Struvite Crystals in Colonies of Bacterionema matruchotii and its Variants

Bacterionema matruchotii acquires intracellular hydroxyapatite after growth in brain heart infusion *(BHI) agar and intracellular whitlockite after growth in Takazoe's synthetic medium when the respective cells are exposed to a metastable calcium phosphate solution (J. ENNEVER, J Periodont 31:302-307, 1960; J. ENNEVER, J. VOGEL, and I. TAKAZOE, Calc Tiss Res 2:296-298, 1968; J. ENNEVER, J. VOGEL, and B. HEACKER, J Dent Res 49:1552, 1970). The present report indicates that both an undissociated and morphologically dissociated strain of this organism form struvite (MgNH4POg6H20) as an extracellular intracolonial crystalline inclusion when grown in BHI agar. The colonial crystallization was demonstrated by inoculating 2 ml of exponential growth phase BHI cultures of B matruchotii, Richardson Strain 13 (F7), the bacillary variant, RF7, and the streptococcal variant, Si (J. L. STRECKFUSS and W. N. SMITH, J Bact 104:1399-1400, 1970) into 50 ml of fresh BHI broth. Samples were removed at zero time and at 2 to 4 hour intervals for 32 hours. A 0.5 ml aliquot of each periodic sample was diluted tenfold in BHI broth, and 0.1 ml of the dilutions was distributed in triplicate on BHI agar with a bent glass rod. The plates were incubated for three to five days at 37 C until colonial growth was apparent. They were then held at room temperature or at 4 C for four to six weeks. Macroscopic intracolonial crystalline inclusions developed in nearly all colonies of F7 and RF7 regardless of growth phase in liquid culture, incubation time, or temperature. No inclusions were found in any of the Si colonies.