Introduction to Microbiology: Fundamental Concepts and Applications (Lecture 1)

What is Microbiology?

Definition and Scope

Microbiology is the study of microorganisms, which are organisms that exist as single cells or clusters of cells. This field includes the study of bacteria, protists, some algae, and some fungi. Bacteria are the primary focus of this course.

• Microorganisms can be unicellular or multicellular.

• Examples include Amoeba, Bacteria, Tapeworm, Bacterial viruses, Algae, and Slime molds.

Cell: The Fundamental Unit of Life

Cell Structure and Composition

The cell is the fundamental unit of all living matter, isolated from other cells by a membrane. It contains various structures and chemicals necessary for function:

• Proteins, nucleic acids, lipids, and polysaccharides are key components.

• These components are reviewed in detail in Chapter 2 (Chemical Principles).

Distinguishing Living Cells from Chemicals

• Self-feeding (nutrition): Uptake of chemicals from the environment and elimination of wastes.

• Self-replication (growth): Chemicals from the environment are turned into new cells.

• Differentiation: Cells can change structure based on function or life cycle.

• Chemical signaling: Cells interact by releasing or taking up chemicals.

• Evolution: Cells evolve new biological properties over time.

Two Ways to View Cells

Chemical Machines vs. Coding Devices

• Chemical Machines: Cells convert energy from one form to another.

  • Metabolism: All chemical reactions in cells.

  • Enzymes: Proteins that catalyze metabolic reactions.

• Coding Devices: Cells process information, similar to computers, using genetic material.

Two Kinds of Cells: Prokaryotes vs. Eukaryotes

Comparison Table

	Prokaryotes	Eukaryotes
Meaning of name	"before" nucleus	"true" nucleus
Nucleus	does not have	has
Membrane-bound organelles	does not have	has
Cell size	generally smaller	generally larger
# Chromosomes	most have 1 (haploid)	multiple chromosomes (diploid)
Examples	Bacteria, Archaea	Animals, Plants, Fungi, Protists

Prokaryotes: The Focus of this Course

Overview of Prokaryotic Cell Structure

• Membrane: Selective permeability barrier found in all cells.

• Cell wall: Provides structural support; not present in all prokaryotes.

• Cytoplasm: Fluid inside the cell; in prokaryotes, DNA floats in the cytoplasm and transcription/translation occur here.

Two Groups of Prokaryotes: Bacteria & Archaea

Classification and Evolution

• Prokaryotes are divided into Bacteria and Archaea.

• Eukaryotes, Archaea, and Bacteria are evolutionarily distinct but share a common ancestor.

Viruses: The Other "Microbe"

Characteristics of Viruses

• Viruses are much smaller than bacteria and eukaryotic cells.

• They are inert unless associated with a host organism.

• Contain genetic information (DNA or RNA, never both) but lack cellular machinery for replication.

• Structure: Protein bag containing nucleic acid.

Linnaeus Binomial Nomenclature System

Genus Species Naming

• Scientific names use Genus species format (italicized or underlined).

• Examples: Escherichia coli or E. coli, Homo sapiens.

• Classification hierarchy: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

The Current Classification System

Domains and Evolution

• Based on DNA sequence analysis, three major domains: Archaea, Bacteria, Eukaryotes.

• Classification system evolved over time (Woese, Whittaker, Linnaeus).

Archaea

Characteristics and Significance

• Extremophiles: Prefer extreme environments (high temperature, high salt, pH extremes, no O2).

• May represent some of the earliest life forms.

• Potential for extraterrestrial life (Mars, Europa, Titan, etc.).

How Do Microorganisms Affect Us?

Microbes and Disease

• Microbes can cause disease (bacterial, viral, fungal, algal diseases).

• Not all microbes are harmful; some are essential for health and well-being.

Microbes in Agriculture

• Bacteria in plant root nodules supply fixed nitrogen to plants.

• Ruminants (e.g., cows) have extra digestive organs containing Archaea and Bacteria to digest plant material.

Microbes in the Food Industry

• Cause food spoilage.

• Used in food production: cheese, yogurt, bread, pickles, wine, beer.

• Microbes influence taste, texture, and color of foods.

Microbes and Energy

• Methane and ethanol production: Microbes convert waste materials into fuel.

• Petroleum processing: Some microbes can degrade petroleum products.

• Alternative energy sources: Algae and seaweed used to produce biofuels.

Microbes and Biotechnology

• Use of microbes in large-scale industrial processes (e.g., production of human insulin from E. coli).

Product	Made in	Use
Human insulin	E. coli	Treatment for diabetes
Human growth hormone (hGH)	E. coli	Treatment for growth defects
Epidermal growth factor (EGF)	E. coli	Treatment for burns
Bovine growth hormone (BGH)	E. coli	Increase milk production in cows
Cellulase	E. coli	Convert cellulose to animal feed
Tissue plasminogen activator (TPA)	Mammalian cells	Treatment for heart attacks
Factor VIII	Mammalian cells	Treatment for hemophilia
Additional info: Table includes other recombinant protein products used in medicine and agriculture.

Microbes and the Future

• Biohydrometallurgy: Use of microbes to extract metals and ores.

• Bioremediation: Use of microbes to clean up environmental pollution (e.g., oil spills).

• Biosensors: Living microbes or enzymes linked with electrodes to detect biological reactions rapidly.

History of Microbiology

Early Theories and Discoveries

• Ancient Greeks and Lucretius theorized disease was caused by invisible particles.

• Microbiology as a science began with the ability to observe microorganisms.

Key Figures

• Robert Hooke (1664): First described fruiting bodies of mold (fungi).

• Antoni van Leeuwenhoek (1676): First described bacteria; used hand-held microscopes to examine pond water, soil, and other materials.

Development of Microbiology

• Early scientists built their own microscopes to observe microorganisms.

• These discoveries laid the foundation for modern microbiology.