Basic Information About Bacteria
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Basic Information About Bacteria

What characteristics do most bacteria share? What is endosymbiosis? Find out here...

What are Bacteria Exactly?

Bacteria are single-celled micro-organisms without a nucleus and a cellular membrane that is made up by protein-sugar molecules. They are a part of the prokaryote kingdom, which is a completely separate group. They are not animals and they are not plants, even though some of them actually show the process of photosynthesis and consequently produce their own nutrients. Most bacteria are between 1 and 10 micrometers long. Bacteria are by far the most common organisms in the world. In general, they can be divided in these three groups:

  • Eubacteria: meaning ‘true bacteria’, this category contains the pathogens (the ones that cause disease) and the bacteria that decompose dead organisms and waste.
  • Cyanobacteria: meaning ‘blue-green bacteria’ (also known as blue-green algae), these bacteria are the ones that behave as plants. They show photosynthesis and thus produce oxygen.
  • Archaeabacteria: meaning ‘ancient bacteria’, this is the group that can be found under extreme circumstances (even so extreme that some scientists believe they could survive in the dreadful atmospheres of other planets) and converts anorganic molecules to energy.


All bacteria share some common characteristics. While being without nucleus, they have a genome that is contained in a single DNA ring. Furthermore they are asexual, with a relatively simple reproductive process, giving rise to daughter-cells with an identical ring of DNA. This all happens without the complicated processes of meiosis and/or mitosis.

Some bacteria move through the slime they excrete, which spreads over the cellular surface. This allows them to ‘glide’ through their environment. Others have tiny hairs (called cilia if there are a lot of them that are really small, or flagella if there are only a few, which are somewhat bigger) they fling around, resulting in movement through their watery homes. Scientists suspect that the eukaryotes (the more complicated cells with a nucleus, that are part of more complex organisms) probably have evolved from the first prokaryotes. And this is how that could have occurred.

From Bacteria to Eukaryotes

Small, separate cells were ingested by larger primitive cells. This was followed by a process called endosymbiosis, which means that the small cells became a part of the bigger ones, while they continued to function separately within this larger organism. This is what happened with, for example, chloroplasts and mitochondria, which once were separate organisms swimming around in some primitive ocean, where they were ingested by a larger organism, but kept their own DNA and genes, starting a life within the organism that ate them.

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