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Counting Bacteria

Counting Bacteria. Serial Dilutions. Because of their very ______ ______, counting the number of bacteria in a sample can be _________ Although _______ _______ are possible with a ______________, they require a lot of time and ___________. Why Count the Number of Bacteria??.

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Counting Bacteria

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  1. Counting Bacteria

  2. Serial Dilutions Because of their very ______ ______, counting the number of bacteria in a sample can be _________ Although _______ _______ are possible with a ______________, they require a lot of time and ___________

  3. Why Count the Number of Bacteria?? • ________ _____________: • How effective drugs are in killing microorganisms? • ___________________: • How many MO in CSF, blood, urine • ___________ ____________: • - Contaminants in food, milk, water

  4. Total Cell Count • The most common method of _______________ the total microbial cells (______ ___ _________) • The ______ ___________ of cell suspension in a __________ _____________ of known _______ using a ________________

  5. Total Cell Count – Both living and dead MO • Disadvantage: ____________________________________________________________________________________________________________ • Advantage: _____________________________________________________________________________________________________________

  6. Total Cell Count – Both living and dead MO • Neubauer ___________ ___________ • Special _______ ____ _______ _______, microscopic marks on slide, known _________

  7. Counting Chamber

  8. Counting Chamber • Use special ______________ ____ _____________________ • Count specific areas of __________________, multiply by __________________ ______________

  9. Instrumentation • * _____________________ (Light Meter) • Each single ____ stops some ______ from ____________________________________________ • One side _____ ________, then test tube containing MO, other side _______ ________________ • Needle reading from scale, then ________________ _____________ telling # of __________________________________________

  10. Coulter Counter • Another method for _____________ _____________ • An electronic instrument “_____________ _________” • Has a tiny tube (_____ ______ _____________) that lets through only one cell at a time

  11. Viable Cell Count – Living Cells Only

  12. Viable Count – Living Cells only An easier method is to ______ ________ _____ __ _____ ______ (nutrient agar plate) and count the number of ________ _____ ______ If the bacteria are ______ ____ ______, each bacterial cell in the original sample should produce a _______ _______

  13. Serial Dilutions Bacterial samples must be _______ considerably to obtain ___________ ___________ To determine the ________ ___ ______ in a bacterial culture carry out _______ ____________

  14. Serial Dilutions Bacterial cell numbers are usually _______ _____ _____________________________ Plating out this sample, undiluted, would lead to the creation of a ___________________ Bacterial Lawn - many individual bacteria colonies that are ______________________ ____________________________________

  15. Serial Dilutions Bacterial cell numbers _____ __ __ _______ This is done by ______ ________ the amount of bacteria you have in your sample A ______ _________ of bacteria sample is mixed with a _____ _______ (sterile broth or water), and then _______ ___________ are made

  16. Serial Dilutions A small amount of _____ ___ ____ _______ _________ ________ is then spread onto an ______ ________ The numbers of bacterial colonies that ______________________________

  17. Serial Dilutions Work ___________ using multiplication with the “___________ ____________” ________ ________ - the ______ ___ ______ that you have diluted the bacteria sample with the diluent solution Make a determination of the numbers of bacteria in ______ ________ _________.

  18. Serial Dilution

  19. Serial Dilutions *Make ________ _____________ *Spread a small amount from each tube onto _______ _______ *Culture bacteria for a ________ __ _________ *Count colonies ________________________________

  20. Membrane Filtration • ________ __________ can also be used to determine the ________ _______________ • In this method ______ _____ ___________ onto membrane filter which is then placed over a ________ ______ __________.

  21. Membrane Filtration • The methodology is similar to conventional _______ ________ _______________. • Membranes have a printed millimeter ________ and colonies can be counted under a _________ _________________.

  22. Factors essential for __________ ________ --proper ________________ --proper ___________________ (space, temperature) --No inhibiting factors Factors that _____________________ __________________________________________ --lack of _____________ --lack of __________ __________________ --presence of an ___________ __________

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