Kingdom bacteria

Bacteria are a kingdom of prokaryotic, unicellular microorganisms. It is difficult to classify specific bacteria, since they mutate so frequently. They are the most diverse and abundant kingdom of life on Earth.

Bacteria can be classified by shape, energy source, or cell wall structure.

Shape
Bacteria can be shaped like a sphere, rod, or spiral. Their forms can be inferred from their names. The suffix -coccus denotes a spherical bacterium. The suffix -bacillus denotes a rod-shaped bacterium. And the suffix -spirillum denotes a spiral shaped bacterium.

Bacteria also live in groups. If the group is a lone pair, it is described with the prefix -diplo. If the group is triangular, it is described with the prefix -staphylo. If the group is long, it is described with the prefix -strepto.

Cell wall
The Gram stain is used to classify bacteria based on their cell wall. The Gram stain detects the presence of a significant peptidoglycan layer in the cell wall of Gram-positive bacteria, which are rendered purple. Gram-negative bacteria turn pink. Simply, though, a Gram-positive bacterium has a thick cell wall while a Gram-negative bacterium does not.

Energy Source
Light

Photosynthetic bacteria can be both autotrophic and heterotrophic, the latter meaning they cannot generate their complete energy requirement from photosynthesis. Photosynthesizing bacteria are called photoautotrophs and photoheterotrophs.

Inorganic compounds

Chemosynthetic bacteria can be both autotrophic and heterotrophic. Autotrophs in this category can obtain energy by breaking chemical bonds in inorganic compounds like ammonia. Heterotrophs must consume inorganic compounds to meet their energy requirements.

Binary fission

 * 1) The cell elongates and the DNA replicates
 * 2) Cell wall and plasma membrane divides
 * 3) Wall forms, bisecting the bacterium
 * 4) Bacterium divides

Conjugation

 * 1) Two bacteria line up and a mating bridge is formed
 * 2) A plasmid (molecule of DNA) is replicated and crosses the bridge
 * 3) The mating bridge dissolves