十万个为什么·科学阅读30篇（4）

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趋磁细菌如何利用地球磁场导航？

Magnetotactic bacteria live in oxygen-poor mud at pond and ocean bottoms.
They build chains of magnetic iron crystals called magnetosomes inside their cells.
These crystals align like tiny compass needles, orienting the whole bacterium north-south.
In the Northern Hemisphere, they swim downward along magnetic field lines toward safer sediments.
In the Southern Hemisphere, their polarity flips so they still move downward geographically.
This navigation helps them avoid toxic oxygen-rich surface waters quickly and efficiently.
Researchers use electron microscopes to image magnetosome arrangement in single cells.
Synthetic versions of these nanoparticles now guide drug delivery in human medicine.
Their simple biology solves a complex physics problem without nerves or brains.
Studying them reveals how life harnesses planetary forces at microscopic scales.