A team of scientists at the California Institute of Technology (Caltech) has accidentally discovered a bacteria that … eats metals. Although many researchers had already theorized that this type of metal-ingesting bacteria had already existed for more than a century, its existence has never been proven. Up to now.
California microbiologists, specifically, found two species of bacteria that feed on manganese (Mn) and use this metal as an energy source . These metal-eating microbes grew in dirty glassware that was left there for several months, and ended up covered in dark oxidized or ‘spent’ manganese, material left over from the feed of these rare bacteria.
Manganese electron thieves
When microbiologist Jared Leadbeater returned to his office after months away, he found that a cream-colored manganese carbonate compound (MnCO3), which coated the glassware he had left in his sink, had darkened. Something had stolen some of its electrons. When examining manganese, a mineral usually combined with iron, they accidentally discovered the tiny microbes. They were autotrophic bacteria, that is, they can produce their own food using an energy source. In this case, bacteria were using the energy of manganese electrons to transform CO2 into usable carbon, in the same way that plants use sunlight to convert CO2 and water into sugars and oxygen during photosynthesis. .
Despite the fact that scientists are aware that bacteria and fungi may be capable of oxidizing manganese or taking away electronics, there was no data to prove the existence of these beings and this curious incident has opened a new window for us in the field. of the science.
“These are the first bacteria to use manganese as a fuel source,” says Leadbetter. “A wonderful aspect of microbes in nature is that they can metabolize seemingly unlikely materials, such as metals, producing useful energy for the cell.”
Manganese is a hard, brittle, silvery metal and also one of the most abundant elements on Earth. The chemical element is too brittle to be useful as a pure metal, so it is used primarily in alloys, such as steel. It is also an essential element in all known living organisms and helps promote bone growth in humans. Manganese oxides take the form of a dark, lumpy substance and are common in nature; They have been found in underground reservoirs and can also form in water distribution systems.
Where do these bacteria come from?
The black coating found on the forgotten labware was oxidized manganese, generated (via chemosynthesis ) by bacteria that likely came from tap water. “There is evidence that relatives of these creatures reside in groundwater, and a portion of Pasadena’s drinking water is pumped from local aquifers,” says the expert.
“There is a comprehensive body of environmental engineering literature on manganese oxides clogged drinking water distribution systems,” says Leadbetter. “But how and why this material is generated has remained an enigma. Clearly, many scientists have considered that bacteria that use manganese for energy could be responsible, but the evidence to support this idea was not available until now .”
This finding will help scientists better understand the geochemistry of groundwater in which manganese appears to play a crucial role in the processes that have shaped the evolution of life on our planet Earth.
Referencia: Hang Yu, Jared R. Leadbetter. Bacterial chemolithoautotrophy via manganese oxidation. Nature, 2020; 583 (7816): 453 DOI: 10.1038/s41586-020-2468-5
