1 hour ago, BarneyDorfman said:But I'm wondering why it is that a starter yeast that has a billion yeastie bugs in it, all multiplying like mad are suddenly going to get taken over by "wild" yeast.
I'm certainly not the first person in this thread to say this but It's almost impossible to keep yeast or any sort of culture at the stage of growth where they are "multiplying like mad," particularly in a home kitchen that lacks the sort of mixing apparatus to ensure uniformity throughout the container used to maintain it. For this, you need a means of continuous supply of nutrients and removal of metabolic products and without that, growth of the primary yeast will slow and that will allow either yeast variants that have developed in your culture, wild yeasts or bacteria to grow, any of which can overwhelm the original yeast and "take over." Meticulous adherence to a specific feeding/splitting schedule is necessary to maintain a culture where the primary (in this case, commercial) yeast remains active and dominant.
1 hour ago, BarneyDorfman said:Are wild yeast tougher than commercial yeasts?
Generally speaking, yes. A wild yeast is likely to be at least somewhat adapted to the conditions of the place where it is growing while commercial yeasts are accustomed to a more controlled and ideal environment. If you've managed to supply and, more importantly, maintain that ideal environment then the commercial yeast will remain dominant in your culture but any variation from the ideal is likely to favor development of wild or naturally occurring variants that may have different characteristics from the original commercial culture.
1 hour ago, BarneyDorfman said:I find it hard to believe that a couple of recently paroled illegal wild yeast immigrants are going to kill off billions of patriotic american commericial yeasties and take my starter yeast bowl over.
There is no need for these rogue yeasts to kill off the original yeast. Unless you have a very complex system to supply nutrients and remove waste, some percentage of your "patriotic american yeasties" will be giving up the ghost of their own accord and those dead cells will block their neighbor's access to nutrients and space to grow, creating areas where other organisms may flourish and take over.
1 hour ago, BarneyDorfman said:But, if that happens, I might report it here. Maybe.
I hope you will. Sharing our experiences is the best part of eGullet!
Edited to add: You've already received generous input from some very knowledgable and experienced bakers here. I am not an expert baker in any way but have answered the questions you posed above from a basic microbiology perspective.
