Chapter 2

• Five basic groups of microorganisms:

  • Bacteria (prokaryote)
  • Fungi, molds, yeast, algae (eukaryotes)
  • Protozoan (parasites)
  • Metazoan (helminths)
  • Virus
• Prokaryotic cell characteristics:

  • No nucleus
  • No membrane-bound organelles
  • Chromosomes not contained in a nucleus
  • Cell wall containing peptidoglycan
  • Ribosomes present
  • Cell division by binary fission
  • No sexual reproduction through meiosis
• Eukaryotic cell characteristics:

  • Has a nucleus
  • Has membrane-bound organelles
  • Chromosomes contained in a nucleus
  • Cell wall may or may not contain peptidoglycan
  • Ribosomes present
  • Cell division by mitotic division
  • Sexual reproduction through meiosis
• Bacterial capsule:

  • Offers protection from various threats
  • Enhances the ability of bacterial pathogens to cause disease
  • Helps in attachment to surfaces and determines virulence factor of organisms
• Appendages:

  I. Flagella:

  • Protein appendages for locomotion
  • Different types based on location and arrangement

  II. Pili (fimbriae):

  • Shorter and straighter than flagella
  • Important for forming attachments during conjugation

  III. Endospores:

  • Resistant asexual spores that develop inside some bacteria cells
  • Highly resistant to various environmental factors
• Cytoplasm/protoplasm:

  • Protein synthesis, energy production, signal transduction, transportation of metabolites
  • Eukaryotes have cytoplasm external to the nuclear membrane, while prokaryotes have it internal to the cellular membrane
• Nucleoid (bacterial chromosome):

  • Single long circular double-stranded DNA molecule
  • Devoid of highly conserved histone protein
  • Contains plasmids with 5-100 genes determining biological functions
• Ribosomes:

  • Microscopic "factories" found in all cells
  • Translate genetic code into chains of amino acids
  • Prokaryotic ribosomes can be inhibited by some antibiotics, while eukaryotic ribosomes are not affected
• Cytoplasmic membrane/plasma membrane:

  • Protects the watery interior of the bacterial cell
  • Made of fat and protein molecules
  • Functions include protection, selective permeability, and allowing materials to move across
• Passive diffusion:

  • Spontaneous process without cellular energy expenditure
  • Molecules move from high to low concentration
• Facilitated diffusion:

  • Type of passive transport using special transport proteins
  • Allows substances like glucose and ions to cross membranes
• Active transport:

  • Process using energy to transfer substances into, out of, and between cells
  • Types include antiport pumps, symport pumps, and endocytosis
• Cytolysis:

  • Cell bursting and releasing contents due to influx of water
  • Concern for cells without a tough cell wall to resist internal water pressure
• Endocytosis:

  • Cells form a vesicle around a specific molecule they want to take in
  • In some types of endocytosis, cells rely on cues to recognize and engulf a particular molecule
• Exocytosis:

  • Cells create a vesicle to enclose something inside the cell for the purpose of moving it outside of the cell, across the membrane
  • Commonly used to export important products like enzymes and hormones
• Functions associated with bacterial cytoplasmic membrane & divisome:

  • Bacterial cells depend on their ability to divide, carried out by a dynamic molecular machine known as the divisome
  • Functions include energy production, containing bases of bacterial flagella, waste removal, and formation of endospore
• Morphological differences:

  • Cocci:
  • Spherical, oval, or flattened on one side
  • Found in clusters, chains, pairs with pointed ends, pairs with kidney bean shape, groups of four, and packets of eight
  • Bacilli:
  • Rod-shaped bacteria with squared ends, round ends, club-shaped, fusiform, and comma-shaped
  • Spirochetes:
  • Spiral in form, tightly-coiled or relaxed/loosely-coiled
  • Pleomorphic:
  • Lacking distinct shape, used to describe all chemical reactions in a cell
• Enzymes in bacteria:

  • Bacteria rely on enzymes for their biochemistry
  • Types of enzymes include endoenzymes (work within the cell) and exoenzymes (produced inside the cell and transported outside for digestion)
• Metabolic characteristics:

  • Oxygen:
  • Enzymes like catalase, peroxidase, and superoxide dismutase break down oxygen products
  • Growth characteristics:
  • Classification based on O2 requirement and characteristics, including obligate aerobe, facultative anaerobe, microaerophilic anaerobe, aerotolerant anaerobe, and obligate anaerobe
• Nutrition:

  • Carbon and energy source:
  • Phototrophs use light, chemotrophs use chemical compounds, autotrophs use inorganic sources, and heterotrophs use organic carbon
  • Capnophilic organisms prefer environments with increased CO2, while salt-loving organisms can survive in high salt concentrations
• Temperature requirement:

  • Psychrophilic: grow below 10°C
  • Mesophilic: grow at 20-40°C
  • Thermophilic: grow at 50-55°C
  • Hyperthermophilic: optimum growth at 80°C or more
• Staining characteristics:

  • Gram-negative organisms:
  • Cell wall composed of thin layer of peptidoglycan covered by an outer membrane of lipoprotein and lipopolysaccharides
  • Gram-positive organisms:
  • Thick layer of peptidoglycan with teichoic and lipoteichoic acid complexes
• Steps in Gram staining:

  • Reagents used: Crystal Violet (primary stain), Gram's Iodine (mordant), Acetone Alcohol (decolorizer), Safranin (counterstain)
  • Procedure involves bacterial smear preparation, staining procedures, and differentiating between Gram-positive and Gram-negative bacteria
• Acid-fast stain:

  • Used to identify acid-fast organisms like Mycobacterium and Nocardia
  • Reagents used: Carbol Fuchsin (primary stain), Phenol (mordant), Acid Alcohol (decolorizer), Methylene Blue or Brilliant Cresyl Green (counterstain)
• Colony:

  • Visible mass of microbial cells originating from a single mother cell
  • Colonial morphology includes characteristics like shape, elevation, color, and margin