1. Viruses & Bacteria
Chapter 2.3 and 7

2. Vocabulary virus capsid lytic infection lysogenic infection retrovirus
vaccine
coccus
bacillus
spirilium
obligate aerobes
obligate anaerobes
facultative anaerobes
binary fission
conjugation
plasmid
pathogen
antibiotic

3. I. Viruses General Characteristics
don’t belong in any kingdom, not considered “alive”
don’t use energy or carry on metabolism
considered acellular or nonliving
no cytoplasm or organelles
only 1 type of nucleic acid (DNA or RNA), cells have both
does not come directly from another virus
can survive without water

4. Viral Characteristics
All viruses are small, only visible through electron microscope
Consist of two parts:
Nucleic acid - DNA or RNA, but never both
Outer protein coat called a “capsid”
Protein coat determines the shape of the virus
Three basic shapes:
Geometric shape, ex: Influenza or HIV
Spiral (helical) shaped, ex: tobacco mosaic virus
Bacteriophage - virus that infects bacteria

5. Tobacco Mosaic Virus Influenza Virus
T4 Bacteriophage
RNA
Capsid
proteins
Head
Tail sheath
DNA
Tail fiber

7. Viral Infection Lytic Cycle
Attachment -virus attaches itself to the host cell
Viruses are very specific for certain cells
Injection - a virus use enzymes to enter the cell wall of host cell and its nucleic acid is injected into the host cell
Replication - viral DNA or RNA takes over the host cell
Host cell copies viral nucleic acids, proteins coat (capsid), and viral enzymes
RNA viruses (retroviruses) have special enzyme to change its RNA into DNA
Assembly - viral parts are put together to form new complete viruses
Release or lysis - new viruses break down host’s cell wall (killing the host cell) and they are released to invade other host cells

8. Lytic Infection
Attachment - virus attaches itself to the receptor site of host cell. Viruses are very specific

9. Injection -virus use enzymes to enter the cell wall of host and its nucleic acid is injected into the host cell

10. Replication - The viral nucleic acid is replicated and produces proteins that form the viral enzymes and capsids
- Host cell replicates viral nucleic acids, coat proteins, and viral enzymes
- RNA viruses (retroviruses) have special reverse transcriptase enzyme to change its RNA into DNA

11. Assembly - viral parts are put together to form new complete viral units

12. Lysis or release - new viruses release enzymes to break down host’s cell wall (killing the host cell) and they are released to invade other host cells

13. What is the definition of Lytic Infection?
Injection of genetic information
Attachment
Replication
Assembly
Lysis or Release of new virus
What is the definition of Lytic Infection?

14. Lysogenic Cycle Attachment - same as lytic cycle
Injection- same as lytic cycle
Splicing - the viral DNA is spliced (inserted) into the DNA of the host
Cellular Duplication - During normal cell division the viral DNA is also copied and passed on with the cell’s own DNA.
Activation - An environmental stress stimulates the viral DNA and it goes into the lytic cycle.

15. How many of you have had cold sores?
Herpes Simplex 1 Virus

16. Lysogenic Infection
Attachment - virus attaches itself to the receptor site of host cell. Viruses are very specific – this is the same as the Lytic Infection.

17. Injection - virus use enzymes to enter the cell wall of host and its nucleic acid is injected into the host cell. Again this is the same as the Lytic Infection.

18. Splicing - the viral DNA is spliced into the DNA of the host

19. Cellular Duplication - During normal cell division the viral DNA is also duplicated and passed on with the cell’s own DNA

20. Activation - An environmental stress stimulates the activation of the viral DNA and stages 3-5 of the lytic cycle begin - Replication - The viral nucleic acid is replicated and produces proteins that form the viral enzymes and capsids

21. Assembly - viral parts are put together to form new complete viral units

22. Lysis or release - new viruses release enzymes to break down host’s cell wall (killing the host cell) and they are released to invade other host cells

24. Lytic cycle
Lysogenic Cycle

25. Retroviruses (RNA viruses)
retrovirus = virus that contains RNA which is copied to DNA (backwards) when it infects a host cell
RNA viruses do not have an enzyme to fix copying mistakes
mutations build up in RNA viruses much more rapidly creating new versions of the virus
Ex: new flu strains each year
AIDS and some cancers are caused by retroviruses
ex: HIV

26. Retroviruses

27. Viruses vs. Cells
DRAW Table 19-11, pg 483

28. Beneficial Effects of viruses
Can be used to insert desirable genetic information into cells
Genetically engineered organisms like tulip coloration
Deliver correct genes into human cells
Used to kill bacteria
Viral Diseases
Ex: rabies, mumps, measles, AIDS,warts, shingles, chicken pox, influenza, polio, hepatitis A, B, & C, common cold & many more

29. Mumps

30. Measles

31. Shingles

32. Polio

33. Combating Viral Infections
our immune system
prevention by vaccines
antiviral drugs - treat the immediate symptoms, but these are not cures
Ex: Tamiflu, Relenza

34. Needle Tip

35. II. Bacteria General characteristics Unicellular and lack a nucleus
Earliest known life forms
Size: 1-5 micrometers

36. Bacterial Structure
DRAW Bacterial Anatomy
All bacteria have an outer cell wall.
Some have a sticky slime layer around cell wall called a capsule.
Very simple internal organization
Cytoplasm with very few organelles
DNA

37. Bacterial Structure Ribosome Cell Membrane Cell Wall Peptidoglycan
Pili
Flagellum
DNA
(nucleoid)

38. Classifying Bacteria Two Domains
Bacteria = (eubacteria) largest group, cell walls contain peptidoglycan (a carbohydrate)
Archaebacteria = lack peptidoglycan, live in extreme environments, & their DNA sequences are more like eukaryotes

40. Identifying Prokaryotes
Shape & Arrangement
Coccus = spherical shaped
single coccus
diplococci (pairs)
streptococci (chains)
staphylococci (clusters)

41. Staphylococci (clusters)

42. streptobacilli single bacillus diplobacilli streptobacilli
Bacillus = rod shaped cells
single bacillus
diplobacilli
streptobacilli
streptobacilli

43. spirillium = spiral shaped

44. Test Your Bacterial Shape and Arrangement Knowledge

46. How they obtain nutrients
decomposer - live on dead things
symbiotes - two organisms living together
parasitic
commensalistic
mutualistic

47. Best Growth Conditions
Warmth; °C
Dark
Moisture
Food
Where can we normally find these conditions?
Movement
Many forms have flagella (whip-like structures) for movement.
Some bacteria have pili which allow them to attach to other things.

48. Feeding & Digestion Autotrophic photosynthetic, ex: cyanobacteria
chemosynthetic, ex: in deep sea hydrothermal vents

49. Why does food get mushy when it rots?
Heterotrophic
extracellular digestion
secrete enzymes
digest their food
absorb food back into their cells by diffusion
Why does food get mushy when it rots?

50. Circulation, Excretion and Respiration
by diffusion
aerobes = require a constant supply of oxygen in order to live
ex: Mycobacterium tuberculosis
2 types of anaerobes
Some must live without oxygen
ex: C. botulinum spores found in honey
Some survive with or without oxygen
ex: Escherichia coli

51. Reproduction Asexual form spore (thick internal wall to enclose DNA)
binary fission - cell division splitting into two equal cells
spore formation – for harsh conditions
form spore (thick internal wall to enclose DNA)
allows spore to wait until conditions are better for growth

52. Sexual conjugation - exchange genetic information
plasmids are independent circular pieces of DNA in bacteria

53. Beneficial Effects - 99% of bacteria
decomposition of organic material
nitrogen fixation in bean plants
Symbiotic relationships, ex: E.coli in our intestines
used to make antibiotics
food production: e.g. yogurt, cheese, vinegar
used as a tool in genetic engineering

54. Harmful Effects - 1% of bacteria
Pathogenic (causes disease)
directly damaging cells as they digest cells for food
indirectly damaging cells by releasing toxins which damage hosts
trigger body's immune response, ex: fever or inflammation
ex: botulism, tuberculosis, gonorrhea, typhoid fever, bubonic plague, diphtheria, cholera, tetanus, etc.
TB X-ray
Diphtheria
Bubonic Plague
Tetanus

55. Other problems caused by bacteria
food spoilage (many species)
food poisoning, ex: Salmonella
disorders like boils, pimples, pneumonia, and some forms of arthritis

56. Diseases Caused By Bacteria
Pathogen
Prevention
Tooth decay
Lyme disease
Tetanus
Tuberculosis
Salmonella food
poisoning
Pneumonia
Cholera
Streptococcus mutans
Borrelia burgdorferi
Clostridium tetani
Mycobacterium tuberculosis
Salmonella enteritidis
Streptococcus pneumoniae
Vibrio cholerae
Regular dental hygiene
Protection from tick bites
Current tetanus vaccination
Vaccination
Proper food-handling
practices
Maintaining good health
Clean water supplies

57. Controlling Bacteria
Antibiotics
compounds that block the growth and reproduction of bacteria, made from fungi and other bacteria
ex: penicillin, streptomycin, tetracycline, etc.
problems with antibiotics
bacteria develops resistance
kills off good bacteria as well as bad
inhibits body's natural immunity

58. lowering temperature slows growth of bacteria, ex: refrigerator
sterilization = process of destroying ALL microorganisms
disinfectants = chemical solutions that kill most pathogens (ex: alcohol in hand sanitizer)
Food Storage & Processing
pasteurization = applying heat to kill pathogens (ex: milk)
lowering temperature slows growth of bacteria, ex: refrigerator
chemical treatments such as salt or vinegar
properly canned food
Sterilizing an inoculating loop
Typical disinfectant
Pasteurization of milk