Disease Diseases I. Bacteria II. Viruses including are disease-causing organisms Biol 105 Lecture 17 Chapter 13a Domain Bacteria Characteristics 1. Domain Bacteria are prokaryotic 2. Lack a membrane-bound nucleus, lack membrane bound organelles 3. Have ribosomes, but different that eukaryotic 4. Generally have a single chromosome Domain Bacteria Characteristics 5. Cell wall present in many species 6. Reproduction by binary fission 7. Great metabolic diversity Bacteria Shapes 1. Coccus spherical 2. Bacillus rod 3. Spirilla spiral shaped Figure 13a.1a Figure 13a.1b Figure 13a.1c 1
Some Bacteria can Cause Disease Pathogenic Bacteria Beneficial Bacteria Disease caused by bacteria are caused by: Toxins or enzymes released by the bacteria By the response of the host Some Escherichia coli cause health problems vomiting and diarrhea, may cause kidney failure Clostridium botulinum bacteria produce the toxin that causes botulism, interferes with nerve function Borrelia burgdorferi bacteria that uses deer ticks to move from host to host, causes Lyme disease Examples of Beneficial Bacteria: Lactobacillus Nitrogen fixing bacteria Phosphorus fixing bacteria Normal flora in body Antibiotics Designing Antibiotics Antibiotic resistance Chemicals that inhibit the growth of microorganisms They work by disrupting the processes that are common to bacteria but not to human cells What target would you use to design an antibiotic? Bacteria populations can rapidly mutate, antibiotic resistance can result The few bacteria that mutate and are resistant to antibiotics will repopulate the area with antibiotic resistant bacteria The overuse and misuse of antibiotics are largely to blame for increasing antibiotic resistance When bacteria become resistant to antibiotics, the drugs are no longer effective Should you take antibiotics if you have a cold caused by a virus? Viruses Virus Characteristics 1. True 2. False 50% True 50% False Viruses are responsible for many illnesses including colds. Antibiotics do not kill viruses 1. Non cellular 2. Not living organisms 3. Have genetic material (DNA or RNA) Many have a protein coat = capsid Some have a fatty membrane = envelope with glycoproteins Are very small Viruses may remain inactive or latent in the host for many years. 2
Typical Virus Virus Replication Steps Viral Replication Glycoprotein Envelope Capsid Viral DNA 1. Attach to a host cell 2. Penetrate host cell by endocytosis 3. Production of genetic material and proteins (Transcription and Translation) 4. Assemble new viral particles 5. Release by budding or by rupturing host cell Step 2: Penetration All or part of the virus enters the host cell. With animal cells, the entire virus enters the cell. Step 1: Attachment The virus attaches to a specific receptor on the host cell. This is responsible for host specificity. Plasma membrane (b) of host cell Step 3: Production of viral genetic information and proteins The virus directs structures in the host cell to make parts of new viruses. Step 4: Assembly of new viruses Newly synthesized viral genetic information and proteins are used to form new viruses. Step 5: Release New viruses leave the cell. Some viruses leave by a process called budding (or shedding), as shown here. (a) Figure 13a.3a Figure 13a.3b Human Immunodeficiency () is a Retrovirus and AIDS is the virus responsible for Acquired Immune Deficiency Syndrome (AIDS) has RNA It uses reverse transcriptase to turn RNA into DNA Viral proteins surrounding the core s genetic information is in the form of RNA. Reverse transcriptase is the enzyme that rew rites s RNA as DNA. The virus contains: mrna Enzymes including: reverse transcriptase, integrase, and protease Core proteins The envelope comes from the cell membrane of the previous host cell. The tip of s protein spike fits into receptors on the host cell, allow ing to enter the cell. s protein spikes are embedded in the envelope of. Figure 17a.7 AIDS: A Global Epidemic At the end of 2007, from 30.6 to 36.1 million people globally were living with an infection Africa is currently the area hardest hit by More than 22.5 million people there were living with /AIDS in 2007 Virus Replication Steps 1. Glycoproteins on envelope bind to CD4 receptors on a host cell = helper T cell 2. Penetrate host cell by endocytosis 3. Uses the enzyme reverse transcriptase to turn its mrna into DNA Virus Replication Steps 4. Uses the enzyme integrase to integrate the viral DNA into the host DNA 5. Transcribes viral DNA to make mrna 6. Translates viral mrna to make viral proteins PLAY AIDS in South Africa 3
Virus Replication Steps 7. Uses the enzyme protease to assemble new viral particles 8. Release by budding attacks the helper T cells. Not only does the attack the helper T cells but they hijack them so they are produce more viruses Why can t we fight like we do other viruses? It multiplies in the immune system and attacks the immune system, making fighting it harder It mutates rapidly so it is hard fight Helper T cells are this type of White Blood Cell Replication 1. Lymphocytes 2. Macrophages 3. Neutrophils 4. Eosinophils 25% 25% 25% 25% For a period of time the viral DNA may not be transcribed, or will be transcribed at a low rate. Then the T cell will begin to transcribe the viral DNA at a high rate Lymphocytes Macrophages Neutrophils Eosinophils Figure 17a.8 Treatments Treatments Treatments There is no cure. These treatments can slow the spread of the virus in the body but not completely get rid of it There are drugs that work to slow the progress of in the body. What targets would you use to design an drug? drugs: 1. Fusion inhibitors 2. Reverse transcriptase inhibitors 3. Protease inhibitors 4. Integrase inhibitors 5. entry inhibitors 4
Transmission and AIDS The target of is Found in all bodily secretions Transmitted by blood, semen, vaginal secretions, and breast milk Major modes of transmission Unprotected sexual contact Contact with contaminated blood From an infected mother to her fetus and through breast milk 1. Cytotoxic T cells 2. Helper T cells 3. B cells 4. Natural Killer cells 25% 25% 25% 25% Cytotoxic T cells Helper T cells B cells Natural Killer cells Read Chapter 14 for next lecture What are the characteristics of bacteria? What are the shapes of bacteria (latin names)? How do bacteria cause disease? What are examples of pathogenic bacteria? What are examples of beneficial bacteria? Be able to discuss antibiotic resistance, including the causes and effects. How would you design an antibiotic, what target would you use? What are characteristics of viruses? What are the steps of viral replication, be able to discuss in detail viral replication? What enzymes and genetic material do particles have and what is their function? How would you design drugs what targets would you attach, what are the classes of drugs currently available? How is spread? Definitions Pathogen, binary fission, antibiotics, capsid, envelope, glycoproteins, latent, integrase, reverse transcriptase and protease, retrovirus 5