biolab activity 4

• Culture media is a source of nutrients supporting the growth of microorganisms in-vitro
• Common ingredients of culture media include peptone, beef extract, yeast extract, distilled water, and agar as a solidifying agent
• Agar is used to harden the media at a 1.5-2% concentration, allowing the growth of bacteria as colonies by streaking on the medium
• Solid Media examples include Nutrient agar, MacConkey agar, Blood agar, and Chocolate agar
• Semi-Solid Media examples are Stuart’s and Amies media, Hugh and Leifson’s oxidation fermentation medium, and Mannitol motility media
• Liquid Media is a general-purpose media supporting the growth of non-fastidious microbes, used for the isolation of microorganisms
• Simple Media contains nutrients in unknown quantities added to bring about a particular characteristic of a microbial strain
• Complex Media is a chemically defined media produced from pure chemical substances
• Synthetic Media is used in scientific research, enhancing the growth of many microorganisms
• Types of culture media based on chemical composition/application: Basal Media requires the addition of other substances like blood, egg, or serum
• Types of culture media based on chemical composition/application: Enriched Media shows the growth of selective microbes or desired microorganisms, inhibiting unwanted microbes
• Types of culture media based on chemical composition/application: Enrichment Media like Selenite F-broth isolates Salmonella typhi from a fecal sample
• Indicator Media differentiates bacteria based on colony color growing on the same plate
• Types of culture media based on chemical composition/application: Transport Media transports specimens after collection to control the overgrowth of organisms
• Storage Media maintains the longevity of bacterial culture
• Types of culture media based on oxygen requirement: Aerobic Media cultivates anaerobic bacteria at low oxygen, reducing oxidation-reduction potential
• Types of culture media based on oxygen requirement:

  • Anaerobic media

  
• Examples of Anaerobic media:

  • RCM (Robertson cooked meat) isolation for Clostridium sp.
  • Thioglycolate broth– It has sodium glycolate that maintains low oxygen
• Common media in routine use:

  • Nutrient Broth: 500 g meat (e.g., ox heart) minced and mixed with 1 liter water, 10 g peptone, 5 g sodium chloride added, pH adjusted to 7.3. Uses: (1) As a basal media for the preparation of other media, (2) To study soluble products of bacteria
• Common media in routine use:

  • Nutrient Agar: Solid at 37°C, 2.5% agar added in nutrient broth, heated at 100°C to melt agar and then cooled
• Common media in routine use:

  • Peptone Water: Peptone 1% and sodium chloride 0.5%, used as a base for sugar media and to test indole formation
• Common media in routine use:

  • Blood Agar: Most commonly used medium, 5-10% defibrinated sheep or horse blood added to melted agar at 45-50°C, blood acts as an enrichment material and an indicator
• Common media in routine use:

  • Chocolate Agar or Heated Blood agar: Prepared by heating blood agar, used for culture of pneumococcus, gonococcus, meningococcus, and Haemophilus
• Common media in routine use:

  • MacConkey Agar: Most commonly used for Enterobacteriaceae, contains agar, peptone, sodium chloride, bile salt, lactose, and neutral red, a selective and indicator medium
• Common media in routine use:

  • Mueller Hinton Agar: Used for disc diffusion sensitivity tests for antimicrobial drugs as per WHO recommendation to promote reproducibility and comparability of results
• Common media in routine use:

  • Hiss's Serum Water Medium: Used to study the fermentation reactions of bacteria which cannot grow in peptone water sugar media, e.g., pneumococcus, Neisseria, Corynebacterium
• Common media in routine use:

  • Lowenstein-Jensen Medium: Used to culture tubercle bacilli, contains egg, malachite green, and glycerol
• Common media in routine use:

  • Dubos Medium: Liquid medium used for tubercle bacilli, drug sensitivity testing can be carried out, contains 'tween 80', bovine serum albumin, casein hydrolysate, asparagin, and salts
• Different sterilization methods used in the laboratory:

  • Heat Method: The most common method of sterilization, heat is used to kill microbes in the substance, extent of sterilization affected by temperature and duration of heating
• Different sterilization methods used in the laboratory:

  • Filtration: Involves filtering with a pore size too small for microbes to pass through, filters with a pore diameter of 0.2 um used for removal of bacteria
• Different sterilization methods used in the laboratory:

  • Radiation Sterilization: Involves exposing packed materials to radiation (UV, X-rays, gamma rays) for sterilization, effectiveness varies based on penetration of different radiation types
• Different sterilization methods used in the laboratory:

  • Chemical method of sterilization: Involves the use of harmful liquids and toxic gases without affecting the material, commonly used gases include a combination of ethylene oxide and carbon dioxide