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Microbiology Notes – Units 1 & 2

Development & Scope of Microbiology

  • Microbiology = study of microbes (living & certain non-living entities)

    • Requires microscopes; individual microbes are usually invisible to naked eye.

    • Microbes are ubiquitous – virtually everywhere.

  • Nursing/health-care context

    • Understand pathogens, opportunistic pathogens & normal biota.

    • Guide aseptic technique, infection control, antimicrobial choice.

  • Study outcomes for Unit 1.1

    • Define microbiology.

    • Explain field development & scope.

    • Relate microbiology to health-service careers.

    • Apply correct terminology in context.

Essential Terminology & Concepts

  • Pathogenic – causes disease.

  • Non-pathogenic – does not cause disease; often beneficial/essential.

  • Opportunistic pathogen – normally commensal; causes disease only when host resistance ↓.

  • Infectious disease – illness produced by pathogenic microbes; transmissible.

  • Saprophyte – lives on/feeds from dead organic matter (decomposer).

  • Protozoa – unicellular, eukaryotic; water/soil inhabitants; some pathogenic.

  • Parasite – lives in/on host; uses host resources; harms or may kill host.

  • Infectious agent – material capable of infection (bacteria, viruses, fungi, protozoa, helminths).

  • Bacteria – prokaryotic, single-celled, no nucleus.

  • Algae – eukaryotic, chlorophyll-containing, photosynthetic.

  • Fungi – multicellular (except yeasts), non-photosynthetic; parasitic or saprophytic.

  • Viruses – sub-microscopic, replicate only inside living cells.

  • Prions – infectious proteins; cause neuro-degenerative diseases.

  • Mycology – study of fungi; scientist = mycologist.

  • Viroids – small, single-stranded RNA agents; plant diseases; lack capsid.

  • Zoonoses – diseases transmissible animal ↔ human.

Pathogens & Opportunists in Health Careers

  • Diagnosis, treatment & prevention depend on recognising:

    • When microbes are pathogenic vs. part of normal flora.

    • Risk factors lowering host immunity → opportunistic infection.

  • Influence development of aseptic technique, antibiotic stewardship, infection surveillance.

Microbial Size & Subgroups (Illustrative Diseases)

  • Viruses → AIDS, influenza, rabies, polio, hepatitis, measles, smallpox, etc.

  • Bacteria → tuberculosis, cholera, tetanus, syphilis, UTIs, plague, anthrax, etc.

  • Fungi → ringworm, thrush, cryptococcosis, histoplasmosis.

  • Algae → rare intoxications.

  • Protozoa → malaria, amoebic dysentery, African sleeping sickness.

Why Study Microbiology?

  • Indigenous biota: normal flora essential to health.

  • Opportunistic pathogens: trigger disease when host compromised.

  • Ecological roles

    • Base of food chains.

    • Nutrient cycling (saprophytes).

    • Bioremediation & microbial ecology.

  • Biotechnology products: antibiotics, enzymes, vaccines, fermented foods.

  • Genetic manipulation: cloning, recombinant proteins.

  • Cellular models for molecular biology.

  • Pathogenesis: infections vs. intoxications; bio-terrorism awareness.

Earliest Evidence of Disease

  • Fossils/mummies: tuberculosis, syphilis, helminths.

  • Bubonic plague (pestilence) – Egypt (3180\,\text{BC} - 1900\,\text{BC}), Rome (790\,\text{BC}), Greece (430\,\text{BC}).

  • Smallpox – China (1122\,\text{BC}).

  • Other ancient diseases – typhus, syphilis (New World).

Microscopy in Microbiology (Unit 1.2)

Optical Principle

  • Each instrument has a resolving power (resolution) – minimum distance at which two points are seen separately.

Compound Light Microscope – Main Parts

  • Ocular (eyepiece)

  • Body tube

  • Nosepiece (revolving)

  • Objectives (scanning, low, high, oil-immersion)

  • Platform / Stage (+ stage adjustment knobs)

  • Arm & Base

  • Condenser + Diaphragm control

  • Light source & intensity knob

  • Coarse & fine focus knobs

Other Microscope Types & Applications

  • Bright-field – stained specimens, routine use.

  • Dark-field – live, unstained organisms (e.g., spirochetes).

  • Phase-contrast – internal structures in living cells.

  • Fluorescence – antibody-labelled organisms.

  • Electron (TEM, SEM) – ultra-high resolution of viruses, cell ultrastructure.

Contributions of Early Scientists (Unit 1.3)

Koch’s Postulates (Experimental Proof of Germ Theory)

  1. Specific microbe present in all cases of disease; absent in healthy hosts.

  2. Isolate microbe & culture purely in lab.

  3. Inoculate pure culture into healthy susceptible host → same disease produced.

  4. Re-isolate identical microbe from experimentally infected host & reculture.

  • When steps 1–4 met → causative agent established.

Exceptions / Limitations

  • Some pathogens cannot be cultured in vitro.

  • Ethical/impractical to inoculate humans; animal models unavailable for certain agents.

  • Polymicrobial (synergistic) diseases require >1 species.

  • Pathogens may lose virulence/adapt when cultured.

Key Historical Figures & Terms

  • Abiogenesis (Spontaneous generation) – life from non-living matter.

  • Biogenesis – life from pre-existing life.

  • Anton van Leeuwenhoek (1632-1723)

    • First to observe live bacteria & protozoa (“animalcules”).

    • Built single-lens microscopes; Father of Microbiology/Bacteriology/Protozoology.

  • Louis Pasteur (1822-1895)

    • Disproved spontaneous generation; supported biogenesis.

    • Coined aerobes vs. anaerobes.

    • Invented pasteurization; vaccines (rabies, anthrax); advanced germ theory; improved hospital hygiene.

  • Robert Koch (1843-1910)

    • Formulated postulates; cultured bacteria on solid media; discovered agents of TB (Mycobacterium\ tuberculosis), cholera (Vibrio\ cholerae); described spores of Bacillus\ anthracis.

Eukaryotic Cell Structure (Unit 2.1)

Foundational Definitions

  • Cell theory – cell = basic unit of life.

  • Protoplasm – living substance (cytoplasm + nucleoplasm).

  • Metabolism – sum of all reactions (anabolism + catabolism) → growth, reproduction, response, mutation.

Major Eukaryotic Components & Functions

  • Cell membrane – phospholipid–protein mosaic; selectively permeable.

  • Nucleus – genetic control centre

    • Nuclear envelope with pores.

    • Chromosomes (linear dsDNA + histones).

    • Nucleolus – rRNA synthesis, ribosome assembly.

  • Cytoplasm

    • Cytosol – fluid matrix; most metabolic reactions.

    • Organelles & inclusion granules.

  • Endoplasmic Reticulum (ER)

    • Rough ER – ribosome-studded, protein synthesis/processing.

    • Smooth ER – lipid synthesis, detoxification.

  • Ribosomes – 80\,S (large 60\,S + small 40\,S); translate mRNA → polypeptides; polysomes.

  • Golgi Apparatus – modifies, sorts & packages proteins; vesicle trafficking.

  • Lysosomes – digestive enzymes (lysozyme); autolysis, phagocytosis.

  • Peroxisomes – generate & degrade H2O2 via catalase.

  • Mitochondria – ATP powerhouse; contain own DNA; endosymbiont origin.

  • Plastids (e.g., chloroplasts) – photosynthesis (plants/algae); chlorophyll.

  • Cytoskeleton – microtubules, microfilaments, intermediate filaments; structure, transport, division \Rightarrow mitosis/meiosis.

  • Cell wall (plants – cellulose; fungi – chitin; algae – cellulose/others). Absent in animals.

  • Flagella/Cilia – motility; eukaryotic arrangement 9 + 2 microtubules.

Prokaryotic Cell Structure (Unit 2.2)

  • Cell membrane – metabolic enzymes; mesosomes.

  • Chromosome – single, circular, supercoiled DNA.

  • Plasmids – extra-chromosomal DNA; antibiotic resistance, toxins, conjugation traits.

  • Cytoplasm – similar chemistry to eukaryotes; lacks organelles.

  • Ribosomes – 70\,S (50\,S + 30\,S).

  • Inclusion/Storage granules – starch, lipid, sulfur, iron.

  • Cell wall – rigid; unique peptidoglycan.

    • Gram-positive: thick peptidoglycan, teichoic acid, no outer membrane.

    • Gram-negative: thin peptidoglycan in periplasmic space, outer membrane (LPS), no teichoic acid.

    • Mycoplasma – no cell wall.

    • Archaea – no peptidoglycan.

  • Glycocalyx – slime layer (loose) or capsule (tight); adhesion, anti-phagocytic, prevents desiccation.

  • Flagella – motility; arrangements: monotrichous, lophotrichous, amphitrichous, peritrichous; axial filaments (spirochetes).

  • Pili/Fimbriae

    • Attachment pili.

    • Sex pili – conjugation DNA transfer.

  • Endospores – dormant survival bodies (Bacillus, Clostridium); resistant to heat, drying, chemicals; not reproductive.

Eukaryotes vs. Prokaryotes (Key Differences)

Feature

Eukaryote

Prokaryote

Nuclear membrane

Present

Absent

Chromosomes

Linear, multiple

Single, circular

Organelles

Membrane-bound

Absent

Ribosomes

80\,S

70\,S

Microtubules

Present

Absent

Spores

Reproductive (fungi, plants)

Endospores for survival

Taxonomy (Unit 2.3)

Definitions

  • Taxonomy – science of classification.

  • Taxon (pl. taxa) – group/category (kingdom, phylum, class, order, family, genus, species, subspecies).

  • Nomenclature – assignment of names.

  • Identification – determining placement of unknown organism.

Binomial System Rules

  1. Each species gets two names (binomial):

    • Genus – capitalised.

    • species – lower-case.

  2. Entire name italicised or underlined, e.g. Escherichia coli.

  3. After first full mention, genus may be abbreviated: E. coli.

Major Classification Schemes

  • Five-Kingdom: Prokaryotae/Monera, Protista, Fungi, Plantae, Animalia.

  • Three-Domain (Woese): Archaea, Bacteria, Eukarya.

Cell Morphology Terms

  • Cocci – spherical.

  • Bacilli – rods.

  • Vibrio – comma-shaped.

  • Spirillum/Spirochete – spiral.

  • Pleomorphic – variable shape.

Cell Arrangement Prefixes/Suffixes

  • Strepto- – chains.

  • Diplo- – pairs.

  • Tetrad – groups of 4.

  • Sarcinae – cubic packets (2 tetrads).

  • Staphylo- – clusters.

These bullet-point notes comprehensively capture the transcript’s content, integrating definitions, historical context, structural biology, microscopy, pathogenesis, and taxonomic rules for exam preparation.