Reassessment of minimal media reveals differences in growth among Porphyromonas gingivalis standard strains.

Porphyromonas gingivalis is one of the etiologic agents of chronic periodontitis. Our previous study showed that the use of minimal media for P. gingivalis allowed to isolate novel inhibitors of P. gingivalis growth. However, growth of P. gingivalis in minimal media was not always reproducible. To explain this phenomenon, we analyzed the growth of seven wild-type ATCC 33277 strains and two wild-type W83 strains in 10 minimal media and three complex media. All nine strains grew in LF (Lactalbumin-Ferric chloride), GC (bovine γ-immunoglobulin G-Calcium chloride), and newly developed mC (milk-Casein) minimal media. Therefore, LF, GC, and mC could be used as minimal media for P. gingivalis. In contrast, other six minimal media containing bovine serum albumin (BSA) supported the growth of several less strains; among these, two media also showed lack of reproducibility in growth among ATCC 33277 strains. On the other hand, four ATCC 33277 strains grew similarly in all 13 media, but two W83 and other three ATCC 33277 strains grew differently in at least one medium. These results suggest that the lack of reproducibility of P. gingivalis growth on minimal media is caused by the presence of BSA, and by differences among the standard strains of P. gingivalis.