Micro Biology Review/Study Questions (Lecture 1-3)

Describe three general reasons why microbiology is important

1. Identifying different pathogens

2. Finding different treatments of said pathogens

3. creation of new antibiotics and controlling their usage

Draw the info graphic of Koch’s postulates to show that an infectious agent is the cause for a disease

Koch’s Postulate Remember Aiir

1. Association

2. Isolation

3. Inoculation (Vaccine)

4. Re-Isolation

Name an infectious disease that may not fit Koch’s postulates based on what we know today?

HIV, Tuberculosis, Prion diseases

Name an infectious disease that may fit Koch’s postulates based on what we know today?

Anthrax

1. Anthrax

• Easy to culture in labs

• Present in all diseased host, absence from healthy host

• Cause the same disease in a healthy animal when introduced

• can be re-isolated from the newly infected host

What differentiates bacteria from archaea

1. Bacteria

• Single- Celled prokaryotes (Prokaryote = prenucleus)

• No membrane bound nucleus

• No other membrane-bound organelles

• DNA in nucleoid

• Most have specific shapes

• Rigid cell wall contains peptidoglycan

• Multiply via binary fission

• many move via flagella

2. Archaea

• Very Similar to bacteria (Shape, Size, and appearance)

• Prokaryotic

• Multiple via binary fission

• May move via flagella

• Rigid Cell walls

Only known for Archaea

• Cell walls lack peptidoglycan

• Cell membrane has more branched and strong bond lipids

• Ribosomal RNA sequences different

• No known pathogens

• RNA polymerase sensitive to alpha amanitin

• Many are extremophiles

Protozoa are eukaryotic? True or False?

True

Differentiate between viruses and viroids?

Viruses affect DNA and RNA sequences

Viroids affect only RNA sequences

Differentiate between prions and viroids?

Prions - Only affect proteins

Viroids - Only affect RNA sequences

What are prions primarily composed of?

They are composed of misfolded proteins that turn healthy proteins into misfolded proteins

What happens in a cell nervous system prion diseases

Name two prions diseases-one in humans, one in animals

Humans - Creutzfeldt-Jakob Disease (CJD)

Animals - Bovine Spongiform Encephalopathy (BSE)

How can prions be transmitted from one animal to another? Can all prions cause diseases across species?

It can be transmitted by consumption of infected flesh; No not all prions causes diseases across species.

How can prion diseases be acquired by humans?

Through wounds (blood to blood contact) and by eating contaminated meats

List Characteristic features of prion diseases

Depression, anxiety, dementia, memory loss, and halluinations

Draw the map of all members of the microbial world (without help)

Draw and label a prokaryotic cell and its parts

What is the general function of a capsule?

1. Helps colonize host: Adherence, attachment and forming biofilms

2. Help evade immune system attacks, aid hiding

3. helps prevent drying of cell

4. Defense against bacterial viruses

5. Crucial virulence factor: Loss of capsule leads to loss of pathogenicity

6. Some vaccines are made using capsules

What is the difference between a capsule and slime layer

Capsule:

• Glycocalyx (Sugar)

• Well - Organized layer, difficult to be washed off

• Tightly bound to the cell wall

• thicker than slime layer

• acts as a virulence factor that helps to escape phagocytosis

Slime Layer:

• Glycocalyx (Sugar) and Glycoprotein (Protein)

• Unorganized layer and can easily washed off

• Loosely bound to the cell wall

• thin glycocalyx layer

• mainly helps in adherence, protects the cell from dehydration and nutrient loss

Why are capsules and slime layers sometimes called a glycocalyx?

Because it is a shell of sugars.

How are capsules related to dental carries?

They are used to create a protective, sticky, bacterial, polysaccharide coating that promotes decay, or as a therapeutic, encapsulated, medicinal (probiotic) delivery mechanism designed to prevent it.

How do capsules aid biofilm formation?

enhancing adherence to surface and providing structural and protective support

How can you determine if a bacterium has a capsule?

You can use a gram stain and look at it through a microscope using a negative stain and when putting it on a sold growth media it will be a shiny/moist appearance and electron microscopes.

How are capsules important for pathogenesis?

Its a defense against white blood cells and the host immune system

Which molecule is unique to domain bacteria and not found in archea or eukarya?

Peptidoglycan (Only found in bacteria)

Draw the structure of peptidoglycan

Subunits are NAM and NAG. The peptide bridge is called Transpeptidase

What will happen to a bacterial cell if you weaken the structure of peptidoglycan?

The structural integrity would be weakened causing the cell either shrivel out or swell due to the weakening structure of the peptidoglycan.

What effect does penicillin have on peptidoglycan?

Penicillin will attack the peptidoglycan and even stop it from producing

What effect does lysozyme have on peptidoglycan?

It breaks down the existing peptidoglycan

Which Gram cell types have porins and why?

Gram Negative have porins that are located on the outer membrane and they are used for passages for ions and other molecules

Which molecule is unique to Gram Positive Cells

teichoic acids

How is the Gram-negative cell wall different from the Gram-positive cell wall?

Gram Negative Cell: (Pink)

• Pink In color

• Thin layer of Peptidoglycan

• No Teichoic Acid

• Has Outer membrane (w/ porins)

• Has Lipopolysaccharides (LPS and Endotoxin)

• General less susceptible to penicillin

• Not sensitivity to lysozyme

Gram Positive Cells: (Purple)

• Purple in color

• Thick Layer of peptidoglycan

• Has teichoic acid

• No outer membrane

• No lipopolysaccharides (LPS)

• No porin protein because no outer membrane

• Generally more susceptible to penicillin

• Sensitive to lysozyme

Where is LPS found?

LPS is only found in Gram-Negative bacteria on the outside of the outer membrane.

What is the medical significance of LPS aka endotoxins?

1. Very strong PAMP

2. Makes Gram negative blood stream bacterial infections more deadly

3. Can cause Septic Shock and Multiple Organ Failure.

Why can Mycoplasma species not be treated with penicillin?

Mycoplasma - Bacteria that do not have a cell wall and they are Pleomorphic (Can change their shape). Penicillin won’t work because the drug attacks cell walls and these bacteria do not have cell walls.

What staining technique is used to stain Mycobacteria? Why cant they stain with Gram stain?

We use a staining technique called Acid Fast because their cell wall as a lot of mycolic acid which it make them impermeable to standard gram staining. Its like a waxy lipid.

What are efflux pumps? Why do they need energy to function?

Efflux Pumps - Help push harmful and non-essential molecules like antibiotics out of the cell. The reason they need energy to function is because they do Active Transportation which means they are going against the concentration gradient which requires ATP.

What is the function of type 3 secretory systems?

The function is:

• Attach to other living cells/microorganisms

• Once attached they start to send certain proteins

• These certain proteins start to change the cell and manipulate it.

How are flagella beneficial for pathogenesis in gastric ulcers and Lyme disease?

Gastric Ulcers: Helicobacter Pylori survive the very acidic environment by secreting urease. After they start to attach and the proteins start to change the surface of the epithelial cells and damage mucus-secreting cells. The inflammation and toxins damage epithelial cells decreasing mucus production then the acidic stomach juices start to damage exposed tissue.

Lyme Disease: Borrelia Burgdorferi, It has a flexible body with flagella all along its body that allows it to bore into the host tissue like a cork screw. It can also change its shape to a cyst form and become dormant.

Give examples of 3 cell different cellular structures embedded in the cytoplasmic membrane

Ion channels, proteins, gap junctions

What are various pili useful for?

Sex Pilus - Connecting two cells and after connection they transfer DNA

Other Pilus on Escherichia coli - Used for attachment to epitheical cells

Pili on E coli Cells - Allows adherence

What are plasmids? How are they unique from the chromosome?

Plasmids: similar structure to a chromosome but they are smaller and do not carry essential genetic information.

What makes them Unique from chromosomes? They can replicate independently while the chromosome can not replicate by themself

Describe some characteristics that are commonly encoded on plasmids

1. Production of enzymes that destroy certain antibiotics

2. Code for multiple proteins

3. Can transfer information that can be helpful to other cells

Give an example of a gene that is always found on the chromosome but not on a plasmid.

Ribosomal RNA (rRNA) Gene

How are bacterial ribosomes different from eukaryotic ribosomes? Why is this essential information from a medical point of view?

Eukaryotic Ribosomes:

• Larger

• More Proteins

• More RNA

• Has a 60s and 40s subunits

• all together is 80s

Prokaryotic Ribosome:

• Smaller

• Less proteins

• Less RNA

• Has a 50s and 30s subunit

• all together is 70s

Medical point of view? The differences are important for drug targeting.

What is an endospore?

Endospore: An unique type of dormant cell produced by certain bacterial species such as members of the genera Bacillus and Clostridium

Name the only two genera that produce endospores

Bacillus and Clostridium

Use the terms sporulate and germinate in describing the "life-cycle" of a spore-forming bacterium.

Sporulation begins with endospore-forming bacteria experience limiting amounts of Carbon and Nitrogen. The cells senses starvation conditions and that triggers them to begin the 8-hour sporulation process. First, The cell stops growing but it still duplicates its DNA. Second, Septum forms, dividing the cell asymmetrically. Third, Larger compartment engulfs the smaller compartment. Fourth, endosore continues to mature, while the smaller compartment develops into a forespore, which will become the core of the endospore. Fifth, The mother cell is degraded and the endospore is released.

Germination can be triggered by a brief exposure to heat or certain chemicals. After exposure, the endospore absorbs water and swells, The spore coat and cortex then crack open, and a vegetative cell emerges. The core wall become the peptidoglycan layer of the vegetative cell.