Hi, I've been conducting an experiment regarding the antimicrobial activity of my soil bacteria against MDR strains using well diffusion method. I'm performing the experiment using bacterial broth as well as its filtered supernatant in parallel. I've noticed that my strains show inhibition zone only when direct broth is employed and no zone is observed in case of filtered supernatant. What could be the possible reason behind this?
Sounds like whatever compound/s in the bacterial broth is binding to the filter when you try to filter the bacterial broth. Not sure what you are filtering out, but try different types of filters.
Perhaps your soil bacteria killing is mediated via type VI secretion system.
The elimination of your bacteria of interest by filtration removes the direct contact thus not permitting the killing.
You can demonstrate that by using a transwell system with sufficient size pores to keep two bacteria separated.
The possible reason behind this is that the filtered supernatant contains no cells of the bacteria, which are needed to inhibit the growth of the MDR strains. The direct bacterial broth contains the actual bacterial cells which are responsible for producing the antimicrobial activity against MDR strains. The filtered supernatant contains molecules released by the bacteria, but these molecules may not be sufficient to inhibit the growth of the MDR strains.
Matthew W Frank Povilas Kavaliauskas Amayuru Sahan I've tried different methods, used the broth form/supernatant after centrifugation and filtered supernatant via well diffusion method/ disc diffusion method/ seed overlay method and cross streak method. The results vary and I get the best inhibition results only when direct broth is used. But the main problem here is that the colony grows in the centre of the inhibition zone around the well, and those pictures can't be reported while submitting the paper to a journal.
The filtered supernatant contains have no enough cells of the bacteria or bacterial product.
The filtered supernatant contains have no enough cells of the bacteria or bacterial product.
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