Growth Stimulating Effect of Pyrroloquinoline Quinone for Microorganisms

Abstract

Two types of growth stimulating effect of pyrroloquinoline quinone (PQQ) for microorganisms are known. The type I PQQ effect was observed in a symbiotic polyvinyl alcohol (PVA) degradation in which one species of Pseudomonas excretes PQQ which in turn enables the other species to grow on PVA (Shimao et al., 1984). The latter can produce a carbon source for the former only when PQQ is supplied. Thus, PQQ is regarded as the essential growth factor of the PVA-degrading bacteria when grown on PVA but not on other usual carbon sources.

The type II growth stimulation by PQQ is characterized by a marked reduction of the lag phase in the presence of PQQ (Ameyama et al., 1984b). In this case, the subsequent growth rate at the exponential phase and the total cell yield at the stationary phase are not affected at all. Unlike the former type, PQQ is not always an essential growth factor and normal cell growth can be seen even in the absence of exogenous PQQ after a relatively prolonged lag time. This type of PQQ effect was discovered in the course of searching for a growth stimulating substance in yeast extract for acetic acid bacteria. Several lines of analytical evidence from studies with other naturally occurring substances indicated that the substance is quite probable to be PQQ or PQQ-adducts.