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History
of Microbiology |
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 During
most of the history of biology, scientists have studied
the things they could see, from plants and animals to the
smallest insects. Until the mid-17th century when Leeuwenhoek
invented the microscope, we never imagined that there was
life small enough to be invisible to the eye. For many years
the microscopic world seemed insignificant: the microscope
was a parlor trick that allowed people to see tiny creatures,
whirling and jigging around. However, in the late 19th century,
Louis Pasteur, Robert Koch and others, realized that these
entertaining creatures were more than a curiosity; they
are sometimes the cause of devastating disease. Koch's research
of tuberculosis and anthrax resulted in his postulating
the 'germ-theory of disease'. Physicians began to understand
how disease was spread and how to mitigate epidemics. The
science of microbiology was born.
In the
last 100 years, microbiology has focused on those bacteria
that cause disease and can be cultivated in the laboratory.
However, molecular techniques are beginning to show us that
bacteria are more important than in the context of disease.
They represent the predominant and most diverse form of
life on this planet. Indeed, experiments are beginning to
suggest that much, perhaps the majority of life on Earth,
may be found below our feet.
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Hazel
Describes Her Science Background and Where She Works |
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I
initially wanted to be a veterinarian, but after spending
five years volunteering as a veterinary nurse I realized
I was more interested in the diseases of the animals
and how to treat them. After obtaining an undergraduate
degree in Applied Biological Sciences, I pursued my
Ph.D. in medical microbiology. Following a few years
studying DNA regulation in the human heart, I realized
my true passion was microbes. Because I felt I needed
a better understanding of environmental microbiology,
I began working for Dr. Norman Pace at the University
of Colorado in Boulder.
Dr.
Pace is interested in a molecule called ribonucleic
acid (RNA), a molecule that has many roles in cells.
While half of the scientists in this laboratory study
how this molecule functions, the other scientists
use it as a marker to detect microbes in the environment.
These researchers are expanding our knowledge of microbial
diversity in the tree of life. Their results have
helped to determine that there are more than the five
classic-kingdoms of life (animals, plants, fungi,
protoctista and monera/bacteria). There are dozens
of distinct divisions of life. Dr. Pace's laboratory
maps these organisms into the big tree of life, and
tells us how life could have evolved, both on this
planet and, perhaps, elsewhere in the Solar System.
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Hazel's
Research |
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I
study Mycobacterium tuberculosis, which causes the
disease tuberculosis. It was initially thought that
tuberculosis was curable with antibiotics, but what
we didn't realize was that M. tuberculosis is insidious
and crafty. The bacterium has evolved methods to render
antibiotics useless. Unless new treatments are found,
M. tuberculosis will kill millions of people in the
next few decades.
I'm
looking at M. tuberculosis in the lung to see if there
are other organisms that allow the bacterium to cause
disease. If there are, perhaps we could treat these
instead of M. tuberculosis, and thus cure the disease.
The
other approach is to look toward extreme environments,
like caves. Over 90% of the antibiotics that are known
now are similar to each other in the way they work.
In order to treat M. tuberculosis, I hope to identify
unique organisms in caves that contain new antibiotics.
Of course, the information obtained from these environments
also tells us more about the evolution of life on
Earth: the chemistry and extreme limits in which life
can survive. The scientists of the Pace Laboratory,
in addition to caves, have looked miles below the
ocean in volcanic vents, in boiling hot-spring pools,
on sheer cliffs and the seas below the Antarctic.
Preliminary results have allowed us to identify new
kingdoms of life. Soon, I hope, they also point to
medical cures.
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Life
in Underwater and Ice Caves |
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Unfortunately
my samples of microorganisms from Greenland
were accidentally destroyed, so I was never
able to examine them. However, we can at least
guess as to what we will find in the ice caves,
when I return with Janot Lamberton, our ice
caving guide and explorer. We know that organisms,
such as bacteria and fungi, can live under extreme
pressure, even pressures as great as we experienced
in the ice-caves in Greenland (the ice was under
about 5 tons/square inch at the bottom of the
caves). We also know that bacteria can live
and grow while frozen away in ice, at temperatures
approaching -20 degrees Fahrenheit. The question
I hoped to answer was whether there are extremophiles
that can survive both the pressure AND the frozen
temperatures. I suspect there are. For example,
organisms belonging to the genus Deinococcus,
are commonly found frozen, but metabolizing,
in the ice and dry valleys of the Antarctic.
We
are still working on the samples from the underwater
caves of Mexico (my lab is very busy!). The
organisms we expect to find there do not receive
any energy from the sun. Therefore, they have
to find different sources of energy, or food,
in the dark caves. We think the bacteria take
advantage of a chemical gradient that is set
up around the halocline. Rain in the Yucatan
picks up sulfides and sulfates from the soil
of the jungle (from the rotten leaves, tree
bits and insect poop!). The sulfates create
weak sulfuric acid, which helps to dissolve
out the caves, making them bigger. The sulfides
form
hydrogen sulfide in the water. We suspect the
microbes living there can take advantage of
both these compounds to generate energy. In
fact, we know that the organisms living in the
caves thrive on this diet - in many of the underwater
caves you have to swim through clouds of bacteria!
There must be a billion-billion organisms in
these clouds! We suspect that the majority of
the extremophiles found in the underwater caves
will be sulfur-metabolizing organisms, such
as Thiobacillus, Sulfolobus and Desulfovibrio.
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