Microbiology Overview

Overview

This lecture introduced the foundational concepts of microbiology, focusing on types of microorganisms, their roles, history of the field, and basic classification and taxonomy, using Talaro's Foundations in Microbiology.

Introduction to Microbiology

• Microbiology is the study of organisms or infectious agents too small to be seen without magnification.
• Organisms are living things that belong to one of the three domains of life: Bacteria, Archaea, Eukarya.
• Small infectious agents (like viruses and prions) are not alive and do not fall into these domains.

Types of Microorganisms

• Microorganisms include bacteria, archaea, fungi, protozoa, algae, and helminths (worms).
• Helminths are studied because their eggs/cysts are microscopic and cause diseases.
• Viruses and prions are infectious agents studied in microbiology even though they are not alive.

Major Fields in Microbiology

• Medical microbiology studies effects of microbes on humans.
• Epidemiology and public health monitor and control disease spread.
• Biotechnology, genetic engineering, and industrial microbiology use microbes for product development.
• Immunology studies host defense against microbes.
• Agricultural and food microbiology study microbes in farming and food safety.

Cell Types and Microbial Structure

• Prokaryotes lack a true nucleus and membrane-bound organelles; include bacteria and archaea.
• Eukaryotes have a nucleus and organelles; include fungi, protozoa, algae, and helminths.
• Viruses are acellular, only DNA or RNA with protein, and are even smaller than cells.

Microbial Size and Microscopy

• Organisms <0.2 mm (200 μm) are microscopic and require a microscope to be seen.
• Most bacterial cells are 1–10 μm; viruses are much smaller (20–100 nm).
• Light microscopes can resolve cells, but electron microscopes are needed for viruses.

Microbes in Ecosystems

• Producers capture sunlight (e.g. algae), consumers eat producers, and decomposers (e.g. fungi) recycle nutrients.

Pathogens and Disease

• Some microbes are free-living and harmless; others are parasites (pathogens) that cause disease.
• Pathogens account for significant mortality, especially in low-income countries.

History and Pioneers of Microbiology

• Early belief in spontaneous generation (life from non-living matter) was disproven by Pasteur (biogenesis).
• Anton van Leeuwenhoek developed early microscopes and observed microorganisms.
• Scientific method is essential: hypothesis, experiment, theory.
• Jenner pioneered vaccination using cowpox for smallpox immunity.
• Pioneers like Semmelweis (handwashing), Lister (aseptic techniques), Pasteur, and Koch (germ theory) advanced the field.

Taxonomy and Classification

• Taxonomy is classifying, naming, and organizing living things based on relatedness.
• Major ranks: domain, kingdom, phylum, class, order, family, genus, species.
• Scientific names use binomial nomenclature: genus (capitalized), species (lowercase), both italicized.

Evolution and Phylogeny

• All species descend from pre-existing species; three domains share a last common ancestor.
• Evolution proceeds toward complexity; taxonomy reflects evolutionary relationships.

Key Terms & Definitions

• Microbiology — study of microscopic organisms and infectious agents.
• Prokaryote — cell without a true nucleus or membrane-bound organelles (bacteria, archaea).
• Eukaryote — cell with a nucleus and organelles (fungi, protozoa, algae, helminths).
• Virus — acellular infectious agent, DNA/RNA with protein coat.
• Pathogen — a microorganism or agent that causes disease.
• Taxonomy — science of classifying organisms.
• Binomial Nomenclature — two-part scientific naming system: genus and species.
• Germ Theory — diseases are caused by specific microorganisms.

Action Items / Next Steps

• Memorize the hierarchy of taxonomy: domain, kingdom, phylum, class, order, family, genus, species.
• Review differences between prokaryotic and eukaryotic cells.
• Prepare for Chapter 4 by reading the assigned textbook section.