Biofilm cell are different than planktonic bacterial cell. We know serial dilution is very effective to count the colony for CFU but how did we count the biofilm cells where they were encapsulated by self polymeric matrix?
This is an interesting question primary because not all bacterial cells in any biofilm are immediately viable. The position in the biofilm and the cells role in the biofilm will predict its state of metabolism. To answer your question directly, you can disrupt the biofilm (depending on where you are growing it) and cultivate it on a similar medium to your biofilm media in a serial dilution method. Or if the cells have difficulty in growing you can use one of the many revival medias . Remember, a proportion of your bacteria may remain viable but perhaps non-culturable. You might want to think about resorting to some live/ dead staining to check this proportion. However even in biofilms this staining is a rough approximation and experiments should be repeated many times. This is more feasible if you use a 96 well plate set-up.
If, on the other hand you just want to measure the amount of biofilm /amount of biofilm inhibition compared to a standard then I would recommend using a crystal violet assay. In this way you are measuring total biofilm not just cells. This is a very simple procedure and does not require any complex equipment apart from a plate reader to read the absorbance of the crystal violet.
If you want to make growth curves you could try to use an isothermal microcalorimeter. It will not count CFU but measured heat, and then you can make the curves based on heat x time.
I know Bioassay methods are used for detecting special metabolites that have effect on biofilm formation. like crystal violet staining, confocal microscoy or mass spectrometry... may you find a way to connect it to measure CFU.
Thank you Gabriel Magno and Fateme Taheri mam for suggestions
If you follow microscopic methods like SEM/Confocal, then its not cfu but cell counting (dead and live both). When we are looking for CFU, it means we are following only viable cells which have ability to divide and form colony.
If you are looking for thickness or strength of biofilm forming ability of bacteria/fungi then biomass assay like crystal violet assay on microtitre plate and reading quantitatively by spectrophotometer in O.D. value is an easy, cost effective and better method.
Lets hope you find answer for your question and please do share it here.
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