We are studying with plastic-degrading microbes.
Although we are getting turbidity increases, we need a different way of measuring bacterial growth as the powdered plastic contributes to the turbidity.
Can anyone recommend a suitable protein assay - or some other suitable measure of growth?
Dear Andrew
you can use a cell viability probe as XTT or Celltiter Blue (Promega - based on rezurin) which will be metabolized from the live bacteria and a colored (or fluorescent)metabolite will be released into the media and detectable after bacteria/pastic removal by centrifugation.
Of course you need to generate a standard calibration curve with bacteria with out plastic to correlate the bacterial cfu/ml (estimated by plating and count in agar plate) or the OD with the probe color intensity.
eg. Article Viability Reagent, PrestoBlue, in Comparison with Other Avai...
https://biotium.com/product/xtt-cell-viability-assay-kit/
good luck
Manuele
How large are the plastic particles? Could you separate them from your sample with a simple filtration through a glass-fiber pre-filter?
To avoid having your bacteria stick to the filter material, and to remove bacteria sticking ot the plastic, ass well, you could add a detergent to your sample.
In principle, you can quantify protein to measure bacterial biomass. Because some of your bacteria are immobilised on the substrate, while others are in the medium, I'd try an assay that reacts with both, but then forms a soluble colour, so I could remove cell walls, plastic substrate etc. by centrifugation. The BCA assay comes to mind (doi:10.1016/0003-2697(85)90442-7).
Another approach might be to label protein (or perhaps easier DNA) with a fluorescent probe (fluoram or any of the intercalating stains) and then measure fluorescence w/o separation. Of course, this would require the substrate to have no fluorescence.
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