what are their origins?
The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago.
Bacteria
The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. 
what bacterial parts are vital to a bacterium Prokaryotic microorganisms what do you mean by bacteria? They are a type of biological cell. describe their intracellular structures? It is surrounded by a cell membrane which encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm. and extracellular? Around the outside of the cell membrane is the cell wall. Bacterial cell walls are made of peptidoglycan (also called murein), which is made from polysaccharide chains cross-linked by peptides containing D-amino acids.
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Bacteria [SEP] Origin and early evolution
in ancient "amitochondrial" protozoa). Later, some eukaryotes that already contained mitochondria also engulfed cyanobacteria-like organisms, leading to the formation of chloroplasts in algae and plants. This is known as primary endosymbiosis.