A team of microbiologists at Caltech has discovered a species of bacterium that feeds on manganese, one of the most abundant elements on Earth.
This SEM image shows manganese oxide nodules generated by Candidatus Manganitrophus noduliformans. The nodules are generally about 0.1 to 0.5 mm in diameter. Image credit: Hang Yu / Caltech.
“These are the first bacteria found to use manganese as their source of fuel,” said lead author Professor Jared Leadbetter, a researcher in the Division of Geological and Planetary Sciences and the Division of Engineering and Applied Science at Caltech.
“A wonderful aspect of microbes in nature is that they can metabolize seemingly unlikely materials, like metals, yielding energy useful to the cell.”
Professor Leadbetter and his colleague, Caltech postdoctoral researcher Hang Yu, examined the possibility that previously unappreciated microorganisms from the environment might oxidize manganese for energy.
They coated a glass jar with a slurry of manganese carbonate (MnCO3) and allowed it to dry, before filling it with municipal tap water from Pasadena, California, and leaving it to incubate at room temperature.
After several months, the cream-colored carbonate coating had oxidized to a dark manganese oxide.
“I thought, ‘What is that?’ I started to wonder if long-sought-after microbes might be responsible, so we systematically performed tests to figure that out,” Professor Leadbetter said.
The newly-discovered bacterium, dubbed Candidatus Manganitrophus noduliformans, belongs to the phylum Nitrospirae and is distantly related to known species of Nitrospira and Leptospirillum genera.
“There is evidence that relatives of these creatures reside in groundwater, and a portion of Pasadena’s drinking water is pumped from local aquifers,” Professor Leadbetter said.
The team’s findings have possible relevance to understanding manganese nodules that dot much of the seafloor.
These round metallic balls, which can be as large as grapefruit, were known to marine researchers as early as the cruises of the HMS Challenger in the 1870s.
The authors wonder if microbes similar to what they have found in freshwater might play a role and they plan to further investigate the mystery.
“This underscores the need to better understand marine manganese nodules before they are decimated by mining,” Dr. Yu said.
The team’s paper was published in the July 15, 2020 issue of the journal Nature.
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H. Yu & J.R. Leadbetter. 2020. Bacterial chemolithoautotrophy via manganese oxidation. Nature 583, 453-458; doi: 10.1038/s41586-020-2468-5
