Microbiology Exam Study Guide: Key Concepts and Review

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INTRODUCTION TO MICROBIOLOGY

Classification of Microorganisms

Microbiology is the study of microscopic organisms, including bacteria, archaea, algae, protozoa, helminths, mites, fungi, viruses, and prions. Understanding their classification is essential for identifying and studying their roles in nature and disease.

Bacteria: Single-celled prokaryotes with diverse metabolic capabilities.
Archaea: Prokaryotes distinct from bacteria, often found in extreme environments.
Algae: Photosynthetic eukaryotes, important in aquatic ecosystems.
Protozoa: Unicellular eukaryotes, often motile and found in water or soil.
Helminths: Multicellular parasitic worms.
Mites: Small arthropods, some of which are parasitic.
Fungi: Eukaryotic organisms including yeasts, molds, and mushrooms.
Viruses: Acellular entities requiring host cells for replication.
Prions: Infectious proteins causing neurodegenerative diseases.

TAXONOMY

Principles of Classification

Taxonomy is the science of classifying organisms based on shared characteristics. It provides a framework for identifying, naming, and grouping organisms.

Taxonomy: The systematic classification of living things.
Three Domains: Bacteria, Archaea, and Eukarya.
Prokaryotes: Organisms without a nucleus (Bacteria and Archaea).
Eukaryotes: Organisms with a nucleus (Eukarya includes fungi, protozoa, algae, helminths).
Major Classifications: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
Scientific Naming: Binomial nomenclature (Genus's species), e.g., Escherichia coli.

Example: Staphylococcus aureus is classified as follows: Domain: Bacteria, Phylum: Firmicutes, Class: Bacilli, Order: Bacillales, Family: Staphylococcic, Genus: Staphylococcus, Species: aureus.

HISTORY OF MICROBIOLOGY

Major Contributors and Their Discoveries

The development of microbiology has been shaped by many scientists. Their discoveries laid the foundation for modern understanding of microbes and disease.

Individual	Contributions
Anton van Leeuwenhoek	First to observe and describe microorganisms using a microscope.
Robert Koch	Established Koch's postulates; identified causative agents of tuberculosis, cholera, and anthrax.
Louis Pasteur	Disproved spontaneous generation; developed pasteurization; vaccines for rabies and anthrax.
Florence Nightingale	Pioneered infection control and hygiene in hospitals.
Joseph Lister	Introduced antiseptic surgery using carbolic acid.
John Needham	Supported spontaneous generation theory (later disproved).
Lazzaro Spallanzani	Disproved spontaneous generation with improved experimental design.
Paul Ehrlich	Developed chemotherapy; discovered Salvarsan for syphilis.
Edward Jenner	Developed the first vaccine (smallpox).
John Snow	Father of epidemiology; traced cholera outbreak to contaminated water.
Hans Christian Gram	Developed Gram staining technique for bacteria.
Ignaz Semmelweis	Promoted handwashing to prevent puerperal fever.
Ferdinand Cohn	Classified bacteria by shape; discovered bacterial endospores.
Alexander Fleming	Discovered penicillin.
Frederick Griffith	Discovered bacterial transformation.

Fathers of Microbiology: Anton van Leeuwenhoek, Louis Pasteur, and Robert Koch are often referred to as the "Fathers of Microbiology" due to their foundational contributions.

Laboratory Instruments: The development of the microscope was critical for microbiology.

Spontaneous Generation: The theory that life arises from non-living matter; disproved by Pasteur's experiments.

Abiogenesis vs. Biogenesis: Abiogenesis is the idea of life from non-life; biogenesis states that life arises from existing life.

BASIC CHEMISTRY FOR MICROBIOLOGY

Atoms, Bonds, and Macromolecules

Understanding basic chemistry is essential for studying microbial structure and function.

Atom: The smallest unit of matter, composed of protons, neutrons, and electrons.
Atomic Number: Number of protons in the nucleus.
Isotopes: Atoms of the same element with different numbers of neutrons.
Valence Shell: Outermost electron shell; determines chemical reactivity.
Covalent Bonds: Atoms share electrons.
Ionic Bonds: Atoms transfer electrons.
Hydrogen Bonds: Weak bonds important in biological molecules.

Macromolecules: Large molecules essential for life, including carbohydrates, proteins, lipids, and nucleic acids.

Carbohydrates: Energy source and structural component. Monosaccharides (simple sugars), disaccharides, polysaccharides.
Proteins: Made of amino acids; function as enzymes, structural components, and signaling molecules.
Lipids: Fats, oils, and phospholipids; important for membranes and energy storage.
Nucleic Acids: DNA and RNA; store and transmit genetic information.

Example Equation:

(Glucose oxidation in cellular respiration)

CELL STRUCTURE

Anatomy and Processes of the Cell

Cells are the basic units of life. Their structure and function are central to microbiology.

Cell Membrane: Phospholipid bilayer controlling entry and exit of substances.
Cell Wall: Provides structural support; composition varies between organisms.
Peptidoglycan: Major component of bacterial cell walls.
Gram-Positive vs. Gram-Negative: Gram-positive bacteria have thick peptidoglycan; Gram-negative have thin peptidoglycan and outer membrane.
Flagella: Structures for motility.
Endospore: Resistant structure formed by some bacteria for survival.
Archaeal Cell Walls: Lack peptidoglycan; may contain pseudopeptidoglycan.

Cell Processes: Transport (active, passive), metabolism, replication, and secretion.

CHARACTERIZATION OF VIRUSES AND PRIONS

Structure and Replication

Viruses and prions are acellular infectious agents with unique properties.

Viruses: Composed of nucleic acid (DNA or RNA) and protein coat (capsid); may have an envelope.
Viral Envelope: Lipid membrane derived from host cell.
Replication: Viruses require host cells; bacteriophage replication includes lytic and lysogenic cycles.
Prions: Infectious proteins causing diseases such as Creutzfeldt-Jakob disease; affect nervous system.

Example: Bacteriophage replication involves attachment, penetration, biosynthesis, maturation, and release.

Endosymbiotic Theory: Eukaryotic organelles (mitochondria, chloroplasts) originated from symbiotic bacteria.

ADDITIONAL INFO

Scientific Method: Used to test hypotheses and develop scientific knowledge.
Microscopy: Essential for observing microorganisms; includes light, electron, and fluorescence microscopy.