Presentation on theme: "Ch 20: bacteria and viruses"— Presentation transcript:
1 Ch 20: bacteria and viruses Pathology - the scientific study of the nature of disease and its causesA 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, AIDSOther 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 knowHost - organism which provides nutrients, etc. to another organismParasite - 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 itDisease - an upset in the homeostasis of the host, resulting in generation of observable changesEpidemic - 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 envelopeViruses 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 DNADouble- or single-stranded RNA
7 Parts of Virus Nucleic acid -Double- or single-stranded DNA or Double- or single-stranded RNAcapsidIs the protein shell that encloses the viral genomeEnvelopesMembranous coverings (derived from the membrane of the host cell)18 250 mm70–90 nm (diameter)20 nm50 nm(b) AdenovirusesRNADNACapsomereGlycoprotein
9 Properties of virusesno cellular components - no cytoplasm, ribosomesthey cannot growonly reproduce inside a host cellthey 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 cellsThis is a bacteriophage, a type of virus that attacks bacteria. It is recognizeable because it looks like the lunar landing spaceship.See animation http://www.youtube.com/watch?v=41aqxcxsX2w&feature=related
11 Bacteriophages - infect bacteria Categories of VirusesBacteriophages - infect bacteriaRetroviruses - have RNA instead of DNA-most viruses are classified by what they infect: animal, plants, etcCheck out this Gallery at VirusworldMore 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 cycleshttps://youtube.googleapis.com/v/Rpj0emEGShQ
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 receptor2. 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 components5. 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 receptorPenetration - the virus is engulfed by the cell (Cell canenter Lysogenic or Lytic Cycle)
15 3. Biosynthesis - viral components are made (protein coat, capsid, DNA/RNA) 4. Maturation - assembly of viral components5. Release - viruses leave host cell to infect new cells (often destroys host)
16 Lytic vs Lysogenic Pathways of viruses Starring the phage named LambdaIntegration: viral DNA incorporated into bacterial DNA in lysogenic cyclePhage- short for bacteriophageLambda is a type of bacteriophageSee: http://highered.mcgraw-hill.com/sites/ x/student_view0/chapter20/lambda_phage_replication_cycle.html
17 Steps in Pathogenesis To cause disease, a pathogen must: Contact the host - be transmissibleColonize the host - adhere to and grow or multiply on host surfacesInfect the host - proliferate in host cells or tissuesEvade the host defense system - by avoiding contact that will damage itDamage 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 peopleThe 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 contaminationMethod 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 paralysisPoliomyelitis is a disease caused by infection with the poliovirus. The virus spreads by:Direct person-to-person contactContact with infected mucus or phlegm from the nose or mouthContact with infected fecesThe 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 cellHIV 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 cellshttps://youtube.googleapis.com/v/RO8MP3wMvqgSee 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 coatPrions - "rogue protein", believed to be the cause of Mad Cow Disease, also may cause Kuru in cannibal tribes http://highered.mcgraw-hill.com/sites/ 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 virusThis 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 virusInactivate VirusUse par of the VirusThe 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 lymphocytesOne 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.https://www.youtube.com/watch?v=B7ITZgag6w0
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 cellHIV 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 cellshttps://youtube.googleapis.com/v/RO8MP3wMvqgSee Also: HIV Coloring Assignment
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.https://www.youtube.com/watch?v=zuAhkH5uifoInfectious-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 mercuryThe 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
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 Structure1. 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 movement3. 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 DNA5. Plasmids are rings of DNA, used in reproduction6. Ribosomes in cytoplasm synthesize proteins
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 AntibioticsAntibiotics work by blocking vital processes in bacteria, killing the bacteria, or stopping them from multiplying.Broad or narrow spectrumQuinolones: use hydroxyl radicals, which are molecules that destroy the lipids and proteins that make up a cell's membrane and damage cell DNA, halting replicationMacrolide: protein synthesis inhibitorsPenicillins: 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 CyanobacteriaPhotosynthesize in the same manner as plants, with chlorophyll aBelieved to have first introduced oxygen into primitive atmosphereFormerly classified as algaeFor symbiotic relationships: like with fungus to form lichensOther photoautotrophs use photosystem I only and do NOT give off O2
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 benefitsMutualistic: both benefitParasitic: one benefits, other is harmedEndospore: 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 lipidsBacteria: glycerol liked to fatty acidsmethanogens- often in deep sea ventsHalophile- need high salt concentrationThermoacidophiles- not acidic environmentsMethanogens 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 environmentsthe red stuff on the rocksA thermoacidophile is an extreme archeon which thrives in acidous, sulfur rich, high temperature environments. Thermoacidophiles prefer temperatures of °C and pH between 2 and 3THE 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 clustersStrep – in chains
75 Bacillus subtilis Gram Positive *this is an example of a "poor" stain, it looks both pink and purple. Gram staining takes practice
76 TetanusRigid muscles from tetanus infectionAlso known as “lockjaw”
77 Clostridium botulism Gram positive Causes food poisoning that is sometimes fatalAll forms lead to paralysis that typically starts with the muscles of the face and then spreads towards the limbs. 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.
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 PestisThe 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.