The Microbial World & You: Foundations of Microbiology

Microbes in Our Lives

Introduction to Microorganisms

Microorganisms, also known as microbes, are organisms that are too small to be seen with the unaided eye. They play essential roles in various ecosystems and human health.

• Microorganisms include bacteria, fungi, protozoa, microscopic algae, and viruses.

• Microbes also include noncellular entities such as viruses.

• Commonly associated with infections and food spoilage, but most microbes are beneficial and help maintain environmental and bodily balance.

• Only a minority of microbes are pathogenic (disease-producing).

• Example: Staphylococcus aureus is a bacterium that can be pathogenic, causing skin infections.

The Microbiome

Definition and Importance

The human body is host to a vast community of microbes, collectively known as the microbiome. These microbes are crucial for health and disease prevention.

• An adult human is composed of approximately 30 trillion body cells and harbors about 40 trillion bacterial cells.

• Microbiome (also called microbiota): The group of microbes that live stably on/in the human body.

• Functions of the microbiome:

  • Helps maintain good health (e.g., Escherichia coli aids digestion).

  • Prevents growth of pathogenic microbes by occupying space and resources.

  • Trains the immune system to distinguish between threats and harmless entities.

Normal and Transient Microbiota

Microbiota can be classified based on their duration and stability within the host.

• Normal microbiota: The collection of acquired microbes on or in a healthy human being.

• Acquisition begins at birth and may persist indefinitely.

• Transient microbiota: Microbes that colonize the body fleetingly.

• Colonization depends on suitable body sites that provide nutrients and the right environment.

• Factors influencing colonization:

  • Temperature

  • pH

  • Presence or absence of chemical compounds

Binomial Nomenclature

Naming and Classifying Microorganisms

Scientific naming provides a universal system for identifying and classifying organisms.

• Carolus Linnaeus established the system of scientific nomenclature in 1735.

• Scientific names are latinized and consist of two parts: genus and species.

• This system is called Binomial Nomenclature.

Structure of Scientific Names

• The first part is the Genus name (capitalized).

• The second part is the species name (lowercase).

• The entire name is underlined or italicized (e.g., Homo sapiens).

• Abbreviations are allowed (e.g., H. sapiens).

• Names may honor scientists or describe characteristics.

Classification Example Table

The following table illustrates the classification of humans and ostriches using binomial nomenclature:

Rank	Human	Ostrich
Domain	Eukarya	Eukarya
Kingdom	Animalia	Animalia
Phylum	Chordata	Chordata
Class	Mammalia	Aves
Order	Primates	Struthioniformes
Family	Hominidae	Struthionidae
Genus	Homo	Struthio
Species	sapiens	camelus

Cell Basics

Overview of Cell Types

Cells are the fundamental units of life. Microbiology distinguishes between two major cell types: prokaryotic and eukaryotic.

• Prokaryotic cells: Lack a nucleus and membrane-bound organelles. Example: Bacteria.

• Eukaryotic cells: Possess a nucleus and membrane-bound organelles. Examples: Fungi, protozoa, algae, and multicellular animals.

• Cell structure is a key factor in the classification and study of microorganisms.

Additional info: The study of microbiology encompasses the diversity, classification, and roles of microorganisms in health, disease, and the environment. Binomial nomenclature is foundational for scientific communication and taxonomy.