PQQ is a growth factor and chemical attractant for a number of bacteria. Bacteria defined as acidobacteria and methylotrophic bacteria produce PQQ. Acidobacteria are common to soil and methylotrophs are organisms that can use reduced one-carbon compounds, such as methanol or methane, as the carbon source for their growth. Of potential importance to human health, PQQ is also utilized as a cofactor by bacteria that do not normally produce it as a part of their metabolism. A good example is Escherichia coli (E. coli), the gram-negative, rod-shaped bacterium that is commonly found in the intestine. When provided PQQ, E. coli utilizes it as an enzymatic cofactor in enzymes important to glucose and alcohol metabolism. Although it seems likely that PQQ supplements may alter metabolic features of E. coli, whether PQQ influences lactobacillus and other organisms that are utilized as probiotics remains to be examined. Making the link between PQQ and probiotic use nevertheless has potential in describing certain effects of PQQ.
With the above said, however, we would be remiss if did not also note that if PQQ has the potential of influencing probiotics. One has to also ask the question whether there is any impact on organisms, such as helicobacter pylori that has been associated with gastritis and gastric ulcers. Only one study has been done that actually examines gut micro flora in the context of PQQ supplementation and its potential effects (Smidt et al., Does the intestinal microflora synthesize pyrroloquinoline quinone? Biofactors. 1991; 3:53-9). That study indicates that it is difficult to demonstrate PQQ synthesis by the microflora that are present in the gut. Using a mouse as a model, there was also little change in the amounts of organisms that were reported to present in the intestine before versus after PQQ supplementation.
In summary, PQQ supplementation may be complementary to probiotic use, but more work needs to be done. We also encourage you to read reviews that indicates the human body may respond differently to the different species and strains of probiotics (e.g., see Hakansson et al., Gut microbiota and inflammation. Nutrients. 2011; 3:637-82).