Nine strains of cariogenic
Streptococcus mutans
and two strains of
Streptococcus sanguis
were tested for their ability to form hydroxyapatite. The cells were examined by X-ray diffraction and electron microscopy for apatite crystals after growth in a synthetic calcification medium. Each of the test isolates, except for one strain of
S. sanguis
, produced intracellular mineral. Two strains of
S. mutans
formed both intra- and extracellular crystals. There was no apparent relationship between calcifiability and serotype.
Lytic cultures of Bacterionema matruchotii were found to release vesicular membranes into the medium which could be obtained virtually free of other cell structures by differential centrifugation. Suspension of the membrane fraction in a metastable calcium phosphate solution resulted in the formation of both amorphous mineral and hydroxyapatite. Examination by electron microscopy showed that mineralization was associated with the membrane bilayers. The results provide further evidence that calcification of B matruchotii is related to intracytoplasmic membranes.
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