Cultivation

• Bacterial growth


  1. Refers to the increase in the number of bacteria rather than in size

  2. Bacteria grow in number and do not grow in size

  3. This growth is affected by various factors such as optimum growth requirements, dynamics of growth, including the use of a medium that can be artificially prepared in the laboratory
• Types of bacteria based on nutritional requirements

  • AUTOTROPH - sources carbon from carbon dioxide
  • CARBOHYDRATES - Glucose, Lactose, Sucrose
  • HETEROTROPH - capable of getting carbon from organic components
• Bacterial growth requirements

  • Nutritional - C- Carbon, N-Nitrogen, E-Energy
  • Environmental - gas, temperature, pH
• Types of bacteria based on energy sources


  • PORTATROPH - capable of getting energy from light
  • CHEMOTROPH - getting chemical energy from organic compounds
  • LITOTROPH - electron sources
  • ORGANOTROPH - getting electrons from organic molecules
• Bacteria can tolerate salt concentration below 6%, however, there are certain bacteria that can survive high salt concentration
• Nutritional requirements for bacterial growth

  1. CARBON - is needed to make cellular constituents or cellular components

  2. NITROGEN - is for making proteins, and nucleic acids

  3. ENERGY - is the form of ATP (Adenosine Triphosphate), to perform metabolic functions and cellular functions
• Halophilic bacteria


  • Staphylococcus spp., Enterococcus spp., Vibrio spp. except Vibrio cholerae & Vibiro mimicus, Bacillus spp
• Contaminants of our culture can include bacteria
• X Factor is haemin, V Factor includes vitamins, ATP, and Haemophilus spp
• Facultative aerobes have the ability to grow in small concentrations of oxygen
• CAP (CHOCOLATE AGAR PLATE)


  • Lysed RBC (heat to increase NADase to have NAD to V factor)
• Anaerobes are bacteria that grow in the absence of oxygen
• An incubator designed with a humidity regulator needs regular checking, but if it lacks one, daily monitoring is necessary
• Sources of blood include 5% defibrinated sheep blood, horse blood, rabbit blood, and human blood (Type O)
• BAP (BLOOD AGAR PLATE)


  • Intact RBC, doesn't have V factor, only X factor
• Microaerophiles prefer small concentrations of oxygen
• Staphylococcus spp.


  • Grown in MSA (Mannitol Salt Agar)
• Strict/obligate anaerobes do not require oxygen to grow
• Aerobes are bacteria that grow in the presence of oxygen
• Additional/Special growth requirements

  • Bacteria that are very difficult to grow and require special or additional requirements to grow in culture media
• Fastidious organisms


  • Bacteria that are very difficult to grow and have special growth requirements
• Bacteria can tolerate salt concentrations below 6%, with certain bacteria surviving high salt environments known as HALOPHILIC bacteria or HALOPHILES
• Satellitism involves obtaining the V factor from surrounding organisms like Haemophilus
• Haemin and Hematin are X Factors, while Nicotinamide, Adenine nucleotide, or NAD are V Factors
• Strict/obligate aerobes absolutely require oxygen to grow
• 18% oxygen is an environmental requirement
• Bacteria replicate via binary fission (asexual reproduction)
• Bacterial growth curve consists of the Lag Phase, Logarithmic Growth Phase, Stationary Phase, and Death Phase
• Types of anaerobic bacteria

  • ANAEROBE - bacteria that grow, live, and survive in the absence of oxygen
  • STRICT/OBLIGATE ANAEROBE - absolutely do not require oxygen to grow, live, and survive (e.g. Clostridium spp., Bacteroides spp., Fusobacterium spp., Peptostreptococcus spp., Porphyromonas spp.)
  • AEROTOLERANT ANAEROBE - bacteria that do not require oxygen but may tolerate or withstand limited exposure to oxygen (e.g. Clostridium perfringens, Bacteroides fragilis, Proprionibacterium, Lactobacillus)
  • CANOPHILIC OR CANOPHILES - bacteria that require 5%-10% CO2 to grow (e.g. Neisseria spp., Haemophilus spp., Aggregatibacter spp., Cardiobacterium spp., Eikenella spp., Kingella spp., Streptococcus pneumoniae)
• pH requirements for bacterial growth

  • Most pathogenic bacteria can grow in a neutral or slightly alkaline environment (pH 7.0 – 7.5)
  • ACIDOPHILIC – acid loving bacteria (e.g. Lactobacillus acidophilus)
  • ALKALIPHILIC – alkali loving bacteria (e.g. Gardnerella vaginalis)
• In the Stationary Phase, nutrients begin to deplete, toxins may be produced, and cell death equals cell division
• Temperature requirements for bacterial growth

  • MESOPHILIC - optimally growing between 20o-40oC
  • PSYCHROPHILIC/CRYOPHILIC - optimally growing between 0-20oC
  • THERMOPHILIC - growing between 50o-60oC
  • HYPERTHERMOPHILIC (EXTREMELY THERMOPHILIC) - optimally growing between 80o-100oC, always sporeforming bacteria
  • EURITHERMOPHILIC - growing at a wide range of temperatures
  • STERNOTHERMOPHILIC - usually growing at a narrow range of temperatures
• High osmotic pressure is required for OSMOPHILIC Bacteria (Archaebacteria spp.)
• In the Death Phase, due to the unfavorable environment, bacterial growth ceases
• Generation time/doubling time is the time required for 1 cell to divide into 2 cells (e.g. Escherichia coli has a generation time of 20 minutes)
• In the Logarithmic Growth Phase, bacteria continue to multiply rapidly
• Slow growing bacteria can take up to 24 hours to replicate (e.g. Microbacterium Tuberculosis)
• Most pathogenic bacteria grow at temperatures between 35-37°C
• Bacterial growth phase refers to the stages of bacterial growth
• Growth rate is a constant number of generations where bacteria are most metabolically active