Microbiology Overview and History

Microbiology Overview

• Microbiology is the study of microorganisms, or microbes.
• Microbes play roles in health care, agriculture, industry, and environmental sciences.
• Humans depend on microbes for food production, medication creation, and breaking down environmental hazards.

Early Years of Microbiology

• Antoni van Leeuwenhoek (1632-1723) invented simple microscopes and observed tiny organisms, calling them "animalcules."
• Microorganisms include bacteria, archaea, fungi, protozoa, algae, and small multicellular animals.
• Carolus Linnaeus (1707-1778) developed a taxonomic system for naming plants and animals.

Bacteria and Archaea

• Bacteria and archaea survive almost everywhere, even in extreme environments.
• Reproduce asexually.
• Bacterial cell walls contain peptidoglycan; some lack cell walls.
• Archaeal cell walls are made of polymers (polysaccharides).

Fungi

• Fungi are eukaryotic organisms with cell walls.
• Obtain nutrients from other organisms.
• Molds (multicellular) grow as filaments and reproduce by spores (sexual and asexual).
• Yeasts (unicellular) reproduce asexually by budding; some produce sexual spores.
• Common fungal diseases include ringworm, fungal nail infections, and vaginal candidiasis.

Protozoa

• Protozoa are single-celled eukaryotes similar to animals in their nutrient needs and cellular structure.
• Mostly reproduce asexually, but some reproduce sexually.
• Most protozoa can move using pseudopods, cilia, or flagella.
• Infectious protozoa include amoeba (dysentery), ciliates (dysentery), flagellates (diarrhea), and non-motile plasmodium (malaria).

Algae

• Algae are unicellular or multicellular eukaryotes.
• Photosynthetic.
• Simple reproductive structures.
• Grouped based on pigmentation and cell wall composition.
• Harmful algal blooms (HABs) can produce toxins that cause illness through contact with contaminated water.

Other Important Microbes and Infectious Agents

• Parasites (helminths) include flatworms (flukes and tapeworms), and roundworms (nematodes).
• Viruses are protein and genetic material that need to infect cells to replicate and have a specific range of host cells.
• Prions are infectious protein particles that cause misfolding of normal brain proteins, destroying healthy brain tissue. Examples include Creutzfeldt-Jakob disease (CJD) and "mad cow" disease

Living and Non-Living Agents Studied in Microbiology

• Microbes are categorized as prokaryotic (bacteria, archaea) or eukaryotic (protists, fungi, algae, helminths, some protozoa, and algae).
• Viruses and prions are not considered living.

Some Diseases Caused by Microorganisms

• Fungi cause ringworm, athlete's foot, and candidiasis.
• Protozoans cause malaria, giardiasis, pneumonia, and toxoplasmosis.
• Bacteria cause anthrax, botulism, cholera, syphilis, UTIs, leprosy, tuberculosis (TB), and pneumonia.
• Viruses cause HIV, hemorrhagic fevers, hepatitis, smallpox, and influenza.
• Prions cause spongiform encephalopathy (CJD).

Normal Microbiota of the Human Microbiome

• Normal microbiota are bacteria, archaea, and eukaryotic microbes that live on and in the human body.
• They play important roles in vitamin production and digestion.
• The Human Microbiome Project (HMP) aims to characterize all of the microbes in the human body.
• The normal flora of several body regions is discussed in terms of the types and numbers of species present (i.e., Skin, mouth, stomach, urogenital tract, and intestines).

The Golden Age of Microbiology

• Scientists in the 1850-1920 period addressed four key questions: spontaneous generation, fermentation, cause of disease, and prevention of infection.
• Louis Pasteur disproved spontaneous generation and developed pasteurization.
• Robert Koch developed methods to identify the causative agents of infectious diseases and formulated Koch's postulates to determine the cause of infectious diseases (e.g., anthrax).

Laboratory Advances

• Koch's lab techniques included simple staining, bacteria photography, estimating bacterial numbers, using Petri dishes, and transferring bacteria to identify bacterial species.
• Koch's postulates remain crucial for identifying the etiology of infectious agents.

Modern Age of Microbiology

• Modern microbiology examines basic chemical reactions of life (metabolism), genetics (transcription, translation, gene control, genomes [sequencing]), the role of microorganisms in the environment (bioremediation), and host response to pathogens.
• Modern biotechnology (e.g., recombinant DNA technology, CRISPR) manipulates microorganisms to benefit humans.
• Chemotherapy, immunology, and serology are crucial in understanding and combating diseases.