Acidophiles
Imagine a swimming pool full of battery acid. Would you want to dive in for a quick
swim? What about just sticking your hand
in? As humans, we have a tough time
tolerating contact with environments of extreme pH, environments that are
either very acidic or basic. We measure
pH as a function of the concentration of hydrogen ions (H+) or
protons in solution. Most life forms are
unable to survive environments of either low or high pH. Take for example, proteins, a key building
block of life. When placed in a solution
of low pH, proteins can quickly become denatured. Despite the ability of pH to antagonize some
of life’s most fundamental molecules, scientists have identified life forms
that not only survive in regions of low pH; they thrive there. These organisms, called acidophiles, are just
another type of life form more broadly known as extremophiles.
The more we explore Earth, the more we are astounded by the
diversity of environments and life we find.
We have identified more than just the hot and the cold places, the wet
and the dry ones. Now we have identified
and are studying new extremes, like those of extreme pH. From the boiling sulfuric hot pots in
Acidophiles have adapted many unique characteristics to
successfully combat their acidic surroundings.
When acidophiles were first recovered, it was anticipated that their
cytoplasm would differ significantly from life in more neutral conditions. However, the cytoplasm of some acidophiles was
surprisingly found to be neutral like other cells. Incidentally, these acidophiles were also
found to have more proton transporters in their cell membranes than other
organisms. This way, the acidophile
could literally pump protons out of the cell.
Other acidophiles had cytoplasm that behaves as a much better buffer
solution against large changes in pH than mesophilic cytoplasm. Yet other acidophiles exhibited cell
membranes with a high concentration of positive charge. All of these adaptations allow these
organisms to thrive in an environment that would be extremely inhospitable to
“normal” life.
In our search for life beyond Earth, our studies of
acidophiles may give us some clues as to the true limits for life as we know
it. By better understanding how life has
adapted to fill specific niches on Earth, we can extrapolate our knowledge to
surmise about similar environments on other planets and moons. For instance, the conditions on Venus and the
extreme volcanic activity on Io are two extraterrestrial environments in which
we might expect to find areas of high acidity.
Knowledge of acidophiles on Earth will assist our search for and
possibly the identification of new life forms on other planets.
Can use many of the same pictures as I cited for the
Extremophiles article.
Works Cited:
Caviccioli, R. (2002). Extremophiles and the search for extraterrestrial life, Astrobiology,
2(3), 281-292.
Rothschild, L J., and Mancinelli, R
L., (2001); Nature, vol. 409, 1092-1101.
Recommendations:
Extreme Environments
Beyond Earth
Life on
Venus
The Nature
of Life
The Tree of
Life
Thermophiles
Psychrophiles
Alkaliphiles
Xerophiles
Halophiles
Radiation
resistant
Barophiles
Anaerobes
Tree of
Life