, I saw

a huge readout—the spores had already got-

ten much bigger. My mere breath had caused

them to grow! After some calculations, I

knew these would be able to power really

strong motors.

We built a little spore-powered 100-gram

toy car to showcase subtilis. It isn’t the

fastest— it takes a minute to cover about

10 centimetres—but it’s the only vehicle ever

to run on evaporated water. Its rotary motor

turns as the spores grow and shrink. Going

forward, I’d like to turn their size-changing

ability into electricity. The method? If we

place large sheets of spores on a body of wa-

ter and connect them to a generator, evap-

oration could produce renewable power

much the same way wind does.

illustration by Britt Spencer