{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

The operational definition of coliform bacteria for

Info icon This preview shows pages 21–23. Sign up to view the full content.

View Full Document Right Arrow Icon
(particularly Hepatitis A Virus). The Operational Definition of Coliform Bacteria for Water Quality Testing Purposes (which is different from the Taxonomic Definition of Coliform Bacteria) is that they are Non-Spore-Forming Gram Negative Rods that ferment Lactose to form Acid and Gas in 24 to 48 Hours at 35°C. The Multiple-Tube Fermentation Method is actually a three Part Test: The Presumptive Test, the Confirmed Test, and the Completed Test (which you’ll undoubtedly remember we covered in the Cholera Lecture). The Presumptive Test -- which is what we’ll be doing Today -- involves inoculating 3 Large Tubes of Lauryl Sulfate Lactose (LSL) Broth with 10 ml of a Water Sample, 3 Standard Tubes of LSL Broth with 1.0 ml of this Water Sample, and 3 Standard Tubes of LSL Broth 0.1 ml of this Water Sample. These 9 Tubes are then incubated at 35°C for 24 Hours ± 2 Hours. Turbidity and Gas Production in any Tube is Presumptive of the Presence of Coliforms. The Presumptive Test can also be used to determine what is referred to as the Most Probable Number (MPN) . This is a Statistical Estimation of the Number of Coliform Bacteria present per 100 ml of Water. Each Set of 3 Tubes can have no Positive Tubes (0), one Positive Tube (1), two Positive Tubes (2) or three Positive Tubes (3) for Coliforms. So each Set of Tubes generates a Number between 0 and 3. The entire Presumptive Test will then generate three Numbers and these can be used to determine MPN from Statistical Charts published by The American Public Health Association. Note that MPN is the Number of Coliforms per 100 ml Environmental Biologists have taken the Presumptive Test and modified it for a more accurate Determination of MPN by using 10 Tubes for each Set (making for a Total of 30 Tubes). This makes for a more accurate Way to monitor Lakes or Streams for Contamination. It also makes for a whole lot of Tubes, which is why we don’t use this Method. What you’ll be doing in Lab is quite Simple. You’ll take a 50 ml Aliquot from the 500 ml Water Sample in each Lab. You’ll inoculate 10 ml of your Water Sample into 3 humongous Tubes containing 10 ml of Double-Strength LSL Broth (so after adding your Water Sample it’ll effectively be Standard-Strength LSL Broth). You’ll inoculate 1 ml (1000 μ l) of your Water Sample into 3 Tubes containing 10 ml of LSL Broth. And you’ll inoculate 100 μ l (0.1 ml) of your Water Sample into 3 Tubes containing 10 ml of LSL Broth. Be sure and check that all the Tubes contain Durham Tubes. And they all get incubated at 37°C for 24 Hours.
Image of page 21

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Lab 6 Page 22 Isolations Pseudomonas Everyone should have Pseudomonas by now. Check your Plates for the characteristic shiny Appearance of Pseudomonas Colonies. Make a Smear from an isolated Colony, confirm that the Bacteria in this Colony are Gram Negative Rods (very small and possibly more like Rugby Balls). Use this same Colony to streak an F Agar Plate (Brown Stripe).
Image of page 22
Image of page 23
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern