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Bacteria

Bacteria. Growth in the laboratory (in vitro). Bacterial nutrition and the design of culture media. Based on bacterial metabolism* Culture pH Culture oxidation- reduction petencial Gaseous requirments Oxzgen. Growth of bacteria. Growth of bacterial cell Growth in ba t ch culture.

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Bacteria

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  1. Bacteria Growth in the laboratory (in vitro)

  2. Bacterial nutrition and the design of culture media • Based on bacterial metabolism* • Culture pH • Culture oxidation- reduction petencial • Gaseous requirments • Oxzgen

  3. Growth of bacteria • Growth of bacterial cell • Growth in batch culture

  4. Growth in batch culture • The lag fase • The exponential fase • The stationary fase

  5. Growth in batch culture

  6. Bacterial growth on solid surface • Agar media • Colony forming units • Bacterial colony

  7. Environmetal conditions optimal temperature, oxygen concentration, pH, water activity

  8. Oxygen concentration • Aerobs • Anaerobs (do not require oxygen) • Obligate anaerobs (die in the presence of O) • Facultative anaerobs (E.coli) • Microaerophilic bacteria

  9. pH • Acidophiles (grow at low pH (0-5,5) • Alcaliphiles (8,5-11,5) • Normal (6,5-7,2)

  10. Temperature ( characteristic ranges) • Psychrophiles: with optimum growth T around 20 C • Mesopihles: between 15 and 45 with optimum around 37 C • Thermophiles: between 30 and 75 with optimum around 55 C • Hyperthermophiles: T grater than 100C

  11. Techniques used to study bacteria • Aseptic (sterile) techniques: • Sterile media • To prevent contamination (accidental intorduction of unknown bacteria) • Sterilisation (autoclave, flaming) • Desinfection (the removal of potentially harmful microbes : B, V,

  12. Growth media: Liquid (for large numbers of bcteria) Solid (for isolation of individual bacteria) Semisolid ( for demonstration of motility) Envinronmental conditions: optimal temperature, oxygen concentration, pH, water activity Baceria are grown (cultured)

  13. Growth media • Defined media (synthetic)- composed form defined ingredients • Complex media – composed from undefined ingredients such as proteolytic digests of meat (peptons) and meat extracts • Nutrient broth, tryptic soya broth • Nutrient agar,… • Blood- an addtive to media

  14. Obtaining bacterial colonies • Pure culture • Isolation – using method called streaking • To strake bacteria on to agar plates we are using a wire (or plastic) loop

  15. Selective and differential media • Selective media: for selection of particular groups of bacterial pathogens ( contain inhibitors i.e. antibiotics, bile salts, dyes, which are suppressing the growth of unwonted bacteria) • Differential media: for differentiation of two species or groups (lactose +, -)

  16. Agar isolated from seaweed • Is not degradated by bacteria • Agar is melted by boiling • Liquid medium can be converted into solid medium by the adition of agar (1- 2%) or semisolid medium (0,6%)

  17. Colonies • Shape • Size • Elevation • Edge • Surface • Opacity • Consistency

  18. Counting of bacteria • Viable counts (according of number of colonies) • Turbimetric measurements • Other methods (RT PCR)

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