BIO 1550 Midterm 1 Study Guide: Foundations of Microbiology

Introduction to Microbiology

Historical Experiments Disproving Spontaneous Generation

• Francesco Redi’s Experiment: Redi demonstrated that maggots do not spontaneously arise from decaying meat, but rather from eggs laid by flies. He used covered and uncovered jars to show that only meat exposed to flies developed maggots.

• Principle: Life does not spontaneously arise from non-living matter; it originates from pre-existing life.

• Louis Pasteur’s Experiment: Pasteur used swan-necked flasks containing broth. Air could enter, but microbes were trapped in the neck. No microbial growth occurred unless the flask was tilted, allowing microbes to contact the broth.

• Principle: Microorganisms are present in the air and can contaminate sterile solutions, but spontaneous generation does not occur.

Aseptic Technique

• Definition: Procedures used to prevent contamination by unwanted microorganisms during laboratory work.

• Application: Used in microbiology labs, medical procedures, and food industry to maintain sterility.

Microscopes and Microbial Diversity

Invention of the Microscope

• Inventor: Antonie van Leeuwenhoek is credited with inventing the first practical microscope and observing microorganisms.

• Impact: Enabled the discovery and study of microorganisms.

Benefits of Microorganisms

• Environmental: Decomposition, nutrient cycling, and bioremediation.

• Industrial: Production of antibiotics, enzymes, and fermented foods.

• Medical: Normal microflora protect against pathogens.

Three Domains of Biological Classification

• Bacteria: Prokaryotic, peptidoglycan cell walls.

• Archaea: Prokaryotic, lack peptidoglycan, often found in extreme environments.

• Eukarya: Eukaryotic, includes algae, fungi, protozoa, and animals.

Microbial Cell Structures and Staining

Gram Staining Concept

• Definition: Differential staining technique to classify bacteria as Gram-positive or Gram-negative based on cell wall structure.

• Gram-positive: Thick peptidoglycan layer, stains purple.

• Gram-negative: Thin peptidoglycan layer, outer membrane, stains pink.

Acid-Fast Staining Concept

• Definition: Used to identify bacteria with waxy cell walls (e.g., Mycobacterium).

• Result: Acid-fast bacteria retain red dye; non-acid-fast lose dye and stain blue.

Archaea and Their Environments

• Characteristics: Prokaryotic, lack peptidoglycan, unique membrane lipids.

• Habitats: Extreme environments (high salt, temperature, acidity).

Bacterial Cell Components

• Cell Wall: Contains peptidoglycan.

• Nucleoid: Region containing DNA.

• Ribosomes: Sites of protein synthesis.

• Other Structures: Flagella, pili, plasmids.

Microflora

• Definition: The community of microorganisms living in and on the human body.

• Functions: Protects against pathogens, aids digestion, synthesizes vitamins.

Peptidoglycan Location

• Found in: Bacterial cell walls, provides structural support.

Characteristics of Algae, Fungi, and Protozoa

• Algae: Photosynthetic, aquatic, eukaryotic.

• Fungi: Non-photosynthetic, decomposers, eukaryotic, cell walls of chitin.

• Protozoa: Unicellular, motile, eukaryotic, no cell wall.

Viruses, Prions, and Viroids

• Viruses: Acellular, very small (20-300 nm), consist of nucleic acid and protein coat, require host for replication.

• Prions: Infectious proteins, cause neurodegenerative diseases (e.g., mad cow disease).

• Viroids: Infectious RNA molecules, affect plants.

Chemical Principles of Microbiology

Ionic and Covalent Bonds

• Ionic Bonds: Formed by transfer of electrons between atoms, resulting in charged ions.

• Covalent Bonds: Formed by sharing electrons between atoms.

Polar and Non-Polar Bonds

• Polar Bonds: Unequal sharing of electrons, resulting in partial charges (e.g., water).

• Non-Polar Bonds: Equal sharing of electrons, no charge separation (e.g., methane).

Hydrogen Bonds

• Definition: Weak attraction between a hydrogen atom and an electronegative atom (e.g., oxygen, nitrogen).

• Importance: Stabilizes DNA, proteins, and water properties.

Amino Acids, Proteins, and Protein Bonds

• Amino Acids: Building blocks of proteins, contain amino and carboxyl groups.

• Protein Bonds: Peptide bonds link amino acids.

Protein Structure

• Primary: Sequence of amino acids.

• Secondary: Alpha helices and beta sheets, stabilized by hydrogen bonds.

• Tertiary: 3D folding, stabilized by interactions among side chains.

• Quaternary: Association of multiple polypeptides.

Protein Denaturation

• Definition: Loss of protein structure due to heat, pH, or chemicals.

• Effect: Loss of function.

Enzymes and Activation Energy

• Enzymes: Biological catalysts that speed up reactions.

• Function: Lower activation energy required for reactions.

• Activation Energy Equation:

$\Delta G = G_{products} - G_{reactants}$

Enzymes lower the energy barrier for the reaction.

Carbohydrates and Formation

• Definition: Organic molecules composed of C, H, and O.

• Formation: Monosaccharides join via glycosidic bonds to form polysaccharides.

Peptide and Glycosidic Bond Formation

• Peptide Bonds: Formed between amino acids during protein synthesis.

• Glycosidic Bonds: Formed between monosaccharides during carbohydrate synthesis.

Dehydration and Hydrolysis Reactions

• Dehydration: Removal of water to form bonds (synthesis).

• Hydrolysis: Addition of water to break bonds (degradation).

Nucleic Acids and Base Pairing

• Nucleic Acids: DNA and RNA, composed of nucleotides.

• Double-Stranded Structure: DNA forms a double helix.

• Base Pairing: A:T and G:C in DNA.

Lipids: Types and Properties

• Triglycerides: Energy storage, composed of glycerol and fatty acids.

• Phospholipids: Major component of cell membranes.

• Steroids: Hormones and membrane structure.

• Nonpolar Properties: Lipids are hydrophobic, insoluble in water.

Phospholipids in Membranes

• Location: Found in cell membranes.

• Arrangement: Hydrophilic heads face outward, hydrophobic tails face inward, forming a bilayer.

Fluid Mosaic Model and Membrane Proteins

• Model: Membranes are dynamic, with proteins embedded in a fluid lipid bilayer.

• Functions: Transport, signaling, structural support.

Cell Membrane & Transport

Osmosis and Water Movement

• Definition: Movement of water across a semipermeable membrane from low solute to high solute concentration.

• Direction: Water moves toward higher solute concentration.

Passive and Active Transport

• Passive Transport: No energy required; includes diffusion and facilitated diffusion.

• Active Transport: Requires energy (ATP); moves substances against concentration gradient.

Exocytosis and Endocytosis

• Exocytosis: Release of substances from cells via vesicles.

• Endocytosis: Uptake of substances into cells via vesicles.

Phagocytosis and Pinocytosis

• Phagocytosis: "Cell eating"; uptake of large particles.

• Pinocytosis: "Cell drinking"; uptake of fluids.

Prokaryotic and Eukaryotic Cell Structures

Gram-Positive vs. Gram-Negative Cell Walls

• Gram-Positive: Thick peptidoglycan, teichoic acids, no outer membrane.

• Gram-Negative: Thin peptidoglycan, outer membrane with lipopolysaccharides.

Feature	Gram-Positive	Gram-Negative
Peptidoglycan	Thick	Thin
Outer Membrane	Absent	Present
Teichoic Acids	Present	Absent
Lipopolysaccharide	Absent	Present

Endospore

• Definition: Dormant, resistant structure formed by some bacteria (e.g., Bacillus, Clostridium).

• Function: Survives harsh conditions (heat, desiccation, chemicals).

Organelles and Their Functions

• Nucleus: Contains genetic material.

• Mitochondria: Energy production.

• Endoplasmic Reticulum: Protein and lipid synthesis.

• Golgi Apparatus: Protein modification and sorting.

• Lysosomes: Digestion of cellular waste.

• Chloroplasts: Photosynthesis (in plants and algae).