Introduction to Microbiology: BIO 359 Study Notes for Nurses

Introduction to Microbiology

What is Microbiology?

Microbiology is the study of microscopic organisms, known as microbes, which include bacteria, viruses, fungi, protozoa, and archaea. These organisms are found everywhere and play essential roles in health, disease, and the environment.

• Microbes are living organisms too small to be seen with the naked eye.

• They are involved in processes ranging from disease causation to environmental cycles.

• Microbiology is foundational for nursing, medicine, and many scientific fields.

Microbes in Everyday Life

Microbes impact many aspects of daily life, often in unexpected ways. Their influence extends far beyond disease.

• Health and Disease: Microbes can cause infectious diseases, but also protect against pathogens and aid in digestion.

• Environmental Roles: Microbes are involved in nutrient cycling, cloud formation, ocean tides, and even rock formation.

• Industrial Uses: Microbes are used in food production (e.g., fermentation), bioremediation, and manufacturing (e.g., antibiotics, plastics).

• Human Physiology: The human microbiome affects immunity, mental health, hormone production, and more.

• Unexpected Applications: Microbes influence fashion (e.g., dye production), music making, and even decision making.

Example: Gut bacteria can affect the sexual preferences of fruit flies, demonstrating the broad influence of microbes on behavior.

Major Groups of Microorganisms

Bacteria

Bacteria are unicellular, prokaryotic organisms found in diverse environments. They reproduce asexually and can be beneficial or pathogenic.

• Prokaryotic: Lack a membrane-bound nucleus.

• Cell Wall: Composed of peptidoglycan (in most bacteria).

• Examples: Staphylococcus aureus (can be part of normal microbiota or cause disease).

Archaea

Archaea are prokaryotic organisms similar to bacteria but with distinct genetic and biochemical characteristics. Many live in extreme environments.

• Prokaryotic: No nucleus.

• Cell Wall: Lacks peptidoglycan; unique membrane lipids.

• Examples: Pyrococcus furiosus (found in hot environments).

Fungi

Fungi are eukaryotic organisms that obtain food from other organisms. They can be unicellular (yeasts) or multicellular (molds).

• Eukaryotic: Have a membrane-bound nucleus.

• Cell Wall: Made of polysaccharides (e.g., chitin).

• Yeasts: Unicellular, reproduce by budding.

• Molds: Multicellular, grow as filaments, reproduce by spores.

Protozoa

Protozoa are unicellular, eukaryotic organisms, often motile and animal-like in behavior.

• Motility: Move using cilia, flagella, or pseudopodia.

• Nutrition: Often ingest food particles by phagocytosis.

Algae

Algae are photosynthetic, eukaryotic organisms found in aquatic environments.

• Photosynthetic: Produce oxygen and organic compounds.

• Cell Wall: Composition varies; often contains cellulose.

Viruses

Viruses are acellular entities composed of nucleic acid (DNA or RNA) enclosed in a protein coat. They require host cells to reproduce.

• Acellular: Not considered living organisms.

• Submicroscopic: Not visible with light microscopes.

• Replication: Only within host cells.

Parasitic Worms (Helminths)

Helminths are multicellular, eukaryotic parasites that can infect humans and other animals.

• Macroscopic: Visible to the naked eye, but have microscopic life stages.

• Examples: Tapeworms, roundworms.

Scientific Naming and Classification

Binomial Nomenclature

Developed by Carl Linnaeus, binomial nomenclature assigns each organism a two-part scientific name: genus and species.

• Genus: Capitalized, italicized or underlined.

• Species: Lowercase, italicized or underlined.

• Example: Staphylococcus aureus

Strains: Variants within a species, e.g., E. coli O157:H7.

Microbiota and the Human Microbiome

Normal Microbiota

Normal microbiota refers to the collection of microbes that reside on and within the human body without causing disease under normal conditions.

• Location Matters: The same species may be harmless in one location but pathogenic in another.

• Protective Role: Normal microbiota can prevent colonization by pathogens ("crowding out").

• Pathogenic Potential: Some normal microbiota can become pathogenic if they enter sterile areas or if the host is immunocompromised.

Example: Staphylococcus aureus is carried asymptomatically by many adults but can cause infections.

Historical Foundations of Microbiology

Key Figures and Discoveries

• Antonie van Leeuwenhoek: First to observe microbes using simple microscopes; called them "animalcules."

• Louis Pasteur: Developed pasteurization, proposed the germ theory of disease, and created vaccines (e.g., rabies).

• Robert Koch: Established pure culture techniques, discovered causative agents of diseases (e.g., anthrax), and formulated Koch's postulates.

• Christian Gram: Developed Gram staining to differentiate bacteria based on cell wall structure.

• Alexander Fleming: Discovered penicillin, the first antibiotic.

Koch's Postulates

Koch's postulates are criteria designed to establish a causative relationship between a microbe and a disease.

1. The suspected causative agent must be found in every case of the disease and absent from healthy individuals.

2. The agent must be isolated and grown in pure culture.

3. When the agent is introduced into a healthy host, the host must develop the disease.

4. The same agent must be re-isolated from the diseased experimental host.

Domains of Life

Three Domains

All life is classified into three domains based on genetic and biochemical differences:

• Bacteria: Prokaryotic, diverse, found in many environments.

• Archaea: Prokaryotic, often extremophiles.

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

Summary Table: Major Groups of Microorganisms

Group	Cell Type	Key Features	Examples
Bacteria	Prokaryotic	Peptidoglycan cell wall, unicellular	Staphylococcus aureus
Archaea	Prokaryotic	Extreme environments, unique membrane lipids	Pyrococcus furiosus
Fungi	Eukaryotic	Chitin cell wall, unicellular or multicellular	Yeasts, molds
Protozoa	Eukaryotic	Motile, ingest food, no cell wall	Amoeba, Paramecium
Algae	Eukaryotic	Photosynthetic, cell wall varies	Green algae
Viruses	Acellular	DNA or RNA in protein coat, obligate intracellular	Influenza virus, bacteriophage
Helminths	Eukaryotic	Multicellular, parasitic	Tapeworms, roundworms

Conclusion

Microbiology is a diverse and dynamic field, essential for understanding health, disease, and the environment. As you begin your studies in BIO 359, remember that microbes are everywhere and influence many aspects of life, often in surprising ways.