The Aug. 24 news story “A world filled with mysterious millions” summarized a study attempting to determine how many species there are on Earth, but the researchers who carried it out ignored the largest and most diverse branch of the tree of life: the microbes.

The most conservative estimates by microbiologists indicate that there are tens of millions of microbial species alone. Unicellular organisms occupy every niche on the planet, from the ice caps to the boiling thermal vents in the deep seas. Every living creature is teeming with trillions of microbes. A teaspoon of soil contains more than 10,000 species of bacteria. Antibiotics and enzymes that make biofuels come from microbes. They produce half of Earth’s oxygen and are essential for plant growth. Beneficial bacteria in the gut aid digestion and boost immunity. Simply put, microbes enable life on Earth.

The Post article quoted an entomologist saying that insects account for 85 percent of life on Earth and he wondered why anyone bothered counting the species of any other organism, saying “nothing else counts.” The microbes beg to differ.

David Hooper and Bonnie Bassler, Washington

The writers are, respectively, president and past president of the American Society for Microbiology.