Wr. Moorer et al., CALCIFICATION OF A CARIOGENIC STREPTOCOCCUS AND OF CORYNEBACTERIUM (BACTERIONEMA) MATRUCHOTII, Journal of dental research, 72(6), 1993, pp. 1021-1026
The main aim of this investigation was to challenge the idea that cari
ogenic streptococci do not calcify. Calcium uptake or calcification of
Streptococcus mutans C180-2, proven to be an acidogenic and cariogeni
c strain, was compared with calcium uptake and calcification of Coryne
bacterium (Bacterionema) matruchotii, known as a ready calcifier. Bact
eria were grown on Brain Heart Infusion Agar (BHIA) and on well-buffer
ed semi-synthetic E-agar, both containing 1.4 mmol/L calcium, 2 g/L gl
ucose, initial pH 7.4. Calcium uptake from BHIA by C. matruchotii (25
mmol Ca/kg wet bacterial cell mass), but not by S. mutans, was found.
Grown as a plaque-like lawn on E-agar, the S. mutans cell mass concent
rated calcium to 63 +/- 11 mmol/kg compared with 145 +/- 61 mmol/kg in
C. matruchotii. X-ray diffraction confirmed the presence of crystalli
ne apatite in the bacterial cell masses. Electron microscopy revealed
crystals and mineralized deposits in both organisms. Heavy calcificati
ons in some cells of S. mutans were seen. Calcification was partly inh
ibited by magnesium ion and by methanehydroxybisphosphonate. S. sobrin
us 6715, as well as freshly isolated S. mutans and S. sobrinus from pa
tients, concentrated very large quantities of calcium, up to 500-fold
from the medium, when maintained for several weeks on E-agar of initia
l pH 7.6. Our observations widen the view on acidogenic bacteria as mi
neralization agents and support the notion that members of the mutans
group of streptococci may be involved in events that trigger heavy int
racellular calcifications and, possibly, dental calculus formation.