Viruses and bacteria

1. Viruses and bacteria

2. Bacteria • The word bacteria is so familiar that we will use it as a common term to describe prokaryotes. • Prokaryotes come in many sizes and shapes, they are unicellular organisms that lack a nucleus. • Classified into two kingdoms….Eubacteria and Archaebacteria

3. Eubacteria • The larger of the two kingdoms • Live almost everywhere…water, land, and within the human body. • Very diverse with many different lifestyles.

4. Eubacteria • They contain a cell wall which is made of a carbohydrate called peptidoglycan. • Also have a cell membrane and cytoplasm. • Some include flagella for movement. • The pili are involved in cell-to-cell contact.

5. Archaebacteria • They are alike to eubacteria in the fact that they are small, lack nuclei, and have a cell wall but chemically they are quite different. • They LACK the carbohydrate called peptidoglycan in their cell walls. • The DNA sequences of key archaebacterial genes are more like those of eukaryotes than those of eubacteria. • Scientists reason that archaebacteria my be the ancestors of eukaryotes.

6. Archaebacteria • They live in harsh environments. • Some produce methane gas. • They can live in oxygen free environments. • Some live in thick mud, intestines of animals, hot springs, or extremely salty environments.

7. Identifying Prokaryotes • Prokaryotes are identified by characteristics such as • Shape • Chemical Nature of Cell Walls • Movement • How they obtain energy.

8. Prokaryotes by Shapes • Rod-Shaped prokaryotes are called bacilli

9. Prokaryotes by Shapes • Spherical prokaryotes are called cocci

10. Prokaryotes by Shapes • Spiral shaped prokaryotes are called Spirilla

11. Prokaryotes by Shapes

12. Prokaryotes by Shapes

13. Prokaryotes by Movement • Some move some do NOT • Some have flagella while others lash, snake, or spiral forward. • Still others glide slowly along a layer of slime like material they secrete.

14. Prokaryotes by Metabolic Diversity • Bacteria will vary depending on their source of energy and whether or not they use oxygen for cellular respiration. • Heterotrophs or Autotrophs

15. Prokaryotes that are Heterotrophs • Some heterotrophic prokaryotes must take in organic molecules for both energy and a supply of carbon they are called chemoheterotrophs. Most animals (humans too) are chemoheterotrophs. • A smaller group of heterotrophs prokaryotes are called photoheterotrophs. These organisms are photosynthetic BUT they also need to take in organic compounds such a carbon sources.

16. Prokaryotes that are Autotrophs • Some groups of autotrophs called photoautotrophs use light energy to convert carbon dioxide and water to carbon compounds and oxygen in a process similar to that of green plants. • These live in an environment where light is abundant like near the surfaces of lakes, streams and oceans. • Ex: cyanobacteria

17. Prokaryotes that are Autotrophs • Other prokaryotes make organic carbon molecules from carbon dioxide but do NOT require light. They are called chemoautotrophs. • Instead, they use energy directly from chemical reactions involving ammonia, hydrogen sulfide, nitrites, sulfur, or iron. • Some chemoautotrophs live in deep in the darkness of the ocean. They obtain energy from hydrogen sulfide gas that flows from hydrothermal vents on the ocean floor.

18. Prokaryotes- Energy • Bacteria need a constant supply of energy. This energy can be released by the process of cellular respiration and fermentation or BOTH. • Obligate Aerobes- require constant source of oxygen • Ex; Mycobacterium tuberculosis…cause tuberculosis • Obligate anaerobes- must live in the absence of oxygen. • Ex: Clostridium botulinum found in soil…it can grow in canned food because it does not require oxygen • Facultative anaerobes- can survive with or without oxygen. Because of this they can live just about anywhere. • Ex: E.coli—lives anaerobically in the large intestines and aerobically in sewage or contaminated water.

19. Prokaryotes- Binary Fission • When a bacterium has grown so that it has nearly doubled in size, replicates its DNA and divides in half, producing 2 daughter cells. • This is known as binary fission. • Does not exchange genetic info….asexual reproduction.

20. Prokaryotes- Conjugation • During Conjugation, a hollow bridge forms between two bacterial cells, and genes move from one cell to the other. • This transfer of genetic information increases genetic diversity in populations of bacteria.

21. Prokaryotes- Spore Formation • Ex: Bacillus anthracis…which causes the disease anthrax is one such bacteria. • During harsh conditions some bacteria have developed a structure called a spore. • This spore will enclose a portion of the bacteria’s DNA and cytoplasm. • It can remain dormant for months or years until more favorable conditions. • This allows the bacteria to survive.

22. Viruses!! • Viruses can be very difficult to understand. • A biologist, Wendell Stanley in 1935 inferred that viruses were NOT alive. • Viruses are particles of nucleic acid, protein, and in some cases lipids. • Viruses differ widely in terms of size and structure • They all enter living cells and once inside use the machinery of the infected cell to produce more viruses.

23. Viruses!! • Most viruses are so small then cannot be seen without an electron microscope. • A typical viruses is composed of a core of DNA or RNA surrounded by a protein coat called a capsid. The simplest viruses contain only a few genes whereas the most complex may have more than a hundred genes.

24. Viruses!! • The capsid includes proteins that enable a virus to enter a host cell. • Once inside the, the viral genes are expressed. • Sometimes the genetic program causes the host cell to make copies of the virus, and in the process the host cell is destroyed. • Because the virus must bind to certain proteins on a cell surface and then use a host’s genetic system MOST viruses are highly specific to the cells they infect.

25. Viruses!! • Plant viruses infect plant cells • Animal viruses usually only infect certain related species • Viruses that infect only bacteria are called bacteriophage.

26. Virus Structures Bacteriophage

27. Virus Structures Tobacco Mosaic Virus

28. Virus Structures Influenza Virus

29. Viral Infection • Once the virus is inside the host cell two different process may occur. • Lytic Infection or Lysogenic Infection

30. Viral Infection • Lytic Infection- a virus enters a cell , make a copy of itself, and causes the cell to burst. • Lysogenic Infection-, a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cells DNA • The viral DNA that is embedded in the host’s DNA is called a prophage. It may remain in the host cell for many generations before becoming active. • Assignment- Draw, color, and label Figure 19.10 on page 481

31. Retroviruses • Some viruses contain RNA as their genetic information are called Retroviruses. • When they infect a cell they must use their RNA to create a DNA copy, which can then be inserted into a host cell. • They get their name “retro” meaning backwards because usually we go from DNA to RNA and in this cause it goes backwards…RNA to DNA • The virus that causes acquired immune deficiency syndrome (AIDS) is a retrovirus.

32. Diseases caused by Bacteria and Viruses • Bacteria and viruses are everywhere in nature. • Its pathogens--disease causing agents that get all the attention. • Bacteria can cause disease in one of two ways. • 1. The bacteria damage the cells and tissues of the infected organisms directly by breaking down the cells for food. • Ex: Tuberculosis • 2. Other bacteria release toxins that travel throughout he body interfering with the normal activity of the host. • Ex: Strep throat and diphtheria

33. Preventing Bacterial Disease • Some bacterial diseases caused by pathogenic bacteria include Lyme disease, tetanus, strep throat and tooth decay. • Many such disease can be prevented by stimulating the body’s immune system with a vaccine. • A vaccine is a preparation of weakened or killed pathogens. • When injected into the body, a vaccine sometimes prompts the body to produce immunity to the disease.

34. Preventing Bacterial Disease • Antibiotics can also be used once the bacterial infection does occur. • Antibiotics are compounds that block the growth and reproduction of bacteria. • Penicillin and tetracycline are antibiotics. • The dramatic increase in human life expectancy during the past two centuries can be attributed to the better understanding on how to prevent and cure bacterial infections.

35. Controlling Bacteria • Although most bacteria are harmless and many are beneficial, the risks of bacterial infection are great enough to warrant efforts to control bacterial growth. • There are various methods used to control bacterial growth, including sterilization, disinfectants, and food processing.

36. Viral Disease in Humans • Like bacteria, viruses produce disease by disrupting the body’s normal equilibrium. • The virus will attack and destroy certain cells in the body, causing symptoms. • Unlock bacterial diseases, viral diseases cannot be treated with antibiotics. • The best way to protect against viruses is prevention often by the use of vaccines. • The symptoms of the infections can often be treated but NOT the viruses.