Can I stabilize RNA in bacteria grown on solid media or substrate using the RNAprotect Bacteria Reagent?
FAQ ID -615

Yes, but you have to make sure that the RNAprotect Bacteria Reagent is diluted in PBS or water prior to use (2 volumes reagent : 1 volume PBS or water) in order to achieve its optimal working concentration. The diluted reagent is directly added to the bacteria growing on the solid substrate, and reagent and bacteria are mixed thoroughly. The reagent is not recommended for stab cultures, since sufficient access of the reagent to all bacteria for immediate RNA stabilization cannot be guaranteed.