Mineralogical transformation and neoformation in granite caused by the lichens Tephromela atra and Ochrolechia parella

Tephromela atra and Ochrolechia parella are among the most abundant lichens colonizing granitic monuments in the region of Galicia (northwest Spain). In this work, their interaction with a two-mica granite used in the construction of the Toxosoutos Monastery (Noia, Galicia) was studied, using optical microscopy, scanning electron microscopy (with back-scattered-electron and energy-dispersive X-ray detection), X-ray diffractometry and atomic absorption spectroscopy to evaluate their physical, mineralogical and chemical effects. Both lichens contributed to physical weathering by penetrating intermineral voids and mineral cleavage planes, disaggregating the rock and entrapping the loosened mineral grains in their thalli. Significant chemical and mineralogical weathering also occurred, including depletion of potassium from biotite, transformation of this mica into hydroxyaluminium-vermiculite, and neoformation of whewellite and calcite in the lichen thalli. Neoformation of these calcium minerals on a calcium-poor rock such as granite is noteworthy, and this is the first time calcium carbonate has been detected within a lichen colonizing a granitic rock. Precipitation of the calcium carbonate was attributed to the local pH in the thalli having been raised due to release of sodium from nearby plagioclase during weathering.     

Ecological approach to the genesis of calcium oxalate patinas on stone monuments

Summary The genesis of calcium oxalate patinas on stone monuments gives rise to controversial opinions. One of the proposed hypotheses links this phenomenon to the past presence of lichens on the exposed surfaces of monuments. However, the growth of a biological species cannot occur if environmental conditions are not compatible with its autoecology. Analysis of variations of the environmental factors that can act as «limiting factors» shows that in most monuments, the various exposures are not always compatible with biological growth. The environmental factor that seems to be the most limiting is the amount of surface water that is frequently below the range of tolerance of even the most xerophylous species. In the case of Trajan's column in Rome, the distribution of oxalate layers shows an opposite trend with respect to what we would expect for lichen colonization. Presently other kinds of biological colonization cannot be excluded.     

Calcium oxalate films on stone monuments — Microbiological investigations

Summary The origin of calcium oxalate films on stone monuments is investigated and discussed in relation to atmosphere-polluting microorganisms that, under certain conditions, can produce oxalic acid. A list of the fungi microorganisms that are presumably involved in the formation of oxalate films is reported.     

Oxalate patinas on ancient monuments: the biological hypothesis

Summary Whewellite and weddellite, calcium oxalate monohydrate and dihydrate respectively, have been found in the form of thin surface layers on limestone and marble monuments and artifacts of various historical periods at different sites. Experimental results indicate that the formation of both minerals must be attributed essentially to the action of oxalic acid secreted by microorganisms (lichens) which live and proliferate on the stone. Oxalic acid attacks the calcium carbonate of the stone surface giving rise to the precipitation of calcium oxalate.     

Fungal physiology and the formation of calcium oxalate films on stone monuments

Summary Extensive, uniform, yellow-brown films are observed on many monuments. The origin of these films, composed predominantly of calcium oxalate, has been investigated by several authors. Oxalate film formation may be related, in some cases, to the activity of such microorganisms as fungi, which presumably form oxalic acid via the metabolic transformation of organic substances already present on the stone. The present work provides an overview of the physiological factors affecting oxalate synthesis by fungi and of oxalic acid in fungi metabolism.     

Herbivory and Calcium Concentrations Affect Calcium Oxalate Crystal Formation in Leaves ofSida (Malvaceae)

Calcium oxalate crystals have potential roles in plants as partof a defence mechanism against herbivores and/or in accumulatingexcess calcium. To date, these potential roles have been studiedindependently. In this experimental study the effects of calciumlevels and herbivory on the production of calcium oxalate crystals(i.e. druse, spherical crystal aggregates) were examined inseedlings of Sida rhombifolia. Seedlings were subjected to threecalcium levels (low, normal or high) and an artificial herbivorytreatment. Calcium levels and herbivory both affected densityof crystals in leaves. Leaves from seedlings grown in low calciumhad a greater crystal density than those grown in high calcium.Leaves from seedlings subjected to herbivory had a greater crystaldensity than those from seedlings not subjected to herbivory.This study provides additional evidence that calcium oxalatecrystal production depends not only on calcium levels but canalso be influenced by external pressures such as herbivory.In addition to their physiological role in plants, these resultssuggest that calcium oxalate crystals can also act as a defencemechanism against herbivores. Copyright 2001 Annals of BotanyCompany Calcium concentrations, calcium oxalate crystals, herbivory, Malvaceae, Sida rhombifolia     

Sat1 is dispensable for active oxalate secretion in mouse duodenum

Mice deficient for the apical membrane oxalate transporter SLC26A6 develop hyperoxalemia, hyperoxaluria, and calcium oxalate stones due to a defect in intestinal oxalate secretion. However, the nature of the basolateral membrane oxalate transport process that operates in series with SLC26A6 to mediate active oxalate secretion in the intestine remains unknown. Sulfate anion transporter-1 (Sat1 or SLC26A1) is a basolateral membrane anion exchanger that mediates intestinal oxalate transport. Moreover, Sat1-deficient mice also have a phenotype of hyperoxalemia, hyperoxaluria, and calcium oxalate stones. We, therefore, tested the role of Sat1 in mouse duodenum, a tissue with Sat1 expression and SLC26A6-dependent oxalate secretion. Although the active secretory flux of oxalate across mouse duodenum was strongly inhibited (>90%) by addition of the disulfonic stilbene DIDS to the basolateral solution, secretion was unaffected by changes in medium concentrations of sulfate and bicarbonate, key substrates for Sat1-mediated anion exchange. Inhibition of intracellular bicarbonate production by acetazolamide and complete removal of bicarbonate from the buffer also produced no change in oxalate secretion. Finally, active oxalate secretion was not reduced in Sat1-null mice. We conclude that a DIDS-sensitive basolateral transporter is involved in mediating oxalate secretion across mouse duodenum, but Sat1 itself is dispensable for this process.     

Plant calcium oxalate crystal formation, function, and its impact on human health

Crystals of calcium oxalate have been observed among members from most taxonomic groups of photosynthetic organisms ranging from the smallest algae to the largest trees.The biological roles for calcium...     

High Sodium-Induced Oxidative Stress and Poor Anticrystallization Defense Aggravate Calcium Oxalate Crystal Formation in Rat Hyperoxaluric Kidneys

Enhanced sodium excretion is associated with intrarenal oxidative stress. The present study evaluated whether oxidative stress caused by high sodium (HS) may be involved in calcium oxalate crystal formation. Male rats were fed a sodium-depleted diet. Normal-sodium and HS diets were achieved by providing drinking water containing 0.3% and 3% NaCl, respectively. Rats were fed a sodium-depleted diet with 5% hydroxyl-L-proline (HP) for 7 and 42 days to induce hyperoxaluria and/or calcium oxalate deposition. Compared to normal sodium, HS slightly increased calcium excretion despite diuresis; however, the result did not reach statistical significance. HS did not affect the hyperoxaluria, hypocalciuria or supersaturation caused by HP; however, it increased calcium oxalate crystal deposition soon after 7 days of co-treatment. Massive calcium oxalate formation and calcium crystal excretion in HS+HP rats were seen after 42 days of treatment. HP-mediated hypocitraturia was further exacerbated by HS. Moreover, HS aggravated HP-induced renal injury and tubular damage via increased apoptosis and oxidative stress. Increased urinary malondialdehyde excretion, in situ superoxide production, NAD(P)H oxidase and xanthine oxidase expression and activity, and decreased antioxidant enzyme expression or activity in the HS+HP kidney indicated exaggerated oxidative stress. Interestingly, this redox imbalance was associated with reduced renal osteopontin and Tamm-Horsfall protein expression (via increased excretion) and sodium-dependent dicarboxylate cotransporter NaDC-1 upregulation. Collectively, our results demonstrate that a HS diet induces massive crystal formation in the hyperoxaluric kidney; this is not due to increased urinary calcium excretion but is related to oxidative injury and loss of anticrystallization defense.     

The effect of calcium oxalate crystallization kinetics on the kinetics of calcium uptake and calcium ATPase activity of sarcoplasmic reticulum vesicles

The ionophore A23187 is a potent inhibitor of oxalate supported calcium uptake if added before uptake is initiated by ATP and is a much weaker inhibitor of uptake once uptake has been initiated. This observation is shown to be due to a failure of oxalate to capture the transported calcium at the beginning of uptake because the rate of calcium oxalate crystallization is initially slow, thereby allowing the ionophore to release the accumulated calcium. This hypothesis is supported by the observation that calcium oxalate crystallization shows a lag phase which is absent when calcium oxalate seeds are in the reaction system. Once calcium uptake has progressed, calcium oxalate seeds are present in the sarcoplasmic reticulum and calcium oxalate crystallization proceeds sufficiently rapidly that the ionophore cannot compete successfully for calcium. That A23187 and oxalate compete for intravesicular ionic calcium is shown by the stimulation which each produces in ATPase activity and by the dependence of ionophore activity on oxalate concentration.The failure of calcium oxalate crystallization to reach equilibrium during the early phase of calcium uptake caused us to examine whether at any time during calcium uptake, crystallization reaches equilibrium. Skeletal sarcoplasmic reticulum accumulated calcium at such a high rate that oxalate, in concentrations up to 20mM, was unable to clamp intravesicular calcium at equilibrium values. The lower rate of calcium accumulation by cardiac sarcoplasmic reticulum and/or perhaps its greater permeability to oxalate apparently allows intravesicular calcium to be clamped by oxalate.     

Isolated Medicago truncatula mutants with increased calcium oxalate crystal accumulation have decreased ascorbic acid levels.

The mechanisms controlling oxalate biosynthesis and calcium oxalate formation in plants remain largely unknown. As an initial step toward gaining insight into these regulatory mechanisms we initiated a mutant screen to identify plants that over-accumulate crystals of calcium oxalate. Four new mutants were identified, from an ethyl methanesulfonate (EMS)-mutagenized Medicago truncatula (cv. Jemalong genotype A17) population, that over-accumulated calcium oxalate crystals. The increased calcium oxalate content of these new mutants, as with the previously isolated mutant cod4, resulted from an increase in druse crystals accumulated within the mesophyll cells of leaves. Complementation and segregation analysis revealed that each mutant was affected at a different locus. This was confirmed through the genetic mapping of each mutation to different linkage groups. Together, these findings emphasize the complexity of factors that can contribute to oxalate biosynthesis and crystal formation in these plants. In addition, each mutant showed a common decrease in ascorbic acid content providing genetic support for ascorbic acid as a precursor in the oxalate biosynthetic pathway for druse crystal formation. Further support was obtained by the ability of an exogenous supply of ascorbate to induce druse crystal formation while other tested organic acids did not induce crystal production.     

The association of different urinary proteins with calcium oxalate hydromorphs. Evidence for non-specific interactions

It has been proposed that various urinary proteins interact specifically with different calcium oxalate hydromorphs and these interactions have important implications regarding the understanding of the onset and progress of kidney stone disease. Calcium oxalate monohydrate and dihydrate crystals were grown and characterised thoroughly to establish sample purity. These crystals were then incubated in artificial urine samples containing isolated urinary macromolecules. Crystal growth was prevented by saturating the incubation mix with calcium oxalate, and this was confirmed through electron microscopy and calcium measurements of the incubation mix. The surface interactions between the different calcium oxalate hydrates and urinary proteins were investigated by the use of Western blots and immunoassays. The same proteins, notably albumin, Tamm-Horsfall protein, osteopontin and prothrombin fragment 1, associated with both hydrates. There was a trend for more protein to associate with calcium oxalate dihydrate, and greater quantities of different proteins associated with both hydrates when Tamm-Horsfall protein was removed from the incubation mix. There is no evidence from this study to indicate that particular proteins interact with specific calcium oxalate hydrates, which in turn suggests that these protein-mineral interactions are likely to be mediated through non-specific charge interactions.     

Heavy metal stress reduces the deposition of calcium oxalate crystals in leaves of Phaseolus vulgaris

Calcium oxalate (CaOx) crystals in plants may serve as a sink for the absorption of excess calcium, and they could play an important role in heavy metal detoxification. In this study, the effect of heavy metals and different calcium concentrations on the growth of calcium oxalate crystals in leaves of Phaseolus vulgaris was investigated. Different analytical techniques were used to determine the influence of exogenous lead and zinc on CaOx deposition and to detect a presence of these metals in CaOx crystals. We found a positive correlation between the calcium concentration in the nutrient medium and the production of calcium oxalate crystals in leaves of hydroponically grown plants. On the other hand, addition of the heavy metals to the nutrient medium decreased the number of crystals. Energy dispersive X-ray spectrometry did not detect the inclusion of heavy metals inside the CaOx crystals. Our investigation suggests that CaOx crystals do not play a major role in heavy metal detoxification in P. vulgaris but do play an important role in bulk calcium regulation.     

A Fourier Transform-Raman Spectroscopic Study of Lichen Strategies on Granite Monuments

The biodeterioration of granite by Lecidea fuscoatra (L.) Ach., Porpidia cinereoatra (Ach.) Hertel & Knoph, and P. macrocarpa (DC.) Hertel & Schwab growing in the same environmental conditions has been studied by using Fourier transform-Raman spectroscopy. Results were significantly different for the three species, with P. cinereoatra being the most active biodeteriorative lichen. This lichen was also the only one in which calcium oxalate and gypsum were identified spectroscopically. Physical disturbances to the substratum were evidenced in all lichens studied by the incoporation of material, such as quartz and feldspar, into their thalli, but this phenomenon varied considerably from species to species. The results indicate that lichen species can adopt different strategies and can have different biodeteriorative effects on granite, independently of environmental conditions and substrate.     

The weathering action of saxicolous lichens in maritime Antarctica

Summary Xanthoria elegans (Link) Th Fr. and Lecidea lapicida (Ach.) were studied on volcanic andesite, and Rhizocarpon geographicum (L.) DC. and Bacidia stipata Lamb on a volcanigenic sediment, using light microscopy, infrared spectroscopy, X-ray diffraction and transmission electron microscopy. Feldspars were present in the rocklichen interface to a lesser extent than in the underlying rock. R. geographicum was found to alter the minerals in the rock on which it grew without producing any new minerals in the rock/lichen interface, in contrast to the observations for this species on granite in temperate regions. Beneath of the thallus of L. lapicida there was calcium oxalate and some micas of the illite type, which may have been degradation products of various phyllosilicates in the rock. B. stipata, an endemic Antarctic lichen, had the greatest capacity to weather the rock and had weddellite (dihydrate calcium oxalate) and calcite in the contact area as well as many bacteria. The presence of crystalline oxalate, imogolite, allophane, carbonates (calcite) and amorphous material not found in the parent rock indicates biomineralization processes attributable to the lichens.     

Calcium oxalate and calcium phosphate capacities of cardiac sarcoplasmic reticulum

Both oxalate-supported and phosphate-supported calcium uptake by canine cardiac sarcoplasmic reticulum initially increase linearly with time but fall to a steady-state level within 20 min. The departure from linearity could be due to a decrease in influx or to an increase in efflux of calcium. Because Ca2+-ATPase activity is linear, a decrease in the influx of calcium is an unlikely cause of the non-linear calcium uptake curves. A possible cause of an increase in calcium efflux is rupture of the vesicles. This hypothesis was tested by investigating the amount of calcium which could be released upon addition of 5 mM EGTA. The amount of rapidly releasable calcium was zero until a threshold calcium uptake of about 4-6 mumol calcium oxalate or calcium phosphate per mg was reached. After that point the rapidly releasable calcium continued to increase with calcium oxalate to reach more than 23 mumol/mg, but stayed constant at about 0.7 mumol/mg for calcium phosphate. The rapidly releasable calcium was attributed to calcium oxalate or calcium phosphate crystals externalized by vesicle rupture. The differences in the amounts of rapidly releasable calcium were attributed to different kinetics of calcium phosphate and calcium oxalate dissolution. Addition of ryanodine caused a marked increase in the threshold for rapidly releasable calcium oxalate. Transmission electron micrographs showed that vesicles can become filled with calcium oxalate crystals, but the vesicles were heterogeneous with respect to their size and their sensitivity to ryanodine. These observations support the hypothesis that calcium oxalate and calcium phosphate capacities are limited by vesicle rupture and that ryanodine increases the capacity by closing a calcium channel in a subpopulation of vesicles that otherwise would not accumulate calcium.     

Effect of cyclosporin A treatment on renal calcium oxalate binding in experimental hyperoxaluria

This study was aimed to investigate the effect of Cyclosporin A administration on renal calcium oxalate binding under hyperoxaluric condition.Cyclosporin A administration or ammonium oxalate treatment increased calcium oxalate binding, which was further increased in kidney treated with cyclosporin A and ammonium oxalate together. The increase of calcium oxalate binding was associated with lipid peroxidation as well as with a concomitant decrease in total thiol in both rat and human kdiney homogenate.Cyclosporin A administration to hyperoxaluric rats resulted with increased calcium oxalate binding protein. However there was no change with specific activity of the protein.In conclusion, Cyclosporin A administration either to normal or hyperoxaluric rats is resulted with increased concentration of calcium oxalate binding protein as well as enhanced activity due to membrane lipid peroxidation.     

Production of Calcium Oxalate Crystals by the Basidiomycete Moniliophthora perniciosa, the Causal Agent of Witches’ Broom Disease of Cacao

Oxalic acid has been shown as a virulence factor for some phytopathogenic fungi, removing calcium from pectin and favoring plant cell wall degradation. Recently, it was published that calcium oxalate accumulates in infected cacao tissues during the progression of Witches’ Broom disease (WBD). In the present work we report that the hemibiotrophic basidiomycete Moniliophthora perniciosa, the causal agent of WBD, produces calcium oxalate crystals. These crystals were initially observed by polarized light microscopy of hyphae growing on a glass slide, apparently being secreted from the cells. The analysis was refined by Scanning electron microscopy and the compositon of the crystals was confirmed by energy-dispersive x-ray spectrometry. The production of oxalate by M. perniciosa was reinforced by the identification of a putative gene coding for oxaloacetate acetylhydrolase, which catalyzes the hydrolysis of oxaloacetate to oxalate and acetate. This gene was shown to be expressed in the biotrophic-like mycelia, which in planta occupy the intercellular middle-lamella space, a region filled with pectin. Taken together, our results suggest that oxalate production by M. perniciosa may play a role in the WBD pathogenesis mechanism.