Speaking of Lactobacilli.....
Just a very geeky fyi for those who are microbiologically curious...
A recent paper published in the Journal of Applied Microbiology looked at the various species of Lactobacillus in the bakery environments of 2 artisan bakeries in Belgium (Scheirlinck et al., 2009). They took samples from the flour, the hands of the bakers, the air, and from the bakery equipment and concluded that: (i) each bakery had a dominant mix of Lactobacillus species (L. spicheri and L. plantarum in one bakery; and mostly L. sanfranciscensis in the other) and (ii) the bacteria did, indeed, circulate around the entire bakery environment.
The authors concluded that these specific strains persist in the doughs over years, and that the air is, indeed, an important carrier of the bacteria. Mostly, though, they were just testing out some methods that they wanted to validate. They also point out that bacteria of the genera Enterococcus, Leuconostoc, Pediococcus, and Weissella are also very plentiful in flour.
However, I'll bet that they really did the study to get some free loaves.