Dmitry Yu. Vlasov

Organic Acids Induce Tolerance to Zinc- and Copper-Exposed Fungi Under Various Growth Conditions

Heavy metals, Zn and Cu, in high concentration (2 mM for Zn and 0.5 mM for Cu) have some inhibiting effect on the growth of Aspergillus niger and Penicillium citrinum. Toxic effects of these metals considerably depend on cultivation conditions including nitrogen sources, pH of nutrient media, and its consistency (presence or absence of agar). In general, nitrate media provides less inhibiting effect on fungal growth under heavy metal exposure than ammonium-containing media. Adding of Zn in nitrate media induces oxalic acid production by fungi. Importance of oxalic acid production in detoxification of heavy metals is confirmed by the formation of Zn-containing crystals in fungal cultures. Cu bringing to the cultural media had no stimulating effect on oxalic acid production as well as no copper-containing crystals were observed. But proceeding from essential increase in oxalic acid production during a long-term fungi adaptation to Cu, it may be proposed that oxalic acid plays some functional role in Cu tolerance of fungi as well. It may be concluded that the role of organic acids and oxalate, in particular, in fungi tolerance and adaptation to heavy metals can be determined by the nature of the metal and its ability to form stable complexes with an acid anion. Stimulating effect of metals on acid production is not universal for all species of fungi and largely depends on metal concentration, nitrogen form in a medium, and other cultivation conditions.

Crystallization of calcium oxalate hydrates by interaction of calcite marble with fungus Aspergillus niger

Abstract The crystallization of calcium oxalates (weddellite and whewellite) by interaction of calcite marble with fungus Aspergillus niger, one of the most active stone destructors, was studied under in vitro conditions. The temporal development of acid production of fungus as well as the sequence of formation and morphogenesis of the growing oxalate hydrates crystals were investigated in detail. Furthermore, the relationships between morphology and growth conditions of crystals within the biofilms on the surface of carbonate rocks are discussed.

The Crystallization of Calcium Oxalate Hydrates Formed by Interaction Between Microorganisms and Minerals

The work is devoted to the research of the interactions between microorganisms, rocks and minerals in simulation experiment conditions. Bacteria and microscopic fungi isolated from different types of rocks were studied as agents of biomineralization processes on the mineral surface in moist chamber and in liquid medium. The formation of calcium oxalates under the influence of fungi (Aspergillus and Penicillium) and bacteria (Bacillus) was observed on the surface of different calcium-bearing minerals: carbonates, phosphates, silicates. The obtained results allow to compare the role of microorganism metabolism, peculiarities of the stone substratum and the experimental conditions (the role of the environment) in calcium oxalate crystallization. It was shown that it is a complicated multifactor process. The metabolic activity of microorganisms affects the morphogenesis of the forming oxalates which can be explained by the difference in solubility of stone substrates in various metabolites. The results of simulation experiments showed that the metabolism of the microbial community is an important factor of secondary mineralization on the surface of rocks and minerals. The present results give a scientific basis for creating new methods for cultural heritage stone monument preservation with the use of modern biotechnologies.

Multiple segmentation of the image series

The combined segmentation method of the same objects in a series of images is proposed.<br/>This method is based on the propagation a single image segmentation results for all images in the series.<br/>Images in the series transformed to the base image and segmented using previously obtained masks.

Biogenic—Abiogenic Interactions in Natural and Anthropogenic Systems

Despite a lack of evidence, pointing the ability of appearance of living from nonliving (inert), the problem is set according to this event sequence. The defining influence of the ambient environment on living processes has not been proven because the composition of all external surfaces is defined by the living activity. Based on the observed facts, this chapter presents a thesis about the primacy of biogenic to abiotic processes.

Decay of the Monuments

The processes of stone and bronze destruction of the monuments in the Necropoleis were studied as a result of the monitoring. All forms of stone weathering, (mechanical damages, deposits, stone loss) are examined, their classification is proposed, the frequency of occurrence on various rock types is assessed. Particular attention is paid to biodegradation of the stone under the influence of microorganisms (bacteria, fungi, lichens and algae), formation of gypsum-rich patina on the surface of carbonate rocks and patina on the surface of bronze monuments.

Changes in the Necropoleis Monuments’ Status Over Time

The history and temporary changes in the condition of outstanding artistic monuments in the museum Necropoleis, made of various materials, are surveyed: those to A.I. Kosikovsky (Paolo Catozzi and A.I. Terebenev, sculptors, 1840), E.A. and V.N. Kochubey (A. Costoli, sculptor, 1856), A.Ya. Okhotnikov (F. Thibaut, sculptor, 1800s), M.V. Lomonosov (J. Stalin, author of the design, 1766), V.V. Stasov (I.Ya. Ginzburg, sculptor, I.P. Ropet, architect, 1908), P.V. Kindyakov (Paolo Catozzi, sculptor, 1828), N.M. Karamzin (of unknown authorship, 1820s) and E.A. and E.N. Karamzin (of unknown authorship, 1850s), A.Ya. Potemkina (of unknown authorship, 1830s). The materials of the monuments are described, the results of restoration work and dated materials science analyses are given.

Methods of Monument Protection from Damage and Their Performance

The experience of the Museum of Urban Sculpture in chemical protection of stone monuments from biodeterioration is discussed. The effectiveness of various chemical biocides was compared. High efficiency of the three-stage treatment of monuments using a combination of different compounds in comparison with the known methods is shown. The effectiveness of the used protective compounds was assessed by the speed of the reinstatement of the microbial community over several years after the treatment of the monument. The potential of laser technologies for the restoration of monuments was proven experimentally. It is shown that the effectiveness of laser removal of biofilms from the stone surface is comparable, and in some cases even exceeds that of chemical treatment. In the case of intensive development of mosses and lichens on the surface of monuments, the effectiveness of laser cleaning significantly exceeds that of chemical biocides. Laser cleaning to remove gypsum-rich patina is also effective, but does not always result in the complete removal of gypsum crystals.

Monitoring of the State of Stone and Bronze Monuments

Methods and approaches to be used in monitoring the monument condition are discussed. The main stages of materials science expert analysis are considered. The technique for qualimetric assessment of the integrated condition of the material and various options of mapping the forms of its deterioration are described: those based on the results of visual inspection, ultrasonic sounding, and also using computer technologies, including 3D laser scanning. The potential and efficiency of comprehensive laboratory instrumental methods for studying the material of the monument and the products of its deterioration are analyzed: polarization microscopy, X-ray powder diffraction, scanning electron microscopy, electron microprobe analysis, IR spectroscopy. The design of the database on the state of sculptural monuments in St. Petersburg, for the storage, analysis and structuring of the material gathered during the monitoring, is presented.

Outdoor Environment of the Monuments in the Necropoleis

A study of the ambient air, soil, vegetation, and biogenic layers on the surface of the monuments was carried out in order to identify environmental factors that have an adverse effect on the condition of the monuments in the Museum necropoleis. It was found out that the corrosivity of the air at the Necropoleis corresponds to the medium category C3 and gradually decreases (primarily due to a reduction in the sulfur dioxide content). The soil near the monuments is another source of contamination of their surface, occurring with the participation of various microorganisms. Selective accumulation of miscellaneous elements on the surface of monuments from the environment and low-molecular organic substances depends, above all, on the species composition of the lithobiont community. The presence of woody plants produces microclimate effects in different parts of the Necropoleis, which has a significant impact on the condition of the monuments.