Bacteria

The Bacterial Cell• Bacteria are

prokaryotes. The genetic material in the cells is not contained in a nucleus.

- Bacteria

Cell Shapes

• Bacteria have one of three shapes: spherical, rodlike, or spiral

How they obtain food• Some are autotrophic, and some are heterotrophic.

• Autotrophic bacteria use the sun’s energy to produce food and oxygen. Some autotrophic bacteria, like those that live deep in the ocean, use chemicals from their surroundings to make their own food.

• Heterotrophic bacteria must obtain their food from other sources such as milk, meat, decaying leaves, and other organisms.

More on Bacteria

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- Bacteria

Reproduction in Bacteria• Bacteria reproduce asexually, by binary fission.

One bacteria cell divides into two identical cells.

• Some bacteria reproduce sexually when two parent cells combine their genetic material to produce a new organism. This is called conjugation. During conjugation, one bacterium transfers some of its genetic material into another bacterial cell through a thin bridge that joins the cells. After the transfer, the cells separate.

How they obtain oxygen

• Most bacteria cells need oxygen from the air around them to break down food. But some bacteria do not need oxygen to break down food for energy. These bacteria will even die if oxygen is present.

Population Explosion-How bacteria populations grow

• Suppose a bacterium reproduces by binary fission every 20 minutes. The new cells survive and reproduce at the same rate. This graph shows how the bacterial population would grow from a single bacterium.

- Bacteria

Endospores

• Sometimes environmental conditions are unfavorable for bacterial growth. Some bacteria survive these conditions by forming endospores which are thick walled resting cells that are inside the bacteria cell. This endospore contains the cell’s genetic material and can survive many years even if they are frozen, heated, or dried out.

Key Terms: Examples:

- Bacteria

bacteria If Leeuwenhoek had owned one of the high-powered microscopes in use today, he would have seen the single-celled organisms known as bacteria in detail.

cytoplasm The region inside the cell membrane, called the cytoplasm, contains a gel-like material.

ribosome Located in the cytoplasm are tiny structures called ribosomes, chemical factories where proteins are produced.

Key Terms: Examples:flagellum

respiration

binary fission

A bacterial cell may also have a flagellum, a long, whiplike structure that helps a cell to move.

The process of breaking down food to release its energy is called respiration.Bacteria reproduce by a process called binary fission, in which one cell divides to form two identical cells.

asexual reproductionKey Terms: Examples:

sexual reproduction

conjugation

Asexual reproduction is a reproductive process that involves only one parent and produces offspring that are identical to the parent.Sexual reproduction involves two parents who combine their genetic material to produce a new organism, which differs from both parents.During a process called conjugation, one bacterium transfers some of its genetic material to another bacterium through a thin, threadlike bridge that joins the two cells.

endosporeKey Terms: Examples:

pasteurization

decomposer

An endospore is a small, rounded, thick-walled, resting cell that forms inside a bacterial cell.

During pasteurization, food is heated to a temperature that is high enough to kill most harmful bacteria without changing the taste of the food.

These bacteria, which live in the soil, are decomposers—organisms that break down large chemicals in dead organisms into small chemicals.

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