BOSTON, Mass. — If microbial life is found on Mars, will it be native
to the planet or something carried there from Earth? Either way, will
it be safe to return samples of such organisms to Earth? Astrobiology,
the search for life elsewhere, says a University of Illinois
microbiologist, is making us look a lot closer at microbial life on
Earth — how it adapts and its relationship to emerging infectious
diseases. "Even if we don’t find life on other planets, we are
learning a lot about life on the Earth, particularly microbial life,"
Abigail Salyers said in an interview about her speech today at the
annual meeting of the American Association for the Advancement of
Science. She challenged scientists to consider far-reaching
possibilities in a talk titled "Are There Medical Implications of
Geomicrobiology?"

Salyers, a professor of microbiology and the College of Medicine at
the UI’s Urbana-Champaign campus, is the outgoing president of the
American Society for Microbiology, the oldest and largest life
sciences organization in the world, with more than 42,000 members.
Her year as president, she said, has made her "an antenna absorbing
the information coming from the members and trying to transmit some
sense of it all."

Although the ASM represents 25 disciplines of microbial
specialization, she said, there has been in the last five years a
blurring of distinctions among them, and an increasing amount of
communication. And now, she said, scientists need to focus more
about life on Earth as the quest for life "out there" is attracting
growing attention.

"The big question for scientists, and which has implications for
Earth, is can you have microorganisms evolve that would be able to
cause disease in humans, animals or plants in a place where there
are no humans, animals and plants?" she said.

Adaptability, Salyers added, "makes the issue a big one for
astrobiology as we send spaceships to other planets." Earth already
has yielded examples of the ability of microbes to exist in seemingly
harsh and hostile environments, and bacteria normally not associated
with disease have turned deadly under unexpected conditions, she said.

Just last month, scientists reported in the journal Science the
discovery of bacteria and fungi deep below the ice, in the rocks
and soil, of Antarctica. For astrobiologists, Salyers said, this
discovery heightens speculation that microbial life could dwell on
or under a similar landscape on Mars or in the ice-covered seas of
Europa and Ganymede, two of Jupiter’s moons. Interestingly, while the
early Viking and Mariner space probes were gathering data from Mars
in the 1970s, scientists on Earth were discovering bacteria and the
Archaea living and thriving in deep-ocean vents and other harshly
cold and hot environments, she said.

Could it be, she asked, that previous probes to Mars — Viking,
Mariner and, more recently, the failed Mars Polar Lander — carried
Earth bacteria that survived the cold vacuum and intense radiation
exposure of space? "Many microbes are not as fragile as we long
thought," she said. If microbial life is found on Mars, it may be
difficult to determine if it began there or was imported from Earth
and adapted to the Martian climate, she said. "Is it possible that
we could populate Mars with bacteria from Earth? And if there is
life on Mars, would the bacteria we introduce prove to be Mars’
version of the Andromeda Strain," she said, referring to the 1971
movie in which scientists are faced with a deadly alien virus.

On Earth, unexpected adaptations do happen. Salyers noted that:

  • In 1976, a mysterious lung-damaging illness to be known as
    Legionnaires’ disease swept through a Philadelphia convention,
    killing 34 people. The causative bacterium was dubbed Legionella
    pneumophila, which lives in water. Microbiologists theorize that
    the bacterium may have adapted to live inside of amoebas, which
    usually digest and kill bacteria. Instead of dying out, the bacteria
    simply hitched a ride to a human host.

  • Another bacterium, Listeria monocytogenes, which is found in soil
    and water, often makes its way into food and causes food poisoning.
    Scientists have discovered that Listeria can survive and multiply
    even during refrigeration.

  • Black-band disease, which has been killing corals in the oceans,
    "may be caused or exacerbated by cyanobacteria," which normally
    dwell as part of phytoplankton in the ocean. Salyers was part of a
    research team, led by UI geologist Bruce Fouke, that reported in
    December that these bacteria might be teaming with human sewage
    and shipyard discharge in a way that kills coral under certain
    conditions.

    • "In recent years, we’ve had unpleasant surprises in the form of
    emerging infectious diseases," Salyers said. "This is a shock. You
    would think that any organism capable of causing disease would have
    done so by now. Yet it is clear that there are microorganisms that
    have not been discovered out there in nature that are capable of
    causing disease.

    "Every time humans do something to benefit human beings, be it
    surgery, construction or air-conditioning, we create new
    opportunities for microorganisms to encounter things they have never
    encountered before," she said. "So, we as scientists must ask, what
    are the limits? Can we predict an emerging infectious disease before
    it happens?

    "We are hoping that by learning more about what bacteria experience
    out in nature, we might be able to determine what makes it possible
    for them to change and cause disease," she said.