Microbes are found by the trillions throughout the human body and account for between 1% and 3% of our body mass. Unlike viruses, bacteria have their own metabolism and create their own energy, and they can also reproduce unassisted. A bacterium consists of a rigid cell wall and cytoplasm, which contains ribosomes, plasmids, and a circular chromosome.
The nucleic acid found in the chromosome of a bacterium is constructed as a double helix held together by hydrogen bonds. It stores and conveys the information needed for antibiotic resistance.
Cytoplasm (which is Greek for “hollow receptacle”) is the living protoplasm of the cell. The jellylike material (light purple) is enclosed by the cytoplasmic membrane (dark purple border).
The cell wall of bacteria is made of peptidoglycan (aka murein) molecules and it is between 7 and 80 nanometers thick, depending on the species. It provides a tough, rigid structure to protect the bacteria from damage.