The Occurrence of Biogenic Calcian Struvite, (Mg, Ca)NH₄PO₄.6H₂O, as Intracellular Crystals inParamecium

Abstract

ABSTRACT. 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 enhanced 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.

Hazenite, KNaMg2(PO4)2{middle dot}14H2O, a new biologically related phosphate mineral, from Mono Lake, California, U.S.A.

“…It is well known now that struvite can form inside living bacteria, as a diagenetic byproduct of bird feces, in kidney stones, or in association with decaying organisms or decomposing organic matter (such as in old graveyards, under floors of stables, in guano, or wastewater treatments). One common feature shared by these environments is high alkalinity, suggesting that high pH conditions are necessary for the formation of struvite and/or similar phosphate minerals (Rivadeneyra et al 1993;Grover et al 1997;Doyle and Parsons 2002;Chen et al 2010). Because of the very hypersalinity and high alkalinity of the Mono Lake water, hazenite is also believed to form in high-pH conditions with the strong involvement of cyanobacterial activities.…”

Molecular aspects of calcium signalling at the crossroads of unikont and bikont eukaryote evolution – The ciliated protozoan Paramecium in focus

“…According to X-ray diffraction analysis the membrane-bounded crystals contain Ca 2+ as (Mg,Ca)NH 4 PO 4 .6H 2 O, struvite, one of the minerals also contained in kidney stones [109]. Their number increases with cell age and they may, therefore, serve as a waste basket, but their role in Ca 2+ regulation is unexplored.…”

Homogeneous Precipitation of Calcium Carbonates by Enzyme Catalyzed Reaction

“…Furthermore, the role of this enzyme, generated by bacteria, in the formation of intracellular crystals of apatite, brushite, and struvite has been documented. These phosphate-containing minerals are involved in stone formation, caused by the urinary tract infections by such bacteria (19)(20)(21)(22). Since the decomposition of urea also causes an increases in the pH, the addition of urease was used to produce metal hydroxide particles, such as aluminum hydroxides (23,24) and aluminum basic sulfate (25).…”