The Magneto-Laboratory Junior Group at the MPI for Marine Microbiology , Bremen Dr. Dirk Schuler
Welcome
at the homepage of the Schuler lab. Our group was established in 3/2000 as a
result of the BioFuture programme of the BMBF . The main focus of our research is to seek an understanding of the
biomineralization of magnetosomes in magnetotactic bacteria. Our funding is
through BMBF , Deutsche
Forschungsgemeinschaft , and MPG .
Willkommen auf der Homepage der Arbeitsgruppe
Schuler. Die Nachwuchsgruppe besteht seit 03/2000 als Ergebnis des BioFuture-Wettbewerbs des BMBF . Hauptgegenstand unserer Forschung ist die Untersuchung der Biomineralisation
von Magnetosomen in magnetotaktischen Bakterien. Unsere Arbeiten werden unterst ь tzt
durch das BMBF , die Deutsche
Forschungsgemeinschaft sowie die Max-Planck-Gesellschaft .
Laboratory
members (1/2005)
Research
Electron micrograph of Magnetospirillum gryphiswaldense. The ability of magnetotactic
bacteria to orient and migrate along magnetic field lines is based on
intracellular magnetic structures, the magnetosomes, which comprise nano-sized,
membrane-bounded crystals of an magnetic iron mineral. The formation of
magnetosomes is achieved by a biological mechanism that controls the
accumulation of iron and the biomineralization of magnetic crystals with a
characteristic size and morphology within membrane vesicles. Magnetosome
biomineralization has stimulated a broad interdisciplinary interest. Recently,
the characteristics of bacterial magnetosomes have been even used as
biosignatures to identify presumptive Martian magnetofossils. In addition, a
number of technological applications of magnetosomes have been considered.
Research in our lab is focused on the microbiology of magnetotactic bacteria
and the biochemistry and molecular biology of magnetosome formation.
Ultimately, we seek to understand the molecular mechanisms that control
magnetite biosynthesis in bacteria.
Projects
·
Ecology and diversity of
uncultivated magnetotactic bacteria
·
Biochemistry and molecular biology
of magnetosome formation in the magnetotactic bacterium Magnetospirillum gryphiswaldense
·
Production and characterization of
bacterial magnetosome particles for their potential use in b
Ecology and diversity of
uncultivated magnetotactic bacteria
Diversity of magnetosome crystals found in various magnetotactic
bacteria from different environments (bar represents 0.1 micrometer). Most of
the bacteria shown have not been isolated in pure culture.
Hunting for magnetotactic bacteria in the mud of the German Wadden
Sea.
Magnetotactic
bacteria (MTB) are major constituents of natural microbial communities. A broad
diversity of morphological and phylogenetic varieties can be found in many
aquatic habitats. However, cultivation of MB has proven difficult because of
their lifestyle adapted to chemically stratified habitats. Consequently, only
few strains of MTB have been isolated in pure culture, which represent only a
minority of the vast diversity of naturally occurring populations from largely
unexplored habitats such as the marine environment.
In our lab,
we are addressing the diversity of uncultivated MTB by various approaches. We
attempt to isolate, cultivate and characterize novel MTB. In addition, we
employ cultivation-independent, molecular methods in the analysis of MTB from
natural environments.
Biochemistry and molecular biology
of magnetosome formation in Magnetospirillum
gryphiswaldense
The
formation of magnetosomes in MTB is one of the most intriguing examples of the
widespread occurrence of magnetic minerals in a diverse range of organisms.
However, the molecular mechanisms controlling the biomineralization process so
far have remained largely unknown. Magnetospirillum gryphiswaldense as a model organism, because it
can be cultivated more readily than most other MTB. M. gryphiswaldense forms a number of cubo-octahedral magnetosome
crystals, which consist of the magnetic iron mineral magnetite (Fe3 O4 ).
Proposed
model for magnetite biomineralization in Magnetospirillum
species. Fe(III) is actively taken up by the cell, possibly via a reductive
step. Iron is then thought to be reoxidized and magnetite is produced within
the magnetosome vesicle. The magnetosome membrane contains specific proteins,
which are thought to have crucial functions in the accumulation of iron,
nucleation of minerals and redox and pH control.
Production and
characterization of bacterial magnetosome particles for their potential use in
biotechnological applications
Suspensions
of isolated bacterial magnetosomes can be considered as biogenic magnetic
ferrofluids. The superior magnetic and crystalline properties of bacterial
magnetosomes make them potentially useful as a highly orderd biomaterial in a
number of applications, e. g. in the immobilization of bioactive compounds, in
magnetic drug targeting, or as contrast agent for magnetic resonance imaging.
In our lab, we seek to establish techniques for the mass production of
bacterial magnetosomes. Isolated magnetosomes are characterized with respect to
their biochemical, biophysical and magnetic properties. In addition, in
collaboration with several partners we evaluate the use of bacterial
magnetosomes in a number of applications.
Pellet of isolated magnetosomes sticking
to a permanent magnet.
Electron micrograph of purified
magnetosomes from Magnetospirillum
gryphiswaldense. Individual magnetosome particles are enclosed by the
magnetosome membrane, which prevents agglomeration.
Selected publications
1.
Flies, C., Jonkers, H.,
deBeer, D., Bosselmann, K., B ц ttcher, M., Schuler, D. Diversity and vertical
distribution of magnetotactic bacteria along chemical gradients in freshwater
microcosms. FEMS Microbiol. Ecol. In press. 2005.
2.
Flies, C., Peplies, J.,
Schuler, D. A combined approach for the characterization of uncultivated
magnetotactic bacteria from various aquatic environments. Appl. Environ.
Microbiol. In press. 2005.
3.
Schultheiss, D., Handrick,
R., Jendrossek, D., Hanzlik, M., Schuler, D. The presumptive magnetosome
protein Mms16 is a PHB-granule bound protein (phasin) in Magnetospirillum gryphiswaldense . J. Bacteriol. In press. 2005.
4.
Handrick, R., Reinhardt, S.,
Schultheiss, D., Reichart, T., Schuler, D., Jendrossek D. Unraveling the
function of the Rhodospirillum rubrum
activator of polyhydroxybutyrate (PHB) degradation: The activator is a PHB
granule bound protein (phasin). J. Bacteriol. 186(8) (2004) 2466-75.
5.
Rehm, B., Schuler, D.
Klein-Kleiner-Am Kleinsten: Nanobiotechnologie, eine Schl ь sseltechnologie
des 21. Jahrhunderts. In :
Biotechnologie 2020. DECHEMA, Frankfurt. 2004.
6.
Hoell, A., Wiedenmann, U.,
Heyen, U., Schuler, D. Nanostructure and field-induced arrangement of
magnetosomes studied by SANSPOL. Physica B 350 (2004)309-313.
7.
Schuler, D. Making magnets
by bacteria: The biomineralization of magnetic nanoparticles. In : Nedkov, I., Tailhades, P. (eds.),
Lectures on Nanoscale magnetic materials. Heron Press Ltd. 2004.
8.
Amann, R., Rossello-Mora,
R., Flies, C., Schuler, D. Phylogeny and in situ identification of
magnetotactic bacteria. In : E.
Baeuerlein (ed.), Biomineralization of Nano- and Microstructures. 2nd ed.,
Wiley-VCH, Weinheim. 2004.
9.
Schuler, D. Biochemical and
genetic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense. In : E. Baeuerlein (ed.),
Biomineralization of Nano- and Microstructures. 2nd ed., Wiley-VCH, Weinheim.
2004.
10.
Schultheiss, D., Kube, M.,
and Schuler, D. Inactivation of the flagellin gene flaA in Magnetospirillum
gryphiswaldense results in nonmagnetotactic mutants lacking flagellar
filaments. Appl. Environ. Microbiol. 70 (6)
(2004) 3624-3631. pdf-file
11.
Grunberg, K., Muller, E.C.,
Otto, A., Reszka, R., Linder, D., Kube, M., Reinhardt, R., and Schuler, D.
Biochemical and proteomic analysis of the magnetosome membrane in Magnetospirillum gryphiswaldense . Appl.
Environ. Microbiol. 70 (2)(2004)1040-50. pdf-file
12.
Schuler, D. Molecular
analysis of a subcellular compartment: The magnetosome membrane of Magnetospirillum gryphiswaldense Arch.
Microbiol. 181 (2004) 1-7. pdf-file
13.
Schubbe, S., Kube, M.,
Scheffel, A., Wawer, C., Heyen, U., Meyerdierks, A., Madkour, M.H., Mayer, F.,
Reinhardt, R., and Schuler, D. Characterization of a spontaneous nonmagnetic
mutant of Magnetospirillum
gryphiswaldense reveals a large deletion comprising a putative magnetosome
island. J. Bacteriol. 185 (2003) 5779-5790. pdf-file
14.
Heyen, U., and Schuler, D.
Growth and magnetosome formation by microaerophilic Magnetospirillum strains in an oxygen-controlled fermentor. Appl.
Microbiol. Biotechnol. 61 (2003) 536-544. pdf-file
15.
Schultheiss, D., and
Schuler, D. Development of a genetic system for Magnetospirillum gryphiswaldense . Arch. Microbiol. 179 (2003)
89-94. pdf-file
16.
Schuler, D. The
biomineralisation of magnetosomes in Magnetospirillum
gryphiswaldense . Int. Microbiol. 5 (2002) 209-214. pdf-file
17.
Grunberg, K., Wawer, C.,
Tebo, B.M., and Schuler, D. A large gene cluster encoding several magnetosome
proteins is conserved in different species of magnetotactic bacteria. Appl.
Environ. Microbiol. 67(10) (2001)
4573-82. pdf-file
18.
Schuler, D. Die
Biomineralisation von Nanokristallen in magnetotaktischen Bakterien.
Biospektrum. 6 (2000) 445-449.
19.
Schuler, D. Formation of
magnetosomes in magnetotactic bacteria. J. Mol. Microbiol. Biotechnol. 1 (1) (1999) 79-86. pdf-file
20.
Schuler, D., and Frankel,
R.B. Bacterial magnetosomes: Microbiology, biomineralization and
biotechnological applications. Appl. Microbiol. Biotechnol. 52 (4) (1999)
464-473. pdf-file
