What is the most common type of bacteria in the world?

The most common type of bacteria in the world is Marine Prochlorococcus. It is a type of cyanobacteria that can be found in the oceans around the world. It was first discovered in the late 1980s, and it is estimated that there are billions of them in every milliliter of seawater.

Prochlorococcus is incredibly important to the ocean's ecosystem, as it is the primary producer of oxygen through photosynthesis. It also plays a vital role in the marine food chain, and scientists believe that it is responsible for up to 20% of the total photosynthesis on the planet.

Although Prochlorococcus is the most common type of bacteria in the world, there are many other types of bacteria that can be found in a variety of different environments. Some of the other common types of bacteria include Escherichia coli, Streptococcus, and Staphylococcus.