Dear Haleema,
I am not too sure of why you have asked this nor what you mean by 'putting a different strain Iungin one al'. However, lots of research groups have begun to develop the simple single strain biofilm models to investigate the development of mixed-strain biofilms, and this is a fundamentally easy thing to do, so long as you can tell some of the strains you are using apart on agar plates.
You could start off by measuring growth and final cell numbers for each of the strains you want to test individually in the growth medium you have chosen. Different growth media, temperatures, and incubation times will all mean that some strain achieve higher densities than others, and this may also reflect on their ability to form biofilms.
The next stage is more difficult, as essentially it would be good to test all pairwise, 3x, 4x ... combinations of the strains together. Although it is still simple to measure total growth, final cell numbers (biomass) and biofilms, it will be impossible to follow a specific strain in the mixture unless it is labelled (e.g., with an antibiotic marker) or has a distinctive colony morphology you can see on a plate.
You could take a different approach and test all of your strains together, and then look to see which strain was the most successful after the end of your incubation. Once again, you need to be able to identify strains apart, and some groups have used NGS / 16S rDNA sequencing to determine the most abundant strain in the mixture.
I get the feeling that you expect that there is a definitive protocol for this sort of work - but there is not. Many groups are working in this field, and you could follow their protocols if they are appropriate for the strains that interest you. But science - and research - is more than following what others do, and there is no reason why some cannot develop their own protocol. The you come to write your work up, you need to be able to defend your decisions, and to discuss your results in the context of other publications who may have used differing techniques.
My philosophy is to give it a try – grow you strains individually and as one mix, and look to see what happens. If the mix produces a good biofilm, think about how you could quantify it and show that it is better / worse than the individual biofilms!
Andrew
thanxx alot I always need yours guidance actually me thinking in paper all where read that in biofilm many strain involve but actually work with individual strain and then assume all present together in any infection.
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