Thursday, 3 May 2012

The first step towards Biomineralisation








The first brick towards Biomineralisation by Marek Coleman 

Biomineralisation is the build up of minerals of some form by cells. Example of this can be seen in most of the animal phyla as well as examples in Diatoms, Rhizaria and prokaryotes. Some of the most amazing and complex biological features created from biomineralization such as, bones, shells, the exoskeletons of Diatoms and the corals. But where or when did these biological structures come from and did they evolve separately.

Geological evidence from the Cambrian Explosion, 525 mya, suggests this is when biomineralisation first occurred.[1] This was inferred from the fact that all evidence of animal life before then was from rare soft-bodied life.[1] From this date there was an explosion of hard-bodied life due to the biomineralisation of various parts of their body.[1] The reason these fossils could be found is that they biomineralised calcium, silicon, phosphate and iron oxide amongst others.[1] This extreme diversity of adaption and use of biomineralisation among chordate, arthropod and mollusca all occurred during the Cambrian explosion, and through a process called “exaptation.[1] Exaptation is replication and adaption of an already used mechanism that is modified through inheritance and mutation to be used for some other process.[1] The trait that is thought to have been exaptated by these three phylum, is magnetite mineralization, which would have come from their last common ancestor. [1]

Magnetite is the simplest form of biomineralisation and the crudest form is found in magnetotactic bacteria.[1] It uses magnetite or other iron compounds to create many magnetite single domain crystals that help them find the optimum orientation in space for their energy needs.[1] Close genetic inquires to 16 specific RNA in bacterium have helped scientists to find phylogenetic relationships between chordates, arthropods, and molluscs.[1] It is thought that some form of endosymbiosis event occurred, and this is why cells are able to create magnetite crystals. [1]




















So in order to understand this process that when understood can help facilitate the scientists in learning how more complex biomineralisation occurs.[1] For this reason further genetic interest surrounds how the magnetotactic bacteria facilitate the creation of magnetite crystals. [1] Bacterioferritin(Bfr) is an enzyme that is involved in the mediation of iron, two genes code for it in the bacteria Magnetospirillum  magnetotacticum. [1] The genes Bfr1 and Bfr2 are unusual as they have a large overlap; this overlap is from the last codon of the first gene overlapping the stop codon and the first of the Bfr2. [1] There is also a difference between M. magnetotacticum and other magnetotactic bacteria in that their Bfr might help mineralise the iron compound rather than nucleate it. [1] Many other genes such as mamQ and mamA are used to create the vacuole that is used in the creation of the magnetite, similar genes and process are used in the same way that other more spectated organisms biomineralise. [2]

By trying to understand how magnetotactic bacteria create it’s single domain magnetite crystals and by using genetic analysis, scientists can then apply this to other organisms and how the genetics apply there. This will lay the first brick towards biomineralisation understanding so that  applications and uses can be applied in biomimetics and the cosmetics industry i.e understanding how diatoms create their exoskeleton and applying this to cosmetics to achieve that sought after sheen. [3]  

 


References

[1] Kirschvink J.L. & Hagadorn, J.W, 2000, ‘A Grand Unified Theory of Biomineralization’ Bäuerlein, E.,ed., 10, pp. 139- 150

[2] Baumgartner.J., Faivre.D. (D.N.F.) ‘Magnetite Biomineralization in Bacteria’ Werner E. G. Müller(eds), Molecular Biomineralization Aquatic Organisms Forming Extraordinary Materials , 52, D.N.F., D.N.F., pp. 4-28


 [3] Mueller.T., (2008) ‘ Biomimetics design by nature’ Johns.C. (eds), National Geographic, April, National Geographic, D.N.F., pp. feature article (?)    


1 comment:

  1. Nice post about biomineralization. Hope you can go further with this page. Please take a look at this german research project of the priciples of biomineralization

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