Magnetotactic bacteria represent a diverse group of Gram-negative microorganisms with respect to morphology, physiology and phylogeny. They have a cosmopolitan distribution in sediments or water columns with horizontal chemical stratification. The highest numbers of magnetotactic bacteria are generally found at the oxic-anoxic transition zone or redoxcline, located at the sediment/water interface or just below the interface. The distribution and abundance of mangetotactic bacteria appear to be dependent on the presence of opposing gradients of oxygen, sulfur or availability of soluble iron. Different species show different preference within vertically physical and chemical gradients. The growth of magnetotactic bacteria, synthesis of magnetosomes and composition of magnetosomes can reflect environmental conditions to a certain degree. Magnetotactic bacteria may play a significant role in biogeochemical cycles, especially in iron cycle. The purpose of this review is to highlight these recent discoveries including our research. Perspectives for further ecological research are discussed.