BACTERIA

Structures in a Typical Bacteria Flagella—long hairlike structures growing from a cell that aid in movement Chromosome—usually a single, circular piece of DNA Ribosome—used for making proteins Plasmid—small circular piece of DNA Cell membrane (a.k.a. plasma membrane)— separates the cell from its external environment Pili—short, hairlike structures involved in reproduction and cell-to-cell contact Cell wall—protects and support the cell Capsule—located around the cell wall; bacteria with capsules are more likely to cause diseases

Reproduction Binary Fission:  Cell division in which the cell forms 2 identical cells  It is a form of asexual reproduction

Reproduction (cont.) Conjugation:  Process of exchanging genetic material though cell- to-cell contact; DNA and plasmids move through the pili from one bacterial cell to another  It is a form of sexual reproduction

Classification of Bacteria Cell Shape :  Spheres—cocci  Rods—bacilli  Spirals--spirilla Respiration:  Aerobes—use oxygen  Anaerobes—do not use oxygen

Classification of Bacteria (cont.) Cell Wall Composition:  Gram positive  Gram negative Nutrition:  Autotrophs  Heterotrophs—most bacteria are heterotrophic

Endospores Thick walled structures that can resist heat, drought, and radiation Bacterial cells can form endospores when living conditions become unfavorable

Transformation Picking up and incorporating DNA from dead bacterial cells

Roles of Bacteria in the Biosphere Decomposers: break down organic materials Bioremediation: bacteria are used to rid the environment of harmful substances (i.e. oil spills) Manufacturing: bacteria are used to ferment sugar to make cheese, yogurt and some beverages

Roles of Bacteria in the Biosphere (cont.) Medicine: bacteria are used to make human proteins such as insulin Nitrogen fixation: provides usable nitrogen for plants; ex: bacteria that live on roots of legumes Symbiosis: relationship between 2 organisms in which at least one of the partners benefits; ex: bacteria found in the intestines of mammals help with digestion and provide vitamins

Pathogens Bacteria that cause diseases are called pathogens Some pathogens use the body’s cells as food; ex: mycobacterium tuberculosis Other pathogens release toxins that can travel throughout the body; ex: streptococcus

Vaccines An injection of dead bacteria or virus will stimulate the immune system to make antibodies The antibodies will provide immunity against the disease

Antibiotics Antibiotics can work to block bacterial cell growth and reproduction Some antibiotics, like penicillin, attack the cell wall of the bacterial cells Penicillin makes holes in the wall causing water to rush into the cell and rupturing it