Summer 2008 Workshop in Biology and Multimedia for High School Teachers

Why don’t antibiotics work for viral infections? Bacterial vs. Viral Infections Why don’t antibiotics work for viral infections? MicrobeLibrary.org; © Jean-Yves Sgro, University of Wisconsin http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleimages/simonson/Images/Streptococcus%20sobrinus%20fig1.jpg Polio Virus Streptococcus Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Bacterial Infections Viral Infections Can you think of some illnesses caused by viruses or bacteria? Bacterial Infections Viral Infections strep throat gastroenteritis cholera tuberculosis food poisoning botulism gangrene necrotizing fasciitis boils, abscesses pneumonia acne meningitis ulcers the flu colds AIDS hepatitis chicken pox gastroenteritis measles mumps E. Bola pneumonia West Nile cervical cancer Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Sample Bacterial Illness: Strep Throat en.wikipedia.org/wiki/Strep_throat http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleimages/simonson/Images/Streptococcus%20sobrinus%20fig1.jpg infectious agent: Streptococcus pyogenes - spherical bacteria usually found in pairs or chains most sore throats are actually caused by viruses and are NOT considered strep throat (~15-35% are strep throat) symptoms: sudden, severe sore throat, fever over 101°F, swollen tonsils and lymph nodes, white or yellow spots on the back of a bright red throat transmission usually by air-born bacteria incubation period prior to symptoms 2-5 days Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Sample Bacterial Illness: Strep Throat en.wikipedia.org/wiki/Strep_throat http://www.microbelibrary.org/microbelibrary/files/ccImages/Articleimages/simonson/Images/Streptococcus%20sobrinus%20fig1.jpg diagnosed with a throat culture and detection of strep-specific molecules treated with antibiotics, usually penicillin for 10 days Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Viral Illness: The Common Cold http://en.wikipedia.org/wiki/Image:Rhinovirus.PNG symptoms: sore throat, runny nose, nasal congestion, cough prevalance: 3 colds/ person/ year incubation period 2-5 days no cure for the common cold (or the flu) Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

basic structural properties of bacteria and viruses Should you ask for an antibiotic when you have a cold or the flu? To understand why antibiotics DO NOT work for viruses, you should understand: how antibiotics work basic structural properties of bacteria and viruses basic biosynthetic pathways of bacteria and viruses Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Structure of a Bacterial Cell Cell Wall -maintains cell structure -composed of peptidoglycan, a polymer of sugars and amino acids Flagella -tail-like structure used for locomotion Plasma Membrane -phospholipid bilayer surrounding cell -contains proteins that play a role in transport of ions, nutrients, and wastes http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Structure of a Bacterial Cell Nucleoid -region DNA is found in prokaryotes DNA -single double-stranded circular chromosome -no histone proteins Plasmid -small circular chromosome -may carry an antibiotic resistance gene Ribosomes -site of protein synthesis (translation) http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Some Features of an Infectious Bacteria virulence factors: molecules produced by a pathogen that aid in its survival in a host capsule: surrounds bacterial cell wall; protects bacteria from phagocytosis pili: allows bacteria to attach to and invade other cells despite mucous and cell-turnover enzymes: break down matrix between cells allowing bacteria to spread throughout tissues http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg Toxins exotoxins: cause lysis of specific host cells enterotoxins: cause secretion of fluid into the small intestine leading to vomiting and diarrhea endotoxins: cell-bound lipopolysaccharides; causes fever and inflammation Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

- occur independent of host cell Bacterial Transcription and Translation - occur independent of host cell transcription occurs using a single RNA polymerase transcription occurs in bacteria independent of a host cell translation occurs using a bacterial ribosome consisting of a large and small subunit Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Bacterial Reproduction -can occur independent of host cell -bacterial chromosome replicates -cell growth occurs (includes cell wall synthesis) -cell elongates (includes cell wall synthesis) and the two chromosomes segregate - ring forms of FtsZ fibers and closes dividing the cytoplasm in two http://en.wikipedia.org/wiki/Image:Binary_fission.png Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Properties of Viruses Basic Structure single stranded OR double stranded RNA or DNA protein shell capsid some have a lipid bilayer with embedded proteins Nucleic acid Protein Capsid Lipid Membrane Adapted from: http://en.wikipedia.org/wiki/Image:Virus_Replication.svg#file Host Cell Influenza Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College. http://microbewiki.kenyon.edu/index.php/Image:8430_lores.jpg

Properties of Viruses Virus Life Cycle virus attaches to host cell virus enters cell via endocytosis capsid degraded host transcribes viral DNA host ribosomes translate viral RNA new viruses assemble Virion Host Cell Nucleus Host Cell Ribosomes Host cell Golgi Host Cell Adapted from: http://en.wikipedia.org/wiki/Image:Virus_Replication.svg#file Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Antibiotic Treatment of Bacterial Infections antibiotics kill bacteria or prevent bacteria from dividing antibiotics are produced naturally by bacteria and fungi antibiotics are mass produced by growing huge cultures of the source microbe Why might microbes produce antibiotics in nature? to prevent the growth of microbe competitors Staphyloccocus aureus antibiotic http://en.wikipedia.org/wiki/Image:Staphylococcus_aureus_%28AB_Test%29.jpg Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College.

Antibiotics: Mechanisms of Action Inhibition of Bacterial Protein Synthesis - some antibiotics bind to the large or small subunit of the bacterial ribosome Examples: neomycin, streptomycin, azithromycin, erythromycin, tetracycline Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College. http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg

Antibiotics: Mechanisms of Action Inhibition of Cell Wall Synthesis -some antibiotics prevent peptidoglycan formation Examples: vancomycin, amoxicillin, ampicillin, penicillin Life Sciences-HHMI Outreach. Copyright 2008 President and Fellows of Harvard College. http://en.wikipedia.org/wiki/Image:Average_prokaryote_cell-_en.svg