Introduction to Microbiology

Microbiology Overview

• Derived from Greek: Mikros meaning small and logos meaning study; focuses on microorganisms.
• Specializes in microorganisms, typically requiring magnification to be seen.
• Microorganisms - include a wide variety of microscopic organisms such as bacteria, archaea, fungi, and viruses.

Major Divisions

• Prokaryotes: Bacteria and Archaea.
• Eukaryotes: Algae, Fungi, and Protozoa.

Three Domains of Life

• Domain Eukarya
• Domain Bacteria
• Domain Archaea

Major Groups of Microorganisms

• Bacteria, Fungi, Algae, Protozoa, Viruses, and Helminths (parasitic worms).

Fields of Microbiology

• Basic Research Fields:

  • Bacteriology: Study of bacteria.
  • Phycology: Study of algae.
  • Mycology: Study of fungi and yeast.
  • Protozoology: Study of protozoans.
  • Parasitology: Focuses on parasitic protozoa.
  • Virology: Study of viruses.
  • Cytology: Structure and function of cells.

• Applied Microbiology:

  • Medical Microbiology: Includes serology and immunology for disease diagnosis and treatment.
  • Environmental Microbiology: Includes bioremediation and agricultural use of microbes.

Importance of Microorganisms

• Essential for nutrient production, energy flow, and recycling in ecosystems.
• Involved in bioremediation and biotechnology applications to address environmental and medical issues.
• Photosynthetic microbes produce over 50% of Earth's oxygen.

Decomposition and Nitrogen Fixation

• Microbes break down organic matter, recycling nutrients.
• Certain bacteria convert atmospheric nitrogen into forms useful for plants.

Microbial Contributions in Medicine

• Antibiotics and drugs are often derived from microbes.
• Probiotics enhance gut health and immune function.

Historical Foundations

• Antoni van Leeuwenhoek: Created the first powerful microscope and observed microorganisms.
• Spontaneous Generation: The theory that life arises from non-living matter; countered by the concept of biogenesis.
• Louis Pasteur: Established germ theory, developed pasteurization, and created vaccines.
• Robert Koch: Developed Koch's Postulates, linking specific microbes to specific diseases.

Microorganism Classification

• Taxonomy: Classification, nomenclature, and identification of organisms.
• Levels of classification include Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.
• Linnaean System: Binomial nomenclature assigns two names (genus and species) to organisms; first use is italicized.

Phylogenetic Relationships

• Classification systems evolved from the traditional five-kingdom system to Woese-Fox's three-domain system, emphasizing genetic relationships via ribosomal RNA sequences.

Physiological Diversity

• Heterotrophs: Use organic compounds for nutrients; include decomposers.
• Autotrophs: Use inorganic sources of carbon (e.g., CO2).
• Chemotrophs: Obtain energy from chemical compounds; Phototrophs utilize light energy.
• Organisms can be classified as aerobes (require oxygen) or anaerobes (do not require oxygen).
• Extremophiles: Thrive in extreme environments, pushing the limits of microbial life.

Microbial Dimensions

• Measurements:
  • Micron (μ): 1 millionth of a meter.
  • Nanometer (n): 1 billionth of a meter.
• Bacteria are generally several micrometers in diameter; viruses measure around 10 nm.

Public Health Considerations

• Emphasis on the role of microorganisms in diseases and their impact on human health, vaccine development, and management of infectious diseases.### Microbial Environments
• Capnophiles: Thrive in CO₂-rich environments (5-10% CO₂).
• Microaerophiles: Prefer low oxygen levels (approximately 5% oxygen).
• Acidophiles: Prefer very acidic conditions (pH 2-5).
• Alkaliphiles: Adapted to extremely alkaline environments (pH > 8.5).
• Thermophiles/Sternothermophiles: Survive in high-temperature conditions.
• Psychrophiles/Cryophiles: Grow in very cold temperatures.
• Piezophiles/Barophiles: Thrive under extreme pressure.
• Halophiles: Thrive in highly salted environments.
• Haloduric: Can survive in salty environments but do not prefer them (e.g., Staphylococcus aureus).
• Radiophiles: Resistant to harmful radiation.
• Xerophiles: Adapted to survive in extremely dry conditions.

Methods for Studying Microorganisms

• Specimen Collection: Sources can include body fluids, tissues, food, water, and soil. Collection methods utilize swabs, syringes, or transport systems that maintain microbe viability.

The Five "I"s of Microbial Processing

• Inoculation: Introducing a sample (inoculum) into a sterile nutrient medium to promote microbial growth. Certain microbes may require living hosts as growth media.
• Incubation: Culturing under controlled conditions to enhance microbial multiplication. This process may take hours to weeks, resulting in visible cultures.
• Isolation: Separating a single microbial species from others through techniques such as streaking or turbidity. Pure culture can be achieved through subculturing.
• Inspection: Observing macroscopic features (color, texture) and microscopic details (cell shape, size, motility) through staining techniques.
• Identification: Utilizing inspection data and specific tests (biochemical, immunologic, genetic) to classify and differentiate microbes.

Cell Types

• Prokaryotic Cells: Small (<5 μm), always unicellular, lack nucleus and membrane-bound organelles, circular DNA, smaller ribosomes (70S), no cytoskeleton, reproduce via binary fission.
• Eukaryotic Cells: Larger, often multicellular, possess a nucleus and organelles, linear DNA, larger ribosomes (80S), contain a cytoskeleton, reproduce via mitosis or meiosis.

Taxonomy of Organisms

• Bacteria: Prokaryotic, peptidoglycan cell walls, reproduce by binary fission (e.g., Escherichia coli).
• Archaea: Prokaryotic, lack peptidoglycan, extremophiles (methanogens, extreme halophiles, extreme thermophiles).
• Fungi: Eukaryotic, chitin cell walls, multicellular molds/mushrooms, unicellular yeasts.
• Protozoa: Eukaryotic, mainly saprobes and commensals, motility via pseudopodia, cilia, or flagella.
• Algae: Eukaryotic, cellulose cell walls, photosynthetic, produce oxygen and organic compounds, important in food chains.
• Helminths: Eukaryotic, multicellular animals, parasitic flatworms and roundworms, have microscopic life stages.
• Viruses: Acellular, obligate intracellular parasites, composed of a genome (DNA or RNA), surrounded by a protein coat (capsid), sometimes encased in a lipid envelope.
• Prions: Infectious proteins causing diseases like BSE and CJD, classified as emerging infectious diseases (EIDs).