Biology Chapter on Immunology and Disease Transmission

Microbiology

• The study of organisms too small to be seen without magnification
• Originated with the invention of the microscope
• Microorganisms include bacteria, viruses, fungi, protozoa, helminths (worms), algae, and prions

Branches of Study Within Microbiology

• Immunology
• Public health microbiology and epidemiology
• Food, dairy, and aquatic microbiology
• Biotechnology
• Genetic engineering and recombinant DNA technology
• Manipulating genes

Microbes Involved in

• Nutrient production and energy flow
• Decomposition
• Biotechnology (production of foods, drugs, and vaccines)
• Genetic engineering
• Bioremediation
• Infectious disease

Classification of Microorganisms (Protists)

I. Cellular

• Prokaryotes: Have no nucleus or a primitive nucleus (pro = before, karyon = nucleus). Examples include archaea, bacteria, and blue-green algae.
• Eukaryotes: Have a mature nucleus. Examples include algae (other than blue-green), fungi, and protozoans.

II. Non-Cellular

• Viruses, viroids, prions

Taxonomy

• The formal system of organizing, classifying, and naming living organisms
• Bacteria: Prokaryotic, unicellular organisms.
• Archaea: Prokaryotic, unicellular organisms that live in extreme environments.
• Algae: Eukaryotic organisms, often unicellular or multicellular, performing photosynthesis.
• Fungi: Eukaryotic, unicellular or multicellular organisms.
• Protozoa: Eukaryotic, unicellular, or multicellular organisms.
• Viruses: Noncellular, seen only by electron microscopy; consist of nucleic acid (NA) surrounded by a protein coat.

Bacterial Life Cycle

• Bacteria can exist in a vegetative form (metabolically active, growing, multiplying, and causing infection)
• In unfavorable conditions, some bacteria form endospores (spores) - a resting, non-growing, and highly resistant form, able to survive for years. When conditions improve, spores return to vegetative form (germination).

Cytoplasmic Organelles

• Mitochondria: Long, fluid-filled sacs (power site); contain ATP
• Ribosomes: Small granules of RNA; some free in cytoplasm, others attached to endoplasmic reticulum. (Protein synthesis)
• Endoplasmic Reticulum (ER):
• Smooth: Lipid synthesis
• Rough: Protein synthesis (for transport)
• Golgi Apparatus: Flat sacs; connected to ER; functions as a "shipping center".
• Lysosomes: Sacs containing digestive enzymes.
• Centrioles: Two rods at right angles; function in cell division.
• Cilia: Short, many, hair-like processes that create wave-like motion to move substances across cell surfaces.
• Flagella: Long, few structures that move the cell.
• Chloroplasts: (found in algae and plant cells); convert sun energy into chemical energy (photosynthesis).

Defense Mechanisms Against Infection

• Nonspecific Mechanisms: Act against all harmful agents; provide non-specific resistance
• Specific Mechanisms: Act against certain agents; provide specific resistance (immunity); lack of resistance is called susceptibility; virulance is the degree of pathogenicity of a specific microbe.

Nonspecific Defense Mechanisms

• Intact skin and mucous membranes
• Fluids (tears, saliva, urine)
• Complements (group of proteins acting in a sequence)
• Interferons (chemical substances)
• Phagocytosis (Two types: Neutrophils, Monocytes/macrophages)
• Inflammation (localized or systemic, characterized by redness, hotness, swelling, may include loss of function.)

Specific Defense Mechanisms (Immunity)

• Cell-mediated Immunity: Produced by T-cells (mainly against viruses and fungi). Includes Killer T-cells (destroy antigens) and Memory T-cells (remember antigen for a faster and stronger response upon re-exposure to the antigen).
• Antibody-mediated Immunity: Produced by B-cells (mainly against bacteria). Includes plasma cells (produce antibodies), Memory B-cells (recognize antigen for rapid secondary response)

Normal Flora/Microbiota

• Resident Flora: Normal flora present throughout a person's life (e.g. S. epidermidis, E. Coli).
• Transient Flora: May remain for a few hours to months (e.g. Bacillus Laterosporus)

Modes of Transmission

• Contact Transmission: Direct (physical contact) or indirect (e.g., fomite, contaminated object).
• Droplet Transmission: Infectious agents spread by respiratory droplets traveling less than 1 meter.
• Airborne Transmission: Infectious agents spread by fluids traveling more than 1 meter.
• Water-borne & Food-borne Transmission: Pathogens spread through contaminated water or food.
• Vector Transmission: Pathogens spread by animals or arthropods.

Applied Microbiology

• Includes subjects like food production, treatment of water, agricultural practices, and bioremediation.