QUIZLET SET

• Key bacterial characteristics


  - ubiquitous

  - numerous

  - more beneficial than pathogenic

  - no nucleus

  - no cytoskeleton

  - no histones

  - cell wall

  - pili and flagella

  - capsule

  - endospores

  - ribosomes
• movement structures


  1. pili

  2. flagella
• bacterial cell wall


  - purpose: protection agains mechanical damage and osmotic lysis

  - non-selective transport

  - differences in structure and chemical composition (e.g. gram + & -)
• peptigoglycan


  chain of alternating subunits of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) cross linked with short peptides; gives rigidity to cell wall; thick in gram +

  
  

  The exception: Mycoplasma
• gram staining technique


  - differentiated bacteria by the chemical and physical properties of their cell walls by detecting peptidoglycan

  - gram + =purple

  - gram- = pink
• gram staining steps


  1. crystal violet

  2. iodine (mordant)

  3. alcohol wash (decolorization)

  4. safranin (counterstain)
• gram positive bacteria


  - thick multilayered peptidoglycan layer; single plasma membrane; high resistance to physical disruption and drying; high susceptibility to ionic detergents

  
  

  - teichoic acids and lipoteichoic acids (linked to peptidoglycan)
• teichoic and lipoteichoic acids (gram +)


  gram +; roles in colonization, infection, immunes invasion, protection against harmful molecules and environmental stress, strong antigenic
• Gram negative bacteria


  - single layer of peptidoglycan

  - inner and outer plasma membrane with periplasmic space (periplasm), low resistance to physical disruption and drying, low susceptibility to ionic detergents

  
  

  - lipopolysaccharides (LPS)
• Lipopolysaccharides (LPS) - gram -


  - virulence factor (can help bacteria cause disease), lipid A component, polysaccharide contest (antigenicity)

  - **the lipid A component is the most virulent part of LPS (endotoxigenic)
• Mycobacteria (genus)


  -thick waxy hydrophobic cell wall

  - rich in mycolic acids

  - acid fast bacteria (do not decolorize with acid alcohol due to the presence of mycelia acids); so gram don't work, they need acid fast staining (zielh-Neelsen staining)
• Mycoplasma


  the exception; NO cell wall, NO peptidoglycan; they can cause pneumoniae; plasma membrane with sterols
• Plasma membrane


  - where bacterial respiration occurs

  
  

  - composition: flexible, PL and proteins, outer faces are hydrophilic and inner are hydrophobic

  
  

  - Functions: active transport of nutrients, waste elimination, electron transport, phosphorylation
• Bacterial transport systems (plasma membrane)

  1. facilitated diffusion

  2. active transport (requires E)

  3. group translocation (more specific for bacteria); e.g. phosphotranferase system: in E. coli- modify the solute during its passage across the membrane (transport of sugars)
• Mesosomes


  invagination of cell/plasma membrane into the cytoplasm; NOT present in all types of bacteria
• nucleoid


  region in the cell currently occupied with the nuclear material; single haploid circular chromosome; double stranded DNA; extensively folded bacterial chromosome

  - excretions: Leptospira and Borrelia burgdorferi
• plasmids (nucleoid)


  small circular pieces of DNA capable of autonomous replication; genes associated with disease (virulent factors), resistance genes to survive in presence of antibiotics and toxic compounds
• flagella


  - whip-like filament that helps in cell motility; present on bacterial surface

  - arrangement: number and position

  - *composition: flagellin; filament+hook+basal body
• Groups of flagella


  1. monotrichous: single flagellum

  2. amphitrichous: 2 & opposite; one in front and one in back

  3. lophotrichous: ponytail flagella

  4. peritrichous: implanted all over cell wall
• endoflagella


  flagella in the periplasmic space; allows corkscrew motility
• pili/ fimbrae


  - allow bacteria to attach to different surfaces (no role in locomotion)

  - structure: fine, straight, # varies

  - *composition: pilin

  - most common in gram - bacteria

  - smaller than flagella
• capsule


  - sugarcoat layer (mostly polysaccharides) that surrounds the cell walls of some bacteria; extracellular polymeric matrix

  
  

  - Functions: nutrient reserve specially when they are exposed to negative conditions, play role in adherence of host-cell, protection from environmental conditions and interfere with phagocytosis

  
  

  - e.g. B. anthraces (defined polypeptide capsule)

  cannot be fully seen in a gram stain
• endospores


  A thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions; ensure survival of bacteria; can last years in the soil

  - state of dormancy(bacteria is not dead but there isn't active metabolism) found and most durable type of cell found in nature

  - formed intracellularly

  - sporulation vs germination

  - e.g. **Clostridium and Bacillus (imp in vet med)
• Sporulation


  endospore formation

  - DNA replication-->formation of septum-->mother cell engulfs forespore-->chromosomes of mother cell disintegrate-->foreshore develops cortex layer
• Bacterial shape and arrangement

  - cocci: circles

  - bacilli: pills

  - budding and appendages bacteria

  - other: filamentous, spirochete, etc.
• Factors required for bacterial growth (sources of metabolic E)

  - aerobic respiration

  - anaerobic respiration

  - fermentation

  - photosynthesis
• aerobic respiration


  requires O2
• anaerobic respiration


  Respiration that does not require oxygen; other final electron acceptor than O2
• fermentation


  lactic acid, acetic acid, CO2, proteolytic
• photosynthesis


  Conversion of light energy from the sun into chemical energy; very few bacteria (usually associated to plants)
• aerobes


  cannot grow without O2
• facultative anaerobes


  grow under both aerobic and anaerobic conditions

  
  

  ** most important in vet med
• anaerobes


  only grow in absence of free O2
• Microaerophiles


  require oxygen in lower levels than present in atmosphere (~2-10%)
• capnophiles


  require CO2 for optimal growth
• Factors required for bacterial growth

  environmental factors- nutrients, pH (7.2-7.4 for most pathogenic), ionic strength and osmotic P, light, T (mesophilic=have optimal growth around 37 C)
• binary fission


  - A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size
• generation time


  length of time required for a single bacterial cell to yield two daughter cells (30 min to 20h)
• Phases of bacterial growth

  1. Lag

  2. Exponential or logarithmic

  3. Maximal stationary

  4. Death or decline
• lag phase


  increase in cell size; active metabolism of cells but no division