As we learn more about cultivating high bacterial counts by making our Lactobacillus reuteri (ATCC PTA 6475 strain) yogurt, one of the concerns we have discussed (on our weekly Undoctored Virtual Meetups) is whether, after using a prior batch of yogurt to grow the next batch, there is degradation of counts or contamination via other species. Some people have therefore chosen to re-inoculate the yogurt every few batches with several tablets of the BioGaia product.
So I looked at our yogurt under a microscope. The batch I used was about the 7th or 8th batch without re-inoculation. In other words, I used a couple of tablespoons from each batch to seed the next batch, but did not add any “fresh” probiotic tablets. Now, this is only an informal assessment, as I did not formally genetically-type or otherwise characterize the organisms beyond a Gram stain. I just examined morphology after the stain. L. reuteri should be a long Gram-positive bacillus, i.e., a blue-staining stringy creature. And this is what I indeed saw (above, circled in yellow) with little of other forms visible. This suggests that L. reuteri remains the dominant organism present in any significant number. (The bacteria are few in number in the photograph because I used the watery whey fraction for my sample, since the thick solid portion was too thick to easily allow me to see with a microscope.)
Compare this slide I made of kombucha that purportedly contains Bacillus coagulans (GBI-30) (as well as the much larger fungus Saccharomyces boulardii, not shown). There appeared to be more variation in Gram-positive morphologies: short bacilli, long bacilli, even some cocci (round).
I shall continue to occasionally examine the composition of our yogurt as I continue to seed each batch with the prior batch without re-inoculation of probiotic. But it looks to me like we are indeed maintaining a fairly strict monoculture of L. reuteri. This is consistent with the effect I am experiencing, also, with marked loss of appetite, an effect to due the boost in oxytocin levels.