1. Viruses and Bacteria

2. What is a Virus? A virus is a tiny, nonliving particle that enters and reproduces inside a living cell. A virus is considered nonliving because they do not have all the characteristics necessary for life. What are the characteristics necessary for life?

3. What is a Virus? Viruses are not cells and do not have cells. Viruses also do not use their own energy to grow or respond to their surroundings. Viruses cannot make or eat food and do not produce waste.

4. What is a Virus? The only thing that makes a virus similar to an organism is that it can multiply. Viruses multiply in a different way than organisms do. They can only multiply when they are inside a living cell.

5. What is a Virus? The organism that a virus enters and multiplies inside of is called a host. – The virus acts as a parasite, which is something that lives in or on a host and causes it harm. – Almost all viruses destroy the cells where they multiply.

6. Virus Shape and Size Viruses can come in all different types of shapes. Viruses also come in different sizes, but all viruses are much, much smaller than even the smallest cells. – This makes viruses even smaller than bacteria.

7. Virus Structure Although viruses look different from each other, they all have a similar structure. All viruses have two basic parts: – A protein that protects the virus – An inner core of genetic material

8. Virus Structure Each virus contains unique surface proteins which allow the virus to attach to a host cell.

9. Active Viruses After entering a cell, an active virus’s genetic material takes over cell functions. The cell quickly begins to produce the virus’s proteins and genetic material. These parts then assemble into new viruses. When the cell is full, it bursts open, releasing hundreds of new viruses as it dies.

10. Hidden Viruses After a hidden virus enters a host cell, its genetic material becomes part of the cell’s genetic material. Hidden viruses do not appear to affect the cell’s functions and may stay inactive for many years.

11. Hidden Viruses Each time the host cell with a hidden virus divides, the virus’s genetic material is copied along with the host’s genetic material. Under certain conditions, the virus then becomes active.

12. Viruses and Disease Many diseases are caused by viral infections. Some of these diseases, like colds, are gone after a short period of time, while others never go away.

13. Gene Therapy In gene therapy, scientists inject genetic material they want reproduced into a virus, and then as the virus enters a host cell, the cell reproduces that genetic material instead of the virus.

14. Bacteria Bacteria were discovered by a Dutch merchant named Anton van Leeuwenhoek. He made this discovery in the late 1600s when he saw wormlike organisms in a sample he was looking at under a microscope.

15. Bacteria Cells Bacteria are single-celled organisms. They are prokaryotes, which means that their genetic material is not held in a nucleus.

16. Bacteria Cells Bacteria cells have cell walls that protect them. Beneath the cell walls is a cell membrane that controls what can go in or out of the cell.

17. Bacteria Cells Like plant and animal cells, bacteria have a gel-like cytoplasm filling the inside of the cell. In the cytoplasm are ribosomes which produce proteins. The genetic material can also be found in the cytoplasm.

18. Bacteria Cells Bacteria cells do not have any of the other organelles that plant and animal cells have. Some bacteria also have flagellum coming off of the cell that help the cell move. See page 49.

19. Bacteria Cells Bacteria cells come in three different shapes: – Spherical – Rodlike – Spiral

20. Bacteria Cells Bacteria can vary greatly in size, the largest being about the size of a period printed in a book. Most are much, much smaller and cannot be seen without the help of a microscope.

21. Bacteria Food Some bacteria are autotrophs, which means they make their own food. – Some use energy from the sun like plants. – Others use energy from chemical substances in their environment.

22. Bacteria Food Other bacteria are heterotrophs, which means they need to eat. – These organisms consume a variety of different food sources.

23. Bacteria Reproduction When bacteria have plenty of food, the right temperature, and other suitable conditions, they thrive and reproduce frequently. – However, these three things are often not all present.

24. Bacteria Reproduction Bacteria reproduce through binary fission. Binary fission is when one cell divides to form two identical cells.

25. Bacteria Reproduction Binary fission is considered asexual reproduction because it only involves one parent. – Because only one parent is involved, the offspring is completely identical to the parent.

26. Bacteria Reproduction Some bacteria can undergo sexual reproduction, which involves two instead of one parent. – This happens through a process called conjugation, where one bacterium gives its genetic material to another.

27. Bacteria Reproduction Conjugation does not produce new bacteria, it just changes the genetic makeup of bacteria.

28. Bacteria Reproduction If the environment that a bacteria is living in is not suitable for reproduction, some bacteria can form endospores. – An endospore is a small, round, thick-walled cell that exists inside of the bacteria cell and contains some cytoplasm and genetic material.

29. Bacteria Reproduction Endospores can survive many years in harsh conditions. Once the conditions are suitable for reproduction, endospores open up and the bacteria begins to grow and multiply.

30. Bacteria in Nature Most bacteria are actually harmless or helpful to people. – In fact, people depend on bacteria.

31. Bacteria in Nature Bacteria are involved in: – Oxygen production – Food production – Environmental recycling – Environmental cleanup – Health – Medicine

32. Bacteria in Nature Oxygen Production – Autotrophic bacteria which use the sun’s energy to make their own food produce oxygen, just like plants. – Since bacteria existed long before plants, and the atmosphere used to lack oxygen, scientists believe oxygen was first added to Earth’s atmosphere by these autotrophic bacteria.

33. Bacteria in Nature Food Production – Many foods would not exist if it weren’t for bacteria. For example: – Cheese – Pickles – Vinegar – Alcohol – Yogurt – Sour cream – Many more

34. Bacteria in Nature Food Production – Some bacteria break down food chemicals, causing them to go bad. – This can be slowed or stopped by refrigeration, heating, or pasteurization. Pasteurization is the heating of liquids so high that harmful bacteria is killed without changing the taste.

35. Bacteria in Nature Environmental Recycling – Some heterotrophic bacteria are decomposers, which means that they break down large chemicals in dead organisms into smaller chemicals. – By breaking down these chemicals, the chemicals can then be reused by living organisms.

36. Bacteria in Nature Environmental Cleanup – Some bacteria is used to help cleanup after oil spills, since they take in this oil as food.

37. Bacteria in Nature Health – Bacteria living in your body helps in all kinds of ways. Some help you digest food. Some make vitamins. Some fight off disease-causing organisms.

38. Bacteria in Nature Medicine – Some bacteria either produce medicine or are used as medicine. Penicillin Insulin