There could be more than one trillion species on Earth and only 0.001 percent (or one thousandth of one percent) have been identified, said a new study from biologists at Indiana University. Put in another way, this data means 99.999 percent of species (most being microorganisms) remain undiscovered.

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And to put that huge number into perspective, there are only an estimated 400 billion stars in our Milky Way galaxy.

IU scientists arrived at this conclusion by creating the largest ever dataset about life on Earth. This massive dataset combined microbial, plant and animal community datasets from government, academic and citizen science sources and combined these with universal scaling laws that can accurately predict species numbers for plant and animal communities.

The IU dataset includes over 5.6 million microscopic and non-microscopic species from 35,000 areas in all the world's continents and oceans, excluding Antarctica. It combines the largest available datasets with ecological models and new ecological rules for how biodiversity relates to abundance. The dataset gave IU scientists a new and rigorous estimate for the number of microbial species on Earth.

The study's results have also found that actually identifying every microbial species on Earth is almost impossible. It also found the number of microorganisms, the most numerous forms of life on the planet, were seriously under-sampled by other studies. The IU study, however, illustrates the extensive diversity of microbes on our planet.

The study was published in the Proceedings of the National Academy of Sciences and co-authored by Jay Lennon, associate professor in the IU Bloomington College of Arts and Sciences' Department of Biology, and Kenneth Locey, a postdoctoral fellow in the department. It was supported in part by the U.S. Army Research Office.

Lennon noted that estimating the number of species on Earth is among the great challenges in biology.

"Of those cataloged species, only about 10,000 have ever been grown in a lab, and fewer than 100,000 have classified sequences," said Lennon.

"Our results show that this leaves 100,000 times more microorganisms awaiting discovery -- and 100 million to be fully explored. Microbial biodiversity, it appears, is greater than ever imagined."

"Until recently, we've lacked the tools to truly estimate the number of microbial species in the natural environment," Lennon noted. "The advent of new genetic sequencing technology provides an unprecedentedly large pool of new information."

Tagsindiana university, Jay Lennon, Kenneth Locey, microorganisms, Species, Earth, Proceedings of the National Academy of Sciences