Microbiology Exam 1: Unit 1 & 2 Overview

Introduction to Microorganisms

• Microorganisms are organisms too small to be seen with the naked eye.

Early Civilizations and Disease

• Aqueducts were constructed to manage sewage and reduce disease.
• Hippocrates emphasized natural causes of disease.
• Thucydides promoted evidence-based analysis of health events.
• Varro suggested that unseen entities (microorganisms) could cause sickness.

Contributions to Microscopy

• Zacharias Janssen invented the first simple microscope.
• Robert Hooke enhanced microscopes with improved features.
• Antony van Leeuwenhoek, known as the "Father of Microbiology," was the first to observe microbes.

Golden Age of Microbiology

• Louis Pasteur established germ theory, disproved spontaneous generation, and created vaccines, notably for rabies.
• Robert Koch identified pathogens responsible for diseases like cholera and anthrax.
• The attenuation principle helped reduce pathogen risks in vaccines.

Taxonomy and Classification

• Taxonomy is the science of classifying living organisms.
• Carolus Linnaeus created the binomial nomenclature system.
• Ernst Haeckel added a fourth kingdom, protista, to taxonomy.
• Robert Whittaker proposed a five-kingdom system, including fungi.
• Carl Woese categorized life into three domains: Bacteria, Archaea, and Eukarya.

Phylogenetic Trees and Kingdoms

• Phylogenetic trees visualize relationships among organisms.
• Six current kingdoms: Animalia, Plantae, Fungi, Protista, Archaea, Bacteria.
• Three main domains: Bacteria, Archaea, Eukarya.
• Taxonomic ranks include: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Cell Theory and Germ Theory

• Cell theory states that all cells originate from pre-existing cells.
• Robert Hooke discovered cells while examining cork.
• Germ theory posits that microbial infections can lead to diseases.

Key Figures in Epidemiology

• Ignaz Semmelweis discovered that handwashing reduced childbirth mortality rates.
• John Snow traced a cholera outbreak to a contaminated water source.
• Joseph Lister advocated for using carbolic acid to minimize postoperative infections.
• Florence Nightingale utilized statistics to highlight infection-related deaths.

Koch's Postulates

• Four criteria to establish a causative relationship between a microbe and a disease:
  • Microbe must be present in all affected individuals.
  • Microbe must be isolated and cultured.
  • Microbe must cause disease when introduced to a healthy host.
  • Microbe must be re-isolated from the new host.

Exceptions to Koch's Postulates

• Some pathogens are not consistently isolated outside the host.
• Certain pathogens cause multiple diseases.
• Some pathogens may affect only specific hosts.

Bacterial Structures

• Eukaryotes and prokaryotes share plasma membranes, cytoplasm, ribosomes, and DNA.
• Prokaryotes possess circular DNA and simpler structures, while eukaryotes have linear DNA and complex organelles.
• Cytoplasm refers to the entire cell content, while cytosol is the fluid component.

Bacterial Reproduction and Morphology

• Bacteria primarily reproduce via binary fission.
• Pleomorphic bacteria exhibit variability in size and shape.
• Various arrangements of bacteria include diplo (pairs), strepto (chains), and staphylo (clusters).

Glycocalyx Functionality

• Glycocalyx is a gelatinous layer surrounding some bacteria, aiding in nutrient trapping, surface attachment, and evading immune response.
• Two forms: Capsule (organized, tightly attached) and Slime layer (less organized, loosely attached).

Flagella and Movement

• Flagella facilitate bacterial mobility; arrangements include monotrichous (one), lophotrichous (cluster), and peritrichous (all around).
• Bacteria with endoflagella (e.g., spirochetes) exhibit unique motility patterns.
• Movement varies under stimulus: more systematic runs in the presence of attractants versus random tumbling without them.

Bacterial Cell Walls

• Bacterial cell walls maintain cell shape and prevent bursting.
• Peptidoglycan is the key component, composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
• Gram-positive walls are thicker and contain teichoic acids; Gram-negative walls are thinner and have an outer membrane with lipopolysaccharides (LPS).

Endotoxins and Virulency

• Lipid A, a component of LPS, acts as an endotoxin causing significant immune responses.
• Porins in Gram-negative bacteria serve as selective barriers affecting virulence.

Fluid Mosaic Model and Cell Membrane

• The fluid mosaic model describes the cell membrane as a dynamic and flexible phospholipid bilayer with interspersed proteins.
• Phospholipids possess hydrophilic heads and hydrophobic tails, creating a semipermeable barrier.

Endospores

• Endospores are resilient, dormant structures produced under adverse conditions by certain bacteria.

Microbial Metabolism

• Metabolism encompasses all cellular chemical reactions, with energy stored as ATP.
• Catabolic reactions break down large molecules to release energy, while anabolic reactions synthesize larger molecules from smaller ones using energy.

Enzymes and Regulation

• Enzymes, as biological catalysts, speed up chemical reactions by binding substrates at active sites.
• Cofactors are inorganic; coenzymes are organic molecules aiding enzyme function.

Glycolysis and Metabolic Pathways

• Glycolysis converts glucose into two pyruvate molecules and comprises two phases: energy investment and energy payoff.
• Major pathways for glucose catabolism include aerobic respiration (using oxygen), anaerobic respiration (alternative electron acceptors), and fermentation (absence of oxygen).