Effect of gamma-immunoglobulin on the asaccharolytic growth of Porphyromonas gingivalis.

BACKGROUND AND OBJECTIVES

A minimal medium is indispensable for examining the growth properties of the asaccharolytic bacterium, Porphyromonas gingivalis. The purpose of the present study was to improve the widely used KGB medium to support good growth of P. gingivalis.

MATERIAL AND METHODS

Growth of P. gingivalis (W50, W83, and ATCC33277) in a minimal medium was monitored by measuring the optical density of the culture during incubation.

RESULTS

W50, W83, and ATCC33277 grew poorly with bovine serum albumin as the sole carbon and nitrogen source, and alpha-ketoglutarate had little or no effect on this poor growth. In contrast, FeCl3 improved the growth of W83 and ATCC33277; however, the use of a high concentration of FeCl3 elicited black pigmentation of the cells. Bovine gamma-immunoglobulin greatly recovered the growth defect. None of alpha-ketoglutarate, citrate, or trace metal ions, when used to supplement KGB medium, was required for growth. We determined the optimal conditions for growth, and developed a new simple minimal medium for P. gingivalis (GA medium). Growth of ATCC33277 in GA medium was dependent on gingipains; Arg-gingipains and Lys-gingipain contributed comparably to proliferation of the bacterium.

CONCLUSION

These data indicate that GA medium is currently the most reliable minimal medium for examining the growth properties of P. gingivalis.