BACT Lec Bacterial Cell Components

• Cell Wall:

  • Also referred to as the peptidoglyacan, or murein layer
  • Gives the bacterial cell shape and strength to withstand changes in environmental osmotic pressures
  • Protects against mechanical disruption of the cell
  • Offers some barrier to the passage of larger substances
• Gram Positive Cell Wall:

  • Has a very thick protective peptidoglycan (murein) layer
  • Contains Teichoic acid and lipoteichoic acid
• Gram Negative Cell Wall:

  • Has a thin peptidoglycan layer
  • Contains a periplasmic space
  • Outer membrane consists of proteins, phospholipids, and lipopolysaccharide (LPS)
  • Functions of the Outer Membrane:

  1. Acts as a barrier to hydrophobic compounds and harmful substances

  2. Acts as a sieve, allowing water-soluble molecules to enter through protein-lined channels

  3. Provides attachment sites that enhance attachment to host cells
• Gram Variability:

  • Natural gram variability: Mobiluncus spp. and Gardnerella vaginalis
  • Acquired gram variability (for gram positive bacteria)
  • Contributing factors: use of old culture, pH of staining reagents, bacterial autolysis, staining reaction time
• Guiding Rules in the Gram Stain Reaction of Medically Important Bacteria:

  • All COCCI are Gram POSITIVE except Neisseria, Branhamella or Moraxella, Veillonella spp.
  • All BACILLI are Gram NEGATIVE except Mycobacterium, Bacillus, Erysipelothrix, Lactobacillus, Corynebacterium, Rothia, Aerobic Actinomyces, Clostridium, and Kurthia spp
• Acid-Fast Cell Wall:

  • Contains a waxy layer of glycolipids and fatty acids (mycolic acid)
• Acid-Fast Staining:

  • Specifically designed for bacteria with long-chain fatty acids in their cell walls
  • Mycolic acid render the cells resistant to decolorization
  • Mycobacteria are the most commonly encountered acid-fast bacteria
• Parts Internal to the Cell Wall:

  • Cytoplasmic/Plasma Membrane:
  • Functions include separating intracellular components, acting as an osmotic barrier, site of electron transport chain
  • Mesosomes: folds or invaginations along the cytoplasmic membrane
  • Free Ribosomes: sites of protein synthesis
  • Inclusion Bodies: serve as storage deposits under certain circumstances
• Parts External to the Cell Wall:

  • Pili (Pilus):
  • Common/Ordinary Pili: shorter, numerous, used for adherence
  • Sex/F Pilus: longer, used for bacterial conjugation
  • Flagella:
  • Exterior protein filaments responsible for bacterial movement
  • Associated with H antigen which is useful for serological typing
  • Glycocalyx:
  • Exterior high molecular weight structure made up of polysaccharides or polypeptides
  • Two forms: Capsule and Slime Layer
• Medically Important Capsulated Bacteria:

  • Neisseria meningitidis
  • Haemophilus influenzae serotype b
  • Streptococcus pneumoniae
  • Klebsiella pneumoniae
  • Bacillus anthracis
• Slime Layer:

  • Loose, thick, viscous material that serves as protection from phagocytosis or helps bacteria adhere to host tissues
• • Neisseria meningitidis

  • Haemophilus influenzae serotype b

  • Streptococcus pneumoniae

  • Klebsiella pneumoniae

  • Bacillus anthracis


  MEDICALLY IMPORTANT CAPSULATED BACTERIA
• SLIME LAYER


  primarily it also serves as a form of protection from phagocytosis, or in some instances, it helps the bacteria to adhere to host tissues or synthetic implants such as prosthetic heart valves
• SLIME LAYER


  loose or diffused, thick, viscous unorganized material that appears to be detached from the bacterial or not firmly attached to the cell wall of the bacteria
• CAPSULE

  For phagocytosis (cell eating/engulfing)
• K Antigen (Kapsule Antigen)


  capsule is associated with
• CAPSULE

  uniform and condensed organized material that is firmly attached to the cell wall of the bacteria.
• capsule

  slime layer


  2 forms of glycocalyx
• GLYCOCALYX


  exterior high molecular weight appendage or structure usually made up of polysaccharide polymers or sometime polypeptides which are produced be certain bacteria depending on environmental and growth conditions surrounding the bacterial cell.
• Salmonella

  H Antigen (HAUCH ANTIGEN) which is very useful is serologically typing and identifying species of:
• H Antigen (HAUCH ANTIGEN)


  flagella is associated with:
• FLAGELLIN

  protein material of flagella
• FLAGELLA

  exterior protein filaments or whip-like projections which is embedded in the cell envelope with a motor attached in a basal body responsible for its propeller-like rotation of the flagella which makes bacteria move.
• Sex/Fertility/F Pilus


  - usually longer and singular, long and hollow protein tubes that is primarily used for bacterial conjugation
• Common/Somatic/Ordinary


  usually shorter, numerous, sticky hair-like appendages that are primarily used for adherence to one another, host cells, and environment surfaces
• Common/Somatic/Ordinary

  Sex/Fertility/F Pilus


  2 types of pili:
• PILIN


  protein material of pili
• PILI


  came from Latin: Hairs
• FIMBRIAE


  came from latin: Fringe
• pili


  protein projections that are thinner and shorter than flagella and are most usually found in gram negative bacteria
• pili

  flagella

  glycocalyx


  PARTS EXTERNAL TO THE CELL WALL
• o Bacillus

  o Clostridium


  2 most important sporulating bacteria:
• Calcium dipicolinate

  Calcium-Dipicolinic Acid Complex


  main composition of endospores
• BACTERIAL SPORES/ENDOSPORES


  It is highly resistant to desiccation, heat, chemical agents
• BACTERIAL SPORES/ENDOSPORES


  serves as a resting or hibernating stage for bacteria when they are exposed to unfavorable conditions.
• BACTERIAL SPORES/ENDOSPORES


  • complex multilayered highly refractile structure that can be found within the cytoplasm of the vegetative cell of the bacteria or in the environment when the bacterial cell has been disintegrated.
• BIPOLAR BODIES


  prominent staining of each end of the bacilli Yersinia pestis using Methylene Blue or WAYSON stain giving it a "safety pin appearance"
• VOLUTIN

  BABES-ERNST BODIES

  METACHROMATIC GRANULES


  contains polyphosphates or inorganic phosphates (Corynebacterium diphtheriae)
• MUCH GRANULES


  contains lipids (Mycobacterium tuberculosis)
• poly-beta-hydroxybutyric acid


  lipid reserves