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in your element the protector John Emsley looks at an element that is vital to life.

anganese is an essential element sharks’ teeth, which are one of the few parts for all species. It has a key role of living things capable of surviving at the in protecting cells against the bottom of the ocean. M – superoxide free radical O2 , and does this Life has been intimately linked to as the enzyme manganese superoxide manganese, and in parts of the ocean devoid dismutase (Mn-SOD) which converts of the success of marine diatoms relies – 2 O2 to H2O2. Manganese is also needed for on this element . This microbial attraction other enzymes, and is involved in glucose to manganese might one day be the basis of metabolism, the utilization of vitamin B1, an alternative source of the metal by using and the operation of RNA. microbes to extract manganese from low- It was only realized in the 1950s that grade , as is currently done for humans need manganese, partly because and gold3. our requirement is so small: the average Manganese metal is not used as such person contains only about 12 mg. The daily because it is too brittle, and 95% of mined intake averages 4 mg, which is more than goes into alloys — mainly steel, to which enough. Many foods provide this element, around 1% is added to improve its strength, especially cereals and nuts. Beetroot has working properties and wear resistance. The one of the highest levels, as has the French alloy known as ‘manganese steel’ contains delicacy, snails. Too much manganese in around 13% manganese, and a patent for the form of dust or fumes, however, can this was granted in 1883 to a 24-year-old send you crazy, and miners of manganese metallurgist, Robert Hadfield of Sheffield. used to suffer the symptoms of This metal is extremely strong and is used ‘manganese madness’ with involuntary for railway tracks, earth-moving machinery, laughing or crying, aggression, delusions safes, army helmets, rifle barrels and prison

and hallucinations. © RICK MORGAN/ALAMY bars, and is still referred to as Hadfield steel. The power of Mn-SOD in protecting Manganese compounds also find living cells was demonstrated in the 1950s certainly pyrolusite, and it was also used as use, for example manganese(iv) dioxide

by the microbe Deinococcus radiodurans. a black by potters. (MnO2) is added to rubber and is used as This organism is able to survive in Manganese ores have also provided an industrial catalyst, and manganese(ii) meat subjected to intense radiation by evidence of changes in planetary diversity (MnO), goes into fertilizers applied accumulating manganese in preference to over the millennia. The lack of manganese to manganese-deficient soils. Potassium

iron, and using it to destroy the devastating in sedimentary rocks in the period permanganate (KMnO4) — with the number of free radicals that between 400 and 1,800 million years ago Mn(vii) oxidation state — is used to the radiation produces. In so doing, it indicated a time when the oceans had low remove organic impurities from waste enables the DNA repair mechanism of oxygen levels1. gases and effluent water. The characteristic cells to continue functioning and not be Pyrolusite is the most common purple of is thus completely overwhelmed. manganese ore, of which around 25 only a minor, albeit colourful, aspect of an Manganese was known long before it million tonnes are mined every year. If element that plays a key part in our lives was isolated as an element. It occurs as the the land-based deposits were ever to be and that of planet Earth. ❐ black ore pyrolusite (), exhausted then we would have to exploit which was used by the cave artists of the manganese nodules on the ocean floor. JOHN EMSLEY is a science writer and the Lascaux region of France more than There are an estimated trillion tonnes (1012) author of Nature’s Building Blocks and 30,000 years ago. The Roman author Pliny of these scattered over large areas, with the other books. the Elder, who perished when Pompeii was North East Pacific being particularly rich e-mail: [email protected] destroyed in 79 ad, wrote of a black powder in them. In 1876 the sailing ship Challenger that glass-makers used to make their was sent to explore the deep oceans and References 1. Maynard, J. B. Econ. Geol. 105, 535–552 (2010). products crystal clear — this was almost it returned with curious, cone-shaped 2. Wolfe-Simon, F. et al. Plant Physiol. 142, 1701–1709 (2006). lumps that had been dredged up from the 3. Das, A. P. et al. Bioresource Technol. 102, 7381–7387 (2011). ocean floor. They turned out to be mainly manganese and seem to have formed around Corrected online 3 October 2014 Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo 978 NATURE CHEMISTRY | VOL 5 | NOVEMBER 2013 | www.nature.com/naturechemistry

© 2014 Macmillan Publishers Limited. All rights reserved in your element

ADDENDUM In Your Element: Manganese the protector John Emsley

Nature Chemistry 5, 978 (2013); published online 24 October 2013; corrected after print 3 October 2014.

In the version of this In Your Element article previously published, it should have stated that some passages in this essay are based on the manganese chapter in the author’s book, Nature’s Building Blocks.

1026 NATURE CHEMISTRY | VOL 6 | NOVEMBER 2014 | www.nature.com/naturechemistry

© 2014 Macmillan Publishers Limited. All rights reserved