The Microbial World & You: Comprehensive Study Notes

Microbes in Our Lives

Microorganisms

Microorganisms are life forms too small to be seen with the naked eye. They include bacteria, fungi, protozoa, microscopic algae, viruses, and some parasites.

• Pathogens: Microbes that cause disease.

• Non-pathogens: Most microbes are harmless or beneficial.

Roles of Microbes

• Pathogenic (disease-producing): Cause diseases in humans, animals, and plants.

• Decomposition: Recycle nutrients by breaking down dead matter.

• Industrial Applications: Used in food production (e.g., cheese, yogurt), pharmaceuticals, and biotechnology.

• Bioremediation: Clean up pollutants and toxic wastes.

• Normal Microbiota: Microbes that live in and on the human body, contributing to health and immunity.

Microbiome / Microbiota

Definition and Importance

• The human body contains about 30 trillion body cells and is colonized by 40 trillion bacterial cells.

• Microbiome: The collective genomes of the microbes (composed of bacteria, bacteriophages, fungi, protozoa, and viruses) that live inside and on the human body.

• Normal microbiota help prevent the growth of pathogens and may produce growth factors such as vitamins B and K.

Colonization

• Microbes can only colonize body sites that provide nutrients and the right environment for their growth.

Human Microbiome Project (2007–2016)

• Goal: To determine the makeup of microbial communities throughout the body and understand their relationship to human health and disease.

Naming & Classifying Microorganisms

Taxonomy

• Developed by Carl Linnaeus.

• Each organism has two names: Genus (capitalized) and species (lowercase), both italicized or underlined.

• Example: Staphylococcus aureus

Types of Microorganisms

• Bacteria

• Archaea

• Fungi

• Protozoa

• Algae

• Viruses

• Multicellular animal parasites

Bacteria

• Prokaryotic (no nucleus)

• Cell walls contain peptidoglycan

• Reproduce by binary fission

• Shapes: cocci (spherical), bacilli (rod-shaped), spirilla (spiral)

Archaea

• Prokaryotic, lack peptidoglycan in cell walls

• Often live in extreme environments (e.g., extreme halophiles, thermophiles)

Fungi

• Eukaryotic (have nucleus)

• Cell walls contain chitin

• Include unicellular yeasts, multicellular molds, and mushrooms

Protozoa

• Unicellular eukaryotes

• Absorb or ingest organic chemicals

• May be motile via pseudopods, cilia, or flagella

Algae

• Eukaryotic

• Cell walls contain cellulose

• Photosynthetic, produce oxygen and carbohydrates

Viruses

• Acellular, consist of DNA or RNA core surrounded by a protein coat

• Obligate intracellular parasites

Multicellular Animal Parasites

• Eukaryotic

• Include helminths (parasitic worms)

Classification of Microorganisms

• Developed by Carl Woese (1978)

• Three domains: Bacteria, Archaea, Eukarya

A Brief History of Microbiology

First Observations

• Robert Hooke (1665): Reported that living things are composed of little boxes, or "cells"

• Antonie van Leeuwenhoek (1673–1723): First to observe live microorganisms

Biogenesis vs. Spontaneous Generation

• Spontaneous Generation: Hypothesis that life arises from nonliving matter

• Biogenesis: Hypothesis that living cells arise only from preexisting living cells

Disproving Spontaneous Generation

• Francesco Redi (1668): Showed that maggots do not arise from decaying meat

• Louis Pasteur (1861): Demonstrated that microorganisms are present in the air; used S-shaped flasks to keep microbes out but let air in

Golden Ages of Microbiology

First Golden Age (1857–1914)

• Relationship between microbes and disease established

• Development of aseptic techniques

• Fermentation and pasteurization discovered by Pasteur

• Koch's postulates established causative link between microbes and disease

Second Golden Age

• Focus on treating diseases caused by microbes

• Development of chemotherapy and antibiotics

• Discovery of penicillin by Alexander Fleming (1928)

Third Golden Age

• Genomics: Study of all organism genes

• Recombinant DNA technology: Manipulation of microbial genes for practical applications

Microbes and Human Disease

Normal Microbiota

• Present in and on the human body

• Prevent growth of pathogens

• Produce growth factors such as vitamins B and K

Emerging Infectious Diseases (EIDs)

• New diseases and diseases increasing in incidence

• Examples: COVID-19, Zika virus, H1N1 influenza, Ebola, Marburg virus

Antibiotic-Resistant Infections

• Examples: MRSA, Clostridium difficile, Vancomycin-resistant Enterococci (VRE)

Recycling Vital Elements

Microbial Ecology

• Study of the relationship between microorganisms and their environment

• Microbes recycle carbon, nutrients, sulfur, and phosphorus that can be used by plants and animals

Sewage Treatment

• Microbes are used to recycle water and treat sewage

Bioremediation

• Use of microbes to remove pollutants

Biotechnology & Recombinant DNA Technology

• Biotechnology: Use of microbes for practical applications (e.g., production of foods and chemicals)

• Recombinant DNA technology: Enables bacteria and fungi to produce a variety of proteins, including vaccines and enzymes

Key Terms and Concepts

• Biofilm: A complex aggregation of microbes attached to surfaces

• Pathogen: A microbe that causes disease

• Antibiotic: A chemical produced by bacteria or fungi that inhibits or kills other microbes

Selected Table: Classification of Microorganisms (According to Carl Woese)

Domain	Examples	Key Features
Bacteria	Escherichia coli, Staphylococcus aureus	Prokaryotic, peptidoglycan cell walls
Archaea	Methanogens, extreme halophiles	Prokaryotic, no peptidoglycan, extreme environments
Eukarya	Fungi, protozoa, algae, plants, animals	Eukaryotic, membrane-bound organelles

Important Equations

• Polymerase Chain Reaction (PCR):

$\text{DNA}_{\text{template}} + \text{Primers} + \text{dNTPs} + \text{Taq polymerase} \rightarrow \text{Amplified DNA}$

Examples and Applications

• Pasteurization: Heating liquids to kill most bacteria and prevent spoilage (e.g., milk, wine).

• Vaccination: Edward Jenner's use of cowpox virus to protect against smallpox.

• Antibiotics: Penicillin discovered by Alexander Fleming, used to treat bacterial infections.

Additional info: These notes expand on the provided lecture slides by including definitions, historical context, and examples relevant to introductory microbiology. The content is organized to align with standard college-level microbiology curricula.