Bacteriophage Life Cycles and Viral Infections

Lytic Cycle: A phage infects a host cell, replicates its genetic material, and lyses (breaks open) the cell to release new phages. This cycle is rapid and results in the destruction of the host cell.
Lysogenic Cycle: A phage integrates its DNA into the host cell's genome, becoming a prophage. The prophage replicates along with the host's DNA without harming the cell. The host cell replicates and divides, passing the prophage to daughter cells. Environmental triggers can cause the prophage to leave the host genome and enter the lytic cycle.
Comparison Lytic vs. Lysogenic:
- Lytic: rapid replication, host cell destruction, direct phage reproduction. Lysogenic: latent infection, integration of phage DNA, viral reproduction without cell death, can switch to lytic cycle.

Plant Viruses : infect plants, disrupting growth, causing diseases like leaf discoloration, stunted growth.
Animal Viruses : infect animal cells, causing diseases varying in symptoms and severity.

Retrovirus: HIV is a retrovirus, a type of virus that carries its genetic instructions in RNA, not DNA.
Reverse Transcriptase: An enzyme unique to retroviruses that uses viral RNA as a template to make complementary DNA (cDNA).
Provirus: The cDNA made from reverse transcriptase integrates into the host cell's DNA becoming a provirus, which can persist indefinitely.
T-cells: HIV targets and infects T-cells, particularly helper T-cells (CD4+ T cells)
AIDS: Acquired Immunodeficiency Syndrome is the advanced stage of HIV infection characterized by a weakened immune system.
Anti-HIV Drugs: Various drugs target different stages of HIV's life cycle to reduce the viral load and slow disease progression.

SARS-CoV-2 (COVID-19): Causes respiratory illness, ranging from mild to severe depending on individual factors.
HIV (Human Immunodeficiency Virus): Infects and destroys immune cells, leading to AIDS.
West Nile Virus: Causes encephalitis (inflammation of the brain) and meningitis (inflammation of the lining surrounding the brain and spinal cord).
Ebola: A severe and often fatal viral hemorrhagic fever.
Avian Flu: A virus that may cross over to humans with potential pandemic risk.

Microbiome/Microbiota: The complex community of microorganisms living in and on an organism, having significant impact on environments and on health.

Bacteria: One domain of prokaryotes, known for their vast diversity and varied metabolisms.
Archaea: Another domain of prokaryotes, noted for adaptations to extreme environments (often known for unusual environments).

Cocci: Spherical bacteria.
Endospores: Dormant, resistant structures formed by some bacteria to withstand harsh conditions.
Bacilli: Rod-shaped bacteria.
Spirochetes: Spiral-shaped bacteria.
Binary Fission: The asexual reproduction in bacteria.

Germ Theory: Infectious diseases are caused by microorganisms. Koch's Postulates: A set of criteria to determine which microbe is responsible for a particular disease. They have revolutionized disease control through the understanding of disease causes and the prevention, diagnosis, and treatment of diseases.

Photoautotrophs: Obtain energy from light and carbon from inorganic sources like carbon dioxide.
Chemoautotrophs: Obtain energy from chemical reactions and carbon from inorganic sources.
Photoheterotrophs: Obtain energy from light and carbon from organic sources.
Chemoheterotrophs: Obtain both energy and carbon from organic sources.

Chemical Recycling: Bacteria play a vital role in nutrient cycling and decomposition.
Disease-causing Bacteria: Some bacteria cause infectious diseases.
Bioremediation: Using bacteria to clean up environmental pollution.
Endotoxins/Exotoxins: Chemical components of bacteria that cause adverse effects.
Antibiotic Usage : Use of medications that specifically kill bacteria.

Petri Dish: A shallow dish used to grow bacteria in a controlled environment.
Agar: A solidifying agent used in petri dishes to support bacterial growth.
Sterilization: The process of eliminating all living organisms from an area or material.
Zone of Inhibition: The clear area around an antibiotic disk where bacteria do not grow in a lab test.

Vaccines: Stimulate the immune system to develop immunity to a pathogen without causing the disease.
Herd Immunity: A level of immunity in a population that protects even those who are not immune.

External Barriers: Skin, mucus, etc., physically prevent pathogens from entering the body.
Internal Defenses: Cells, proteins, and responses that eliminate pathogens within the body, including neutrophils and macrophages.
Inflammatory Response: A localized response to tissue injury or infection characterized by redness, swelling, heat, and pain; aids in eliminating pathogens.
Lymphatic System: A network of vessels and tissues that carries lymph throughout the body.

Immune System: The body's systems of protection, comprising cells and proteins, against infection, disease, and foreign bodies.
Antigen: A substance that triggers a response from the immune system.
Antibody: A protein that binds to an antigen to neutralize or destroy it.
Humoral Response: Antibodies produced by B cells.
Cell-Mediated Response: T cells directly attack and destroy infected cells.
Active Immunity: Immunity acquired through exposure to an antigen or through vaccination.
Passive Immunity: Immunity acquired through receiving antibodies directly from another source.
Vaccination: Introduction of a specific antigen to induce immunity without developing the disease.
RNA Vaccine: An emerging technology using mRNA instead of the complete viral pathogen to stimulate immunity.
Lymphocytes: Specialized cells of the immune system.
Clonal Selection: The process of differentiating and activating lymphocytes capable of responding to a specific antigen.
Monoclonal Antibodies: Antibodies that are all derived from a single B cell clone.
Primary Immune Response: Initial response to an antigen, typically slower and less robust.
Secondary Immune Response: Subsequent responses to the same antigen, faster and stronger due to memory cells
Memory Cells: Lymphocytes that "remember" previous exposure to an antigen, enabling faster and stronger responses in subsequent encounters.

Allergies: An overreaction of the immune system to an allergen.
- Allergens: Substances that cause allergic reactions.
- Anaphylactic Shock: Severe, life-threatening allergic reaction.
- Mast Cells: Immune cells involved in allergic reactions.
- Histamine: A chemical that mediates allergic reactions.
- Epinephrine (EpiPen): A medication used to treat severe allergic reactions.
Autoimmune Diseases: Immune system attacks the body's own tissues.
- Examples: Type 1 diabetes, multiple sclerosis, lupus, rheumatoid arthritis
Immunodeficiency Diseases: Weakened immune response.
- Examples: SCID (Severe Combined Immunodeficiency), HIV/AIDS, cystic fibrosis
Organ Transplant Rejection: The immune system recognizing and attacking transplanted tissue.