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 MG...in 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!

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1) 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

2) 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.


Anonymous said...

I am shocked with this article; it shows how little we know about Bacteria. The LSMMG growth signal play a role in the virulence of S.T. as the regulon, operon promoter and gene expression act differently in MG (WOW).
I might add Histones may play a role too (my prediction). This phenotype changes are amazing and brings us to a new level. We could be heading for more discoveries that help humanity or else if it is in the wrong hand. I am glad you made me read this article.

Sam, La Cité