Micro Exam 1

• Microorganisms are small organisms, most of which are so small that they can't be seen without a microscope
• Main types of microorganisms include: prokaryotes, bacteria, archaea, viruses, eukaryotes, protists, fungi
• Pathogenic microorganisms include some bacteria and viruses
• Main differences between prokaryotic and eukaryotic cells:

  • Prokaryotic cells store genetic material in the nucleoid located in the cytoplasm (no nucleus)
  • Eukaryotic cells store genetic information in the nucleus
• Fungi:

  • Eukaryotic
  • Either unicellular or multicellular
  • Obtain food from other organisms
  • Have cell walls
  • Yeasts are unicellular, molds are multicellular
• Archaea:

  • Prokaryotic
  • Unicellular
  • Some have similar shapes to bacteria but can also have more geometric shapes
  • Cell wall structure, genetic composition, and metabolic pathways are different from bacteria
  • Cell wall containing pseudopeptidoglycan
• Protozoa:

  • Eukaryotic
  • Unicellular
  • Capable of locomotion
  • Provide nutrients for other organisms
• Bacteria:

  • Prokaryotic
  • Unicellular
  • Shapes: coccus (round), bacillus (rod), curved (vibrio, spirochete, spirillum)
  • Cell walls contain peptidoglycan
  • Some are photosynthetic
• Algae:

  • Eukaryotic
  • Either unicellular or multicellular
  • Photosynthetic
  • Have simpler reproductive structures than plants
  • Provide most of earth's oxygen
  • Cell walls surrounded by cellulose
  • Have diatom structures
  • Make agar plates solid
• Helminths are often studied in microbiology because parasitic infections are diagnosed by observing microscopic eggs and immature stages of worms in blood, feces, urine, and lymph
• Viruses are acellular and non-living. They are studied in microbiology because they can act as pathogens, infecting various cell types and requiring a host to reproduce
• Taxonomy involves the classification, description, identification, and naming of living organisms. Phylogeny deals with evolutionary relationships
• Viruses are not included in the phylogenetic tree of life because they lack the characteristics of living organisms, such as cellular structures and typical metabolic processes
• Immunology is studied in microbiology due to the complex interactions between the host immune system and microbes
• Types of microscopy:

  • Brightfield Microscope: Yes, best for seeing live or dead cells
  • Darkfield Microscope: Yes, best for seeing live cells
  • Phase-Contrast Microscope: Yes, best for seeing live cells
  • Differential Interference Contrast (DIC) Microscope: Yes, best for seeing live cells
  • Fluorescence Microscope: Yes, best for seeing viruses
  • Transmission Electron Microscope (TEM): No, best for seeing viruses and dead cells
  • Scanning Electron Microscope (SEM): No, best for seeing dead cells
• To view viruses: electron microscopy (TEM for internal view, SEM for 3D surface images)

  To view bacteria: light microscopy for staining and live specimens

  To view fungi: light microscopy for higher resolution and magnification
• Microbiology emerged as a scientific field of study in the 1800s, around 200 years after Leeuwenhoek first reported "animalcules"
• Steps in the scientific method: observation, question, hypothesis, prediction, experiment, analyze, conclusion
• • Woese: Used rRNA to compare all forms of life and distinguish organisms distinct from bacteria and eukarya
• Founding Microbiologists:

  • Leeuwenhoek: Created the first microscope and coined microbes as "animalcules"
  • Redi: Disproved spontaneous generation theory by showing maggots came from flies
  • Needham: Disagreed with Redi and tried to disprove his theory
  • Spallanzani: Disproved Needham's rebuttal by showing growth only in unsealed flasks
  • Pasteur: Invented swan-shaped flasks, associated with fermentation and pasteurization
  • Koch: Formed the Germ theory of disease and formulated Koch's Postulates
• Example of binomial nomenclature: Staphylococcus aureus (italicized on a computer, underlined and capitalized on paper)
• Three domains of life: bacteria, archaea, eukarya
• Glycocalyx:

  • A gelatinous, sticky substance that surrounds the outside of some bacterial cells
• Capsules are more protective against antibiotics because of their organized layers of polysaccharides/proteins which form a protective layer around the cell and can trick immune cells
• Capsules protect bacteria from being recognized by the host immune response because they are very slippery and made of similar chemicals found in the human body
• Pilus is a type of fimbria, but a flagellum is not:

  • Pilus has hair-like appendages on the surface like fimbriae and functions as a motility structure, adherence, or conjugation
  • Flagellum serves a different purpose; it has whip-like appendages responsible for bacterial motility through liquid but not adherence
• Bacterial flagellum has three main parts: filament, flagellin hook, and basal body
• Bacteria move based on the number of flagella they have:

  • Monotrichous: bacteria with a single flagellum at one end, move in a straight line
  • Lophotrichous: bacteria with multiple flagella at one end, have more erratic movements
  • Amphitrichous: bacteria with flagella at both ends, move in a straight line with the ability to change direction quickly
  • Peritrichous: bacteria with flagella all over the cell, have a tumbling movement
• Bacterial cell wall shapes: coccus (round), bacillus (rod), and curved (vibrio, spirochete, and spirillum)
• Gram-positive bacterial cell walls stain purple after Gram staining because they have a thick cell wall composed mainly of peptidoglycan that retains the color
• Peptidoglycan monomer is composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM)
• Lysozyme cleaves the bond between NAG and NAM in peptidoglycan
• Gram-negative outer membrane components:

  • Lipopolysaccharides (LPS)
  • Porins
  • Braun’s lipoprotein
  • Phospholipids
  • Periplasmic space
• Periplasm is the space located between the inner and outer membranes of Gram-negative bacteria
• Gram-negative cells need porins for passive diffusion of molecules across the membrane due to their outer membrane
• LPS structure: Lipid A, oligosaccharide, and the O-antigen, found in Gram-negative bacteria
• Bacterial cell membrane is mainly composed of phospholipids and proteins in a phospholipid bilayer embedded with proteins
• Cell membrane vs. cell wall:

  • Cell wall is rigid and protective, providing structural support and protection, while the cell membrane is flexible and selectively permeable, regulating transport and maintaining shape and integrity
• Bacterial cell membrane lipid composition and stability differ from archaeal cell membrane lipid composition and stability
• Cell membrane is selectively permeable due to the hydrophobic and hydrophilic layers within the membrane