Supermicrobes (I)

Supermicrobes (I)

“Supermicrobes” mini-posts series aims to highlight bacteria, archaea or virus with the most peculiar characteristics.

Magnetospirillum and its magnetotaxis

Electron microscope image: K. H. Downing, H. Sui, L. R. Comolli and H.-Y. Holman. 2004. Electron Tomographic Studies of Bacterial Structure and Function. Microsc Microanal 10(Suppl 2). Copyright 2004 Microscopy Society of America

 

Magnetospirillum has the honor to start the “Supermicrobes” series. It is a magnetotactic bacteria capable of orientating itself and swim using flagella following the magnetic field lines around the globe. As other magnetotactic bacteria it contains magnetosomes, a type of organella containing magnetic crystals made of  iron minerals organized in chains (black dots in the right picture).

Magnetosomes provide permanent magnetic dipole moment. Said otherwise, they allow bacteria to behave as a compass to orient themselves and remain in the preferred habitat in the water column or sediment (usually zones with low oxygen concentration).

 

 

Geogemma barossii, the peak of thermal endurance

Hydrothermal vent: NOAA Photo Library. Imatge microscopi: Derek Lovley, University of Massachusetts, Amherst.

 

In second place, we present the living being with highest known resistance to high temperatures.

It’s the case of the archaea Geogemma barossii, also known as “strain 121” (of spherical morphology and containing flagella, as in the electron micrograph picture in the lower right-hand side of the figure). This archaea lives in hydrothermal vents at +2000 meters of depth and uses iron oxide for respiration. Its name makes reference to the capacity to grow and reproduce at 121ºC. In fact, G. barossii can survive up to two hours at 130ºC and then grow again when temperature decreases.

The capacity of microorganisms to grow at high temperatures is really important to define the sterilization treatments of many materials (mainly of clinical use). Fortunately, the strain 121 is not a threat to human health because it cannot grow at temperatures around 37ºC, too cold for them.

 

References

Lefèvre C, Frankel R, Bazylinski D. 2011. “Magnetotaxis in Prokaryotes”. eLS. Chichester, UK Publisher: John Wiley & Sons, Ltd.

Kashefi, Kazem; Lovley, Derek R. (2003). “Extending the upper temperature limit for life”. Science. 301 (5635): 934.

 

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