Viruses & Bacteria

What Do You Already Know? What are the differences between bacteria and viruses? Are all bacteria harmful? Are bacteria and viruses living? If you have a cold, should you take an antibiotic? Why or why not? What is the best/easiest way to avoid getting sick?

Viruses Tiny particles containing DNA and RNA Requires a host cell to survive Have SOME (not ALL) characteristics of life!

Virus Structure All viruses have the same basic structure! Inner core made up of nucleic acid. Capsid  protein coat surrounding the inner core

Examples Bacteriophage – virus that infect bacteria Influenza, HIV

How Do Viruses Work? https://www.youtube.com/watch?v=Rpj0emEGShQ Must have a host cell (can be any living cell, but viruses are specific!) Attach  Capsid of a virus binds to receptors on surface of host cell Inject  Injects its DNA/RNA into host Assemble  host cell begins making viruses (it’s been HIJACKED!) Repeat  host cell eventually bursts, releasing hundreds of newly formed viruses to infect surrounding cells

Lytic Cycle Virus enters host cell. Virus destroys cell’s DNA. “Tricks”/”reprograms” cell to make virus parts. New viruses are built/assembled inside cell. Cell bursts (dies) releasing viruses!

Lysogenic Cycle (longer name, longer cycle) Virus enters host cell. Virus inserts its genetic information into the host’s DNA molecule. At this point, it doesn’t interfere with the cell’s function, it is copied along with the cell’s DNA, and passed on to future cells. Virus DNA can be activated and enter the lytic cycle at any time. (reproducing viruses and killing the cell.)

Viruses can cause disease too! Common Cold Hepatitis A, B, C Herpes Mononucleosis Warts Chickenpox Flu AIDS Ebola

There are vaccines to protect us against some viruses! The good news is… There are vaccines to protect us against some viruses! https://www.youtube.com/watch?v=rb7TVW77ZCs&app=desktop

Viruses in the News… Zika Virus http://www.cdc.gov/media/dpk/2016/dpk-zika-virus.html http://www.wdrb.com/story/31436597/first-case-of-zika-virus-reported-in-kentucky

Viruses in the News… Ebola https://www.youtube.com/watch?v=XCrOde-JYs0 https://www.youtube.com/watch?v=sRv19gkZ4E0

Review! https://www.youtube.com/watch?v=PHp6iYDi9ko

Viroids & Prions Infectious agents! (non-living) Viroids  short strands of circular RNA with no protein coat, typically affect plants Prions  small, misfolded proteins, affect animals (one causes Mad Cow disease)

Bacteria Prokaryotic Unicellular Contain DNA and ribosomes https://www.youtube.com/watch?v=kxM_9DL2GYw Prokaryotic Unicellular Contain DNA and ribosomes Have ALL the characteristics of living things! Reproduce through binary fission

Evolution Bacteria reproduce very quickly (via binary fission). This means evolution can occur very quickly! Bacteria can exchange genetic info in 3 ways:

Basic Structure of Bacteria Cell wall – for protection, support, rigidity, made of peptidoglycan (sugars and amino acids) Cell membrane Cytoplasm Ribosome Plasmids – circular DNA, used to exchange DNA between bacteria Capsule – covers outside cell wall May have pili, flagella, etc.

Bacteria have 3 distinct shapes: Spherical (cocci) Rod-shaped (bacilli) Spiral (spirilla)

Gram Staining of Bacteria Process used to separate bacteria into 2 large groups, based on chemical and physical properties of their cell wall, for medical diagnosis purposes. Gram positive bacteria: Those bacteria when they are stained in gram stain results in purple color  (more peptidoglycan in cell wall) Gram negative bacteria: Those bacteria when they are stained in gram stain results in pink color. MOST pathogenic bacteria are gram negative!

Uses of Bacteria Food (buttermilk, yogurt, cheese, sauerkraut, pickles, olives, etc…) Decompose organic matter (recycle nutrients from dead organisms; break down sewage into simple compounds) Nitrogen fixation (chemically changes nitrogen gas into a usable form for plants) Human health (bacteria on skin help prevent infection, bacteria in gut aid digestion) Biotechnology (used to make antibiotics, insulin, human growth hormone, vitamins)

Pathogenic Bacteria Bacteria typically cause disease by: Releasing toxins  bacteria release a toxin (poison) into the bloodstream and it travels throughout the body

…BUT they cause a variety of diseases! Pathogenic Bacteria… Less than 1% of bacteria cause disease in humans, animals, & plants! …BUT they cause a variety of diseases! Food poisoning Tuberculosis Cholera Syphilis Ulcers Strep Throat