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Ch 20: bacteria and viruses

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1 Ch 20: bacteria and viruses
Pathology - the scientific study of the nature of disease and its causes A  PATHOGEN is any disease causing agent.  Quick Exercise:  How many diseases can you think of? The A to Z of Germs...”

2 Some diseases are communicable (can pass to others), such as:
anthrax, swine flu, herpes, common cold, malaria, salmonella, AIDS Other diseases are not contagious: cancer, lupus, arthritis, allergies This unit will focus on the first type:  the disease, its agents, treatment and history and will cover three main areas of pathology 1.  Viruses  (virology) 2.  Bacteria  (bacteriology) 3.  Parasites (parasitology)

3 Host - organism which provides nutrients, etc. to another organism
Definitions you know Host - organism which provides nutrients, etc. to another organism Parasite - organism which lives at the expense of (and may even harm) its host; the parasite is generally smaller than the host and is metabolically dependent upon it Disease - an upset in the homeostasis of the host, resulting in generation of observable changes Epidemic - when a disease affects a community  Pandemic - when a disease affects the world

4 Adenovirus - cause of the common cold
Viruses: Are very small infectious particles consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope Viruses are pathogens that attack cells from the inside by hijack the cells own DNA and use it against you.  A virus cannot be treated with antibiotics, it can only run its course until your immune system kicks it out. ..Even then, the virus may lay dormant within the cells and come back at a later date


6 Viral genomes may consist of
Double- or single-stranded DNA Double- or single-stranded RNA

7 Parts of Virus Nucleic acid
-Double- or single-stranded DNA or Double- or single-stranded RNA capsid Is the protein shell that encloses the viral genome Envelopes Membranous coverings (derived from the membrane of the host cell) 18  250 mm 70–90 nm (diameter) 20 nm 50 nm (b) Adenoviruses RNA DNA Capsomere Glycoprotein

8 Virus Structure

9 Properties of viruses no cellular components - no cytoplasm, ribosomes they cannot grow only reproduce inside a host cell they consist of 2 major parts - a protein coat (capsid), and hereditary material (DNA or RNA) they are extremely tiny, much smaller than a cell and only visible with advanced electron microscopes

10 Parasitic Nature  Obligate intracellular parasites (they cannot exist independently) Specific to hosts (human, dog, some can cross species)  Specific to cells , the common cold is a virus that specifically attacks cells of the respiratory track (hence the coughing and sneezing and sniffling). HIV specifically attacks white blood cells This is a bacteriophage, a type of virus that attacks bacteria. It is recognizeable because it looks like the lunar landing spaceship. See animation

11 Bacteriophages - infect bacteria
Categories of Viruses Bacteriophages - infect bacteria Retroviruses - have RNA instead of DNA -most viruses are classified by what they infect: animal, plants, etc Check out this Gallery at Virusworld More virus images at the end of this presentation!

12 Viral Reproduction  Lytic cycle = reproduction occurs, cells burst Lysogenic cycle = reproduction does not immediately occur (dormancy)  Virulent = viruses that undergo both cycles

13 Steps of virus production (lytic cycle)
Viruses multiply, or replicate using their own genetic material and the host cell's machinery to create more viruses. Viruses cannot reproduce on their own, and must infect a host cell in order to create more viruses. Steps of virus production (lytic cycle) Attachment- capsid combines with receptor 2. Penetration - the virus is engulfed by the cell                    (Cell can enter Lysogenic or Lytic Cycle) 3. Biosynthesis - viral components are made                        (protein coat, capsid, DNA/RNA) 4. Maturation - assembly of viral components 5. Release - viruses leave host cell to infect new cells                      (often destroys host) (See McGraw Hill animation)

14 Penetration - the virus is engulfed by the cell (Cell can
Attachment- capsid combines with receptor Penetration - the virus is engulfed by the cell (Cell can enter Lysogenic or Lytic Cycle)

15 3. Biosynthesis - viral components are made                        (protein coat, capsid, DNA/RNA)
4. Maturation - assembly of viral components 5. Release - viruses leave host cell to infect new cells   (often destroys host)

16 Lytic vs Lysogenic Pathways of viruses
Starring the phage named Lambda Integration: viral DNA incorporated into bacterial DNA in lysogenic cycle Phage- short for bacteriophage Lambda is a type of bacteriophage See: x/student_view0/chapter20/lambda_phage_replication_cycle.html

17 Steps in Pathogenesis To cause disease, a pathogen must:
Contact the host - be transmissible Colonize the host - adhere to and grow or multiply on host surfaces Infect the host - proliferate in host cells or tissues Evade the host defense system - by avoiding contact that will damage it Damage host tissues - by physical (mechanical) or chemical means [Image: An emergency hospital ward in Kansas during the 1918 flu]

18 Ignaz Semmelweis (1850) Observed that women in the maternity wards died of childbed fever. He proposed that it was caused by doctors doing autopsies on the deceased women and then carrying the disease causing agent to healthy women who were in labor. His solution: Wash your hands before delivering babies! *The Germ Theory did not exist at this time

19 The Germ Theory (around 1860)
Single most important contribution by the science of microbiology to the general welfare of the world's people The theory that microorganisms may be the cause of some or all disease. Key to developing the germ theory of disease was a refutation of the concept of spontaneous generation. Specific aseptic techniques are employed to avoid microbial contamination Method of prevention of spoilage of liquid foodstuffs – Pasteurization

20 Jonas Salk -polio vaccine
viral disease that can affect nerves and can lead to partial or full paralysis Poliomyelitis is a disease caused by infection with the poliovirus. The virus spreads by: Direct person-to-person contact Contact with infected mucus or phlegm from the nose or mouth Contact with infected feces The virus enters through the mouth and nose, multiplies in the throat and intestinal tract, and then is absorbed and spread through the blood and lymph system. Vaccine: agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins. The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and keep a record of it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.


22 Human Immunodeficiency Virus (HIV)
Causes the disease AIDS  Retrovirus (RNA inside a protein coat)  Reverse Transcriptase makes DNA from the virus RNA  DNA inserts into host DNA  Proteins are assembled from the DNA code  Viruses assembled from the proteins  Viruses released from the cell HIV destroys a type of defense cell in the body called a CD4 helper lymphocyte.These lymphocytes are part of the body's immune system, the defense system that fights infections. (Link) HIV Animation - how virus infects cells See Also: HIV Coloring Assignment

23 Emerging Viruses: illnesses not previously known
AIDS, West Nile Virus, SARS, Ebola, Bird Flu  Could be mutations of known viruses  Could be viruses exposed when new areas were developed  Could have jumped species (avian flu, swine flu)

24 Related to Viruses  Viroids - even smaller than viruses, consist of RNA strands that lack a protein coat Prions - "rogue protein", believed to be the cause of Mad Cow Disease, also may cause Kuru in cannibal tribes x/student_view0/chapter20/how_prions_arise.html

25 Vaccines are made by growing a weakened or killed form of the virus
How Do Vaccines Work? Once you have gotten a virus, such as chicken pox, your body develops the immunity to that virus.   Vaccines are made by growing a weakened or killed form of the virus This form of the virus is injected into a person's body, which causes an immune response, and immunity to the virus. Vaccines are all different and specific, but have the same general goal: weaken the virus or bacteria in a way that allows the recipient to develop an immune response without developing any symptoms of infection. 3 ways they are made: Weaken the virus Inactivate Virus Use par of the Virus The HPV vaccines work like other immunizations that guard against viral infections. The investigators hypothesized that the unique surface components of HPV might create an antibody response that is capable of protecting the body against infection, and that these components could be used to form the basis of a vaccine. The HPV surface components can interact with one another to form virus-like particles (VLP) that are not infectious, because they lack DNA. However, these VLPs can attach to cells and stimulate the immune system to produce antibodies that can prevent the complete papillomavirus, in future encounters, from infecting cells. Although HPV vaccines can help prevent future HPV infection, they do not help eliminate existing HPV infections. EX: HPV vaccine

26 - Attacks immune cells: white blood cells called T lymphocytes
Developing a vaccine for AIDS is difficult because it is a RETROVIRUS.  RNA mutates easily and each individual virus can be slightly different from the others.  In fact, different viruses can exist within the same person. Why so dangerous? - Attacks immune cells: white blood cells called T lymphocytes One of the reasons why we do not yet have a cure for HIV infection is that the virus infects cells of the immune system that would normally fight such an infection. The main targets of HIV are white blood cells named CD4 T lymphocytes (so called because they have the protein CD4 in their membrane), and while more than 20 different drugs are available today to help control HIV, all of them act by blocking the cycle that HIV follows to infect these CD4 T lymphocytes. However, these treatments do not fully act on another cell of the immune system, the dendritic cell, which takes up HIV and spreads it to target CD4 T lymphocytes.

27 Human Immunodeficiency Virus (HIV)
Causes the disease AIDS  Retrovirus (RNA inside a protein coat)  Reverse Transcriptase makes DNA from the virus RNA  DNA inserts into host DNA  Proteins are assembled from the DNA code  Viruses assembled from the proteins  Viruses released from the cell HIV destroys a type of defense cell in the body called a CD4 helper lymphocyte.These lymphocytes are part of the body's immune system, the defense system that fights infections. (Link) HIV Animation - how virus infects cells See Also: HIV Coloring Assignment

28 RV = rotovirus; DTaP = diptheria, tetanus, pertussis (whooping cough);  Hib = haemophilus influenza type B;  PCV = pneumococcal vaccine; IPV = inactivated polio virus;  MMR = measles, mumps, rubella,  

29 1. What are the risks of vaccines? Are they safe?
Some parents are opting out of immunizations due to fears about vaccine safety.   In response, government agencies are producing commercials to encourage parents to get their child vaccinated. Infectious-disease specialists say these cases are due to a breakdown of what's known as "herd immunity." In order for a community to be fully protected against a disease, 80 to 90 percent of its population needs to have been vaccinated, says pediatrician Lance Rodewald, M.D., director of the Immunization Services Division of the CDC. Whenever coverage drops significantly below that level, a school, a church, or a neighborhood becomes susceptible to the disease. Babies who aren't old enough to get the shot yet are at the greatest risk of becoming sick. However, at least seven large studies in major medical journals have now found no association between the MMR vaccine and ASD -- and this February, The Lancet officially retracted Dr. Wakefield's original paper. (Revelations that he had failed to disclose connections to lawyers involved in vaccine litigation also emerged.) In March, the U.S. Court of Federal Claims, Office of Special Masters, a group of judges appointed to handle cases of families who believe immunizations were responsible for their child's autism, ruled that thimerosal in vaccines does not increase the risk of the disorder. (In 2008, a federal judge did award compensation to the family of Hannah Poling, a child with mitochondrial disorder, a rare condition that can show symptoms of autism, which she was diagnosed with shortly after receiving five vaccines.) Several demographic analyses have also found that autism rates continued to rise even after thimerosal was removed from all vaccines except some flu shots. So why are there so many stories of children developing autism shortly after immunizations -- not just in the media, but also in the Vaccine Adverse Event Reporting System, the federally cosponsored program that collects reports of suspected vaccine-related injury or illness? Experts believe that the association is almost certainly coincidental. Children get their first dose of the MMR vaccine at 12 to 15 months, the age at which autism symptoms typically become noticeable, says Paul Offit, M.D., director of the vaccine education center at Children's Hospital of Philadelphia and the author of Autism's False Profits: Bad Science, Risky Medicine, and the Search for a Cure. "It's the same reason why there are reports of SIDS deaths after DTaP (diphtheria, tetanus, and pertussis) immunizations," says Dr. Offit. "Infants start the DTaP vaccine between 2 and 6 months, which is the time they're also most likely to die from SIDS." In fact, some autism activists now believe that we should't even do more studies about a possible vaccine connection because they take attention and money away from important research that is investigating other potential causes of the disorder. "We have to move forward and be willing to accept what science tells us: Vaccines do not cause autism," says Alison Singer, president of the Autism Science Foundation and the mother of a child with autism. Discuss: 1.  What are the risks of vaccines?  Are they safe? 2.  Would you have your own child vaccinated? 3.  Should the government force immunizations?

30 Pro and Cons of vaccines
Vaccines can save children's lives. The ingredients in vaccines are safe in the amounts used. Major medical organizations state that vaccines are safe.: CDC, Food and Drug Administration (FDA), Institute of Medicine (IOM), American Medical Association (AMA), American Academy of Pediatrics (AAP), UNICEF, US Department of Health and Human Services (HHS), World Health Organization (WHO), Public Health Agency of Canada, Canadian Paediatric Society, National Foundation for Infectious Diseases (NFID), and American Academy of Family Physicians (AAFP). Adverse reactions to vaccines are extremely rare. Vaccines protect the "herd.” Vaccines save children and their parents time and money. Vaccines protect future generations. Vaccines eradicated smallpox and have nearly eradicated other diseases such as polio. Vaccine-preventable diseases have not disappeared so vaccination is still necessary. Vaccines provide economic benefits for society. Vaccines can cause serious and sometimes fatal side effects. Potentially harmful ingredients. thimerosal, an organic mercury The government should not intervene in personal medical choices. Mandatory vaccines infringe upon constitutionally protected religious freedoms. Vaccines can contain ingredients some people consider immoral or otherwise objectionable. (use part of stem cell line from 1960s) Vaccines are unnatural, and natural immunity is more effective than vaccination. Diseases that vaccines target have essentially disappeared. Most diseases that vaccines target are relatively harmless in many cases, thus making vaccines unnecessary. (chicken pocks, measles)

31 Various Images of Viruses for Your Viewing Pleasure





36 H1N1





41 BACTERIA: are microscopic Prokaryotes. (“before nucleus”)
Bacteria are classified into two kingdoms: Eubacteria (true bacteria) Archaebacteria (Ancient Bacteria). BACTERIA: are microscopic Prokaryotes.  (“before nucleus”) -Adapted to living in all environments (even some extreme) – they exist EVERYWHERE

42 Bacteria Structure 1. Outside the plasma membrane of most cells is a rigid cell wall that keeps the cell from bursting or collapsing  2. Flagella is used for movement 3.  Pilli (Fimbrae) help bacteria cling to surfaces (cilia) (Prokaryotes do not have organelles or a membrane bound  nucleus!) 4.  Nucleoid region contains a circular loop of DNA 5.  Plasmids are rings of DNA, used in reproduction 6.  Ribosomes in cytoplasm synthesize proteins


44 Cell Membrane – regulates what comes in and out of the cell
Cell Wall – maintains shape and form Capsule – found in virulent bacteria, helps evade immune system

45 II.  Reproduction in Prokaryotes
Binary fission is the splitting of a parent cell into two daughter cells; it is asexual reproduction in prokaryotes. 


47 Genetic recombination can occur in 3 ways in bacteria: 1
Genetic recombination can occur in 3 ways in bacteria:  1. Conjugation occurs when a bacterium passes DNA to a second bacterium through a tube (sex pilus) that temporarily joins two cells; the plasmid (DNA) is then exchanged


49 2.Transformation involves bacteria taking up free pieces of DNA secreted by live bacteria or released by dead bacteria. 

50 3. transduction: bacteriophages transfer portions of bacterial DNA from one cell to another.
-Plasmids can carry genes for resistance to antibiotics and transfer them between bacteria by any of these processes


52 Plasmid – an extra bit of DNA, used in sexual reproduction
Plasmids are also used in genetic engineering Some bacteria form resistant endospores in response to unfavorable environmental conditions.

53 Antibiotics Antibiotics work by blocking vital processes in bacteria, killing the bacteria, or stopping them from multiplying. Broad or narrow spectrum Quinolones: use hydroxyl radicals, which are molecules that destroy the lipids and proteins that make up a cell's membrane and damage cell DNA, halting replication Macrolide: protein synthesis inhibitors Penicillins: work by destroying the structure of a cell wall

54 Prokaryotic Nutrition
Bacteria differ in their need for, and tolerance of, oxygen (O2). a.   Obligate anaerobes: no O2 are unable to grow in the presence of O2; this includes anaerobic bacteria that cause botulism, gas gangrene, and tetanus. b.   Facultative anaerobes: O2 optional are able to grow in either the presence or absence of gaseous O2. c.   Aerobic organisms: need O2 (including animals and most prokaryotes) require a constant supply of O2 to carry out cellular respiration. staphylococcus is a gram-positive, facultative anaerobe

55 Autotrophic Prokaryotes
a.   Photoautotrophs are photosynthetic and use light energy to assemble the organic molecules they require. b.   Chemoautotrophs make organic molecules by using energy derived from the oxidation of inorganic compounds in the environment. Reduce CO2 by oxidizing ammonia, nitrites and nitrates (nitrogen fixing bacteria),

56 Cyanobacteria Photosynthesize in the same manner as plants, with chlorophyll a Believed to have first introduced oxygen into primitive atmosphere Formerly classified as algae For symbiotic relationships: like with fungus to form lichens Other photoautotrophs use photosystem I only and do NOT give off O2

57 Nitrogen Cycle

58 Heterotrophic Prokaryotes:
a. chemoheterotrophs that take in pre-formed organic nutrients. ( most common free living bacteria) b. aerobic saprotrophs, decompose almost any organic molecule (in presence of oxyge)     Detritivores (saprophytic bacteria) are critical in recycling materials in the ecosystem; they decompose dead organic matter and make it available to photosynthesizers. Bacteria have an important role to play in breaking down materials in the environment. Some are harmful and break down material we'd rather keep, like this image of an infection of necrotizing fasciitis (flesh-eating bacteria)

59 Symbiotic relationship
Commensalism: one benefits Mutualistic: both benefit Parasitic: one benefits, other is harmed Endospore: dormant form of a pathogen that can become active in favorable conditions

60 Archaea “ancient bacteria” “extreme prok
Archaea “ancient bacteria” “extreme prok.” (but more closely related to eukaryote) Prokaryote with glycerol linked to hydrocarbon lipids Bacteria: glycerol liked to fatty acids methanogens- often in deep sea vents Halophile- need high salt concentration Thermoacidophiles- not acidic environments Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They are classified as archaea, a domain distinct from bacteria. They are common in wetlands, where they are responsible for marsh gas, and in the digestive tracts of animals such as ruminants and humans, where they are responsible for the methane content of belching in ruminants and flatulence in humans.

61 the red stuff on the rocks
THERMOACIDOPHILE – extreme archeon which thrives in acidous, sulfur-rich, high temperature environments the red stuff on the rocks A thermoacidophile is an extreme archeon which thrives in acidous, sulfur rich, high temperature environments. Thermoacidophiles prefer temperatures of °C and pH between 2 and 3 THE FUTURE BELONGS TO ARCHAE!

62 Bacteria Shape & Naming
The Gram stain procedure (developed in the late 1880s by Hans Christian Gram) differentiates bacteria. a. Gram positive bacteria stain purple, whereas Gram negative bacteria stain pink. b. This difference is dependent on the thick or thin (respectively) peptidoglycan cell wall.

63 Bacteria Shapes Cocci – spheres Bacilli – rods Spirilla - spirals
Staph – in clusters Strep – in chains

64 Streptococcus


66 Gram Negative

67 Gram Positive


69 Identify Gram Negative, Bacillus

70 Gram Positive, Bacillus

71 Identify Gram Positive Staphylococcus

72 Streptococcus Strains are responsible for strep throat, and flesh eating bacteria

73 Staphylococcus aureus
Staph means “bunch of grapes” in greek. oxacillin-resistant Staphylococcus aureus

74 Staph Infection

75 Bacillus subtilis Gram Positive
*this is an example of a "poor" stain, it looks both pink and purple.  Gram staining takes practice

76 Tetanus Rigid muscles from tetanus infection Also known as “lockjaw”

77 Clostridium botulism Gram positive
Causes food poisoning that is sometimes fatal All forms lead to paralysis that typically starts with the muscles of the face and then spreads towards the limbs.[1] In severe forms, it leads to paralysis of the breathing muscles and causes respiratory failure. In view of this life-threatening complication, all suspected cases of botulism are treated as medical emergencies, and public health officials are usually involved to prevent further cases from the same source.[1]

78 A form of botulism is used in BOTOX treatments, as it paralyzes the muscles of the face and effectively smooths wrinkles. Results may vary.

79 Yersinia Pestis The black plague, this bacteria was carried on the fleas of rats.  It was responsible for the deaths of thousands of Europeans from the 8th to the 14th century.

80 Bacillis Anthracis (Anthrax)

81 Bacillus (unknown strain)

82 Mycoplasmas Rickettsia rickettsi Causes pneumonia
Rocky Mountain Spotted Fever, carried by ticks

83 E. Coli

84 Spirilla Bacteria

85 Salmonella

86 Name this Bacteria Answer: Staphylococcus

87 Plush Germs Syphilis E. Coli

88 Gonorrhea The Plague (Black Death)

89 Culturing Bacteria




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