Bacteria are the most ancient of the famous groups of the organisms existing on the earth. The age of the most ancient bacteria found scientists-archeologists and paleontologists - so-called archaebacterias - contains more than 3.5 billion years. The most ancient bacteria lived at the time of an archaeozoic era when on Earth there was nothing more live.
The first bacteria possessed the most primitive mechanisms of food and transfer of genetic information and belonged to prokaryotic microorganisms - i.e. deprived of a kernel.
Eukaryotic or nuclear bacteria with higher degree of the organization of genetic material appeared on the planet only 1.4 billion years ago.
Bacteria became the most ancient life forms prospering and now, for a number of reasons.
First, thanks to the primitive building the microorganisms can "adapt" to all possible living conditions. Bacteria live and more than 90 degrees breed both in polar ices, and in hot springs with water temperature, at any concentration of various chemical compounds now. Bacteria can exist as in aerobic (containing a certain level of oxygen) conditions, and in anaerobic conditions (without oxygen). Their ways of obtaining energy - from absorption of sunlight and before use as energy for metabolism and reproduction of various chemicals, biological structures. The bacteria decomposing oil, other chemical compounds and using this energy for the activity are known. The first bacteria possessed the most primitive bodies of obtaining energy and just absorbed by usual diffusion chemicals which in a bacterial cage underwent the chemical reactions which are followed by energy allocation. Secondly, the elementary mechanisms of reproduction (the simplest option - division in two) occurring at very fast speed increased quantity of bacteria with the greatest possible speed, than increased their survival and increased a possibility of mutations in population of bacterial cages, including and the useful mutations promoting improvement of fitness of colonies of bacteria to the existing environmental conditions. Fast reproduction and variability of populations of microorganisms provided them high survival in the corrosive environment existing on Earth billions years ago.