A bacterial cell is the simplest autonomous life form that can exist in this world. The only way for it to reproduce is to first make a duplicate of all necessary molecules and macromolecular structures and then split itself into two cells (binary fission), each containing one complete set of all necessary molecules and macromolecular structures. Once a cell was fully constructed, it was important that the duplication processes used in reproduction function reliably to ensure the integrity of the information through millions of replications. Of course, the environment to which the cells are exposed will change over time and they will need to adapt in order to continue to live and reproduce. The creation angels introduced a variety of extra informational packets (genes) to provide for all foreseen environmental changes for the cells to use when needed. They produced bacteriophages (viruses) as tools with which to place new genetic information into bacteria and thereby create new species. They also build in ways to change the cellular information when the environment changed in unforeseen ways.
The biochemical activity of the archaebacteria altered the composition of the water and the atmosphere, paving the way for placement of bacteria. The first cells were necessarily anaerobic because there was still very little oxygen in the atmosphere. Among the early bacteria were some cells similar to the present-day cyanobacteria, formerly known as blue green algae. Fossils of cyanobacteria, found in ancient rock forms called stromatolites, indicate that the cyanobacteria were put into the environment about 2.5 to 3.4 billion years ago.
Cyanobacteria were given a mechanism to capture energy from sunlight called photosynthesis (photosystem I), which used energy from the sun for the synthesis glucose from CO2 and H 2O and released oxygen. These organisms were the first to introduce oxygen into the atmosphere.
As the oxygen content in the atmosphere increased over the millennia, aerobic (oxygen using) bacteria that used this oxygen to metabolize glucose in the process known as aerobic respiration were developed and placed in appropriate places (again primarily at liquid-solid interfaces) all over the earth. Bacteria were the only life forms on earth for about two billion years; eukaryotes (protists) were introduced about 1.5 billion years ago and fungi-like things put into the biosystem about 900 million years ago (0.9 billion years ago).