Microbiology Exam 1 Study Guide: Chapters 1–6

Chapter 1: Introduction to Microbiology

Scientific Contributions and Historical Figures

This section covers the foundational scientists and their impact on microbiology.

• Antonie van Leeuwenhoek: First to observe and describe microorganisms using a microscope.

• Louis Pasteur: Disproved spontaneous generation, developed pasteurization, and contributed to vaccine development.

• Robert Koch: Established Koch's postulates, linking specific microbes to specific diseases.

• Other contributors: Lister (antiseptic surgery), Semmelweis (handwashing), Jenner (smallpox vaccine), Koch, Nightingale (nursing and hygiene).

Key Terms:

• Prokaryotic vs. Eukaryotic Organisms: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have both.

• Scientific Method: Systematic approach to research involving observation, hypothesis, experimentation, and conclusion.

• Spontaneous Generation: The disproven idea that life arises from non-living matter.

• Koch's Postulates: Criteria to establish a causative relationship between a microbe and a disease.

Example: Pasteur's swan-neck flask experiment disproved spontaneous generation by showing that sterilized broth remained free of microbes unless exposed to air.

Chapter 2: Chemical Foundations of Microbiology

pH Scale and Nucleic Acids

This chapter introduces basic chemistry concepts relevant to microbiology.

• pH Scale: Measures acidity or alkalinity; ranges from 0 (acidic) to 14 (basic), with 7 as neutral.

• Nucleotides: Building blocks of nucleic acids (DNA and RNA).

• Nitrogenous Bases: Adenine, Thymine, Cytosine, Guanine, and Uracil (in RNA).

• Classes of Nucleic Acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid); DNA stores genetic information, RNA is involved in protein synthesis.

Example: DNA is composed of four nitrogenous bases: adenine, thymine, cytosine, and guanine.

Chapter 3: Cell Structure and Function

Prokaryotic and Eukaryotic Cells

This chapter explores the structure and function of microbial cells.

• Major Processes of Living Cells: Metabolism, growth, reproduction, response to stimuli, and homeostasis.

• Cell Wall Comparison: Prokaryotic cell walls contain peptidoglycan (bacteria), while eukaryotic cell walls (plants, fungi) have cellulose or chitin.

• Glycocalyx: A protective, sticky layer outside the cell wall; important for adherence and evasion of host defenses.

• Slime Layers vs. Capsules: Slime layers are loosely attached; capsules are firmly attached and more organized.

• Flagella: Structures for motility; arrangement and structure differ between bacteria and eukaryotes.

• Pili and Fimbriae: Hair-like structures for attachment (fimbriae) or DNA transfer (pili).

• Gram Stain: Differentiates bacteria into Gram-positive (thick peptidoglycan, purple) and Gram-negative (thin peptidoglycan, pink) based on cell wall structure.

• Acid-Fast Bacteria: Have waxy cell walls; resist decolorization by acids (e.g., Mycobacterium).

• Ribosomes: Sites of protein synthesis; prokaryotic (70S) and eukaryotic (80S) ribosomes differ in size and structure.

• Endosymbiotic Theory: Proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

Example: The Gram stain is a critical diagnostic tool in clinical microbiology.

Chapter 4: Microbial Classification and Identification

Staining and Taxonomy

This chapter covers methods for classifying and identifying microorganisms.

• Staining Techniques: Gram, acid-fast, and endospore stains differentiate bacteria based on cell wall and structural properties.

• Binomial Nomenclature: System of naming organisms using genus and species (e.g., Escherichia coli).

• Three Domains: Bacteria, Archaea, and Eukarya, as proposed by Carl Woese based on ribosomal RNA sequences.

• Identification Procedures: Include staining, biochemical tests, and molecular methods.

Example: Acid-fast staining is used to identify Mycobacterium tuberculosis.

Chapter 5: Microbial Metabolism

Metabolic Pathways and Energy Production

This chapter explains how microorganisms obtain and use energy.

• Metabolism: Sum of all chemical reactions in a cell, including catabolism (breakdown) and anabolism (synthesis).

• ATP Phosphorylation: Three types: substrate-level, oxidative, and photophosphorylation.

• Enzyme Activity: Enzymes lower activation energy; affected by temperature, pH, substrate concentration, and inhibitors.

• Glycolysis, Krebs Cycle, Electron Transport Chain: Central metabolic pathways for energy production.

• Fermentation: Anaerobic process producing ATP and byproducts like lactic acid or ethanol.

• Photosynthesis: Conversion of light energy to chemical energy; involves light-dependent and light-independent reactions.

Example: In glycolysis, one molecule of glucose is converted to two molecules of pyruvate, producing ATP and NADH.

Equation:

$\text{C}_6\text{H}_{12}\text{O}_6 + 2\text{NAD}^+ + 2\text{ADP} + 2\text{P}_i \rightarrow 2\text{C}_3\text{H}_4\text{O}_3 + 2\text{NADH} + 2\text{ATP} + 2\text{H}_2\text{O}$

Chapter 6: Microbial Growth and Nutrition

Growth Requirements and Measurement

This chapter discusses how microbes grow and how their growth is measured.

• Categories by Carbon and Energy Source: Autotrophs (CO2 as carbon source), heterotrophs (organic carbon), phototrophs (light energy), chemotrophs (chemical energy).

• Oxygen Requirements: Obligate aerobes, obligate anaerobes, facultative anaerobes, aerotolerant anaerobes, microaerophiles.

• Toxic Forms of Oxygen: Superoxide radicals, hydrogen peroxide, hydroxyl radicals; microbes have enzymes (e.g., catalase, superoxide dismutase) to neutralize them.

• Nitrogen Fixation: Conversion of atmospheric nitrogen to ammonia by certain bacteria; essential for biosynthesis.

• Biofilms: Communities of microbes attached to surfaces; formed via quorum sensing.

• Streak Plate Method: Technique to isolate pure bacterial colonies.

• Cultural Media: Types include nutrient agar, selective, differential, and enriched media.

• Binary Fission: Asexual reproduction in bacteria; leads to exponential growth.

• Growth Curve: Four phases: lag, log (exponential), stationary, and death.

• Measuring Growth: Direct methods (plate counts, microscopy) and indirect methods (turbidity, metabolic activity).

Example: Facultative anaerobes like Escherichia coli can grow with or without oxygen.

Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
Cell Wall Composition	Peptidoglycan (bacteria)	Cellulose (plants), chitin (fungi), or absent
Ribosome Size	70S	80S
Examples	Bacteria, Archaea	Fungi, Protozoa, Plants, Animals

Additional info:

• Some details, such as the specific steps of the Gram stain or the structure of ATP, can be found in standard microbiology textbooks for further study.

• Reviewing chapter summaries and critical thinking questions will reinforce understanding of these concepts.