1. Bacteria and Viruses Biology II 2007

3. Bacteria  All bacteria are prokaryotes.  Prokaryotes are single-celled organisms that lack nuclei.  They are identified by their shapes, the chemical nature of their cell walls, the ways they move, and the ways they obtain energy.  Prokaryotes typically range from 1 to 5 micrometers, making them much smaller than eukaryotes (10 to 100).

4. Bacteria  Bacteria are vital to maintaining the living world.  Some are producers that capture energy by photosynthesis.  Others help to break down the nutrients in dead matter and the atmosphere, allowing other organisms to use the nutrients.  There are two kingdoms of prokaryotes or bacteria: Eubacteria and Archaebacteria.

5. Eubacteria  Eubacteria is the larger of the two bacteria kingdoms.  They live almost everywhere.  Some live in the soil, while others infect large organisms and cause disease.  Eubacteria are usually surrounded by a cell wall that protects the cell form injury and determines its shape.

6. Eubacteria  The cell wall of eubacteria consists of a carbohydrate called peptidoglycan.  Inside the cell wall is the cell membrane and then the cytoplasm.

8. Archaebacteria  Under a microscope, archaebacteria are very similar to eubacteria.  Archaebacteria lack peptidoglycan in the cell wall and their membrane lipids are quite different.  The DNA sequence of key archaebacterial genes are more like those of eukaryotes than those of eubacteria.  Many scientists believe that archaebacteria may be the ancestors of eukaryotes.  Most archaebacteria live in very harsh environments.

9. Identifying Prokaryotes--Shapes  Rod-shaped prokaryotes are called bacilli.  Spherical prokayotes are called cocci.  Spiral and corkscrew-shaped prokaryotes are called spirilla.  Some bacteria form long chains or gather in clusters.

11. Identifying Prokaryotes—Cell Walls  Scientists use a method called gram staining to differentiate between the two different types of cell walls in eubacteria.  Gram-positive bacteria have a cell wall of peptidoglycan and absorb only the violet stain.  Gram-negative bacteria have an additional lipid layer and absorb the red counter-stain.

12. Identifying Prokaryotes-- Movement  Some bacteria are propelled by flagella, which are whip-like structures used for movement.  Other bacteria lash, snake, and spiral forward.  A few bacteria glide slowly across a layer of slime-like material they secrete.  Many bacteria do not move at all.

13. Identifying Prokaryotes— Energy  Bacteria can obtain their energy in two different ways:  make own food (autotrophs)  by feeding on other organisms (heterotrophs)

14. Autotrophs  Bacteria that carry out photosynthesis are called photoautotrophs. These organisms convert light energy into chemical energy.  Bacteria that obtain their energy directly from inorganic molecules are called chemoautotrophs.  get their energy from chemical reactions involving ammonia, hydrogen sulfide, nitrites, sulfur, or iron

15. Heterotrophs  Many bacteria are like humans and obtain energy by taking in organic molecules and breaking them down.  Other bacteria are photosynthetic but still need specific organic molecules for proper nutrition. These organisms are called photoheterotrophs.

16. Identifying Prokaryotes— Energy  Bacteria need a constant supply of energy. This energy is released by cellular respiration, which requires oxygen, and fermentation, which does not.  Organisms that require oxygen are called obligate aerobes.  Organisms that are poisoned by oxygen are called obligate anaerobes.  Organisms that can survive with or without oxygen are called facultative anaerobes.

17. Do you think that chemoautotrophs are aerobic or anaerobic? Explain your answer.

18. Identifying Prokaryotes—Growth and Reproduction  Many can divide as often as once every 20 minutes. However, bacteria are limited by food and space like other organisms.  Some bacteria under go binary fission, which involves the organism doubling its DNA and splitting in half to form two daughter cells.  Bacteria can undergo conjugation, in which one bacterium transfers its genetic material to another bacterium.  Other bacteria can form spores when conditions are not favorable. One such spore is called an endospore. An endospore can remain dormant for months or centuries.

19. If I were contaminated by a single bacterium that divided every 20 minutes, how many bacteria would be present in 48 hours?

20. Is binary fission considered sexual or asexual reproduction Is binary fission considered sexual or asexual reproduction? Explain your answer.

21. Bacteria E. coli Gonnorhoeae ClostridiumStaphlycoccus

22. Bacteria in Nature--Decomposers  If all bacteria died, life could not continue. Plants would leach all of the nutrients from the soil and would eventually die. Soon, the animals that depended on the plants for nourishment would also die.  As decomposers, bacteria help the ecosystem recycle nutrients.  Bacteria break down dead matter into simpler substances, which are released into the soil and taken up by the roots of plants.  As recyclers, bacteria perform important steps in sewage treatment. Bacteria break down complex compounds in the sewage into simpler ones, producing purified water, nitrogen and carbon dioxide gases, and left over products that are used for fertilizers.

23. Bacteria—Nitrogen Fixers  Plants and animals depend on bacteria for nitrogen, which is the building block for protein.  Even though the atmosphere is made up of approximately 80% nitrogen gas, plants cannot use that nitrogen directly.  Nitrogen must be “fixed” chemically to ammonia or other nitrogen compounds.  Certain bacteria are the only organisms with the ability to fix nitrogen in such a way.

24. What it is called when bacteria “fixes” nitrogen into usable ammonia?

25. Bacteria—Nitrogen Fixers  Many plants have symbiotic relationships with nitrogen fixing bacteria.  The bacterium Rhizobium lives on the roots of soybeans and other legumes. The bacteria gets food (sugars) and the plant receives nitrogen.

26. Bacteria and Disease  Bacteria can be found everywhere in nature, but only a few are actually harmful.  A bacterium that causes disease is known as a pathogen.  Bacteria can cause disease in two general ways.  Some damage the tissues of the infected organism directly by breaking them down for food.  Other bacteria release toxins (poisons) that harm the body.

27. Bacteria and Disease  Heterotrophic bacteria cause damage by damaging cells and tissues.  Most food poisonings are a direct result of toxins released by bacteria.  Many bacterial diseases can be prevented by stimulating the body’s immune system with vaccines.  If a bacterial infection does occur, there are a number of drugs and natural compounds that can be used to attack and destroy the invading bacteria.

28. What do you call a drug that can attack and destroy bacteria?

29. Common Bacterial Diseases DiseasePathogenCharacteristics Impetigo Staphylococcus aureus; Streptococcus pyogenes Superficial skin infection Folliculitis Staphylococcus aureusInfection of hair follicle Toxic Shock Syndrome Staphylococcus aureusFever, rash, and shock Acne Propionibacterium acnes Inflammatory lesions origninating with accumulations of sebum that rupture a hair follicle Botulism Clostridium botulinumCauses paralysis and respiratory failure

30. Common Bacterial Diseases DiseasePathogenPrevention Tooth decayStreptococcus mutansRegular dental hygiene Lyme diseaseBorrelia burgdorferiProtection from ticks TetanusClostridium tetaniCurrent tetanus vaccination Salmonella food poisoning Salmonella enteritidisProper food-handling PneumoniaStreptococcus pneumoniae Maintaining good health

31. Human uses of Bacteria  Humans use bacteria everyday to create and/or manufacture certain food products.  Foods in which bacteria is used: cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut, and wines.  Bacteria are also used in industry to digest petroleum, which help clean up oil spills.  New research suggests that bacteria adapted to extreme environments can be used for medicines and the food industry.

32. Controlling Bacteria  Most bacteria are harmless, and many are even beneficial. However, humans still wish to control bacterial growth due to outbreaks of “bad” bacteria.  Sterilization destroys bacteria by subjecting them to either to great heat or to chemical action. Most bacteria are killed in boiling water or disinfectants.  To prevent food spoilage, one can refrigerate foods. Bacteria grow slowly are cool temperatures.  Other methods of killing bacteria in foods is by boiling, frying, or steaming, which raise the temperature of the food to a point where the bacteria are killed.

33. Anaerobic

34. 4000 times the mass of the Earth… If the bacteria had an unlimited supply of food and space.

35. Asexual

36. Nitrogen fixation

37. antibiotics