We are doing a research on Biofilm formation of Bacteria, for knowing each isolate strong, moderate or weak, by calculations tables of Standard deviation, Variance and Cutoff (Ct) etc… and with the help of Microsoft Excel but the results in the program differ from the hand written and don’t know the best way to calculate and compare the results, any help will be very appreciated, Thank you
Ali
Dear Ali,
There are probably many ways you can differentiate bacterial biofilm formation and I'd suggest either following the procedure described in a research paper working on the species or strains you are interested in, or by using your own criteria. We characterise our air-liquid interface biofilms using a combined biofilm assay measuring biofilm strength, attachment levels and total growth - which means we can describe 'biofilms' using one or all three quantitative measurements. We tend not to use 'no biofilm' control strains, as many biofilm-formers produce such weak and poorly attached structures it is not clear when a 'no biofilm' becomes a measurable one (though we can use a sterile microcosm/culture as the negative control if appropriate).
I can't comment on your problems with Excel, but one simple way is to graph the mean results from your experimental replicates, and divide these into quartiles about the median (i.e., from the minimum values to Q1, from Q1 to the median, from the median to Q3, and from Q3 to the maximum value). You could then simply state that no or poor biofilm formers are min - Q1, biofilm formers are Q1 ≤ Q3, and good biofilm-formers are Q3 - max (if you liked, you could divide your bacteria into no biofilm, poor biofilms, good biofilms and very good biofilms – the number of categories is up to you, but you can't have lots when you have relatively few bacteria to distribute across these categories).
There are statistical tests you could use, and assuming that data (or residuals) are Normally distributed, you could say that no or poor biofilms are not significantly different to a no-biofilm control, etc., but this gets messy because it is hard to know when a very poor biofilm is effectively no biofilm, etc.
Andrew
The calculation and statistical analysis of a microtiter plate assay for biofilm formation of bacteria involve several steps. Here's a general outline of the process:
It's important to note that the exact details of the calculations and statistical tests can vary depending on the specific experimental design and requirements. Therefore, it is advisable to consult relevant literature, scientific papers, or a statistician for specific guidance on the statistical analysis of your microtiter plate assay for biofilm formation.
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