Magnetotactic bacteria, first discovered 30 years ago, are motile prokaryotes that swim along geomagnetic field lines. They produce unique intracellular structures called magnetosomes, which contain magnetic mineral crystals surrounded by a lipid bilayer. Recent advances in isolation techniques and genetic studies have significantly improved understanding of magnetosome formation and function. Magnetotactic bacteria are diverse, with various morphologies, and are found in aquatic environments, particularly near the oxic-anoxic interface. They play a role in biogeochemical cycles of elements like iron, nitrogen, sulfur, and carbon. These bacteria are sensitive to oxygen and typically produce magnetosomes under low oxygen conditions. Magnetosomes are highly purified, with specific sizes and shapes, indicating precise biological control. They are composed of either iron oxide (magnetite) or iron sulphide (greigite), with some bacteria producing both. The mineral composition is tightly regulated, and magnetosomes are often chemically pure. Magnetotaxis, the magnetic behavior of these bacteria, is not a true tactic response but involves passive alignment along magnetic field lines. Magnetotactic bacteria exhibit different swimming behaviors, such as two-way or one-way swimming, depending on their environment. Magnetotaxis is influenced by both magnetic and oxygen gradients, with some bacteria showing magneto-aerotaxis, which combines magnetic and oxygen sensing. The synthesis of magnetosomes involves complex steps, including vesicle formation, iron uptake, transport, and controlled mineralization. Iron is taken up by the cell, transported into the magnetosome vesicle, and then mineralized. The magnetosome membrane plays a crucial role in controlling crystal growth and shape. Proteins like Mms6 and MamA are involved in magnetosome formation, and their presence is essential for proper magnetosome synthesis. Mutants of magnetotactic bacteria often lack magnetosomes and show altered iron uptake. Genomic islands may contain genes responsible for magnetosome synthesis, explaining their presence in diverse bacteria. The study of magnetosomes has provided insights into biomineralization and the evolution of magnetic behavior in prokaryotes.Magnetotactic bacteria, first discovered 30 years ago, are motile prokaryotes that swim along geomagnetic field lines. They produce unique intracellular structures called magnetosomes, which contain magnetic mineral crystals surrounded by a lipid bilayer. Recent advances in isolation techniques and genetic studies have significantly improved understanding of magnetosome formation and function. Magnetotactic bacteria are diverse, with various morphologies, and are found in aquatic environments, particularly near the oxic-anoxic interface. They play a role in biogeochemical cycles of elements like iron, nitrogen, sulfur, and carbon. These bacteria are sensitive to oxygen and typically produce magnetosomes under low oxygen conditions. Magnetosomes are highly purified, with specific sizes and shapes, indicating precise biological control. They are composed of either iron oxide (magnetite) or iron sulphide (greigite), with some bacteria producing both. The mineral composition is tightly regulated, and magnetosomes are often chemically pure. Magnetotaxis, the magnetic behavior of these bacteria, is not a true tactic response but involves passive alignment along magnetic field lines. Magnetotactic bacteria exhibit different swimming behaviors, such as two-way or one-way swimming, depending on their environment. Magnetotaxis is influenced by both magnetic and oxygen gradients, with some bacteria showing magneto-aerotaxis, which combines magnetic and oxygen sensing. The synthesis of magnetosomes involves complex steps, including vesicle formation, iron uptake, transport, and controlled mineralization. Iron is taken up by the cell, transported into the magnetosome vesicle, and then mineralized. The magnetosome membrane plays a crucial role in controlling crystal growth and shape. Proteins like Mms6 and MamA are involved in magnetosome formation, and their presence is essential for proper magnetosome synthesis. Mutants of magnetotactic bacteria often lack magnetosomes and show altered iron uptake. Genomic islands may contain genes responsible for magnetosome synthesis, explaining their presence in diverse bacteria. The study of magnetosomes has provided insights into biomineralization and the evolution of magnetic behavior in prokaryotes.