Bacteria and Viruses Bacteria u Bacteria are microscopic

Bacteria and Viruses

Bacteria u Bacteria are microscopic, unicellular (one-celled) organisms that lack a nuclear membrane u Bacteria can live on land, in water, and in the air – They also live in and on both living and dead plants and animals u Most bacteria are heterotrophs. – Heterotrophs are organisms that cannot make their own food

Shapes of Bacteria u Coccus - round or sphere shaped u Bacillus – rod shaped u Spirillum – spiral shaped

Structure of Bacteria u. A bacterium is made up of a thick cell wall that encloses and protects cellular material

Bacterial Nutrition u Some bacteria live separately and others remain together to form colonies – Colonies are large groups of bacteria

Bacterial Nutrition u There are bacteria that live as parasites – A parasite absorbs food materials from other living organisms called their hosts u Others digest and absorb food materials from dead organisms – These bacteria are called saprophytes

Beneficial Bacteria u Most bacteria are beneficial (helpful) to humans u Bacteria are decomposers that cause decay – Decomposers are organisms that break down dead organisms and return the nutrients to the soil

Beneficial Bacteria u Many bacteria are used to produce food and life -saving drugs – Bacteria are used to make cheese, pickles, yogurt, vinegar, and sauerkraut

Beneficial Bacteria u By using methods of gene transplanting, bacteria have been encouraged to produce substances such as insulin

Beneficial Bacteria u The human intestinal tract contains millions of bacteria – Many of these bacteria help the digestive process and others produce vitamins

Beneficial Bacteria u Bacteria are also used in the tanning of leather, the curing of tobacco, and the production of food for feeding cows

Harmful Bacteria Some bacteria are not beneficial to man u Bacteria spoil food by secreting enzymes into the food causing it to rot u – Along with enzymes, other substances produced by bacteria are released into the food – Some of these substances are toxic, making the food poisonous to humans and other organisms

Harmful Bacteria u Bacteria in large numbers can pollute (dirty) lakes, streams, and drinking water u During respiration, bacteria reduce the dissolved oxygen content in water supplies

Harmful Bacteria u Many bacteria are pathogenic – A pathogen is an organism that causes disease and/or infection – Some bacterial diseases of humans are tuberculosis, tetanus, and strep throat

Controlling Harmful Bacteria u Antiseptics, disinfectants, and antibiotics are used to control pathogenic bacteria – An antibiotic is a chemical that can stop the growth of some bacteria – Bacteria are able to produce types that are resistant to certain antibiotics – When this happens, new antibiotics must be developed.

Controlling Harmful Bacteria u Bacteria can also be killed in foods by – pasteurization – canning – chemical preservatives – radiation – steam/pressure – salt curing – dehydration (drying)

Harmful Anaerobic Bacteria u Some bacteria can live anaerobically and cause botulism – A dangerous type of food poisoning, in foods that have not been properly canned

Harmful Anaerobic Bacteria u Two other anaerobic bacteria can cause venereal diseases – Gonorrhea (causes sterility) – Syphilis (can result in death) A venereal disease is a contagious disease that a person gets through sexual contact u Both diseases can be treated successfully by antibiotics if detected early enough u

Viruses u. A virus is not a cell u It is made up of genetic material inside a protein coat u Viruses do not carry on most metabolic activities

Viruses u They can only reproduce inside a living cell called the host cell u Outside the host cell, a virus is “lifeless” and often exists as a crystal u A virus has no means of locomotion

Virus Reproduction

Negative Virus Influences u They cause infections in both plants and animals u Some viruses cause tumors and warts u They also destroy cells and are responsible for human diseases such as – polio – measles – mumps – influenza – hepatitis – colds – AIDS

Human Papilloma Virus - Warts Rabies Virus Influenza Virus - Flu Human Immunodeficiency Virus AIDS

Positive Virus Influences u Certain viruses are used in the control of insect pests u Others are used in genetic research u Scientists have been able to use viruses to biologically control caterpillars of the European pine sawfly and the gypsy moth