Hi,

Bacillus subtilis is a good model for antimicrobial studies for Gram-positive bacteria because it is not a pathogenic strain and you can work in a biosafety level 1 lab. Also, growth media and conditions are well standardized for Bacillus studies. Although, for human pathogenic strains the lab needs to be prepared and get a specific license to work with. Best wishes.

it is super sensitive, so you get good result always :)

Although B. subtilis may be a good gram+ strain to work with for the reasons mentioned by others, it may not be a representative strain for precisely the reason that it is not pathogenic and is primarily an environmental bacteria. However it is easy to work with and is a good place to start your research.

BUT beware that it produces spores so it is not a typical gram positive bacterium for sensitivity testing. The spores are much less susceptible. You would be better using a strain of Staphylococcus epidermidis for this purpose

Since it is a spore former and gram positive bacteria and more importantly a contaminant of hygenic environments where food and medical products is produced , it is frequently taken as one of the models for sterilization testing e.g. radiation.

Bacilli are almost exclusively gram-positive bacteria and I think it all depends on the level of study. B.subtilis is a more studied bacillus that's why.

I think we need to return to the question. The way that it is set, the questioner needs a "safe" organism to use in antimicrobial susceptibility tests. It matters whether these tests are those used for clinical susceptibility, or for a research investigation of a "new" agent. If for use in clinical susceptibility tests, then standard CLSI or EUCAST specify the test bacteria for the agents tested. It is very unusual in such circumstances to use a spore-forming bacterium. As I said above, the spores are many times less susceptible than their vegetative forms, so this would have to be taken into account and standardised.