Unusual three-way bestows magnetic sense to single-celled organism

How do microorganisms orient themselves to find the optimal habitat?

Scientists have thoroughly investigated so-called magnetotactic bacteria, which use the Earth's magnetic field as a biological compass.

Some eukaryotic single-celled organisms—that is, more complex organisms like ciliates, which, unlike bacteria, have a cell nucleus—also possess this capability.

But how they acquire it has largely remained a puzzle. ...