Microbiology I - General Bacteriology Quiz

Microbiology I - General Bacteriology

• Course instructor: Assist. Prof. Dr. Halit ŞÜKÜR
• University: Near East University
• Faculty: Veterinary Medicine
• Department: Microbiology

Anatomic Structure of Bacteria

• Two main sections: external and internal structure
• Figure 1 illustrates a prokaryotic cell structure
• External structure components:
  • Cell wall
  • Capsule
  • Flagella
  • Fimbriae (pilus)
• Internal structure components:
  • Cytoplasmic membrane
  • Cytoplasm
  • Mesosom
  • Nucleotide
  • Ribosome
  • Cytoplasmic granules
  • Endospore
  • Pigment
  • Others (plasmid, phage, transposon, trace element)

Cytoplasmic Membrane

• Located beneath the cell wall
• Thin and generally the same structure in all bacteria
• Consists of two layers
• Structure includes proteins and phospholipids on the surfaces facing the periplasmic space and cytoplasm
• Hydrophobic ends of phospholipids are in the inner region
• Membrane proteins exist in two forms: peripheral and integral

Cytoplasmic Membrane-Function

• Surrounds and protects the cytoplasm
• Allows selective permeability and osmosis
• Contains enzymes:
  • Cytochrome enzymes
  • Enzymes in lipid synthesis
  • Enzymes in cell wall synthesis
  • TCA enzymes
  • DNA replicase enzymes
• Regulates activities (hydrolytic and energy metabolism) of some enzymes
• Involved in DNA replication
• Constituent of the origin of mesosome
• Plays a role in cell division and sporulation

Cytoplasmic Membrane - Selective permeability and transport

• Passive transport (diffusion):
  • Slow, does not require energy
  • Plays a role in concentration, electrical, and pressure differences
• Active transport:
  • Requires energy
  • Involves carrier proteins (enzymes, permease enzymes)
  • Examples:
    • β-galactosidase system for lactose
    • Phosphotransferase system in transition membrane

Cytoplasm

• Composed of liquids, organic, and inorganic materials

Mesosome

• Originates from the cytoplasmic membrane
• Vesicular or lamellar type
• Opens into the periplasmic space
• Involved in replication and transport processes

Ribosome

• Composed of RNA and protein
• Size: 70S (50+30)
• Abundant in growing bacteria
• Involved in protein and enzyme synthesis

Nucleotide

• DNA: double-stranded helix

Cytoplasmic Granules

• Volutin (Babes-Ernst) granules:
  • Polymerized inorganic metaphosphate (polymetaphosphate)
  • Source of energy and phosphate
  • Visualized by Neisser and Albert staining
• Lipid granules:
  • Lipid particles (polybetahydroxybutyrate)
  • Source of carbon and energy
  • Visualized with Sudan black
• Polysaccharide granules:
  • Glucose homo or heteropolymer
  • Source of carbon and energy
• Sulfur granules:
  • Found in sulfur bacteria
  • Source of energy

Endospore

• Formed when food sources are limited
• Resistant to physical (frost, dry, heat) and chemical (toxic substances) effects
• Protects bacteria
• Structures are durable, isolated from 3000 year old soil samples
• Can be oval or round
• Stained by Modified Ziehl-Neelsen or Spore staining
• Positions: central, subterminal, terminal, lateral
• Examples:
  • Clostridium botulinum (subterminal)
  • Clostridium tetani (terminal)
  • Bacillus anthracis (central)

Endospore Structure (from inside to out)

• Core
• Cytoplasm
• Cytoplasmic membrane of spore
• Cell wall of spore
• Cortex
• Outer membrane (dipicolinic acid, DPA)
• Exosporium

Sporulation

• Process of developing spores
• Called "Sporulation"
• Process of getting vegetative forms is called "Germination"
• Endotrophic and exotrophic sporulation
  • In Bacillus spp.: endotrophic sporulation
  • In Clostridium spp.: exotrophic sporulation

Sporulation (continued)

• Needs carbon and energy
• Stimulated by amino acids and metal ions
• Accumulation of poly-beta hydroxybutyric acid at one end or center of the bacterium
• Nuclear material elongates and moves to one end
• Location of nuclear material near where sporulation will occur
• Septum formation from mesosomes
• Cortex formation by accumulation of peptidoglycan, dipicolinic acid, and Ca
• Exosporium formation
• Sporulation duration: 5–13 hours

Sporulation (Process)

• Spore septum isolates newly replicated DNA and cytoplasm
• Plasma membrane surrounds DNA and cytoplasm
• Spore septum forms, creating forespore
• Peptidoglycan layer forms between membranes
• Spore coat forms
• Endospore is released from the cell

Germination

• Development of vegetative forms from spores
• Activation by oxygen, pH, temperature, humidity, and nutrients
• Environmental conditions related
• Breaking of disulfide bonds (in outer membrane and exosporium)
• Germination: amino acids, minerals, and water enter the cell, activating lytic enzymes
• Extension outward: new vegetative cell elongates from within the spore
• Vegetative form development occurs within 2 hours

Pigment

• Bacteria growing on media form colonies with specific colors
• Aerobic bacteria species have larger number of species in terms of pigment compared to anaerobes
• Divided into two main groups:
  • Non-photosynthetic pigments (water-soluble and non-water-soluble)
    • Example: Pseudomonas aeruginosa, pyocyanin (blue-green), fluorecein (yellow-green)
  • Photosynthetic pigments (according to structures: carotenoids, anthocyanins, melanins, etc.)

Plasmid

• Double-stranded circular DNA
• Gives bacteria antibiotic resistance and special characteristics

Transposons (Tn)

• Short DNA sequences found on chromosomes or plasmids of bacteria
• Mobile
• Contribute to antibiotic resistance

Bacteriophages

• Nucleic acid (DNA or RNA) and protein-like capsid
• Cause lysis of bacteria
• Some integrate into bacterial DNA and replicate with it (prophage)