Those species were sampled from nine environments diverse and extreme enough, like hydrothermal vents, that researchers could reasonably expect to hold unique species. And that's what they found. None of the 201 species had ever been sequenced before. As the authors write, "our single-cell genome data set provides an 11% greater coverage of known phylogenetic diversity than currently available genomes."
"This is what we call 'microbial dark matter,'" Tanja Woyke, a researcher at the DOE's Lawrence Berkeley National Laboratory, said. "They are branches in the tree of life that have no representatives."