In my today’s post I will be talking about microbes which carry their very own compass and always remain align in the direction of Earth’s magnetic field that is Magnetotactic bacteria (MTB). These Magnetotactic bacteria were described for the first time by Salvatore Bellini in 1963 in the publication of University of Pavia. Bellini found these bacteria in bog sediment while visualizing under microscope, he found that certain bacteria were remained aligned in direction of North Pole, therefore he named those bacteria as magnetosensitive bacteria. After Bellini work, these bacteria again got featured in an article in Science journal in 1975 by Blakemore from Woods Hole Oceanographic Institution. He found that they remain oriented in the direction of Earth’s magnetic field, so he renamed them as Magnetotactic bacteria (1).
Magnetotactic bacteria can be differentiated on basis of form in which they produce magnetic particles; magnetite or gregite. These magnetite producing bacteria thrive in anoxic condition or in oxic-anoxic transition zone (OATZ). In anaerobic condition they use nitrates, sulfate or nitric acid as a final electron acceptor to produce magnetic particles. About the origin of MTB scientists make assumptions that they might have evolved in Proterozoic era, in this era the atmospheric oxygen was increased which resulted in reduction of dissolution of iron in water, as a result they started storing it intracellular and this later on accepted as magnetosomes (2). These MTB can be found in different morphotypes like rods, spherical, ovoid and spiral. They all are motile and Gram-negative, the arrangement of flagella differs in different species for example they can be polar, bipolar or even in tufts.(3). They are chemolithoautotrophic (group of bacteria utilizes reduced inorganic compounds by oxidation as their source) as they are dependent on reduced sulphur compounds which in present in large amount in oxic-anoxic transition zone or even in sediments in low or no oxygen condition. (4).
Magnetotactic Bacteria and their Role in Biomineralization(5). Let me just give a brief explanation about these proteins.
(6). TPR domain (Tetratricopeptide repeat) is a structural motif consists of 34 amino acids; it has been found that 3-16 amino acids fold to form protein-protein interaction. The α-helix pair repeats fold to form a solenoid domain which is known as TPR domain. Protein complexes like Anaphase-promoting complex, Hop adaptor protein (mediates association of molecular chaperones) and PEX-5, receptor of PTS-1 (Peroxisomal targeting sequence) shows presence of TPR domain (7). PDZ domain is structural domain consists of 80-90 amino acids, this protein plays role in anchoring receptor proteins in membrane to cytoskeletal components. These domains play a key role in signal transduction complexes (8).(9).
There are lots of applications associated with magnetosomes. Magnetosomes can be used for the purification of water; Scientists have explored the magnetic property and microaerophilic nature of these MTB to predict the oxygen concentration and reduction in sediments and water column (10). Along with prediction of oxygen concentration, it can be also used in waste management. Orientation magnetic separation process is used to check the purity of water. In this process Magnetotactic bacteria were placed in glass culture chamber and into this chamber contaminated water is added into them. The metals contaminant present in water will bind to these MTB and get aligned towards the North Pole and will move towards the separator, the property which is making the use of MTB for this process possible is that they get easily counted and recorded by magnetic recording head and provide an idea about population number and concentration of metals (11).
Compartmentalization in the bacterial cell are sometime a mechanistic way to save themselves, to store food, to carry out biomineralization or to use it as a navigation tool like as in the magnetotactic bacterial species. Magentotactic bacteria are named so because of their behavior towards earth's magnetic field which they very efficiently use for their movement. Before the bacterial movement always believe to be in a random way or in a zig-zag motion, anticlock-wise will go forward and clock-wise will tumble around but these bacterial species has shown the movement according to the attraction towards the magnetic field. Most frequently these magnetic compartment are being used to search the food source and ions source and also being used to search the appropriate environment for the survival. Not only the magnetic property, these compartments also give several other importance to the different species. The biomineralization supporting bacteria helps in the process of biomineralization and like this several applications are also shows their importance in the field of microbiology.