Ref ID : 7411
John E. Grover, Alan F. Rope, and Edna S. Kaneshiro; The Occurrence of Biogenic Calcian Struvite, (Mg, Ca)NH4PO4/6H2O, as Intracellular Crystals in Paramecium. J.Eukaryot.Microbiol. 44(4):366-373, 1997
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Intracellular crystals are conspicuous refractile "inclusion bodies" commonly found in many protozoans, but very few have been identified mineralogically. We have isolated crystals from axenically grown mass cultures of Paramecium tetraurelia, and purified them using differential centrifugation. The crystals' structure and chemistry were analyzed using x-ray powder diffraction and energy-dispersive electron microprobe techniques. The morphology was studied by means of scanning electron microscopy. The crystals were identified as the orthorhombic mineral, calcian struvite, (Mg, Ca)NH4PO4/6H2O. Struvite from P. tetraurelia exhibited a variety of crystal habits, including hemimorphic forms, epitactic overgrowths and several types of twins. A linear correlation between computed hydration number and Mg content suggests that the crystal composition may reflect the range of conditions under which struvite nucleation and growth occur. The mineral struvite also occurs in association with guano and other rich organic products, and can be biologically induced to precipitate extracellularly. Extracellular struvite has been well characterized in pathogenic calculi (kidney stones) of humans and cats, where precipitation is enchanced by bacterial urease activity that produces ammonia in the urinary tract. This is the first study demonstrating that struvite is also biologically controlled to form as an intracellular mineral. These crystals may have formed within lipid-rich, membrane-bound vesicles in Paramecium.