1. Microorganisms
Chapter 20
Sec. 2 Viruses

2. Are viruses alive?
Viruses are so small they can only be seen with an electron microscope.
But is a virus alive?
Viruses can only reproduce by infecting a host cell.
Viruses do not grow, instead they are assembled.
Viruses are not made of cells.
Viruses do not carry out metabolic processes to maintain homeostasis.
But, viruses do have genetic material – DNA or RNA
Is a virus alive? Recall the criteria to be a living thing: made of cells, grow and reproduce, maintain homeostasis, carry out metabolism, able to pass on traits

3. Viral Structure Basic structure: Nucleic acid core (RNA or DNA)
Protein coat or capsid – a protein sheath that surround the nucleic acid core
Some viruses have an envelope – a membrane that surrounds the capsid
has receptors to help the virus bind to host cells
Nucleocapsid – envelope that covers the nucleic acid
Tail fibers – some viruses called bacteriophages that infect bacterial cells have a tail with tail fibers.
Have the students add nucleocapsid

4. Viral Structure Continued
Glycoproteins – proteins on the outside of the envelope which attach to carbohydrate molecules on host cells.
Reverse Transcriptase – only in RNA viruses – transcribes (translates) the viral RNA into viral DNA and is then inserted into host cell.
Tail fibers – some viruses called bacteriophages that infect bacterial cells have a tail with tail fibers.

5. Virus Shape Viruses have many different shapes.
When talking about this slide include the different types of shapes for students to add in: A) helical B) polyhedral C) round and D) bacteriophage

6. Virus Categories
Viruses are split into two categories based on their nucleic acid core:
DNA viruses either insert their DNA into the host cell or the DNA remains separate, but uses the host’s enzymes and nucleotides to make new copies of its DNA and more viruses.
The DNA may be single-stranded or double stranded.
Examples include: smallpox and Hepatitis B
RNA viruses use reverse transcriptase to transcribe their RNA into DNA, insert the DNA into the host cell’s DNA, and then is transcribed into viral mRNA to make new viruses.
Most often called retroviruses
Examples include: HIV, Rhinovirus

7. Viral Reproduction Viruses can only reproduce inside a host cell.
Two cycles by which viruses can reproduce:
Lytic life cycle
Lysogenic life cycle

8. Lytic Cycle
Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell.
The viral nucleic acid takes over protein synthesis, creating new viruses.
The host cell bursts, lyses, and releases the newly formed viruses and then dies.
Viruses that reproduce only by the lytic cycle are called virulent.

9. Lytic Cycle
The diagram is to coincide with an activity of the students drawing out the cycle.

10. Lysogenic Cycle The viral DNA becomes part of its host cell’s DNA.
This virus is called a prophage.
When the host cell replicates its own DNA, it also replicates the provirus.
New cells that are produce contain the provirus
New viral particles are NOT assembled and the host cell is not destroyed.
After a period of time – days, months, or even years – the provirus may leave the host’s DNA and enter a lytic cycle.
Sometimes the virus never enters the lytic cycle and becomes a permanent part of the host’s DNA
A virus whose reproduction includes the lysogenic cycle is called a temperate virus.

11. Lysogenic Cycle
Lysogenic cycle. Go through the steps of how the virus replicates in this cycle. To be paired with an activity where the students create the lysogenic cycle.

12. Combined Lytic and Lysogenic Cycles

13. Viroids and Prions
Viriods and prions are molecules that are able to reproduce and cause disease.
Viroids are a single strand of RNA without a capsid.
The RNA of a viroid is much smaller than that of a viruses.
Replicate inside a host’s cell to make new viroids
Disrupt a cell’s regulation of growth
Some viroids have caused abnormal development and stunted growth in plants such as cucumbers and potatoes.

14. Viroids and Prions
Prions are mistake versions of proteins that are found in the brain.
They attach to normal proteins and cause them to take on the shape of the prion.
The normal protein then stops functioning.
This causes a chain reaction of misfolding among the other proteins which destroys brain tissue.

15. Prions Continued
Cause a disease in humans known as Creutzfeldt-Jakob disease
You may also be familiar with Mad Cow Disease in cows.
Another disease is chronic wasting disease in deer and elk

16. Microorganisms
Chapter 20
Sec. 1 Bacteria

17. Prokaryotes Let’s recall what a prokaryote is . . . .
Single-celled, no membrane bound organelles, no nucleus
Oldest living things on Earth
Fossils date back 3.5 billion yrs ago
Divided into two major groups
Archea
Bacteria

18. Archea
Found in many places, including extreme environments such as salt lakes and hot springs.
methanogens, halophiles and thermoacidophiles
Structurally they are different from Bacteria.
Some Archaean molecules are more similar to those found in eukaryotes.
Includes cyanobacteria which helped produce oxygen through photosynthesis to make the current Earth atmosphere
Oldest fossil is 3.5 billion years old and found in Western Australia.
Notes: Methanogens produce methane gas, are anaerobic, and live in swamps. Halophiles live in extremely salty conditions like the Dead Sea and are used for vaccines and indicators of environmental conditions. Thermoacidophiles live in extremely hot and acidic environments like Yellowstone and are used in the production of biofuels and bioplastics.

19. Eubacteria Most prokaryotes belong to this domain.
Virtually found everywhere.
Broken into groups based on three shapes.
Spirillum, coccus, and bacillus.
Talk about the shapes

20. Bacterial Structure
Bacterial DNA is a single chromosome clustered in a mass called a nucleoid.
May have extra loops of DNA called plasmids.
Bacterial plasmids are used in current medical research to help find cures for diseases.

21. Bacterial Structure Ribosomes and other enzymes Cell membrane
Flagella for movement
Pili to adhere to surfaces

22. Bacterial Structure

23. Bacterial Structure Rigid cell wall
Made of peptidoglycan, a protien-carbohydrate compound
Presence or absence of a cell wall helps biologist to group bacteria
Use a technique called gram-staining to identify two groups of bacteria
Gram-positive or gram-negative

24. Gram-Staining
Dies (crystal violet and safranin) are used to stain the peptidoglycan layer of the bacterial cell.
Gram-staining helps doctors decide what type of antibiotics can be used to treat the infection.

25. More on Gram-Staining
Anthrax bacteria (purple rods) in cerebrospinal fluid sample. The other cells are white blood cells.
Anthrax bacteria (purple rods) in cerebrospinal fluid sample. The other cells are white blood cells.
Anthrax bacteria (purple rods) in cerebrospinal fluid sample. The other cells are white blood cells.
Anthrax bacteria (purple rods) in cerebrospinal fluid sample. The other cells are white blood cells.
Ask student if anthrax is gram positive or negative. Ask students the shapes of Staph and E. coli. Also, bring the names back to classification (genus and species
A Gram stain of mixed Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative).
A Gram stain of mixed Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative).

26. How do Bacteria obtain energy?
Bacteria are grouped based on their energy sources.
3 groups
Photoautotrophs – energy from photosynthesis
Chemoautotrophs – energy from inorganic compounds
Heterotrophs – energy and nutrients from other organisms

27. Bacterial Reproduction
Bacteria reproduce using 3 different methods.
1) Binary Fission – single cell divides into two identical cells
2) Endospore Formation – formation of a thick-walled stucture that protects the bacterial DNA and a small bit of cytoplasm from harsh conditions
Can survive boiling, radiation, and acid
Can survive for hundreds of years

28. Bacterial Reproduction continued
3) Genetic Recombination – ways that bacteria can form new genetic combinations
Conjugation occurs when two bacteria exchange information.
Transformation occurs when bacteria take up DNA fragments from their environment.
Transduction occurs when genetic material (such as a plasmid) is transferred by a virus.

29. Chapter 20 Sec. 3 Bacteria, Viruses and Humans
Microorganisms
Chapter 20
Sec. 3 Bacteria, Viruses and Humans

30. Viruses, Bacteria, and Humans
Pathology – the study and the diagnosis of disease.
Pathogen – anything that causes a disease.
Toxin - a poison that is produced by bacterial pathogens and that damage cells.
Ex: Botulism occurs when canned food is contaminated with endospores of the bacterium Clostridium botulinum

31. Bacterial Disease
Bacteria cause disease by producing toxins or by destroying body tissue.
Ex: Group A streptococcus bacteria produce strept throat, but if untreated the bacteria can get into muscle or skin tissue and cause necrotizing fasciitis (when the flesh dies off).
We treat bacterial diseases with antibiotics.

32. Antibiotics
First discovered by the scientist Alexander Fleming in 1927.
penicillin
Antibiotics – a drug that kills or slows the growth of bacteria.
Ex: amoxicillin, zithromycin, ciprofloxacin
Each antibiotic targets a specific group or specific bacteria

33. Antibiotic Resistance
Antibiotic resistance – as time goes on many bacteria are becoming resistant to antibiotics because of overuse of the antibiotic or mutations for resistance.
Overuse of hand-sanitizers and not taking the recommended dose are contributing factors

34. Useful Bacteria
Bacteria make oxygen, decompose organisms, and make nitrogen available to other organisms
Ex: nitrogen fixing bacteria combine nitrogen and oxygen and make it available for plants.
Bacteria help humans digest food and exist virtually on every inch of the human body.
Nodules on roots of this soy bean plant are full of nitrogen fixing bacteria.
Nodules on roots of this soy bean plant are full of nitrogen fixing bacteria.
Nodules on roots of this soy bean plant are full of nitrogen fixing bacteria.

35. Useful Bacteria Continued
Bacteria are used in many industries such as sewage treatment facilities and cleaning up oil spills.
Bacteria are also used to make a variety of foods.
Ex: pickles, yogurt, soy sauce, and sourdough bread

36. Viral Disease
Because viruses enter host cells to reproduce, it is difficult to develop a drug that kills the virus without harming the living host.
Viruses can be transmitted by any action that brings virus particles into contact with a host cell.
Ex: common cold, Influenza A and B, and HIV

37. Vaccines
Vaccine – is a weakened form of a pathogen that prepares the immune system to recognize and destroy the pathogen.
Most common types:
Killed virus – uses killed virus to create an immune response
Ex: influenza and hepatitis
Live – attenuated virus – uses live, but modified virus to create an immune response, but the virus does not get the person sick.
Ex: measles and mumps
Talk about antivirals and tamaflu

38. Developed Vaccines
Since viruses have the ability to enter into the host cell they are also able to mutate quite rapidly.
This makes producing vaccines sometimes difficult.
Some viruses have been shown to cause some types of cancer.
Ex: Hepatitis B (liver cancer) and Human papilloma virus (cervical cancer).
Gardasil vaccine – given to teenage girls to protect against cervical cancer