Carbonate and Oxalate Crystallization by Interaction of Calcite Marble with Bacillus subtilis and Bacillus subtilis–Aspergillus niger Association

Ammonium N-(pyridin-2-ylmethyl)oxamate (AmPicOxam): A Novel Precursor of Calcium Oxalate Coating for Carbonate Stone Substrates

Ammonium N-(pyridin-2-ylmethyl)oxamate (AmPicOxam), synthesized from O-methyl-N-(pyridin-2-ylmethyl)oxamate, was spectroscopically and structurally characterized and assayed as a novel precursor for the protection and consolidation of carbonate stone substrates. An in-depth characterization of treated and untreated biomicritic limestone and white Carrara marble samples was carried out by means of SEM microscopy, X-ray powder diffraction, helium pycnometry, determination of water transport properties, and pull-off tests. The improved solubility (1.00 M, 16.5% w/w) of the title compound with respect to ammonium oxalate (0.4 M, 5% w/w) results in the formation of a thicker protective coating of calcium oxalate (CaOx) dihydrate (weddellite) on marble and biomicrite samples after the treatment with 5% and 12% w/w water solutions, producing a reduction in the stone porosity and increased cohesion. Theoretical calculations were carried out at the DFT level to investigate both the electronic structure of the N-(pyridin-2-ylmethyl)oxamate anion and the hydrolysis reaction leading from AmPicOxam to CaOx.

Metabolite Profile of the Micromycete Lecanicillium gracile Isolated from Plaster and Limestone

Lecanicillium gracile is a recently described micromycete species isolated from mineral-based building materials (plaster and limestone) in interiors of cultural heritage sites in Russia. In this work, the composition of L. gracile metabolites, as well as of the culture liquid, have been characterized. The results suggest that L. gracile is a promising candidate for the search for novel biologically active compounds. During the exponential growth phase, the diversity of metabolites in the mycelium was low; the metabolome profile demonstrated predominant accumulation of monosaccharides and polyols. In the stationary phase, the metabolite diversity in the L. gracile mycelium was high; apparently, at this stage biosynthesis dominated over energy-producing processes. L. gracile synthesized extracellular polymer compounds and shifted medium рН to the alkaline range. When fungi are developing on rock substrates, their extracellular polymer matrix not only serves to facilitate the formation of biofilms with other microorganisms of lithobiont communities, but also, at alkaline pH values, it promotes the formation of secondary calcite on calcium-containing substrates, such as limestone and marble. That is, L. gracile possesses certain biochemical traits that facilitate its long-term growth on rock substrates and reflect the specific character of interactions between the fungus and the substrate materials.

Experience of Using Antifungal Rocima GT for Protection of Paper from Biological Damage Caused by Fungi

This study proposes a method for the chamber disinfection of paper with biocide in the form of fine, volatile droplets using antifungal Rocima GT. This method provides a fungicidal effect, and within a short exposure time, a fungistatic one. At a concentration of 5% Rocima GT solution, the minimum treatment time to ensure the complete disinfection of paper was 15 min. The proposed method of disinfection by a chemical mist was less harmful to paper than disinfection using a swab saturated in a biocide solution. It was noted that when using Rocima GT at insufficient concentrations to inhibit fungal growth completely, Rocima GT can induce, as well as suppress, organic acid produced by Aspergillus niger depending on the concentration.

Microorganisms in Superficial Deposits on the Stone Monuments in Saint Petersburg

The composition of superficial deposits in urban environment and their importance in the development of the lithobiotic community of microorganisms has been investigated. Polyols, organic acids, mono- and disaccharides, as well as some amino acids, are the predominant low molecular weight organic components in superficial deposits, although the conditions on the stone surface are undoubtedly oligotrophic. Superficial deposits accumulate heavy metals, including Fe, Mn, Zn, Cu, Pb, and Cd, in surface sediments, among which the potentially toxic elements Zn, Cu, and Pb are accumulated in rather high concentrations. On model of Aspergillus niger as an example, it was shown micromycetes are resistant to heavy metals and retain their physiological activity when grown on this substrate. According to cultural studies, as well as metagenomic analysis, stress-resistant fungi and dark organotrophic bacteria are the main inhabitants of surface sediments. Probably, in the conditions of accumulation of superficial deposits on the stone, these organisms are the main inhabitants of the surface of the stone. With the development of more multi-species lithobiotic communities, they form the core of these communities. In the urban environment this type of primary colonization of the stone is likely realized.

Biofilm Medium Chemistry and Calcium Oxalate Morphogenesis

The present study is focused on the effect of biofilm medium chemistry on oxalate crystallization and contributes to the study of the patterns of microbial biomineralization and the development of nature-like technologies, using the metabolism of microscopic fungi. Calcium oxalates (weddellite and whewellite in different ratios) were synthesized by chemical precipitation in a weakly acidic environment (pH = 4-6), as is typical for the stationary phase of micromycetes growth, with a ratio of Ca2+/C2O42- = 4.0-5.5, at room temperature. Additives, which are common for biofilms on the surface of stone in an urban environment (citric, malic, succinic and fumaric acids; and K+, Mg2+, Fe3+, Sr2+, SO42+, PO43+ and CO32+ ions), were added to the solutions. The resulting precipitates were studied via X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS). It was revealed that organic acids, excreted by micromicetes, and some environmental ions, as well as their combinations, significantly affect the weddellite/whewellite ratio and the morphology of their phases (including the appearance of tetragonal prism faces of weddellite). The strongest unique effect leading to intensive crystallization of weddellite was only caused by the presence of citric acid additive in the medium. Minor changes in the composition of the additive components can lead to significant changes in the weddellite/whewellite ratio. The effect of the combination of additives on this ratio does not obey the law of additivity. The content of weddellite in the systems containing a representative set of both organic acids and environmental ions is ~20 wt%, which is in good agreement with natural systems.

Ammonium monoethyloxalate (AmEtOx): a new agent for the conservation of carbonate stone substrates

Ammonium monoethyloxalate (AmEtOx) is proposed as a consolidanting agent for carbonate stones such as biomicritic limestone and marble, resulting in the formation of a microcrystalline passivating phase of calcium oxalate (whewellite and weddellite).

Accumulation of Elements in Biodeposits on the Stone Surface in Urban Environment. Case Studies from Saint Petersburg, Russia

The pattern of elements accumulation in biodeposits formed by living organisms and extracellular products of their metabolism (biofouling, primary soils) on different bedrocks (of the monuments of Historical necropoleis in Saint Petersburg) were studied by a complex of biological and mineralogical methods (optical microscopy, SEM, EDX, XRD, ICP MS, XRFS). The content of 46 elements in biodeposits with various communities of microorganisms is determined. The model recreating the picture of the input and selective accumulation of elements in biodeposits on the stone surface in outdoor conditions is assumed. It is shown that the main contribution to the elemental composition of biodeposits is made by the environment and the composition of the microbial community. The contribution of leaching under the action of microbial metabolites of mineral grains, entering biodeposits from the environment, is significantly greater than that of the underlying rock.