BACTERIA Structures in a Typical Bacteria n n

BACTERIA

Structures in a Typical Bacteria n n Chromosome— usually a single, circular piece of DNA Ribosome—used for making proteins Plasmid—small circular piece of extrachromosomal DNA Flagella—long hairlike structures growing from a cell that aid in movement Flagella Chromosome Plasmid Ribosome

Structures in a Typical Bacteria (cont. ) n n 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 supports the cell Capsule—located around the cell wall; bacteria with capsules are more likely to cause diseases Cell Membrane Flagella Cell Wall Pilus Plasmid Chromosome Capsule Ribosome

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

Reproduction (cont. ) n Conjugation: ¨ Process of exchanging genetic material through 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 n Cell Shape: ¨ Spheres—cocci ¨ Rods—bacilli ¨ Spirals—spirilla n Respiration: ¨ Strict Aerobes—require oxygen ¨ Strict Anaerobes—do not use and, in fact, die in the presence of oxygen ¨ Facultative Anaerobes—survive with or without oxygen

Classification of Bacteria (cont. ) n Cell Wall Composition: ¨ Gram positive—have thick cell walls that retain the Gram stain (purple) ¨ Gram negative—have thin cell walls that don’t retain the Gram stain (pink) n Nutrition: ¨ Autotrophs ¨ Heterotrophs—most heterotrophic bacteria are

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

Transformation n Picking up and incorporating DNA from dead bacterial cells

Importance of Bacteria Decomposers: break down the nutrients in dead matter n Bioremediation: bacteria are used to rid the environment of harmful substances (i. e. oil spills) n Manufacturing: bacteria are used to ferment sugar to make cheese, yogurt and some beverages n

Importance of Bacteria (cont. ) n n n Medicine: bacteria are used to make human proteins such as insulin Nitrogen fixation: process that converts nitrogen gas to a usable form for plants 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 n Some pathogens break down the body’s cells to use as food; ex: mycobacterium tuberculosis n Other pathogens release toxins that can travel throughout the body and interfere with the host’s normal activities; ex: streptococcus n

Vaccines A preparation of dead or weakened pathogens that prompts the immune system to produce antibodies n The antibodies will provide immunity against the disease n

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