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The Mi­crobe of the Year 2019: The world's smal­lest com­pass needle

Feb 4, 2019

Have you ever heard of the "Magnetic spiral from Greifswald"? Probably not, but most likely you have already encountered it, albeit unknowingly. The magnetic spiral inhabits the muddy bottom of ponds, rivers, lakes and oceans. It is tiny, very fascinating and full of potential. That's why it was elected this year's "Microbe of the Year".

The Mag­netic Spiral from Gre­if­swald is of­fi­cially called Magnetospirillum gryphiswaldense. The genus Magnetospirillumhas a very spe­cial abil­ity: It con­tains a tiny mag­netic needle. This needle, com­posed of nano­scopic crys­tals of a mag­netic iron ox­ide, al­lows this mi­crobe to ori­ent it­self to the Earth's mag­netic field. The mi­crobe uses this abil­ity, to­gether with a built-in oxy­gen sensor, to nav­ig­ate into just the right layer of mud in which it feels most com­fort­able.

Mag­neto­spir­il­lum at the Max Planck In­sti­tute in Bre­men

In the early six­ties, Sal­vatore Bellini from Italy dis­covered the first so-called mag­netotactic bac­teria. However, their ex­plor­a­tion did­n’t quite get un­der way. In 1990, Dirk Schüler, then a stu­dent in Gre­if­swald, suc­ceeded in isol­at­ing Magnetospirillum from the mud of a small river. This made re­search much easier: Now these bac­teria could be ef­fi­ciently cul­tiv­ated and soon after also ge­net­ic­ally ma­nip­u­lated.

A few years later, Schüler moved to Bre­men to work at the Max Planck In­sti­tute for Mar­ine Mi­cro­bi­o­logy, where he headed a ju­nior re­search group from 1999 to 2006. Again, he de­voted him­self  to re­veal­ing the secrets of mag­netic bac­teria. To­gether with the in­sti­tute’s Dir­ector Rudolf Amann, the now emer­itus dir­ector Friedrich Wid­del and other sci­ent­ists, he in­vest­ig­ated their biod­iversity in sed­i­ments of lakes and coastal seas. "An­other re­search fo­cus of Schüler’s re­search group at the Max Planck In­sti­tute in Bre­men was the form­a­tion and ar­range­ment of the mag­netic particles, the so-called mag­neto­somes, in­side the Magnetospirillum cells," says Amann.

Magnetospirillum gryphiswaldense in division with magnetite crystals (red) and membrane vesicles (yellow) and the special cytoskeleton (green) as well as flagella for locomotion (ochre). Mauricio Toro-Nahulepan, University of Bayreuth/ Jürgen Plitzko, MPI for Biochemistry, Martinsried
Magnetospirillum gryphiswaldense in division with magnetite crystals (red) and membrane vesicles (yellow) and the special cytoskeleton (green) as well as flagella for locomotion (ochre). Mauricio Toro-Nahulepan, University of Bayreuth/ Jürgen Plitzko, MPI for Biochemistry, Martinsried

For Schüler, who holds the chair of mi­cro­bi­o­logy at the Uni­versity of Bayreuth since 2014, the time in Bre­men was very im­port­ant. "Thanks to the free­dom of re­search at the Max Planck In­sti­tute and the many op­por­tun­it­ies for co­oper­a­tion, I was able to lay im­port­ant found­a­tions for my fur­ther re­search on mag­netic bac­teria," he ex­plains.

From fossils to mi­croro­bots

Dividing cell of Magnetospirillum gryphiswaldense with magnetite crystals (transmission electron microscope image).
Dividing cell of Magnetospirillum gryphiswaldense with magnetite crystals (transmission electron microscope image). © Frank Mickoleit, University of Bayreuth

In geo­phys­ical terms, mag­netic bac­teria are also an ex­cit­ing re­search ob­ject: Once the bac­teria die, the mag­neto­somes are re­leased. They of­ten re­main in the soil and, as fossils, re­veal im­port­ant de­tails about how the Earth's mag­netic field has changed in earlier times.

But Magnetospirillum is not only in­ter­est­ing for a bet­ter un­der­stand­ing of nature. Bi­o­tech­no­lo­gical ap­plic­a­tions are also be­com­ing in­creas­ingly im­port­ant. The tiny mag­nets are very sim­ilar in size and shape and are highly mag­net­ized. To date, it has not been pos­sible to ar­ti­fi­cially pro­duce particles with such pre­ci­sion and prop­er­ties. They could be used as con­trast agents in mag­netic res­on­ance ima­ging (MRI) and other bio­med­ical ap­plic­a­tions. Mag­neto­somes might help fight­ing tu­mours. Also, mag­netic mi­crobes could be loaded with drugs and then dir­ec­ted right to a de­sired site of ac­tion in the body - mi­croro­bots as tiny am­bu­lances. Schüler's cur­rent re­search, fun­ded by the renowned ERC Ad­vanced Grant, also fo­cuses on bi­o­tech­no­lo­gical as­pects, amongst oth­ers. He and his col­leagues hope to de­velop and test new meth­ods to trans­fer mag­netic prop­er­ties to or­gan­isms that do not nat­ur­ally have such prop­er­ties.

Mi­cro­bi­o­logy in the garden pond

Scanning electron microscope image of Magnetospirillum gryphiswaldense.
Scanning electron microscope image of Magnetospirillum gryphiswaldense. © Frank Müller, University of Bayreuth

Now - would you like to take a look at the mag­netic mi­crobes your­self? It's not that dif­fi­cult: For ex­ample in a pond or stream, there are many dif­fer­ent types: rods, spheres, spir­als and even mul­ti­cel­lu­lar con­sor­tia. “With a mi­cro­scope mag­ni­fy­ing at least 100 times, you look at the edge of a drop of mud to which you hold a small rod mag­net,” ex­plains Schüler. “The mag­netic bac­teria per­sist­ently swim in one dir­ec­tion and col­lect at the edge of the drop, on the mag­netic south pole.” If you turn over the mag­net, the bac­teria also turn. “If you’ve ever en­riched bac­teria with a simple mag­net and ex­amined them un­der the mi­cro­scope, you will not for­get the eureka ef­fect.”

 

Fanni Aspetsberger

 

For fur­ther in­form­a­tion:

Please dir­ect your quer­ies to:

Prof. Dr. Dirk Schüler
Prof. Dr. Dirk Schüler (© Christian Wißler, Universität Bayreuth)

De­part­ment of Mi­cro­bi­o­logy
Uni­versity of Bayreuth

Prof. Dr. Dirk Schüler

phone:  +49 (0)921 55-2729
dirk.schueleratuni-bayreuth.de

Prof. Dr. Rudolf Amann
Prof. Dr. Rudolf Amann (© A. Kegel, MPI-Bremen)

Dir­ector
Max Planck In­sti­tut for Mar­ine Mi­cro­bi­o­logy Bre­men

Prof. Dr. Rudolf Amann

phone: +49 (0)421 2028-930
ramann@mpi-bremen.de

presse@mpi-bremen.de

 
 
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