Microbial Life in Acidic Environments

Created by Mindy Richlen, Marine Biological Laboratory

Microorganisms that are able to develop under extreme conditions have recently attracted considerable attention because of their peculiar physiology and ecology. These extremophiles also have important biotechnological applications. Acidic environments are especially interesting because, in general, the low pH of the habitat is the consequence of microbial metabolism and not a condition imposed by the system as is the case in many other extreme environments (temperature, ionic strength, high pH, radiation, pressure, etc.).

- Gonzalez-Toril, E., Llobet-Brossa, E., Casamayor, E.O., Amann, R., and R. Amils. 2003. Microbial Ecology of an Extreme Acidic Environment, the Tinto River. Appl. Environ. Microbiol. 69: 4853-4865.

What are acidophiles?

Acidophiles are organisms that can withstand and even thrive in acidic environments where the pH values range from 1 to 5. Acidophiles include certain types of eukaryotes, bacteria and archaea that are found in a variety of acidic environments, including sulfuric pools and geysers, areas polluted by acid mine drainage, and even our own stomachs.
Lemonade Spring, Yellowstone National Park

How do acidophiles regulate their pH?

Normally, high acid levels destroy cells. However, acidophiles have evolved a variety of specialized mechanisms to maintain their internal cellular pH at a constant level (usually 7.2). These mechanisms include "passive" regulation (not requiring the cell to expend energy) and "active" regulation (requiring energy).

Why are they important?

Sulfur cycling and acid mine drainage
Acidophiles have been the focus of substantial research in recent years, particularly regarding their role in acid mine drainage. One of the most well-known acidophiles with respect to this important environmental problem is Ferroplasma, which was found growing at pH 0 in acid mine drainage in Iron Mountain in California.
Gastrointestinal pathogens and human health
Other microbes, while not acidophiles, are studied because their acid-resistance systems allow them to survive the low pH in our own stomachs and cause disease. Two such microbes are Escherichia coli, a well-known gastrointestinal pathogen, and Helicobacter pylori, which causes stomach ulcers.

Acidophile Collections

General Collection: Resources such as news articles, web sites, and reference pages provide a comprehensive array of information about acidophiles.

Advanced Collection: Compiled for professionals and advanced learners, this collection includes resources such as journal articles, academic reviews, and surveys.

For Educators: This collection includes activities, assignments, and reading materials created specifically for educators.

Additional Resources

For additional resources about Acidophiles, search the Microbial Life collection.

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