For the BART™ Test, Sulfate-Reducing Bacteria, how should a pink ring around the ball and cloudiness in the media under the ball be interpreted?

Document ID

Document ID TE1753

Version

Version 3.0

Status

Status Published

Published Date

Published Date 06/19/2018
Question
For the BART™ Test, Sulfate-Reducing Bacteria, how should a pink ring around the ball and cloudiness in the media under the ball be interpreted?
Summary
Pink ring and cloudiness on BART™ Test, Sulfate-Reducing Bacteria

 
Answer
When either a pink ring is formed around the ball, or there is cloudiness in the culture media underneath the ball using the BART™ Test, Sulfate-Reducing Bacteria (SR B) a negative result for SR B is implied (as long as there is no black base or black ball/top reaction).  

The pink ring most commonly relates to the bacterial genera Chromobacterium, Flavobacterium, or Serratia forming a pink to red pigment, usually at the interface between the ball and the surface of the culturing medium.

Clouding is common when there is growth of anaerobic (fermentative) bacteria able to utilize some of the nutrients within the BART™ tester.

In either case, these events would be considered negative for the sulfate producing bacteria (instead, other non-SR B bacteria are growing).

The only other bacteria that may generate a pink color (most likely as red to purple) are purple sulfur bacteria that can sometimes be detected in waters that are very reductive, with high sulfur content.

Clouding as described is extremely common. In the manufacturer's experience, most SR B tests on natural water samples will show these types of reactions, though a pink product reaction is rare (<5%). In the development of the SR B tester it has been found to be the most effective for separating the two major groups of hydrogen sulfide generators using either sulfates or sulfur-amino acids.

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