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Fecal Coliforms - Water Samples - Holding Times -also R2A Medium

M. LeChevallier lechevallier1 at comcast.net
Sat Dec 21 01:46:12 EST 2002


R2A is designed as a low nutrient medium. For optimal counts, incubate at
20-25 C (room temp is OK) for 7 days (in the dark).  Best to count the
plates using a magnified colony counter as many colonies will be very small.
35 C is not an good incubation temperature for most natural waterborne
bacteria.  35 C is used for coliform and bacteria of fecal origin as it more
closely mimics the warm gut environment.
"Jorge1907" <jorge1907 at aol.comcomm> wrote in message
news:20021219190246.12055.00000133 at mb-df.aol.com...
> John et al.
>
> We often cite Standard Methods for Water and Wastewater - assuming its
authors
> have done the needed research of the literature.
> I ahve a recent observation on R2A medium that i found troubling.
Standard
> methods says it may be incubated at 35C as well as at a lowet temp and one
lab
> I recently visited had assumed this meant the bugs grew faster.
> However, i recently came across Geldreich's original description of R2A
and saw
> the growth plots clearly showing one to almost 2 log differneces between
35 and
> 28C incubation times.
> Does any of you have data saying the yields are more similar or justifying
35C?
>  I found nothing at PubMed.
> There are more things in heaven and earth, Horatio,
> Than are dreamt of in your philosophy





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