Microbiology Final Exam

Study Guide

What is the difference between viruses and bacteria?

Viruses

• Not living cells

• Require a host cell to reproduce

• Contain DNA or RNA

• Much smaller than bacteria

• Not killed by antibiotics

Bacteria

• Living single-celled organisms

• Can reproduce independently

• Contain both DNA and RNA

• Can often be treated with antibiotics

What is Bacteriophage?

A virus that infects bacteria. It attaches to a bacterial cell and injects its genetic material

Parts of a Bacteriophage

• Head (capsid) contains DNA

• DNA

• Tail sheath

• Tail fibers (attach to bacteria)

• Base plate (helps inject DNA)

What is the lytic cycle?

The virus immediately reproduces and destroys the host cell

1. Attachment

2. Penetration

3. Replication

4. Assembly

5. Release

What is the lysogenic cycle?

The viral DNA inserts into the host DNA and remains inactive until triggered

Lytic vs Lysogenic Cycle

Lytic

• Immediate replication

• Host cell dies

• Produces many viruses

Lysogenic

• Viral DNA stays dormant

• Host cell survives

• Can later switch to lytic

What triggers a lysogenic virus to enter the lytic cycle?

• UV radiation

• Chemicals

• Stress

• DNA damage

• Changes in the host cell

How are bacteriophages used in medicine?

• Kill antibiotic-resistant bacteria

• Phage therapy

• Biotechnology research

• Genetic engineering

What causes Polio?

• Virus: Poliovirus

• Attacks the nervous system

• Prevented by vaccination

What causes Hepatitis?

• Hepatitis A

• Hepatitis B

• Hepatitis C

• Hepatitis D

• Hepatitis E

Primarily infect the liver

What causes Herpes?

• Herpes Simplex Virus (HSV)

• HSV 1 → Oral Herpes

• HSV 2 → Genital Herpes

What causes HPV?

• Human Papillomavirus (HPV)

Can cause:

• Warts

• Cervical Cancer

• Other cancers

What causes Measles?

• Measles Virus

Symptoms:

• Fever

• Cough

• Rash

What causes COVID-19?

• SARS-CoV-2

Symptoms:

• Fever

• Cough

• Shortness of Breath

• Loss of taste and smell

What causes Smallpox?

• Variola Virus

• Causes severe rash and fever

• Eradicated worldwide through vaccine

Host cell

A living cell that a virus infects to reproduce.

Vaccine-preventable disease

A disease that can be prevented through vaccination

Viral Latency

A period when a virus remains inactive inside the host without causing symptoms

What are the five major microbial groups?

• Bacteria

• Algae

• Fungi

• Protozoa

• Prions

Compare bacteria, algae, fungi, protozoa, and prions

Bacteria → Prokaryote

Algae → Eukaryote

Fungi → Eukaryote

Protozoa → Eukaryote

Prions → Not cells

What is a prokaryote?

An organism that:

• Has no nucleus

• Has no membrane-bound organelles

• Usually single-celled

What is a Eukaryote?

An organism that:

• Has a true nucleus

• Has membrane-bound organelles

• Can be single-celled or multicellular

Prokaryote vs Eukaryote

Prokaryote

• No nucleus

• No organelles

• Smaller

• Bacteria

Eukaryote

• Has nucleus

• Has organelles

• Larger

• Fungi, algae, protozoa

Characteristics of algae

• Eukaryotic

• Photosynthetic

• Live in water

• Produce oxygen

• Have chloroplasts

Characteristics of fungi

• Eukaryotic

• Absorb nutrients

• Cell walls contain chitin

• Can be yeast or molds

• Reproduce using spores

Characteristics of protozoa

• Eukaryotic

• Single-celled

• No cell wall

• Usually move using cilia, flagella, pseudopods

• Often parasites

Characteristics of prions

• infectious proteins

• No DNA or RNA

• Cause brain diseases

• Extremely resistant to sterilization

What is the function of mitochondria?

The mitochondria produce ATP through cellular respiration.

How do algae obtain nutrients?

Algae are autotrophs.

They make their own food using photosynthesis

How do fungi obtain nutrients?

Fungi are heterotrophs

They absorb nutrients from dead or living organic matter.

Compare algae and fungi nutrition

Algae

• Autotroph

• Photosynthesis

• Chlorophyll

Fungi

• Heterotroph

• Absorb nutrients

• No chlorophyll

Why are prions medically important?

They cause fatal brain diseases, including

• Creutzfeldt-Jakob disease

• Mad Cow Disease

Prions cannot be destroyed by normal sterilization methods

Endospore

A dormant, highly resistant structure formed by some bacteria to survive harsh conditions.

Fungal Spore

A reproductive cell produced by fungi for reproduction and dispersal.

Protozoa

Single-celled eukaryotic microorganisms that usually move and ingest food

Prion

An infectious misfolded protein that causes degenerative brain diseases.

Protista

A diverse group of mostly single-celled eukaryotes that includes:

• Algae

• Protozoa

• Slime molds

What are cocci?

Round or spherical-shaped bacteria

What are bacilli?

Rod-shaped bacteria

What are spirilla?

Spiral-shaped (rigid) bacteria

What are Vibrios?

Comma-shaped bacteria

What is an endospore?

A dormant, highly resistant structure produced by some bacteria to survive:

• Heat

• Drying

• Chemicals

• Radiation

Why are endospores important?

They help bacteria survive harsh conditions and make them difficult to eliminate with normal disinfectants.

What is biofilm?

A community of microorganisms attached to a surface and protected by a sticky matrix.

Why are biofilms important in healthcare?

• Protect bacteria from antibiotics

• Protect bacteria from the immune system

• Cause healthcare-associated infections

How do bacteria become antibiotic resistant?

• Mutations

• Gene transfer between bacteria

• Producing enzymes that destroy antibiotics

• Changing antibiotic target sites

• Pumping antibiotics out of the cell

What is MRSA?

• Resistant to many antibiotics

• Common hospital-acquired infection

• Causes skin, wound, and bloodstream infections

What is VRSA?

• Resistant to vancomycin

• Very difficult to treat

• Less common than MRSA

What are healthcare-associated pathogens?

Microorganisms that commonly cause infections in hospitals or healthcare settings

Staphylococcus epidermidis causes

• Device-associated infections

• Catheter infections

• Prosthetic joint infections

Mycobacterium tuberculosis causes

• Tuberculosis (TB)

Usually affects the lungs

Salmonella Enterica causes

• Gastroenteritis (food poisoning)

• Typhoid fever

Usually spread through contaminated food or water

Clostridium Botulinum causes

• Botulism

Produces a neurotoxin that causes paralysis

Gardnerella Vaginalis causes

• Bacterial Vaginosis

Bartonella Henselae causes

• Cat scratch disease

Usually spread through cat scratches or bites

Chlamydia Trachomatis causes

• Chlamydia

• Trachoma

Clostridium Difficile causes

• Antibiotic-associated colitis

• Severe diarrhea

Often develops after antibiotic use

Clostridium perfringens causes

• Gas gangrene

What is microscopy?

The use of a microscope to observe microorganisms that cannot be seen with the naked eye.

What is molecular testing?

Tests that detect the DNA or RNA of microorganisms.

Why is specimen collection important?

Proper specimen collection ensures accurate laboratory results and diagnosis.

What is innate immunity?

• present at birth

• rapid response

• non-specifc

• no memory

What is acquired immunity?

• Develops after exposure

• specific response

• has memory

• involves B cells and T cells

Innate vs Acquired Immunity

Present at birth → Develops after exposure

No memory → Has memory

Rapid response → Slower first response

Non-specifc → Specific

What is active natural immunity?

Immunity developed after becoming infected and recovering from a disease.

What is active artificial immunity?

Immunity produced after receiving a vaccine.

What is passive natural immunity?

Temporary immunity received naturally from the mother.

What is passive artificial immunity?

Temporary immunity received through injected antibodies.

What is vaccination?

The administration of a vaccine to stimulate the immune system to produce immunity without causing disease.

Why are vaccines important?

• To prevent disease

• Stimulate antibody production

• Create memory cells

• Reduce disease spread

What are memory cells?

Long-lived B and T lymphocytes that “remember” a pathogen and respond quickly if exposed again.

What are antibodies?

Proteins made by B cells that recognize and destroy specific pathogens

What is antibody production?

When B cells are activated, they become plasma cells that produce antibodies against a specific antigen

What is cell-mediated immunity?

An immune response carried out by T cells instead of antibodies

B cells vs T cells

B cells

• Produce antibodies

• Humoral immunity

T Cells

• Kill infected cells

• Cell-mediated immunity

What is humoral immunity?

Humoral immunity is immunity mediated by B lymphocytes that produce antibodies to fight pathogens found outside cells

What are B lymphocytes?

• Produce antibodies

• Become plasma cells

• Form memory B cells

• Responsible for humoral immunity

What are T lymphocytes?

T cells protect against infected cells

What are CD8+ T cells?

Also called cytotoxic T cells

• Kill virus-infected cells

• Destroy cancer cells

• Destroy abnormal body cells

What are natural Killer cells?

Part of hte innate immune system

They destroy:

• Virus-infected cells

• Tumor cells

What are macrophages?

Large white blood cells that:

• Engulf pathogens

• Remove dead cells

• Present antigens to T cells

What are eosinophils?

White blood cells that:

• Fight parasitic infections

• Participate in allergic reactions

• Release toxic chemicals to kill parasites

What are dendritic cells?

Antigen-presenting cells that:

• Capture pathogens

• Present antigens to T cells

• Activate adaptive immunity

What is an autoimmune disease?

A disease in which the immune system mistakenly attacks the body’s own healthy tissues

What is Systemic Lupus Erythematosus?

An autoimmune disease that can affect:

• Skin

• Joints

• Kidneys

• Heart

• Brain

What is type 1 Diabetes?

An autoimmune disease in which the immune system destroys the insulin-producing beta cells of the pancreas.

What is Hashimoto’s Thyroiditis?

An autoimmune disease in which the immune system attacks the thyroid gland, often causing hypothyroidism

What is Addison’s disease?

An autoimmune disease that damages the adrenal glands, reducing cortisol and aldosterone production.

What is the first line of defense ?

The body’s physical and chemical barriers that prevent pathogens from entering.

What is the role of the skin?

The skin acts as a physical barrier that prevents the microorganisms from entering the body.

It also produces oils and has a slightly acidic pH that inhibits bacterial growth.

What is the role of mucous membranes?

Mucous membranes produce mucus that traps bacteria, viruses, and other particles before they enter the body.

What is the role of cilia?

Cilia are tiny hair-like structures in the respiratory tract that move mucus and trapped pathogens out of the airways.

What is the role of tears?

• Wash microorganisms away from the eyes

• Contain Lysozyme, en enzyme that destroys bacterial cell walls

What is the role of saliva?

• Washes microbes from the mouth

• Contains lysozyme

• Begins digestion while helping prevent infection

What is the role of stomach acid?

• Very acidic (low pH)

• Kills many microorganisms swallowed with food or drink

What is the role of urination?

Urination flushes bacteria out of the urinary tract, helping prevent urinary tract infections

What is the second line of defense?

The body’s innate internal defenses that respond after pathogens enter the body

• Inflammation

• Fever

• Phagocytosis

• Chemotaxis

What is inflammation?

A protective response to injury or infection

What is fever?

a rise in body temperature that:

• slows the growth of infection

• helps the immune system work more effectively

What is phagocytosis?

The process by which immune cells engulf and destroy microorganisms