Extreme Biology: Part Deux
These microbes both tolerate and actually require elevated levels of salt for growth. Generally, halophiles are photosynthetic. Moderate halophiles tolerate 3-15% NaCl. Extreme halophiles live in solutions of 18-30% NaCl, including the Dead Sea.
Xerophiles
While all known microorganisms require water for growth; the amount of water
needed varies according to species. Fungi, in particular, have the capacity to
withstand desiccation. This is why fungi distribute themselves so well
(becoming air borne in search of suitable habitats).
Endolithic
Microorganisms also colonize the interior of rocks and other hard substrates.
To the right is a rock with green bands from endolithic algae. Algae retreat to
and exist in this habitat for its increased level of protection from
intolerable levels of irradiation, high or low temperatures, and dry surface conditions.
The microbes are quite common; we just don't notice them.
The discovery of extremophiles points out the extraordinary adaptability of microbial life-forms and further raises the prospect of finding at least microbial life elsewhere in the Solar System and beyond.
Organisms in Space?
On April 20, 1967, the unmanned lunar lander Surveyor 3 landed near Oceanus Procellarum on the surface of the moon. One of the things aboard was a television camera. On November 20, 1969, Apollo 12 astronauts Pete Conrad and Alan L. Bean recovered the camera. When NASA scientists examined it back on Earth they were surprised to find specimens of Streptococcus mitis that were still alive. These bacteria had survived for 31 months in the vacuum of the moon's atmosphere. Should NASA have been surprised? There are other bacteria that thrive under near-vacuum pressure on the earth today. We now know that the vacuum of space is not a fatal problem for bacteria.
6) If you were designing a mission to look for life on Mars, where and how would you start looking?
For a full chart of Extremophiles, click here