bacterial growth, structure and their ,metabolism

• Prokaryotic microorganisms include bacteria and cyanobacteria
• Prokaryotes have a simple make-up without sub-cellular organelles
• The typical size of a prokaryote is about 1um diameter
• Eukaryotic microorganisms possess a complex cellular structure
• Eukaryotes contain membrane-bound organelles such as mitochondria, lysosomes, endoplasmic reticulum, and golgi bodies
• Cell Envelope consists of:

  • Cell Wall
  • Plasma / Cell / Cytoplasmic Membrane
  • Capsule (some / not all)
• The cell envelope includes chemically and functionally distinct layers, with the cell wall and cytoplasmic membrane being the most prominent
• The capsule or glycocalyx may also be part of the cell envelope if present
• Cell Wall components:

  • Peptidoglycan
  • Determines the shape of the cell
  • Composed of a cross-linked polymeric mesh
  • Glycan is a linear polymer of alternating monosaccharide subunits (backbone)
  • Peptido is a short string of amino acids forming a network with high tensile strength
• Gram(+) Bacteria Cell Wall:

  • Thick, multilayered, peptidoglycan cell walls exterior to the cytoplasmic membrane
  • Peptidoglycan in most gram(+) species is covalently linked to teichoic acid
  • Teichoic acids are major cell surface antigens and are integrated into the peptidoglycan layers
  • Lipoteichoic acids are lipid modified and integrated into the outer leaflet of the cytoplasmic membrane
• Gram(-) Bacteria Cell Wall:

  • More complex structure with 2 membranes (outer and periplasmic)
  • The periplasmic space contains the thin peptidoglycan layer, degradative enzymes, and transport proteins
  • Outer membrane contains lipopolysaccharide (LPS) with antigenic polysaccharide portion (O-polysaccharide) and toxic lipid portion (lipid A)
• Flagella:

  • Long, semirigid, helical, hollow tubular structures composed of flagellin protein
  • Enable bacteria to move in a directed fashion
  • Anchored in the cell membranes by a basal body
  • Highly antigenic
• Pili (Fimbriae):

  • Function as attachment structures promoting specific cell-to-cell contact
  • Attachment can be between bacterial cell and host eukaryotic cell or between bacterial cells
• Spores & Sporulation:

  • Some gram-positive rods undergo profound structural and metabolic changes to form endospores
  • Endospores are dormant cells resistant to heat, desiccation, and chemicals
  • Spores are released from the original cell and are highly resistant life forms
• Bacterial Growth and Metabolism:

  • Bacterial growth involves metabolic tasks to grow and divide
  • Bacteria reproduce by binary fission, increasing cell number exponentially
  • Bacterial metabolism can generate energy through aerobic respiration, anaerobic respiration, or fermentation
• Aerobic Respiration:

  • Oxygen serves as the terminal electron acceptor in the electron transport chain
  • Oxygen is reduced to water, generating energy for aerobic bacteria
• Anaerobic Respiration:

  • Inorganic compounds other than oxygen serve as terminal electron acceptors
  • Acceptors can be molecules like nitrate or sulfate, used by facultative or obligate anaerobes
• Fermentation:

  • Anaerobic process where organic metabolic intermediates serve as final electron acceptors
  • Some bacterial species utilize fermentation for energy production