→ ntubear:林有餘真可愛 推140.112.225.194 12/22
※ 引述《hoganbang (幹了蠢事)》之銘言：
: 請問magnetotactic bacteria攜帶重金屬的機制是什麼?有人可以告訴我嗎?
: 謝謝喔!
1)如果是班上同學，下面這一篇加減看，然後提到的文獻也可以看看吧
http://www.agu.org/revgeophys/moskow01/node2.html
2)如果是路人.....你是不會自己去查喔...google你是不會用喔...圖書館是不會用喔
Magnetotactic Bacteria
Magnetotactic bacteria (MTB) orient and migrate along the geomagnetic field
towards favorable habitats, a behavior known as magnetotaxis. Since the first
report of magnetotactic bacteria by Blakemore [1975], subsequent studies have
shown that MTB are a morphologically diverse and cosmopolitan group of
aquatic microorganisms inhabiting freshwater and marine environments ranging
from aerobic to anoxic. Three significant findings since the last IUGG report
on biomineralization are (1) an increase in the types of environments where
MTB are found besides microaerobic to include anaerobic and aerobic
[ Bazylinski, 1990; Matsunaga et al., 1991; Sakaguchi et al., 1993]; (2) an
increase in the number of identified phases besides magnetite (FeO) to
include ferrimagnetic greigite (FeS), possible pyrrhotite (FeS), and
non-magnetic pyrite (FeS) [ Mann et al., 1990a; Farina et al., 1990;
Bazylinski, 1990]; and (3) the discovery of non-magnetotactic magnetite
producing bacteria [ Lovley, 1990].
In natural habitats, large populations of MTB are usually found near the
oxic-anoxic transition zone, which is usually located at the sediment-water
interface in freshwater environments or displaced upward into the water column
in marine semi-anaerobic environments [ Stolz, 1992; Bazylinski and Frankel,
1992]. In the latter types of environments, magnetite and greigite producing
MTB exist in horizontal zones at specific water depths depending on the
vertical chemical and redox gradients [ Stolz, 1992; Bazylinski, 1991].
Petermann and Bleil [1993] identify several different types of living MTB in
deep sea sediments from the South Atlantic, some at water depths of 2000 m.
Magnetic bacteria containing intercellular magnetite particles have also been
identified in the uppermost horizon of a waterlogged soil in Germany
[ Fassbinder et al., 1990]. Although population densities of the magnetic
bacteria were too low at the time of sampling to contribute significantly to
the magnetism of the soil, the authors suggest that population densities can
change dramatically depending on microenvironmental conditions. However, the
question of a biogenic magnetic component in soil must await further
confirmation and study.
Magnetotactic bacteria from reducing environments with high concentrations of
HS contain Fe-sulphide particles instead of Fe-oxides [ Mann et al., 1990a;
Farina et al., 1990; Bazylinski and Frankel, 1992]. The sulphide minerals were
identified by indexing single crystal electron diffraction patterns [ Mann et
al., 1990a; Heywood et al., 1990, 1991]. Several types of bacteria have been
studied including a rod shaped bacterium containing only greigite particles
[ Bazylinski, 1990], a multicellular magnetotactic prokaryote (MMP) containing
a mixture of greigite and pyrite particles [ Mann et al., 1990a], and another
bacterium containing both magnetite and greigite particles [ Bazylinski et al.,
1993a]. In another study, ferrimagnetic pyrrhotite (FeS) was proposed as the
iron-sulfide mineral in a similar (or perhaps the same) MMP from Brazil [
Farina et al., 1990]. No single crystal diffraction patterns have yet been
obtained that unequivocally identify the phase as pyrrhotite, so the report
of FeS in MTB remains problematical. Finally, Sakaguchi et al. [1993] report
a magnetotactic sulphate-reducing bacterium that produces intercellular
magnetite and extracellular magnetic iron-sulfide particles. This discovery
extends the range of magnetite producing microorganisms to sedimentary levels
where sulphate reduction occurs.
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