1. Bacteria are one of the simplest forms of life and they appeared on Earth long before other forms of life. It is estimated that bacteria have been present for about 3.4 billion years and they are found almost everywhere on Earth.

2. If we take all living organisms, we can split them into two major types. Organisms

3. Eukaryotes, Organisms Eukaryotes

4. And prokaryotes Organisms Eukaryotes Prokaryotes

5. This diagram illustrates some of the differences and similarities between eukaryotic and prokaryotic cells. Genetic Material

6. A eukaryotic cell has (click) a nucleus which is enclosed by a membrane. Genetic Material

7. Whereas a prokaryotic cell (click) has its genetic material right in the cytoplasm, and it is not enclosed by a membrane Genetic Material

8. Eukaryotic cells contain mitochondria Genetic Material

9. But we can see that the prokaryotic cell does not have any of these organelles in its cytoplasm. Genetic Material

10. Prokaryotic cells have a cell wall. Genetic Material

11. But so do many eukaryotic cells, (click) such as plants. Genetic Material Plants

12. Some prokaryotic cells have a hard outer coating called a capsule. Genetic Material Plants

13. We see that both eukaryotes and prokaryotes have (click) ribosomes in their cells. These are needed by both types of organisms to produce proteins. Genetic Material Plants

14. And we see that the cells of both eukaryotes and prokaryotes (click) have a cell membrane. This is crucial for all cells, as it is needed to contain all of the cell’s parts. Genetic Material Plants

15. So we can summarize what we looked at here, the cells in eukaryotes contain organelles such as mitochondria, but they also have a golgi body, lysosomes, endoplasmic reticulum, and in the case of plants, chloroplasts. Organisms Eukaryotes Prokaryotes Cells contain organelles such as: Mitochondria Golgi body Lysosomes Endoplasmic reticulum Chloroplasts (in plants) The nucleus contains genetic material and is surrounded by a membrane.

16. In Eukaryotes, genetic material of a cell is in a nucleus which is surrounded by a nuclear membrane. Organisms Eukaryotes Prokaryotes Cells contain organelles such as: Mitochondria Golgi body Lysosomes Endoplasmic reticulum Chloroplasts (in plants) The nucleus contains genetic material and is surrounded by a membrane.

17. The cells of Prokaryotes contain no mitochondria, golgi body, lysosomes, endoplasmic reticulum, or chlroplasts. They are much more primitive than eukaryotes. Organisms Eukaryotes Prokaryotes Cells contain organelles such as: Mitochondria Golgi body Lysosomes Endoplasmic reticulum Chloroplasts (in plants) The nucleus contains genetic material and is surrounded by a membrane. Cells contain no mitochondria, Golgi body, lysosomes, endoplasmic reticulum, or chloroplasts The nucleus contains genetic material and is surrounded by a membrane.

18. The genetic material in a prokaryotic cell is simply floating around in the cytoplasm. It is not contained in a nucleus. Organisms Eukaryotes Prokaryotes Cells contain organelles such as: Mitochondria Golgi body Lysosomes Endoplasmic reticulum Chloroplasts (in plants) The nucleus contains genetic material and is surrounded by a membrane. Cells contain no mitochondria, Golgi body, lysosomes, endoplasmic reticulum, or chloroplasts The genetic material is in the cytoplasm

19. Eukaryotes include all life forms except bacteria and some species of blue-green algae. So animals and plants are all eukaryotes. Eukaryotes

20. We’ll make a note here that Eukaryotes include all life forms except bacterial and some species of blue-green algae. Organisms Eukaryotes Prokaryotes All life forms except bacteria and some blue-green algae Bacteria Blue-green algae

21. Prokaryotes include bacteria and some species of blue-green algae. Escherichia coli bacteria Blue-green algae Prokaryotes

22. We’ll make a note of that here. (click) Prokaryotes can be bacteria (click) or blue-green algae Organisms Eukaryotes Prokaryotes All life forms except bacteria and some blue-green algae Bacteria Blue-green algae

23. Let’s take a closer look at a bacterium. This diagram represents one type of bacterium. We’ll look at some of the important structures and organelles A Bacterium

24. Bacteria are surrounded by an outer coating, called a capsule. This protects the bacterium. It is actually a factor in disease because it protects bacteria from being attacked by our immune system. A Bacterium Capsule Outer protective coating

25. Right inside the capsule is the cell wall, shown in yellow in this diagram. This helps keep the cell together and offers more protection. A Bacterium Capsule Outer protective coating Cell Wall

26. The cell membrane is the next layer, shown in green on this diagram. The cell membrane helps control what enters or leaves the bacterial cell. A Bacterium Capsule Outer protective coating Cell WallCell Membrane

27. Like all other living cells, bacterial cells contain ribosomes. These are the organelles which manufacture proteins. All the ribosomes in bacteria are free-floating in the cytoplasm. Bacterial cells do not have endoplasmic reticula. A Bacterium Capsule Outer protective coating Cell WallCell Membrane Ribosomes Manufacture proteins

28. This is called a plasmid. Plasmids are strands of DNA which are separate from the main bacterial DNA, which is in the center. They provide a blueprint for the cell to produce certain types of proteins. A Bacterium Capsule Outer protective coating Cell WallCell Membrane Plasmid Separate piece of DNA Ribosomes Manufacture proteins

29. These are pilli. They are hair-like appendages found on the outside of many bacteria. Some viruses can attach to these and infect bacterial cells. Some of these are also used to connect to other bacteria and exchange genetic material. A Bacterium Capsule Outer protective coating Cell WallCell Membrane Plasmid Separate piece of DNA Pilli Hair-like appendages Ribosomes Manufacture proteins

30. The cytoplasm is the gel-like liquid that fills the interior of a bacterial cell. Many organelles float around in the cytoplasm. A Bacterium Capsule Outer protective coating Cell WallCell Membrane Plasmid Separate piece of DNA Pilli Hair-like appendages Cytoplasm Ribosomes Manufacture proteins

31. This is the main piece of bacterial genetic material, or DNA. It is not contained in a membrane-bound nucleus, like DNA is in eukaryotic cells. This DNA in a bacterium is often called a nucleoid because it is not a true nucleus. A Bacterium Capsule Outer protective coating Cell WallCell Membrane Bacterial DNA Called a nucleoid Plasmid Separate piece of DNA Pilli Hair-like appendages Cytoplasm Ribosomes Manufacture proteins

32. This tail-like appendage is called a flagellum. It whips back and forth and helps bacteria move around. Some bacteria like this one, has one flagellum, while others have more than one. A Bacterium Capsule Outer protective coating Cell WallCell Membrane Bacterial DNA Called a nucleoid Plasmid Separate piece of DNA Pilli Hair-like appendages Cytoplasm Flagellum Ribosomes Manufacture proteins

33. Bacteria can be classified as having three main shapes.

34. Cox-eye are spherical, or egg-shaped bacteria. Cocci Spherical or egg-shaped bacteria

35. Bacilli are rod-shaped bacteria Bacilli Rod-shaped bacteria

36. And spirilla are spiral-shaped bacteria Spirilla Spiral-shaped bacteria

37. Many bacteria are beneficial to us. Let’s look at a few of them.

38. Lactobacillus Acidophilus is naturally present in the human digestive system. It is added to some yogurts as a probiotic, which helps us digest milk products. Lactobacillus Acidophilus is naturally present in the human digestive system. It is added to some yogurts as a probiotic, which helps us digest milk products.

39. Lactococcus lactis is used in making cheese and buttermilk. It helps turn a sugar in milk called lactose, into lactic acid.

40. Es share eek ee ya coal eye is naturally present in the large intestine of humans and other warm-blooded species. It produces some B vitamins and vitamin K, needed for blood clotting. There are many strains of E coli bacteria. Most are harmless, but there are some strains that can cause disease. Escherichia coli is naturally present in the large intestine of humans and other warm-blooded species. It produces some B vitamins and vitamin K, needed for blood clotting.

41. Bacteria that are harmful and can cause disease are said to be pathogenic

42. The word Pathogenic means “able to cause disease” Pathogenic means “able to cause disease”

43. Helicobacter pylori Is found in the stomach of some people. In some cases, it can cause stomach ulcers. Helicobacter pylori Is found in the stomach of some people. In some cases, it can cause stomach ulcers.

44. Escherichia coli O157:H7 is a strain of E. coli that can cause severe diarrhea and in some cases, kidney failure. It can be contacted by eating contaminated raw green-leaf vegetables or uncooked meat. Although contamination is rare, it occasionally occurs, and leads to recalls of certain food products. Escherichia coli O157:H7 is a strain of E. coli that can cause severe diarrhea and in some cases, kidney failure. It can be contacted by eating contaminated raw vegetables or uncooked meat.

45. Salmonella N-tare-ica is contacted by eating food from infected cattle or poultry. It can sometimes be found in raw eggs. It can cause a type of “food poisoning” called salmonella. Salmonella enterica is contacted by eating food from infected cattle or poultry. It can sometimes be found in raw eggs. It can cause “food poisoning”.

46. Clostridium bot chew lin um causes botulism, which is contacted by eating improperly prepared home-canned foods that are low in acid. It can also occur from infected wounds. Botulism can be fatal if not treated very quickly. Clostridium botulinum causes botulism, which is contacted by eating improperly prepared home- canned foods that are low in acid. It can also occur from infected wounds.

47. Borrelia burg door furry causes Lyme Disease. It is contacted mainly through tick bites. If bitten by a tick, seek medical attention immediately. Untreated Lyme disease is very serious. Borrelia burgdorferi is the main cause of Lyme Disease. It is contacted mainly through tick bites. If bitten by a tick, seek medical attention immediately. Untreated Lyme disease is very serious.

48. We’ve looked at only a few bacteria here, (click) Scientists have identified thousands of species of bacteria but it has been estimated that there are millions of bacterial species on Earth. Scientists have identified thousands of species of bacteria but it has been estimated that there are millions of bacterial species on Earth. The total mass of all the bacteria on Earth is greater than the total mass of all plants and animals. The number of bacterial cells in our body is about ten times the number of our cells.

49. In fact, it is thought that the total mass of all the bacteria on Earth is greater than the total mass of all of the plants and animals. Scientists have identified thousands of species of bacteria but it has been estimated that there are millions of bacterial species on Earth. The total mass of all the bacteria on Earth is greater than the total mass of all plants and animals. The number of bacterial cells in our body is about ten times the number of our cells.

50. It is interesting to note that the number of bacterial cells living in our body is about ten times the number of our cells. Scientists have identified thousands of species of bacteria but it has been estimated that there are millions of bacterial species on Earth. The total mass of all the bacteria on Earth is greater than the total mass of all plants and animals. The number of bacterial cells in our body is about ten times the number of our cells.

51. "Cell types" by Science Primer (National Center for Biotechnology Information). Vectorized by Mortadelo2005. - SVG version of Image:Celltypes.png.. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Celltypes.sv g#mediaviewer/File:Celltypes.svg http://commons.wikimedia.org/wiki/File:Esche richiaColi_NIAID.jpg License: CC0 Public Domain / FAQFree for commercial use / No attribution requiredFAQ Acknowledgements for Images Used

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53. This image is a work of the Centers for Disease Control and Prevention, part of the United States Department of Health and Human Services, taken or made as part of an employee's official duties. As a work of the U.S. federal government, the image is in the public domain.Centers for Disease Control and PreventionUnited States Department of Health and Human ServicesU.S. federal governmentpublic domain Acknowledgements for Images Used

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55. "Lactobacillus acidophilus (259 09) Lactobacillus acidophilus (Döderlein bacillus)" by Doc. RNDr. Josef Reischig, CSc. - Author's archive. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Lactobacillus_acidophil us_(259_09)_Lactobacillus_acidophilus_(D%C3%B6derlein_bacill us).jpg#mediaviewer/File:Lactobacillus_acidophilus_(259_09)_La ctobacillus_acidophilus_(D%C3%B6derlein_bacillus).jpg "Lactococcus lactis" by Minyoung Choi from Cupertino, CA, USA - Streptococcus lactis. Licensed under CC BY-SA 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Lactococcus_lactis. jpg#mediaviewer/File:Lactococcus_lactis.jpg Acknowledgements for Images Used

56. "Immunohistochemical detection of Helicobacter (1) histopatholgy" by User: KGH - User:KGH. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Immunohistochem ical_detection_of_Helicobacter_(1)_histopatholgy.jpg#medi aviewer/File:Immunohistochemical_detection_of_Helicobac ter_(1)_histopatholgy.jpg "EColiCRIS051-Fig2" by USDA (Pina Fratamico Microbiologist/Lead Scientist) - USDA source. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:EColiCRIS051- Fig2.jpg#mediaviewer/File:EColiCRIS051-Fig2.jpg Acknowledgements for Images Used

57. "Salmonella enterica serovar typhimurium 01" by Centers for Disease Control and Prevention - Centers for Disease Control and Prevention. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Salmonella_enteric a_serovar_typhimurium_01.jpg#mediaviewer/File:Salmonell a_enterica_serovar_typhimurium_01.jpg "Clostridium botulinum 01" by Content Providers: CDC - This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #2107. English | Slovenščina | +/−. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Clostridium_botulinum_01. png#mediaviewer/File:Clostridium_botulinum_01.png Acknowledgements for Images Used

58. "Borrelia burgdorferi (CDC-PHIL -6631) lores" by Photo Credit:Content Providers(s): CDC - This media comes from the Centers for Disease Control and Prevention's Public Health Image Library (PHIL), with identification number #6631. English | Slovenščina | +/−Cropped and uploaded originally to (http://en.wikipedia.org/wiki/Image:Borrelia_image.jpg). Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Borrelia_burgdorferi_(CDC- PHIL_ 6631)_lores.jpg#mediaviewer/File:Borrelia_burgdorferi_(CDC- PHIL_-6631)_lores.jpg Acknowledgements for Images Used "Average prokaryote cell- en" by Mariana Ruiz Villarreal, LadyofHats - Own work (Source: Typical prokaryotic cell, Chapter 4: Mutagenicity of alkyl N- acetoxybenzohydroxamates, Concept 1: Common Features of All Cells, Cells - Structure and Function). Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Average_prokaryote_cell- _en.svg#mediaviewer/File:Average_prokaryote_cell-_en.svg