The operons and genes related to magnetosome biogenesis in magnetotactic bacteria

Magnetosomes are natural magnetic nanoparticles with special properties that are synthesized by magnetotactic bacteria. Bacterial magnetosomes have become increasingly attractive for researchers in biology, medicine, geology and other fields of scientific researches. It is significant to explore a promising nanomaterial for multiple applications in science and industry. Magnetosomes contains magnetic particles that are enclosed by intracellular membrane. These particles can be either ferrimagnetic crystal of magnetite (Fe3O4) or the iron sulfide greigite (Fe3S4). Three crystal morphologies including roughly cuboidal, roughly rectangular, bullet-shaped have been found in magnetotactic bacteria. Magnetosomes are organized as well-ordered chains which orient magnetotactic bacteria in geomagnetic fields. The question ‘what and how is genetic material responsible for magnetosome genesis and following diversity’ was raised when biologists tried to understand the formation mechanism of magnetosome in the last century. Now almost two decades have passed since 2000, magnetosome biogenesis still remains one of the hotspots in scientific researches. Both bioinformatic analyses and gene deletion experiments are extensively carried out in the study of magnetosome biogenesis. Consequently, multiple operons and genes are found to be involved in the process of magnetosome formation. This article introduces important findings in the field of operons and genes as controllers of magnetosome biogenesis. The mamAB operon is found to be more critical than other operons to magnetosome biogenesis and it is necessary for rudimentary biomineralization in bacteria. Less than 10 genes within the mamAB operon are essential for the magnetosome formation. Moreover, other four small operons ( mamGFDC , mamXY , mms6 and feoAB1 ) play non-critical roles for magnetosome biogenesis. Non-essential genes can be found in both the mamAB operon and non-critical operons. In addition, several genes and genomic regions outside of magnetosome-related operons such as the mms16 gene in Magnetospirillum magneticum AMB1 or the mad gene clusters in Deltaproteobacteria are also related to magnetosome synthesis. These discoveries provide insights into the molecular mechanisms of magnetosome biogenesis. Some researchers have separated the whole process of magnetosome formation into three or five key steps, they proposed several hypothesized mechanisms of magnetosome formation in magnetotactic bacteria by summarizing functional genes and proteins in each of key steps. The Arakaki’s model in 2018 is a relatively comprehensive model of magnetosome formation and can offer detail information about molecular and cellular mechanisms. With rapid development of research on magnetotactic bacteria emerging in China in recent years, Chinese scientists have made various types of research achievements such as discoveries of novel magnetotactic bacteria, calculations of diversity of magnetotactic bacteria in specific water areas and evolutionary mechanism of microbial magnetoreception. It is expected that more valuable achievements would be obtained from bacterial research than ever before. Natural magnetic nanoparticles have potentials to bring many advancements in science and they can help overcome technical challenges in various scientific fields. To release the power within magnetosomes, biologists are required to reveal the genetic foundation of magnetosome biogenesis and help material scientists invent new technology using biological knowledge. Magnetosome researches are attracting more and more scientists from all areas of science. Interdisciplinary research has become an increasingly common method of study in magnetosome. How well the material scientists can cooperate with other scientists will be crucial for important discoveries in magnetosomes in the future.