ColiformColiform Bacteria in Bacteria in Water:Water:

A Measure of Water QualityA Measure of Water Quality

Sarah PalmerSarah Palmer

Tri-Valley ROPTri-Valley ROP

STEP/ETEC, LLNLSTEP/ETEC, LLNL

Significance of ColiformsSignificance of Coliforms

Coliform bacteria are a common and Coliform bacteria are a common and widely spread group of bacteriawidely spread group of bacteria

Eschierichia coliEschierichia coli is a species found in the is a species found in the lower gastrointestinal tract of many lower gastrointestinal tract of many vertebrates and is indicative of FECAL vertebrates and is indicative of FECAL CONTAMINATION!CONTAMINATION!

Why Test?Why Test?

E. coliE. coli itself is not dangerous to most itself is not dangerous to most healthy individuals at healthy individuals at lowlow concentration, concentration, BUT may indicate the presence of far BUT may indicate the presence of far more serious pathogens (and who wants more serious pathogens (and who wants poop in the water?)poop in the water?)

It is also relatively easy to test forIt is also relatively easy to test for

Easy to kill the test cultures once they are Easy to kill the test cultures once they are growngrown

Testing for Drinking Water SafetyTesting for Drinking Water Safety

In the following slide we have a 5 minute In the following slide we have a 5 minute “mini-course” in bacteriology“mini-course” in bacteriology

Make note of the proceduresMake note of the procedures

What are What are negative controlsnegative controls??

What are What are positive controlspositive controls??

How can we test for How can we test for ColiformColiform Contamination?Contamination?

Testing for Testing for ColiformColiform in the in the classroomclassroom

Use of a Lactose Broth with pH indicatorUse of a Lactose Broth with pH indicator Straightforward, easy to useStraightforward, easy to use Some false positivesSome false positives

Use of a commercially available Defined Use of a commercially available Defined Substrate Media Substrate Media (From IDEXX Laboratories, (From IDEXX Laboratories, Colilert™)Colilert™) More expensiveMore expensive Easy to useEasy to use Few false positivesFew false positives

Use of Lactose BrothUse of Lactose Broth

Lactose broth supports the growth of E. coli. Bromocresol purple turns from purple to yellow as the medium is acidified due to bacterial growth and metabolism

A Defined Substrate IndicatorA Defined Substrate Indicator

As coliforms grow in the defined substrate, they use ß-galactosidase to metabolize ONPG and change it from colorless

to yellow.

A More Specific IndicatorA More Specific Indicator

E. coli use ß-glucuronidase to metabolize MUG and create fluorescence. Since most non-coliforms do not have these enzymes, they are unable to grow and interfere.

Classroom ApplicationClassroom Application

Development of Development of a yellow color a yellow color indicates the indicates the presence of presence of coliform bacteriacoliform bacteria

Clear is negative Clear is negative for coliform for coliform typestypes

SpecificitySpecificityTubes that turn Tubes that turn yellow AND yellow AND fluoresce under a fluoresce under a UV lamp are UV lamp are positive for the positive for the E.coli form of the E.coli form of the coliform group.coliform group.

This indicates This indicates FECAL FECAL contamination.contamination.

E. coliE. coli has many sources: has many sources:Reliable testing isReliable testing isan important toolan important tool

ReferencesReferences

IDEXX Laboratories (2003) IDEXX Laboratories (2003) ColilertColilert™. ™. http://www.idexx.com/Water/Products/colilhttp://www.idexx.com/Water/Products/colilert/science.cfmert/science.cfm

Gurpol Deol,M.Sc. (2003) Zone 7 Water Gurpol Deol,M.Sc. (2003) Zone 7 Water Agency Del Valle Plant, personal Agency Del Valle Plant, personal communicationscommunications