Bacteria & Viruses

DO NOW: WHAT ARE THE CHARACTERISTICS OF VIRUSES? BACTERIA? WHAT KINGDOM DO EACH OF THESE BELONG? ARE THEY LIVING? WHY OR WHY NOT ?

What do you already know?  What are the differences between viruses and bacteria?  Are all bacteria harmful?  When you get a cold, should you take an antibiotic to help you get better?  What’s the best and easiest thing to do to avoid getting sick?

Bacteria  Bacteriology is the study of bacteria  Bacteria are prokaryotic, unicellular organisms containing DNA and ribosomes.  Bacteria have ALL the characteristics of living things.  Bacteria have the greatest percentage of the biomass on Earth!

Bacterial Structure  Basic structure of bacteria: Ribosome Pili DNAFlagellum Peptidoglycan* Cell wall Cell membrane

Bacterial Structure  Bacteria have three distinct shapes: spherical (cocci) rod-shaped (bacilli) spiral (spirilla)

Bacteria  Bacteria have a variety of important uses:  Help make interesting food (buttermilk, yogurt, cheese, sauerkraut, pickles, and olives, etc…)  Decompose organic matter (recycle nutrients from dead organisms; break down sewage into simpler compounds)  Nitrogen fixation (chemically changes nitrogen gas, N 2, into ammonia, NH 3, so plants can make amino acids)  Human health (bacteria on skin help prevent infection & bacteria in gut helps digest food & make vitamins)  Biotechnology (used to make antibiotics, insulin, human growth hormone, vitamins, and other drugs)

How Do Pathogenic Bacteria Work?  Bacteria produce disease in one of two ways:  Using cells for food : The bacteria break down healthy cells for food, destroying tissues  Releasing toxins : The bacteria produce a toxin (poisonous protein) that is released into the bloodstream where it can travel throughout the body, disrupting normal activity and damaging tissues

Bacteria  A rather vocal minority (less than 1%) of bacteria cause disease in humans, animals, and plants.  Bacteria can cause a variety of diseases:  Food Poisoning– Scarlet Fever  Tuberculosis– Whooping Cough  Cholera– Bacterial Meningitis  Syphilis– Pneumonia  Ulcers– Leprosy  Strep Throat– Tetanus VIDEO CLIP: Understanding Bacteria

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Viruses  Virology is the study of viruses  Viruses are “biological entities” containing either DNA or RNA that require another cell to survive.  Viruses have some, but not all, of the characteristics of life. *So are viruses living or non-living?*  Viruses seem to exist only to make more viruses!

Viral Structure  Capsid (protein coat)All viruses have the same basic structure: Nucleic acid core (DNA or RNA) Capsid (Protein coat)

How Do Viruses Work?  In order to replicate and make copies of itself, viruses need a host cell. What could be a host cell?  Without a host cell, viruses cannot function (i.e.- are harmless!)

How Do Viruses Work?  Attach: The capsid of the virus binds to receptor proteins on the surface of a host cell, tricking the host cell into thinking it’s not a foreign invader.  Inject: The virus then injects its genetic material (DNA or RNA) into the host cell.  Assemble: The viral genes are expressed, turning the host cell into a virus-making factory.  Repeat: The host cell eventually bursts, releasing the hundreds of newly formed viruses to infect surrounding cells! VIDEO CLIP: How Viruses Work

Viruses  Viruses can cause disease in humans, animals, plants, and even bacteria!  Viruses can cause a variety of diseases:  Common cold– Polio  Hepatitis A, B & C– Influenza  Herpes– Mumps  Mononucleosis– Measles  Warts– Viral Meningitis  Chickenpox– AIDS VIDEO CLIP: Viral Disease

Protection  There are a few big ways to protect yourself against pathogens (disease causing agents)  Antibiotics (drugs to kill bacteria)  Antivirals (drugs to treat viruses)  Vaccination (using your body’s own immune system to preemptively guard against attack)

Antivirals  Antivirals can only be used to treat certain viral infections!  Does not “kill” or disarm the virus permanently; only shortens symptoms by 1-2 days.  Usually only prescribed to patients with life threatening symptoms or those that have a greater chance of developing complications (because of their age or they have a high-risk medical condition).  Just like antibiotics, there is evidence of antiviral resistance too!

Vaccination  Vaccines can only be used to prevent infections (both viral and bacterial) from leading to disease.  “Trick” your immune system to make antibodies that destroy foreign “bodies” or particles (such as bacteria and viruses). Your body remembers how to make these antibodies when the real thing invades.  Made from a weakened virus, inactivated virus, or by using only part of the virus/bacteria itself. VIDEO CLIP: Vaccination