Bacteria

Bacteria are among the smallest living organisms, but they usually band together in colonies. Bacteria can be autotrophic, make their own food, or heterotrophic, feed off of other organisms.

Cell Design

Bacteria cells are unicellular and prokaryotic. They have a cell wall, cell membrane, free – floating DNA, cytoplasm, ribosome, and cilia or flagella. Bacteria are classified into three different shapes –

coccus (round), bacillus (rod), and spirillum (spiral).

Two Branches of Bacteria

1. Archeobacteria is the oldest type of bacteria. They live in acidic water, sulfur hot springs and extremely salty water. Only found in inhospitable environments.

2. Eubacteria is the most common type of bacteria, today. It is also found everywhere.

Adaptations to an Environment

A regular bacteria cell cannot hold up when it is subjected to inhospitable environments. When the cell feels threatened, it will make an endospore. An endospore is a copy of the bacteria’s DNA and a little cytoplasm in a resistant form. It can resist heat, dry conditions, radiation, and boiling. Bacteria cells also produce plasmids. A plasmid is a small loop of DNA that can be transmitted to other bacteria cells. Plasmids are useful because they can be resistant to antibiotics.

Uses by Man

Man has found uses for different types of bacteria, such as

antibiotics, food manufacturing, and some insect pesticides.

Bacteria are also used to purify sewage treatment plants.

Three Types of Heterotrophic Bacteria

1. Parasites – obtain nutrients by living in or on organisms.

2. Saprobes – feed off of the waste of other organisms.

3. Decomposers – feed off of dead organisms.

Leptospina – causes disease in livestock.
Streptococcus – kills white blood cells and causes strep throat and scarlet fever.

Escherichia coli – causes food poisoning.

Lactobacillus – causes tooth decay.
Bacillus anthracis – anthrax in sheep and humans.
Staphylococcus – staph infections.
Clostriclium tetani – tetanus in humans.
Streptomycin – used in life saving medicines.

Nitrogen Fixation

Bacteria take unusable forms of nitrogen and make it into usable form, such as nitrates or nitrites. Nitrogen fixation usually takes place in one specialized bacteria cell in a colony called heterocyst.

Decomposition

Bacteria, such as saprobes and decomposers, feed off of dead organisms or the wastes of organisms. They release nutrients back into the soil so that plants can use them.