Pre-reduced media preparation

[Mark Spanevello]

Nisha Singh wrote:

> We are seeking assistance in the preparation of pre-reduced media for
> the
> cultivation of anaerobic bacteria.  We are using the preparation
> methods
> of Holdemann et al., Anaerobic Laboratory Manual, 4th edn.  (1977).
> We
> have found that the indicator (resazurin) does not undergo a colour
> change after boiling, as recorded in the manual, ie. from purple to
> colourless in 5-10 min.  In our experiments the indicator changes from
>
> purple to pink in 20 min and does not change to colourless, even after
>
> prolonged boiling.  After cysteine hydrochloride addition and
> autoclaving, the indicator in the media changed from colourless to
> purple
> even when placed in an anaerobic chamber. Cooling the media under
> nitrogen gas after boiling has also been unsuccessful. Is anyone able
> to
> help us? Thank you
>
> Loren Goldstone and Kimoni Rampersad
> Technikon Natal, Durban, South Africa
> E-mail: research at einstein.ntech.ac.za


Resazurin is also a pH indicator, so if the pH is below around 5 or 6, a
colour change may not occur.  I would check the pH of the media to
ensure its pH indicator qualities are not affecting its activity as a
reductive indicator.
--
Mark Spanevello

Faculty of Science and Technology
Griffith Univeristy
Nathan Campus
Nathan, Qld, Australia,  4111

Ph:  (07) 3875-7622
Fax: (07) 3875-7656

email : M.Spanevello at sct.gu.edu.au
        mark at trishul.sci.gu.edu