Hobbies And Interests
Shape and Size
Most bacteria have a rod-like, round or spiral shape. A fourth, rarer shape of bacteria is vibrios, which looks like a comma. Bacteria typically have a length measuring a few microns. If you lined up 1,000 bacteria end-to-end, they would have the width of a pencil line.
Cell Wall Structure
Bacteria are also classified by their different cell wall structures. "Gram stain" bacteria have cell walls that are defined by a series of reagents and stains. "Gram negative" bacteria have a thin wall layer and an outer membrane that stains red. "Gram positive" bacteria have a thick wall layer, stain violet and don't have an outer membrane.
Gaseous oxygen
Bacteria react to gaseous oxygen in one of three ways. Aerobic bacteria need a continual source of oxygen to survive. Anaerobic bacteria are the opposite -- exposing them to gaseous oxygen kills them. Instead, they obtain their energy from other compounds. Facultative anaerobes can survive with or without oxygen, but prefer to be in oxygen environments.
Energy
Bacteria obtain energy from a variety of sources. Heterotrophs obtain energy by consuming and breaking down other complex organic compounds. Autotrophs create energy through photosynthesis or chemosynthesis. Green and purple bacteria and cyanobacteria are examples of bacteria that use photosynthesis.