Number of microorganisms in the world

Here is the number of microorganisms on the planet:

AnimalTypePopulationSource yearSource
BacteriaMicro organism4 x 10^482011NPR
PhytoplanktonsPlant5 x 10^262017Weborus estimation
ProtozoaProtist1 x 10^252017Weborus estimation
NematodaEcdysozoaire1 x 10^222017Weborus estimation
GastrotrichsMeiobenthic1 x 10^192017Weborus estimation
CopepodsCrustacean1 x 10^182017Weborus estimation
RotifersMicro organism1 x 10^172017Weborus estimation
Antarctic krillsCrustacean5 x 10^142011NPR

It’s hard to imagine all these microbial cells moving around the globe. It goes beyond the understanding. It is like imagining what represents all the galaxies, stars and planets of the Universe, or even the infinity of the Universe.

There are nearly 10 million species of bacteria. There are only 10,000 of them that are known. On a human body alone there are 1,000 billion bacteria on the skin, 10 billion in the mouth, 100,000 billion in the intestine. There are thus ten times more bacterial cells than human cells. We are more a bacteria vessels than something else. The size of the bacteria varies from 0.5 to 5 μm in length. The bacteria had only one chromosome. It is present everywhere on Earth, in any type of environment. Even in extreme environments, like ice floes or hydrothermal chimneys.

We found a bacterium in the Canadian permafrost that was 500,000 years old and was still alive. Or another one sleeping in a salt crystal that was 250 million years old. In space, the bacteria become at least 3 times more virulent. Bacteria can not live on Mars because of ultraviolet radiation and perchlorate, they are quickly destroyed according to scientists.

Bacteria do not have life expectancy, because they do not age. To multiply, they divide into two. There is no parent or child. A bacterium splits between every 12 minutes and every 24 hours depending on the species or the conditions of its place of life. In a dry environment, they can be transformed into spore to survive. It is estimated that the amount of bacteria is still the same on the planet and when one is born, another dies.

A bacterium can die by being digested with antibiotics, immune cells, autolysis by their own reaction to the environment, they can be ingested by the lymphatic system or by other so-called cannibal bacteria. Mutual bacteria can die if their host also dies, unless they found the way to go on a new host.

We could add the tardigrade, considered as an animal close to nematodes. It can survive at least 2,000 years via cryptobiose. Its size has an average of 1 mm long. There are over 1,000 species. Some can survive in space. It can survive X-rays, ultraviolet radiation, high pressures (up to 1,200 atmospheres). They can survive most toxic products through chemobiology. They are resistant to extreme salinity, desiccation (very dry desert). They can live under temperatures of -459 ° F to 302 ° F. They can live in the absence of oxygen thanks to anaerobiosis. The oldest fossil is 90 million years old. They degrade very quickly once dead, it is difficult to find older fossils. An active tardigrade that does not do cryptobiose has a life expectancy of one year and 3 months on average.

There is at least 1 quindecillion (thousand of billion of quintillion of quintillion) of microorganisms on Earth.