Indian scientists have coupled silver molecules with carbonate ions to hugely enhance the metal's antibacterial activities. If adopted, the unexpected breakthrough could save 1,300 tons of silver, worth roughly $766 million dollars, each year.

Silver is already widely used in medicine as well as the fields of food sanitation and water purification to the tune of around 6,000 tons per year, or about a quarter of annual production. A silver concentration of just 50 parts per billion in drinking water kills more than 99% of bacteria. For this reason, silver is used to disinfect drinking water in many developing countries and even onboard the International Space Station.

In an effort to improve the antimicrobial power of silver, the researchers added various anions to water containing 50 parts per billion of silver. Carbonate, composed of one carbon atom and three oxygen atoms, showed the most potential. Upon further experimentation, they found that a mixture of just 25 parts per billion of silver with the addition of a 20 parts per million of carbonate was enough to reduce E. coli levels in water 100,000 times over. 50 parts per billion of silver alone reduced E. coli amounts 100 times over.

Further testing elucidated why the pairing of silver and carbonate is so successful. Like a boxer strategically softening up his opponent, carbonate destabilizes bacteria's peripheral membrane proteins, allowing silver to sneak in and deliver its knockout blow with far less resistance.

Each year, diarrhea kills 760,000 children under the age of five. According to the World Health Organization, safe drinking water is one of the best ways to prevent the infection. The researchers are hopeful their discovery will make it easier to spread proper water sanitation throughout the developing world.

"This work leads to a new paradigm in the field of affordable water purification by reducing the cost of antimicrobial treatment, particularly in the developing world, without disinfection by-products."

Environmentalists also have reason to cheer the finding. Silver nanoparticles currently leach into oceans and rivers via waste treatment, and this may be damaging marine ecosystems by killing off the good bacteria that support them. Thus, lower silver concentrations in drinking water may be good news for marine bacteria.

(Image: Alchemist-hp, Swathy et. al.)

Source: Swathy, J.R. et al . Antimicrobial silver: An unprecedented anion effect. Sci. Rep. 4 , 7161; DOI:10.1038/srep07161 (2014)