Fungal biodeterioration and preservation of cultural heritage, artwork, and historical artifacts: extremophily and adaptation.

SUMMARYFungi are ubiquitous and important biosphere inhabitants, and their abilities to decompose, degrade, and otherwise transform a massive range of organic and inorganic substances, including plant organic matter, rocks, and minerals, underpin their major significance as biodeteriogens in the built environment and of cultural heritage. Fungi are often the most obvious agents of cultural heritage biodeterioration with effects ranging from discoloration, staining, and biofouling to destruction of building components, historical artifacts, and artwork. Sporulation, morphological adaptations, and the explorative penetrative lifestyle of filamentous fungi enable efficient dispersal and colonization of solid substrates, while many species are able to withstand environmental stress factors such as desiccation, ultra-violet radiation, salinity, and potentially toxic organic and inorganic substances. Many can grow under nutrient-limited conditions, and many produce resistant cell forms that can survive through long periods of adverse conditions. The fungal lifestyle and chemoorganotrophic metabolism therefore enable adaptation and success in the frequently encountered extremophilic conditions that are associated with indoor and outdoor cultural heritage. Apart from free-living fungi, lichens are a fungal growth form and ubiquitous pioneer colonizers and biodeteriogens of outdoor materials, especially stone- and mineral-based building components. This article surveys the roles and significance of fungi in the biodeterioration of cultural heritage, with reference to the mechanisms involved and in relation to the range of substances encountered, as well as the methods by which fungal biodeterioration can be assessed and combated, and how certain fungal processes may be utilized in bioprotection.

A novel fluorescent sensor for diammonium and metal ions based on a supramolecular charge-transfer complex of bis(aza-18-crown-6)-containing dienone.

A bis(aza-18-crown-6)-containing 2,5-di(benzylidene)cyclopentanone and a bis(ammoniopropyl) derivative of 1,2-di(4-pyridyl)ethylene in MeCN were found to form a supramolecular charge-transfer complex, which can act as an "off-on" fluorescent sensor for the Ca2+ and 1,12-dodecanediammonium ions. The molecular structure of this complex in solution was studied by density functional theory calculations.

Antibacterial activity of CuO-Ag Janus like nanoparticles against recombinant strain Escherichia coli.

The toxic action of CuO-Ag Janus particles and a bicomponent mixture of CuO and Ag particles have been studied against a recombinant strain Escherichia coli K12 TG1 with cloned luxCDABE genes of marine bacteria Photobacterium leiognathi 54D10. An original method was used for the preparation CuO-Ag Janus like  nanoparticles by simultaneous electrical explosion of twisted Cu and Ag wires in a mixture of argon and oxygen gases. The bioluminescence inhibition on recombinant strain E. coli shows that CuO-Ag Janus NPs were effective. The concentration by 50% (EC50) for CuO-Ag Janus NPs was 0.03 ± 0.001 mg/ml (p < 0.05). The bioactivity of the bicomponent mixture of CuO and Ag NPs (EC50) was 0.25 ± 0.002 mg/ml (p < 0.05). The effective concentration of CuO-Ag Janus NPs against E. coli was comparatively lower than those of bicomponent mixture CuO and Ag against which explains the higher activity of CuO-Ag Janus NPs. The toxicity values of CuO and Ag as monocomponent nanoparticles were 2-32 times lower compared with the bicomponent nanoparticles. A dose-dependent inhibition of bacterial luminescence developed over time was noted. The result of contact E. coli with CuO-Ag Janus particles was 100% suppression of bacterial luminescence from the first minutes of contact occured starting with a content of 2.0 mg/ml and within the next 180 min. The effect of bioactivity prolonged in the final concentration of nanopowder (EC100 = 0.0625 ± 0.002 mg/ml) (p < 0.05). CuO-Ag Janus particles exhibited more pronounced antibacterial activity compared to CuO, Ag nanoparticles and their mechanical mixture.

Synthesis, Structure and Photochemistry of Dibenzylidenecyclobutanones.

A series of symmetrical dibenzylidene derivatives of cyclobutanone were synthesized with the goal of studying the physicochemical properties of cross-conjugated dienones (ketocyanine dyes). The structures of the products were established and studied by X-ray diffraction and by NMR and electronic spectroscopy. All the products had E,E-geometry. The oxidation and reduction potentials of the dienones were determined by cyclic voltammetry. The potentials were shown to depend on the nature, position, and number of substituents in the benzene rings. A linear correlation was found between the difference of the electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum. This correlation can be employed to analyze the properties of other compounds of this type. Quantum chemistry was used to explain the observed regularities in the electrochemistry, absorption, and fluorescence of the dyes. The results are in good agreement with the experimental redox potentials and spectroscopy data.

Structure-Property Relationships of Dibenzylidenecyclohexanones.

A series of symmetrical dibenzylidene derivatives of cyclohexanone were synthesized with the goal of studying the physicochemical properties of cross-conjugated dienones (ketocyanine dyes). The structures of the products were established and studied by X-ray diffraction, NMR spectroscopy, and electronic spectroscopy. All products had the E,E-geometry. The oxidation and reduction potentials of the dienones were determined by cyclic voltammetry. The potentials were shown to depend on the nature, position, and number of substituents in the benzene rings. A linear correlation was found between the difference of the electrochemical oxidation and reduction potentials and the energy of the long-wavelength absorption maximum. This correlation can be employed to analyze the properties of other compounds of this type. The frontier orbital energies and the vertical absorption and emission transitions were calculated using quantum chemistry. The results are in good agreement with experimental redox potentials and spectroscopic data.

Effect of depleted uranium on a soil microcosm fungal community and influence of a plant-ectomycorrhizal association.

Fungi are one of the most biogeochemically active components of the soil microbiome, becoming particularly important in metal polluted terrestrial environments. There is scant information on the mycobiota of uranium (U) polluted sites and the effect of metallic depleted uranium (DU) stress on fungal communities in soil has not been reported. The present study aimed to establish the effect of DU contamination on a fungal community in soil using a culture-independent approach, fungal ribosomal intergenic spacer analysis (F-RISA). Experimental soil microcosms also included variants with plants (Pinus silvestris) and P. silvestris/Rhizopogon rubescens ectomycorrhizal associations. Soil contamination with DU resulted in the appearance of RISA bands of the ITS fragments of fungal metagenomic DNA that were characteristic of the genus Mortierella (Mortierellomycotina: Mucoromycota) in pine-free microcosms and for ectomycorrhizal fungi of the genus Scleroderma (Basidiomycota) in microcosms with mycorrhizal pines. The precise taxonomic affinity of the ITS fragments from the band appearing for non-mycorrhizal pines combined with DU remained uncertain, the most likely being related to the subphylum Zoopagomycotina. Thus, soil contamination by thermodynamically unstable metallic depleted uranium can cause a significant change in a soil fungal community under experimental conditions. These changes were also strongly affected by the presence of pine seedlings and their mycorrhizal status which impacted on DU biocorrosion and the release of bioavailable uranium species.

Correction to: a new Rhodococcus aetherivorans strain isolated from lubricant-contaminated soil as a prospective phenol-biodegrading agent.

The published online version contains mistake in Table 3.

A new Rhodococcus aetherivorans strain isolated from lubricant-contaminated soil as a prospective phenol-biodegrading agent.

Microbe-based decontamination of phenol-polluted environments has significant advantages over physical and chemical approaches by being relatively cheaper and ensuring complete phenol degradation. There is a need to search for commercially prospective bacterial strains that are resistant to phenol and other co-pollutants, e.g. oil hydrocarbons, in contaminated environments, and able to carry out efficient phenol biodegradation at a variable range of concentrations. This research characterizes the phenol-biodegrading ability of a new actinobacteria strain isolated from a lubricant-contaminated soil environment. Phenotypic and phylogenetic analyses showed that the novel strain UCM Ac-603 belonged to the species Rhodococcus aetherivorans, and phenol degrading ability was quantitatively characterized for the first time. R. aetherivorans UCM Ac-603 tolerated and assimilated phenol (100% of supplied concentration) and various hydrocarbons (56.2-94.4%) as sole carbon sources. Additional nutrient supplementation was not required for degradation and this organism could grow at a phenol concentration of 500 mg L-1 without inhibition. Complete phenol assimilation occurred after 4 days at an initial concentration of 1750 mg L-1 for freely-suspended cells and at 2000 mg L-1 for vermiculite-immobilized cells: 99.9% assimilation of phenol was possible from a total concentration of 3000 mg L-1 supplied at daily fractional phenol additions of 750 mg L-1 over 4 days. In terms of phenol degradation rates, R. aetherivorans UCM Ac-602 showed efficient phenol degradation over a wide range of initial concentrations with the rates (e.g. 35.7 mg L-1 h-1 at 500 mg L-1 phenol, and 18.2 mg L-1 h-1 at 1750 mg L-1 phenol) significantly exceeding (1.2-5 times) reported data for almost all other phenol-assimilating bacteria. Such efficient phenol degradation ability compared to currently known strains and other beneficial characteristics of R. aetherivorans UCM Ac-602 suggest it is a promising candidate for bioremediation of phenol-contaminated environments.

Surface morphology data of tantalum coatings obtained by electrospark alloying.

The article presents the data of scanning electron microscopy of the surface morphology of tantalum coatings produced by electrospark alloying. To perform the statistical analysis of open porosity and morphological parameters of the coatings, raw digital images of the structure were studied. In this case, "AGPM" software for the analysis of geometric parameters of microobjects was used. When processing digital images of the surface morphology, open porosity, total quantity, average size and dispersion of the structural elements (particles and pores) were determined, and typical distribution patterns of structural elements were obtained from linear dimensions.

Biogeochemical spatio-temporal transformation of copper in Aspergillus niger colonies grown on malachite with different inorganic nitrogen sources.

This work elucidates spatio-temporal aspects of the biogeochemical transformation of copper mobilized from malachite (Cu2 (CO3 )(OH)2 ) and bioaccumulated within Aspergillus niger colonies when grown on different inorganic nitrogen sources. It was shown that the use of either ammonium or nitrate determined how copper was distributed within the colony and its microenvironment and the copper oxidation state and succession of copper coordinating ligands within the biomass. Nitrate-grown colonies yielded ∼1.7× more biomass, bioaccumulated ∼7× less copper, excreted ∼1.9× more oxalate and produced ∼1.75× less water-soluble copper in the medium in contrast to ammonium-grown colonies. Microfocus X-ray absorption spectroscopy revealed that as the mycelium matured, bioaccumulated copper was transformed from less stable and more toxic Cu(I) into less toxic Cu(II) which was coordinated predominantly by phosphate/malate ligands. With time, a shift to oxalate coordination of bioaccumulated copper occurred in the central older region of ammonium-grown colonies.

Biosorption: current perspectives on concept, definition and application.

Biosorption is a physico-chemical and metabolically-independent process based on a variety of mechanisms including absorption, adsorption, ion exchange, surface complexation and precipitation. Biosorption processes are highly important in the environment and conventional biotreatment processes. As a branch of biotechnology, biosorption has been aimed at the removal or recovery of organic and inorganic substances from solution by biological material which can include living or dead microorganisms and their components, seaweeds, plant materials, industrial and agricultural wastes and natural residues. For decades biosorption has been heralded as a promising cost-effective clean-up biotechnology. Despite significant progress in our understanding of this complex phenomenon and a dramatic increase in publications in this research area, commercialization of biosorption technologies has been limited so far. This article summarizes existing knowledge on various aspects of the fundamentals and applications of biosorption and critically reviews the obstacles to commercial success and future perspectives.

X-ray absorption spectroscopy (XAS) of toxic metal mineral transformations by fungi.

Fungi can be highly efficient biogeochemical agents and accumulators of soluble and particulate forms of metals. This work aims to understand some of the physico-chemical mechanisms involved in toxic metal transformations focusing on the speciation of metals accumulated by fungi and mycorrhizal associations. The amorphous state or poor crystallinity of metal complexes within biomass and relatively low metal concentrations make the determination of metal speciation in biological systems a challenging problem but this can be overcome by using synchrotron-based element-specific X-ray absorption spectroscopy (XAS) techniques. In this research, we have exposed fungi and ectomycorrhizas to a variety of copper-, zinc- and lead-containing minerals. X-ray absorption spectroscopy studies revealed that oxygen ligands (phosphate, carboxylate) played a major role in toxic metal coordination within the fungal and ectomycorrhizal biomass during the accumulation of mobilized toxic metals. Coordination of toxic metals within biomass depended on the fungal species, initial mineral composition, the nitrogen source, and the physiological state/age of the fungal mycelium.

Zinc phosphate transformations by the Paxillus involutus/pine ectomycorrhizal association.

In this research, we investigate zinc phosphate transformations by Paxillus involutus/pine ectomycorrhizas using zinc-resistant and zinc-sensitive strains of the ectomycorrhizal fungus under high- and low-phosphorus conditions to further understand fungal roles in the transformation of toxic metal minerals in the mycorrhizosphere. Mesocosm experiments with ectomycorrhizas were performed under sterile conditions with zinc phosphate localized in cellophane bags: zinc and phosphorus mobilization and uptake by the ectomycorrhizal biomass were analyzed. In the presence of a phosphorus source, an ectomycorrhizal association with a zinc-resistant strain accumulated the least zinc compared to a zinc-sensitive ectomycorrhizal association and non-mycorrhizal plants. Under low-phosphorus conditions, mycorrhizal seedlings infected with the zinc-resistant strain increased the dissolution of zinc phosphate and zinc accumulation by the plant. Extended X-ray absorption fine structure analysis of both mycorrhizal and nonmycorrhizal roots showed octahedral coordination of zinc by oxygen-containing ligands such as carboxylates or phosphate. We conclude that zinc phosphate solubilization and zinc and phosphorus uptake by the association depend on ectomycorrhizal infection, strain of the mycobiont, and the phosphorus status of the matrix.

Nutritional influence on the ability of fungal mycelia to penetrate toxic metal-containing domains.

Metal-contaminated soils often contain a spatially heterogeneous distribution of metal concentrations, and the ability of fungi to colonize such metal-contaminated domains will be influenced by the nutritional resources available. An experimental system based upon tessellated agar tiles was used to study the influence of nutrients upon the ability of soil fungi Trichoderma virens and Clonostachys rosea to colonize spatially discrete toxic metal (copper and cadmium) containing domains. The growth parameters recorded demonstrated a decrease in apparent metal toxicity with increasing concentration of available carbon source. It was shown that maximum hyphal extension rates and the efficacy of carbon substrate utilization of both species decreased with increasing concentration of toxic metals. It was also observed that in the gap between metal-free and metal-containing tiles, the presence of toxic metals led to negative chemotropic reactions and cessation of growth, swelling and lysis of some hyphal tips. Penetration of the hyphae into the metal-containing domain was often followed by the formation of very dense mycelia or mycelial 'bushes' representing an associative (constraining, exploitative or 'phalanx') growth strategy of the mycelial system. After the fungi entered the toxic metal-containing domains, they often produced long sparsely-branched or branchless explorative hyphae representing a dissociative (expansive, explorative or 'guerrilla') growth strategy. Our data therefore demonstrate that fungi efficiently use both 'phalanx' and 'guerrilla' states of the mycelial system as well as shifts in these growth strategies as a response to toxic metal stress combined with nutritionally-poor conditions.