Bacteria & Viruses

What are the characteristics of viruses? Bacteria? What kingdom do each of these belong? Are they living? Why or why not ?

Kingdoms – Eukar

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 Video

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)

Are bacteria harmful or useful?

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

Viruses Living or Nonliving?

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 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. Any living cell can become a host cell (human, animal, plant, and even bacterial cells!)  Without a host cell, viruses cannot function (i.e.- are harmless!)  Although any cell can theoretically become a host cell, specific viruses will only infect specific cells (EX: HIV will only infect human T cells, a part of your immune system)

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)

Antibiotics Antibiotics can only be used to treat bacterial infections! Target specific structures on bacteria to kill them. First made from a fungus (penicillin), now most are made artificially. Unfortunately, antibiotic resistance (where the antibiotic doesn’t kill the target bacteria anymore) is becoming a major problem.

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

Viruses and the flu

To Review....  What are the differences between viruses and bacteria?  Are all bacteria harmful? Explain.  When you get a cold, should you take an antibiotic to help you get better? Why?  What’s the best and easiest thing to do to avoid getting sick?

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Bacteria Virus Both