Preexposure of hydroxyapatite (HA) to polyphosphate reduced the near-equilibrium acid solubility of HA, the mineralization of HA, and the exchange of PO4 between medium and HA. Appreciably longer exposure times were required for maximal effects of trimetaphosphate (TMP) than of pyrophosphate (PP), tripolyphosphate (TPP), and hexametaphosphate (HMP). Calcifying solution solubilized small amounts of the HA-bound polyphosphates. This occurred to the smallest extent in the case of TMP, a fact which could have relevance for the superior anticaries effect of TMP.

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SUMMARY: Among a large number of strains of aerobic sporing bacilli only Bacillus cereus, B. mycoides and, to a lesser extent, B. anthracis were able to produce turbidity and formation of a curd in saline extract of egg-yolk. None of the other species tested, namely, B. alvei, B. alcalophilus, B. brevis, B. carotarum, B. Circulans, B. coagulans, B. fusifomnis, B. licheniformis, B. macerans, B. megatherium, B. pumilus, B. polgmgxa, B. orpheecs, B. repens and B. subtilis caused any opalescence in the yolk medium. The yolk reaction was due to the action of phospholipinase produced by the organisms. As in the case of Cl. we&hii a-toxin, the yolk curd-forming activity of B. cereus and B. mycoides also was associated with haemolytic activity. The substances responsible for these activities appear to be sirhilar, and may be identical. The yolk reaction has proved useful for the rapid identification of B. cereus, as it is more specific than any of the other distinguishing tests hitherto employed. The three positive organisms, B. cereus, B. mycoides and B. anthracis, have been considered by previous workers on the grounds of morphology and antigenic structure to be closely related. Nagler (1989) described the effect of CZ. welchii cultures and toxic filtrates on human serum in producing an opalescence and curding (Nagler reaction) ; later Macfarlane, Oakley & Anderson (1941) found that egg-yolk saline (a lecithovitellin emulsion) is even more sensitive than human serum (the lecithovitellin (L.v.) reaction). Macfarlane & Knight (1941) then showed that the production of oialescence in egg-yolk emulsion was due to the action of a lecithinase, which split phosphocholine from lecithin, in the CZ. welchii toxic filtrates which was probably identical with the a-toxin. Since then, the Nagler reaction and the lecitho-vitellin (L.v.) reaction have been extensively used for the titration of a-toxin of CZ. welchii (Nagler, 1939; van Heyningen, 1941 a) and for the rapid identification of certain clostridia (Hayward, 1941(Hayward, , 1948.It is interesting that Nagler (1989) observed a non-pathogenic aerobic sporebearing bacillus which caused an opalescence in human serum like that caused by CZ. welchii; but the effect was not inhibited by CZ. welchii antitoxin. Crook (1942) and Hayward (1943) also mentioned that some aerobic bacteria caused similar opalescence. In the light of these observations we have sought for similar enzymes in the aerobic spore-bearing bacilli. The work started with a survey of the Bacillus group to ascertain which of them produced an eggyolk reaction. A test of 260 identified strains, comprising 24 species, showed that only B. cereus, B. mycoides and some strains of B. anthracis were positive.In comparison with other characteristics generally used for the differentiation of the BaeilZzcs group, the yolk reaction seems to be much more selective. One can hardly find any other characteristics which are confined to only two or three species of this very large group of organisms, and the test deserves the ...

The polyphosphates pyro-, tripoly-, trimeta- and hexametaphosphate were bound to hydroxyapatite (HA) in much larger amounts in an H₂O-labile (removed by H₂O washing) than in an H₂O-stable (crystal) compartment. Approximately 1 PO⁴ group was liberated per polyphosphate molecule bound in both compartments. Incubation of HA containing polyphosphates in the crystal compartment gave rise to the liberation of PO₄, most of which came from HA-catalyzed polyphosphate hydrolysis, but some of which came from solubilization of HA and possibly from displacement of crystal PO₄ via exchange. Crystal-bound phosphonates (ethanehydroxy-11-diphosphonate and methane diphosphonate) neither hydrolyzed nor exchanged further with crystal PO₄. The relative amounts of binding and hydrolysis of the test substances as well as their relative effects in solubilizing HA in H₂O, reducing HA acid solubility and inhibiting mineralization and microcrystal aggregation were determined. The results are discussed with respect to known or implied anticaries activity.

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