“Dark microbial matter” — uncultured microbes whose characteristics have never been described — could be dominating nearly all the environments on the earth, scientists say. The study, published in the journal mSystems , is the first to estimate the population of microbes that have not yet been grown in a lab culture.
Researchers from the University of Tennessee in the U.S. believe that as many as a quarter of the microbes on earth could come from the roughly 30 phyla — a taxonomic classification between kingdoms and classes — of microbes that have never been cultured.
To estimate how many uncultured microbes call this planet home, researchers collected every DNA sequence deposited in public databases by researchers all over the world, totalling 1.5 million, and compared them to 26,000 DNA sequences of microbes and bacteria that have already been cultured.
The study can be a valuable tool in fields such as medicine, where scientists have described cases of culture-resistant pathogens.
“It is possible that these microbes can’t grow on their own in culture because they die if they are removed from their intricate relationships with each other or their particular environment,” said Karen Lloyd of the University of Tennessee.
