three part question:

1. Looking for a quick (<1 hr.), easy, and cheap method to detect bacteria,
2. ability to differentiate (viable and non-), and
3. Is there a way to convert colonies into # of bacteria?

Current method is the modified SM 9215 D membrane filter method, used to monitor of heterotrophic bacteria in ultra-pure water.
Average count: < 1 colony per litre.

chromotography? labeling with molecular probes viability dye? <1hr would be the tough criteria. I would like to see some responses.

Are you interested in isolating single or multi-species bacteria? With single species bacteria you should be able to come up with a PCR detection assay (if it doesn't already exsist for your species). If you are talking multi-species detection from environmental samples than this probably won't work as well...

As a follow up to my previous comment ... There are pitfalls to PCR detection methods (i.e. detection of nucleic acid does not imply viability, therefore confirmitory outgrowth will be required for each positive result using this method). Here is a recent paper talking about this issue:

JOURNAL OF CLINICAL MICROBIOLOGY, Nov. 2004, p. 54035405 Vol. 42, No. 11
An Unexpected Experimental Pitfall in the Molecular Diagnosis of
Bacterial Endophthalmitis
Luana Ugahary,1 Wendy van de Sande,2 Jan C. van Meurs,1 and Alex van Belkum2*

Here is a recent paper comparing two methodologies for identification of mycobacteria. Please note that these methods can be applied to other organisms...


Comparative evaluation of polymerase chain reaction and restriction enzyme analysis: Two amplified targets, hsp65 and rpoB, for identification of cultured mycobacteria
Diagnostic Microbiology and Infectious Disease, In Press, Corrected Proof, Available online 19 January 2005,
Wattana Cheunoy, Therdsak Prammananan, Angkana Chaiprasert and Suporn Foongladda