Bacteriology 1

• Bacteriology


  The study of bacteria
• Bacteria


  • Ubiquitous and numerous
  • Beneficial and pathogenic
  • Very small, visible to the naked eye
• Bacterial morphologies and arrangements

  • Sphere shaped (cocci)
  • Rod shaped (bacilli)
  • Appendaged bacteria
• Bacterial sizes


  • Diameter range from 1 to 5 micrometers
  • The largest bacterium known is the Thiomargarita magnifica, 2.0cm long
• Prokaryotes (bacteria)


  • Unicellular organisms
  • Lack of membranous organelles and true nucleus
• Components all bacteria have

  • Cytoplasm
  • Ribosomes
  • Nucleoid
  • Plasma membrane
  • Complex and rigid cell wall
• Components some bacteria have

  • Capsule
  • Flagella
  • Pili/fimbriae
  • Plasmids
• Things some bacteria can produce

  • Endospores
• Cytoplasm


  Jelly-like aqueous solution (cytosol) that facilitates major chemical reactions of the cell and contains the nucleoid (DNA) and ribosomes
• Nucleoid (DNA)


  The bacterial chromosome, mostly single (haploid) and circular, containing the essential genes for the life of the bacteria (core-genome)
• Plasmids


  Circular double stranded DNA that can be conjugative (passed to other bacteria) and contain additional genes not essential for the bacteria, such as virulence and antibiotic resistance genes
• Ribosomes


  The cellular protein factory, composed of proteins and rRNA, with a large (50s) and small (30s) subunit, used for therapy and phylogeny
• Components of the bacterial envelope

  • Cytoplasmic or plasma membrane
  • Membrane associated proteins
  • Cell wall (peptidoglycan layer)
  • Allows characterization of Gram-negative and Gram-positive bacteria
• Cytoplasmic membrane


  Flexible structures composed of phospholipids and proteins, with hydrophilic exterior and hydrophobic interior, no sterols
• Membrane associated proteins


  Involved in stabilization, transport, electron transport for respiration, and enzymes
• Cell wall


  Composed of a peptidoglycan layer, providing protection against damage and osmotic lysis, non-selective transport, and differences in structure and composition allow characterization of Gram-positive and Gram-negative bacteria
• Components of the Gram-negative bacterial envelope


  • Outer membrane containing lipopolysaccharide (endotoxin) and porins/transporter proteins
• Mycobacteria


  • Bacterial envelope containing mycolic acids, thick waxy hydrophobic wall, acid fast staining identification
• Mollicutes (Mycoplasma)


  • No cell wall, highly pleomorphic and osmotically unstable, the smallest bacteria described
• Capsule


  Glycocalyx, an extracellular matrix, only in some bacterial species
• Flagella


  Anchored to the bacterial cell envelope, multi-protein structure (engine), variable number and position, function in locomotion/motility
• Pili/fimbriae


  Fine, straight, hair-like appendages attached to cell wall, known as "adhesins", most common on Gram-negative bacteria, function in adhesion to host tissues and contribute to antigenicity
• Endospores


  Cryptobiotic state of dormancy and most durable type of cell, produced by some Gram positive bacteria, ensure survival during adverse environmental conditions