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Microbial growth3

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Microbial growth3

  1. 1. Veterinary Medicine Brawijaya University
  2. 2.  The growth of a population is an increase in the number of cells  The requirements for microbial growth are both physical and chemical
  3. 3. Temperature  Psychrophiles (cold loving)  Mesophiles (moderate-temperature loving)  Thermophiles (heat-loving) pH  Most bacteria grow best at pH 6.5 - 7.5  Acidophiles  tolerant to acidity Osmotic pressure  They require water for growth and made up of 80-90% water  In hypertonic solution,most microbes undergo plasmolysis  In hypotonic solution wrinkle  Halophiles, can tolerate high salt concentrations
  4. 4. Carbon  Carbon is the structural back-bone of living matter  Half the dry weight of bacterial cell is carbon  Chemoheterotrophs, use an organic molecule  Autotroph (chemoautotroph or photoautotroph) derive their carbon from carbon dioxide Nitrogen  Nitrogen is needed for protein and nucleic acid synthesis  Nitrogen can be obtained from the decomposition of proteins or from NH4 + or NO3 -  A few bacteria are capable of nitrogen (N2) fixation
  5. 5. Oxygen  On the basis of oxygen requirements, organisms are classified as obligate aerobes facultative anaerobes aerotolerant anaerobes microaerophilic capnophilic  Aerobes, facultative anaerobes, and aerotolerant anaerobes must have the enzymes superoxide dismutase (2O2 - + 2H+  O2 + H2O2) and either catalase (2H2O2  2H2O + O2) or peroxidase (H2O2 + 2H2  2H2O) Other chemicals required for microbial growth include sulfur, phosphorus, trace elements, and, for some organisms, organic growth factors
  6. 6.  A culture medium is any material prepared for the growth of bacteria in a laboratory  Microbes that grow and multiply in or on a culture medium known as a culture - Agar is a common solidifying agent for a culture medium - Broth medium is a liquid medium - Semisolid medium
  7. 7. TYPE PURPOSE Chemically defined media Growth of chemoautotrophs and photoautotrophs, and microbiolo- gical assay Complex media, made up of nutrient such as extract from yeast, meat, or digest of protein exp: nutrient agar or nutrient broth Most heterotrophic bacteria and fungi are routinely grown on complex media Reducing media Cultivation of anaerobic bacteria Contain ingredients, such as sodium thioglycholate, that chemically combine with dissolved oxygen and depleted the oxygen in the culture medium
  8. 8. TYPE PURPOSE Differential media McConkey, Urease medium, Salmonella Shigella Agar (SSA), BloodAgar Plate (BAP) Differentiation of colonies of desired microbes from others Selective media Bismuth Sulfite Agar (BSA), Eosin Methylene Blue (EMB), Thiosulphate Citrate Bile Salt Sucrose(TCBS) Suppression of unwanted microbes; encouraging desired microbes
  9. 9. Enrichment media Selenite broth Alkali PeptonWater (APW) Similar to selective media but designed to increase numbers of desired microbes to detectable level Enriched media BAP, Chocolate Agar Plate (CAP), Brain Heart Infusion (BHI) For fastidious bacteria Transport media Cary-Blair (V. cholerae) Amis (Nesseria gonorrhoe) It was needed if the specimens was taken from far places
  10. 10. Bacterial Division  Bacteria normally reproduce by binary fission, in which a single cell divides into two identical cells  Fungi reproduce by budding, aerial spore formation, or fragmentation  Bacterial division occurs according to a logarithmic progression : 2 cells  4 cells  8 cells  etc. GenerationTime  The time required for a cell to divide or a population to double is known as the generation time  Most bacteria have generation time 1 – 3 hours; other require more than 24 hours per generation Pathogenic Mycobacterium require > 8 weeks
  11. 11.  During the lag phase, there is little or no change in the number of cells, but metabolic activity is high  During the log phase (exponential growth phase), bacteria multiply at the fastest rate possible under the conditions provided  During the stationary phase, there is equilibrium between cell division and death  During the death phase, the number of deaths exceeds the number of new cells formed
  12. 12.  A standard plate count reflects the number of viable microbes and assumes that each bacterium grows into a single colony; plate count are reported as number of colony forming units (CFU)  In filtration, bacteria are retained on the surface of a membrane filter and then transferred to a culture medium to grow and subsequently be counted  The most probable number (MPN) method can be used for microbes that will grow in a liquid medium; it is statistically estimation  In a direct microscopic count, the microbes in a measured volume of a bacterial suspension are counted with the use of a specially designed slide Petroff- Hausser cell counter
  13. 13. Turbidity  A spectrophotometer is used to determine turbidity by measuring the amount of light that passes through a suspension of cells  McFarland standard Metabolic Activity  Acid production or oxygen consumption DryWeight  For filamentous organisms such as fungi, measuring dry weight is a convenient method of growth measurement
  14. 14. -Thank You For Your Attention-