Deltaproteobacteria, and the coccus MC-1 (Frankel et al. 1997) are also available
in pure culture and have been studied in more detail. All greigite-forming MTB or
other unusual types such as the multicellular magnetotactic prokaryote (MMP),
which consists of an assembly of multiple flagellated bacterial cells containing
magnetosome chains or the very large Magnetobacterium bavaricum have not yet
been obtained in axenic culture and are thus less well investigated (Vali et al. 1987;
Farina et al. 1990; Rodgers et al. 1990) (Table 1.1).
1.2.3 Genetics
To understand what distinguishes magnetotactic bacteria from non-magnetotactic
species, their molecular biology and genetics have been studied in recent years,
providing new insights into biomineralization. Genetic information has been
obtained from the freshwater species M. magneticum (Matsunaga et al. 2005),
M. gryphiswaldense (Ullrich et al. 2005), M. magnetotacticum (http://genome.jgipsf.org/magma/magma.home.html), the marine species Magnetococcus MC-1
(Schubbe et al. 2009), the vibrio strain MV-1, and the Deltaproteobacterium
Desulfovibrio magneticus (Nakazawa et al. 2009). Comparative genome analyses
have identified a common MTB-specific subset of genes, which was termed
“magnetosome island” (MAI), and which presumably provides the magnetitebiomineralizing capability and potentially also magnetotactic functionalities
Table 1.1 Cultured and some unusual examples of magnetotactic bacteria, their respective cell
morphologies, and magnetosome properties
Species
Cell
morphology
Magnetosome
size
Magnetosome
morphology
Magnetosome
number
Magnetospirillum
magneticum
helicoidal
~50 nm
cuboctahedral
>15
Magnetospirillum
magnetotacticum
helicoidal
~40 nm
cuboctahedral
Up to ~40
Magnetospirillum
gryphiswaldense
helicoidal
~40 nm
cuboctahedral
Up to ~60
Magnetococcus (marinus)
MC-1
coccus
80–120 nm
elongated pseudohexagonal
prismatic
<15
Magnetovibrio MV-1
vibrio
40–60 nm
elongated pseudohexagonal
prismatic
~10
Desulfovibrio magneticus vibrio
~40 nm
bullet-shaped
~10–15
Magnetobacterium
bavaricum
rod
110–150 nm
hook-shaped
~1,000
Coccoid MTB
coccus
~250 nm
elongated
<10
Multicellular
magnetotactic
prokaryote (MMP)
ovoid
~90 nm
irregular
Up to ~65 per
cell
1 Magnetite Biomineralization in Bacteria
7
in pure culture and have been studied in more detail. All greigite-forming MTB or
other unusual types such as the multicellular magnetotactic prokaryote (MMP),
which consists of an assembly of multiple flagellated bacterial cells containing
magnetosome chains or the very large Magnetobacterium bavaricum have not yet
been obtained in axenic culture and are thus less well investigated (Vali et al. 1987;
Farina et al. 1990; Rodgers et al. 1990) (Table 1.1).
1.2.3 Genetics
To understand what distinguishes magnetotactic bacteria from non-magnetotactic
species, their molecular biology and genetics have been studied in recent years,
providing new insights into biomineralization. Genetic information has been
obtained from the freshwater species M. magneticum (Matsunaga et al. 2005),
M. gryphiswaldense (Ullrich et al. 2005), M. magnetotacticum (http://genome.jgipsf.org/magma/magma.home.html), the marine species Magnetococcus MC-1
(Schubbe et al. 2009), the vibrio strain MV-1, and the Deltaproteobacterium
Desulfovibrio magneticus (Nakazawa et al. 2009). Comparative genome analyses
have identified a common MTB-specific subset of genes, which was termed
“magnetosome island” (MAI), and which presumably provides the magnetitebiomineralizing capability and potentially also magnetotactic functionalities
Table 1.1 Cultured and some unusual examples of magnetotactic bacteria, their respective cell
morphologies, and magnetosome properties
Species
Cell
morphology
Magnetosome
size
Magnetosome
morphology
Magnetosome
number
Magnetospirillum
magneticum
helicoidal
~50 nm
cuboctahedral
>15
Magnetospirillum
magnetotacticum
helicoidal
~40 nm
cuboctahedral
Up to ~40
Magnetospirillum
gryphiswaldense
helicoidal
~40 nm
cuboctahedral
Up to ~60
Magnetococcus (marinus)
MC-1
coccus
80–120 nm
elongated pseudohexagonal
prismatic
<15
Magnetovibrio MV-1
vibrio
40–60 nm
elongated pseudohexagonal
prismatic
~10
Desulfovibrio magneticus vibrio
~40 nm
bullet-shaped
~10–15
Magnetobacterium
bavaricum
rod
110–150 nm
hook-shaped
~1,000
Coccoid MTB
coccus
~250 nm
elongated
<10
Multicellular
magnetotactic
prokaryote (MMP)
ovoid
~90 nm
irregular
Up to ~65 per
cell
1 Magnetite Biomineralization in Bacteria
7