Friday, September 28, 2007

Microbes on Mars (lets hope they aren’t too virulent)

Martians are generally imagined as three fingered, green, bald headed creatures; however, recent theory suggests that the Martians may be or have been microorganisms.

It is believed that Mars may have once had water on its surface. As we all know, on Earth, water means life. Channels and craters on Mars differ from those on the Moon or Mercury, which make scientists believe that water may be present on Mars. As it turns out, Mars has massive polar ice caps (complete with a permafrost layer) which, if melted, would produce enough water to cover the entire planet “eleven meters” deep.

Water, as a liquid however, cannot exist except at very low elevations because of the weak atmosphere. Still, it is thought because of the unusual craters and striations across the planet that beneath the ice lays even more water. In 2002, the Mars Odyssey spacecraft used its gamma ray spectrometer and confirmed that there is “enormous quantities of water ice beneath the surface of Mars.”

It is further argued that there must have been -or still is- water on Mars due to its “debris pattern and colouring” though this is possibly due to carbon dioxide frost or dust movement. However, many believe that the presence of hematite and goethite (“usually formed in a wet environment”) found on Mar’s surface is indicative of water’s presence and lends hope to there having been life on Mars. To further that hope, in December of 2006, scientists believed that the geological changes shown in photographs at the time suggest that water occasionally flows over parts of the surface.

In addition to water possibly being on its surface, Mars boasts a small atmosphere with methane gas pockets throughout. Due to the methane pockets and polar ice caps, the most recent theory is that if microbes existed on Mars they would be much like our terrestrial methanogens. Methanogens can live deep in ice (such as in Antarctica or Greenland). If this is true, Mars may already be supporting life. If not, microbes are known for their adaptability and tenacity; it is possible that they are dormant.

Many of the experiments done on Mars (1970’s) to see if microbial life existed there were done with saline as the main “internal fluid” in mind. It is now thought that these series of tests would have only drowned or burned the possible life forms. With the cold and dry (water is not really observable) climate it is thought that, should the microorganisms exist, they would be made up of water and hydrogen peroxide as it freezes at a much lower temperature.

Among the previous theories lies another: the possibility that microbes on Mars have magnetisomes. A meteorite, named ALH84001, is believed to contain the fossilized remains of microbes from Mars.

However, until it is proven without a doubt that Mars has water, it is impossible to tell whether alien microbes have lived on our neighbouring planet.


Tuesday, September 25, 2007

Deadly space bugs

It is known that microgravity (MG) affects the way cells react. For example, astronauts coming back to Earth after a long time spent under very low gravity show signs of bone resorption and muscle mass loss. Bacteria react to low gravity too. In a paper published in 2002, Dr. Cheryl Nickerson and her team (see reference and link to pdf file below) discovered that the expression of many genes is in fact affected by MG (Figure on right). As can be seen, some genes are expressedm or not under normal gravity (1xg) but this expression pattern can be almost completely reversed under MG (or LSMMG - Low Shear Modeled Micro Gravity).

Because gene expression seems to be influenced by microgravity, the obvious experiment was now to determine if the virulence of bacteria is increased un der other words are microbes susceptible to become "superbugs" in space? The answer, sadly, seems to be YES!

In another study, to be published in PNAS, Dickerson and fisrt author James Wilson show that some virulence genes are in fact turned on by microgravity. In a mere 12 days in september, during spaceflight STS-115, Salmonella tiphymurium became more virulent. According to the authors, the shape of bacteria did not change but they seem to form a biofilm which is more difficult to eliminate by the immune system. In fact, when these "spacebugs" were fed to mice, they show a 3-times increase in virulence.

Space is definitively a weird place to be...even for bacteria! Astronauts beware...bring your Purell!

For audio of this story follow this link


James W. Wilson, Rajee Ramamurthy, Steffen Porwollik, Michael McClelland, Timothy Hammond, Pat Allen, C. Mark Ott, Duane L. Pierson, and Cheryl A. Nickerson. Microarray analysis identifies Salmonella genes belonging to the low-shear modeled microgravity regulon
PNAS 2002 99: 13807-13812

Wilson et al. Space flight alters bacterial gene expression and virulence and reveals a role for global regulator Hfq.
PNAS doi/10/1073/pnas.0707155104.

NOTE: This blog post is also published on my other blog