Germs and bacteria are microscopic organisms which are found in every part of the world, in the air, in stagnant water, in soil and rocks and in our body especially in the mouth and intestines.
Germs are single-celled microscopic organisms which also include viruses and fungi. Bacteria are unicellular organisms with different shapes and sizes.
Most of the bacteria present on Earth are useful and indispensable bacteria for the balance of the ecosystem. Just think of the bacteria of the our bacterial florauseful for digestion and absorption of nutrients, or germs and bacteria used for production of some foods like cheese and bread.
Others, on the other hand, are extremely harmful and can lead to the onset of extremely serious pathologies, which can even lead to death such as pneumonia and meningitis.
Discovery of germs and bacteria
There are about one trillion bacterial species in the world and it is difficult to estimate the precise amount of microorganisms present.
However, it is estimated that there are about 10^30 cells and most germs and bacteria are known to have one length of about 0.001 mmtherefore if all these microorganisms present on the Earth were stacked on top of each other, the length of approximately 10 billion light years. To give an estimate of the length, just think that it would be such as to be able to wrap the Milky Way more than 20,000 times.
Despite the incredible length, the line of bacteria would not be easy to spot because it would be extremely small 75 times thinner than a hair.