1. Bacteria and Viruses
© Lisa Michalek

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

4. Shapes of Bacteria Coccus - round shaped Bacillus – rod shaped
Spirillum – spiral shaped

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

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

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

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

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

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

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

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

13. Harmful Bacteria Some bacteria are not beneficial to man
Bacteria spoil food by secreting enzymes into the food causing it to rot
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

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

15. Harmful Bacteria 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

16. Controlling Harmful Bacteria
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.

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

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

19. Harmful Anaerobic Bacteria
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
Both diseases can be treated successfully by antibiotics if detected early enough

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

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

22. Virus Reproduction

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

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

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