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?

Bacteria have ALL the characteristics of living things. prokaryotic, unicellular organisms Have DNA and ribosomes. Bacteria have ALL the characteristics of living things. Bacteria have the greatest percentage of the biomass on Earth!

Basic structure of bacteria: Bacterial Structure Basic structure of bacteria: Cell wall Cell membrane Ribosome Peptidoglycan* Flagellum DNA Pili

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

Variety of important uses: Bacteria Variety of important uses: Help make interesting food (buttermilk, yogurt, cheese, sauerkraut and pickles) Decompose organic matter (recycle nutrients from dead organisms; break down sewage into simpler compounds) Nitrogen fixation (chemically changes nitrogen gas, N2, into ammonia, NH3, 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)

VIDEO CLIP: Understanding 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

http://www.youtube.com/watch?v=yToii3-p-NI

*So are viruses living or non-living?* 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!

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

To replicate & make copies of itself, viruses need a host cell. How Do Viruses Work? To replicate & 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: Capsid of the virus binds to receptor proteins on host cell, tricking the host cell into thinking it’s not a foreign invader. Inject: Virus injects its genetic material (DNA or RNA) into 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 can cause a variety of diseases: 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)

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

http://www.youtube.com/watch?v=3xRttWuf3wQ

Bacteria Virus Both