BIO Exam 1: Ch 1

Introduction to Microbiology

Theories of Evolution and Science

Microbiology is grounded in scientific theories that explain the diversity and adaptation of life. The theory of evolution describes how organisms change over time to adapt to their environments, a process observable in all living things.

• Evolution: The gradual accumulation of structural and functional changes in organisms over long periods.

• Scientific Theories: Well-tested explanations, not random guesses, that have withstood extensive experimentation and observation.

• Testability: Theories must be testable and falsifiable through scientific methods.

• Example: The ongoing documentation of evolutionary changes in microbial populations, such as antibiotic resistance.

Introduction to Prokaryotic and Eukaryotic Cells

Prokaryotic Cells

Prokaryotes are the earliest and simplest forms of life, dating back approximately 3.5 billion years. They include Bacteria and Archaea.

• Characteristics: Single-celled, lack a nucleus, and have simple cellular organization.

• Domains: Bacteria and Archaea.

Eukaryotic Cells

Eukaryotic cells are more complex and evolved from prokaryotic ancestors. They possess a true nucleus and membrane-bound organelles.

• Domains: Eukarya (includes protists, fungi, plants, and animals).

• Evolution: Eukaryotes evolved from prokaryotes, leading to greater complexity and multicellularity.

Endosymbiotic Theory

The endosymbiotic theory explains the origin of mitochondria and chloroplasts in eukaryotic cells.

• Key Idea: Mitochondria and chloroplasts were once free-living aerobic prokaryotes that were engulfed by larger anaerobic prokaryotes.

• Evidence: These organelles have their own DNA and replicate independently within the cell.

• Example: Mitochondria in animal cells and chloroplasts in plant cells.

Taxonomy and Classification of Microorganisms

Taxonomy

Taxonomy is the science of classifying living organisms, providing a universal language for identification and study.

• Founder: Carl von Linnaeus.

• Nomenclature: Scientific names are italicized; genus is capitalized, species is lowercase (e.g., Escherichia coli).

• Classification Hierarchy:

Level	Description
Domain	Broadest category (e.g., Bacteria, Archaea, Eukarya)
Kingdom	Next level (e.g., Animalia, Plantae)
Phylum	Major lineage within a kingdom
Class	Group within a phylum
Order	Group within a class
Family	Group within an order
Genus	Group within a family
Species	Most specific level; organisms that can interbreed

• Identification: Determining the exact identity of a microorganism using classification and nomenclature.

Microbiology in Everyday Life

Applications and Importance

Microorganisms are ubiquitous and play vital roles in various sectors.

• Healthcare: Pathogen identification, vaccine development, antibiotic production.

• Agriculture: Soil fertility, pest control.

• Industry: Fermentation (e.g., yeast in baking and brewing), bioremediation (cleaning oil spills).

• Environmental Science: Water and sewage treatment.

• Human Dependence: Food production, medication synthesis, environmental detoxification.

Pathogens and Disease

• Pathogen: A microbe that causes disease.

• Statistics: About 1,400 known human pathogens; less than 1% of microbes are pathogenic.

• True Pathogens: Always cause disease in humans.

• Opportunistic Pathogens: Cause disease only in weakened hosts (e.g., elderly, immunocompromised).

Historical Milestones in Microbiology

Golden Age of Microbiology

• Timeframe: 1860s–1920s.

• Key Event: 1945, first flu vaccine developed.

Spontaneous Generation vs. Biogenesis

• Spontaneous Generation (SG): The outdated belief that life arises from non-living matter.

• Biogenesis: Life arises only from pre-existing life.

• Louis Pasteur: Disproved SG using swan-neck flask experiments; developed pasteurization and vaccines for anthrax and rabies.

Germ Theory of Disease

• Concept: Microbes cause specific infectious diseases.

• Robert Koch: Identified causative agents of anthrax, tuberculosis, and cholera.

• Koch's Postulates:

Postulate	Description
1	The same organism must be present in every case of the disease.
2	The organism must be isolated and grown in pure culture.
3	The isolated organism should cause the same disease when introduced into a healthy host.
4	The organism must be re-isolated from the experimentally infected host.

Notable Scientists

• Edward Jenner: Developed the smallpox vaccine; considered the father of immunology.

• Florence Nightingale: Founder of modern nursing.

• Alexander Fleming: Discovered penicillin, leading to the development of antibiotics.

Scientific Method and Scientific Reasoning

Scientific Method

• Begins with a question.

• Formulate a hypothesis (testable explanation).

• Analyze observations and data.

• Draw conclusions (support or refute the hypothesis).

Law vs. Theory

• Law: A precise statement or mathematical formula predicting specific occurrences (describes what happens).

• Theory: Explains how and why phenomena occur.

Microbial Communities and Laboratory Techniques

Biofilms

Biofilms are structured communities of microorganisms attached to surfaces and embedded in a self-produced matrix.

• Examples: Dental plaque (film on teeth).

• Stages: Attachment, growth, detachment.

Microbial Growth and Environments

• Microbes can survive in diverse environments.

• Each species requires specific growth conditions.

• Growth media can help identify the source of microbes (e.g., brain, stomach, lungs).

• Microbial colonization can begin before birth.

Aseptic Culture Techniques

• Pure Culture: Isolating a single type of microbe from a mixed sample.

• Streak Plate Technique: Used to isolate colonies for study.

• Colony: A group of cells derived from a single parent cell.

• Mixed Culture: Contains more than one type of microbe.

• Importance: Accurate identification guides appropriate treatment (e.g., diagnosing strep throat).

Differential Staining Techniques

• Gram Stain: Differentiates bacteria into gram-positive and gram-negative based on cell wall structure.

• Acid-Fast Stain: Identifies bacteria with waxy cell walls (e.g., Mycobacterium).

• Staining Steps (Gram): Crystal violet, iodine, acetone, safranin.

Microscopy in Microbiology

Microscope Development

• Zacharias Janssen: Built one of the earliest microscopes.

• Antoni van Leeuwenhoek: Father of microscopy; improved lens design and observed microbes.

Types of Light Microscopy

• Bright Field: Standard illumination; best for stained specimens.

• Dark Field: Enhances contrast in unstained samples.

• Phase Contrast: Visualizes live, unstained cells by enhancing differences in refractive index.

• Differential Interference Contrast (DIC): Produces 3D-like images of live cells.

Electron Microscopy

• Resolution: Improves with shorter wavelengths.

• Visible Light: Smallest wavelength ~400 nm.

• Electron Beams: Wavelength ~1 nm, allowing much higher resolution.

• Transmission Electron Microscope (TEM): Visualizes internal structures.

• Scanning Electron Microscope (SEM): Visualizes surface details.

Host-Microbe Interactions

Types of Symbiotic Relationships

• Host: The organism that harbors the microbe.

• Parasitism: Microbe harms the host.

• Mutualism: Both host and microbe benefit.

• Commensalism: Microbe benefits; host is unaffected.

Normal Microbiota and the Human Microbiome

• Human Microbiome Project (HMP): Aims to characterize all microbes associated with the human body.

• Normal Microbiota (Flora): Includes bacteria, archaea, and eukaryotic microbes that reside in and on the human body.

• Statistics: 27% of adults carry Staphylococcus bacteria; most normal microbiota are harmless.