Microbiology and Origins of Life

Antoni van Leeuwenhoek

• Considered the Father of Bacteriology
• First person to observe and record living microbes
• Developed the first single-lens microscope
• Described bacteria, algae, protozoa, and fungi as "animalcules"

Origin of Life Theories

• Two main hypotheses: Spontaneous generation (abiogenesis) and biogenesis
• Spontaneous generation: living organisms arise spontaneously from non-living matter
• Biogenesis: living organisms arise from pre-existing life

Disproving Spontaneous Generation

• Herodotus believed crocodiles originated from mud
• Van Helmont believed that maggots originated from meat
• Francesco Redi and Lazzaro Spallanzani disproved spontaneous generation through experiments

Louis Pasteur

• Considered the Father of Modern Microbiology
• Coined the terms "microbiology", "aerobic", and "anaerobic".
• Disproved spontaneous generation and proved biogenesis
• Developed pasteurization for sterilization
• Showed that microbes are responsible for fermentation
• Developed vaccines against rabies
• Demonstrated that anthrax is caused by bacteria and produced the vaccine for it

Importance of Microbiology for Nursing

• Nurses are involved in controlling infection in hospitals
• Microbiology provides knowledge for:
  • Isolation of causative agents
  • Determination of antibiotic sensitivity and drugs for treatment
  • Prevention of infectious diseases through vaccines and immunization
  • Sterilization and Disinfection
• Helps nurses understand normal flora and harmful microorganisms, and their effects
• Provides knowledge on modes of transmission, signs and symptoms, and handling of infected patients

Classification of Organisms

• Organisms are classified into two main groups: prokaryotes and eukaryotes

Viruses

• Very small and simple non-living organisms
• Replicate only inside host cells
• Considered neither prokaryotes nor eukaryotes
• Structure:
  • Strand of nucleic acid (DNA or RNA)
  • Protein coat (capsid)
  • May have an envelope or tail

Prokaryotes

• Two main types: bacteria and archaea
• Bacteria: unicellular prokaryotes with peptidoglycan in their cell walls
• Archaea: unicellular prokaryotes without peptidoglycan in their cell walls
• Exist in diverse environments

Prokaryotic Cells

• Do not have a true nucleus or most other cell organelles
• Smaller in size compared to eukaryotic cells

Eukaryotes

• Includes: protozoa, fungi, plants, and animals
• Possess a nucleus and other cell organelles
• Larger and more complex than prokaryotic cells

Eukaryotic Cells

• Have a true nucleus and other cell organelles
• Enclosed by a plasma membrane

Differentiating Eukaryotes and Prokaryotes

• Eukaryotes:
  • Larger size
  • Nucleus surrounded by a nuclear membrane
  • Larger ribosomes
  • May have flagella
  • Possess organelles
  • Multiple chromosomes
  • Cell wall in plants
  • Lysosomes in animals
• Prokaryotes:
  • Smaller size
  • No true nucleus, only a nucleoid
  • Smaller ribosomes
  • Flagella present
  • Have pili
  • Single circular DNA strand
  • Have a cell wall
  • No lysosomes
  • May have a capsule

Fungi

• Eukaryotes with a chitin cell wall
• Some have septa (holes that allow organelles and cytoplasm to pass)
• Non-motile
• Medical fungi categories:
  • True yeasts: unicellular, reproduce asexually by budding and sexually by forming spores
  • Molds: multicellular, consist of mycelia composed of filaments called hyphae
  • Yeast-like fungi: have pseudo mycelium

Protozoa

• Single-cell eukaryotic motile organisms
• Important medical groups:
  • Amoeba: Entamoeba species, mode of motility: pseudopodia
  • Sporozoa: intracellular infection, e.g., malaria
  • Mastigophora: mode of motility: flagella
    • Gastrointestinal flagellates: e.g., Giardia intestinalis
    • Urogenital flagellates: e.g., Trichomonas vaginalis
    • Tissue and blood flagellates: e.g., Trypanosoma, Leishmania

Branches of Microbiology

• Bacteriology: study of bacteria
• Parasitology: study of parasites
• Immunology: study of immunity
• Virology: study of viruses
• Mycology: study of fungi

Prokaryotes (Single Cell Organisms)

• Possess both DNA and RNA
• Have a cell wall
• Divide by binary fission
• No nucleus or mitochondria
• Have a nucleoid (bacterial chromosome) with a closed circle of double-stranded DNA

Classification of Bacteria

• Classified based on Morphology, Arrangement, and Staining:
  • Filamentous bacteria: Streptomyces
  • True bacteria:
    • Cocci:
      • Gram-positive: Staphylococcus
      • Gram-negative: Neisseria
    • Bacilli:
      • Gram-positive: Bacillus
      • Gram-negative: Brucella
  • Spirochetes: slender, spiral bacteria, e.g., Treponema
  • Mycoplasma: smallest bacteria, lack a rigid cell wall
  • Rickettsiae: lack teichoic acid
  • Chlamydiae: lack peptidoglycan, obligate intracellular parasites

Morphology (Size and Shape) of Bacteria

• Average size: one-tenth the size of eukaryotic cells
• Range from 1-10 μm in length and 0.2-1 μm in width
• Shapes: Cocci, Bacilli, Vibrios, Spirochetes, Spirilla

Arrangement of Bacteria

• Single, Pairs, Tetrads, Chains, Clusters

Staining (Gram Stain)

• Most useful staining procedure in bacteriology
• Developed by Hans Christian Gram
• Differentiates bacteria into two main groups:
  • Gram-positive: appear violet (blue)
  • Gram-negative: appear red (pink)

Structure of the Bacterial Cell Wall

• Multi-layered structure external to the cytoplasmic membrane
• Contains Peptidoglycan (murein), responsible for cell wall rigidity
• Peptidoglycan structure:
  • Consists of two amino sugars: N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
  • Four amino acids: L-alanine, D-glutamic acid, Diaminopimelic acid, D-alanine
  • Linked by polypeptide bonds

Classification Based on Cell Wall

• Almost all bacteria are divided into two groups based on cell wall peptidoglycan and permeability factor:
  • Gram-positive bacteria: thick layer of peptidoglycan
  • Gram-negative bacteria: thin layer of peptidoglycan

This quiz explores significant contributions to microbiology, including the pioneering work of Antoni van Leeuwenhoek and Louis Pasteur. Delve into the theories of the origin of life, including spontaneous generation and biogenesis, and understand the experiments that debunked early misconceptions. Test your knowledge on these foundational concepts in microbiology.