They'll die from starvation and lack of oxygen if you mean storing them in dry places. The media must remain damp. Beneficial bacteria harbor the hard surfaces particularly in filter media.
There are some forms of bacteria that can go dormant under certain conditions... but it does not seem that the "beneficial bacteria" (AOBs & NOBs) that we work with fall under this category...
I have read studies that suggest that they can survive on a very reduced diet, but it would require to remain submerged and fueled with oxygen...