Obligate acidophilic bacteria of the genus Acidithiobacillus are widely used and well known in the biomining industry. Over the past decade, it has been shown that bacterial activity can be determined in short-term experiments via amperometric measurements of microbial oxygen consumption, as changes in the Clark electrode current are proportional to changes in the concentration of dissolved oxygen. This article presents a study of Acidithiobacillus sp. strain Thio1, which was isolated from pyrite–chalcopyrite copper ore and is closely related to A. ferrooxidans. Oxygen consumption by strain Thio1 was measured during the bacterial oxidation of substrates as changes in the electrode current. To evaluate the acute respiratory response of the bacteria to Cu, Zn, and As, respiration suppression was measured at increasing concentrations of the toxicants. The proposed amperometric method is not a substitute for the long-term biogeotechnological evaluation of strain activity using specific ore or pulp samples. At the same time, it can be used as a complementary microbiological method. The proposed approach offers distinct advantages: testing takes mere minutes (rapid analysis), and comparisons of substrates or toxicants can be performed using a single biomass sample (standardization). The amperometric method also demonstrated that oxygen was consumed during the corrosion of solid specimens (steel and chalcopyrite) by Acidithiobacillus sp. strain Thio1. However, applying this method to biocorrosion requires further study because the proportion of oxygen consumption directly related to microbial corrosion remains unknown.

The microbial accumulation of heavy metals and phosphate is of interest for the bioremediation of polluted waters. In this work, we showed that at cultivation of the bacterium Rhodococcus ruber SiAl in the medium with 2.0 mM Fe³⁺ for stationary growth stage, up to 99

The ability of bacteria to absorb metal ions and phosphates allows the development of processes for bioremediation of the environment and wastewater from heavy metals and excess phosphates. In this work, the ability of the “iron bacterium” Sphaerotilus montanus VKM B-2519 to remove manganese, iron, and phosphate from culture medium was studied. The bacterium removed Mn2+ but not Fe2+ from the culture medium during growth. At an initial concentration of 3 mmol/L Mn2+, about 40

Autotrophic sulfur-oxidizing bacteria can play a key role in the metal bioleaching from low-grade sulfide-containing ores. The most commonly used bioleaching group is presented with acidophilic bacteria of the order Acidithiobacillales. We studied the diversity of bacteria in the arsenopyrite gold-bearing ore and also discovered a wide distribution of neutrophilic non-thermophilic bacteria Thermithiobacillus plumbiphilus in this ore, as well as its drainage and flotation concentrate. For the first time, T. plumbiphilus was isolated from the natural arsenic-containing mineral material. The first description of complete genome for the species T. plumbiphilus was also carried out and discovered genes providing the As resistance. Culturing the isolated strain T. plumbiphilus AAFK confirmed the found bacterial resistance to arsenite and cocadylate during the effective thiosulfate oxidation. Experiments on the arsenopyrite bioleaching showed that T. plumbiphilus AAFK can be used as an auxiliary bacterial culture capable of oxidizing reduced / intermediate sulfur compounds. The genetic basis of the T. plumbiphilus AAFK resistance to the arsenic compounds is discussed; the mechanisms are similar with the ones known for acidophilic thiobacilli. The biofilm formation is shown for the first time for T. plumbiphilus; presumably, it could provide some protection and immobilization of the cells. Structures of the T. plumbiphilus AAFK cells and their production of outer membrane vesicles are described and discussed.

Glucose–fructose syrups were studied for the first time as a carbon source for the biosynthesis of citric acid (CA) by the yeast Yarrowia lipolytica. The producer Y. lipolytica VKM Y-2373 was selected, and the growth conditions were optimized (syrup concentration, 30 g/L; pH, 6.0; aeration, 20

In this 10th contribution to the Fungal Systematics and Evolution series published by Sydowia, 14 species are formally described: Amanita cingulatoides from Canada, A. confundens, A. elongatior, A. fusca, A. fuscozonata, A. leptorhacopus, A. magna, A. olivaceodisca, A. piceina, A. pulla, and A. quercifulva from Canada and the USA, Hebeloma uzunii from T & uuml;rkiye, Pleurotus overstrandensis from South Africa, and Saksenaea ozerskayae from Russia. Pluteus keselakii is reported for the first time from Czechia and Slovenia. Three invalidly published names are validated with corrected typification: Cortinarius balteatoindicus, C. indopurpurascens, and C. ulkhagarhiensis. Finally, Thaxterogaster shoreae is combined into Cortinarius.

Bacterial leaching is a well-known green technology proposed for the extraction of valuable metals into solution. However, this biotechnology has some “bottle neck” problems too. Arsenopyrite, a gold-bearing ore, is a refractory mineral material that is hardly soluble and contains toxic arsenic compounds which decrease any bioleaching production. The most common biotechnology used for this process is provided with the species Acidithiobacillus ferrooxidans: autotrophic and acidophilic bacterial strains including ones resistant to inorganic arsenic compounds. Common attempts to dissolve arsenopyrite with increasing volumes of sulfuric acid provoke acidification of the environment and its pollution with toxic compounds. In our research, we compared two A. ferrooxidans strains of different origin: TFBk isolated from arsenopyrite ore (pre-adopted to arsenic), the Republic of Kazakhstan, and ShA-GNK isolated from silicate nickel-ferrous ore (laterite, without arsenic), the Russian Federation. The studied genomes of both strains showed the presence of the same genes providing defense against arsenic compounds, but the resistance to toxic compounds was higher in the strain that had never been exposed to any high As concentration under the natural conditions. Both strains showed a weak oxidation of the arsenopyrite flotation concentrate (AFC). In accordance with the published data, supplementation of the medium with formate stimulated bacterial growth in the culturing medium. However, this supplementation to the leaching solution decreased the arsenopyrite oxidation during the first stage of the AFC leaching because formate was used as an alternative energy substrate, but subsequently gave a higher iron yield later.

Biodegradation of mineral materials is object of great research interest. Its positive practical application is related with industrial bioleaching for microbial recovery of valuable metals from the low-grade ores and solid wastes. Its negative significance is related with biodestruction of building materials and includes both metal biocorrosion and mineral biodegradation. The most studied theme is bioleaching sulfide ores that is accompanied with the microbial sulfide oxidation. Meanwhile, biodegradation of silicates is still an insufficient studied problem. In this paper, authors present a research on possible role of the so-named “silicate bacilli” in biodegradation of the arsenopyrite gold-bearing flotation concentrate which is refractory, toxic, and contains aluminosilicates. The paper belongs both to materials science and microbiology and describes biodegradation of silicate materials, namely: (1) isolation of the silicate bacilli from the concentrate and their identification, (2) experiments on the biodegradation of the concentrate with the strains, (3) bacterial formation of micro-voids on the mineral surface, (4) study on the strain resistance to toxic mineral arsenic via genetic analyses of their genomes. In general, the work presents the first suggestions about ways of the surface biodestruction in solid aluminosilicates that realized by silicate bacteria.

Most Fusarium species are known as endophytes and/or phytopathogens of higher plants and have a worldwide distribution. Recently, information discovered with molecular tools has been also published about the presence of these fungi in the microbiome of truffle fruiting bodies. In the present work, we isolated and identified three Fusarium strains from truffle fruiting bodies. All isolates were assigned to the same species, F. commune, and the strains were deposited in the All-Russian Collection of Microorganisms under accession numbers VKM F-5020, VKM F-5021, and VKM F-5022. To check the possible effects of the isolated strains on the plants, the isolates were used to infect sterile seedlings of Sarepta mustard (Brassica juncea L.). This model infection led to a moderate suppression of the photosynthetic apparatus activity and plant growth. Here, we present characteristics of the F. commune isolates: description of the conidial morphology, pigmentation, and composition of the mycelium fatty acids. Overall, this is the first description of the Fusarium cultures isolated from truffle fruiting bodies. Possible symbiosis of the F. commune strains with truffles and their involvement in the cooperative fatty acid production are proposed.

— Three karst lakes were investigated in the Nizhny Novgorod region: Staropustynskie lakes Svyato and Nekrasov Bay and Lake Svetloyar. The studied lakes belonged to the mesotrophic-eutrophic polyhumous type and were characterized by stable stratification with signs of meromixis. Their water columns were divided into aerobic and anaerobic zones, with the bottom water containing sulfide. Fe(II) compounds were also present in the Staropustynskie lakes. In the Lake Nekrasov Bay, the mixolimnion showed a high rate of oxygenic photosynthesis, up to 1.2 µg С L –1 day –1 , as well as a maximum of anoxygenic photosynthesis in the chemocline (0.030–0.706 µg С L –1 day –1 ) at a depth of 1.5−2.5 m. The peak of dark CO 2 assimilation (0.146 µg С L –1 day –1 ) occurred at a depth of 1.5 m in the oxycline zone. Anoxygenic phototrophic bacteria (APB) were found in the Lakes Nekrasov Bay and Svyato at the boundary of light penetration. Green sulfur bacteria with short cell prosthecate outgrowths, “ Ancalochloris sp.,” predominated. Consortia “ Chlorochromatium aggregatum ” and filamentous chlorobacteria “ Chloronema giganteum ” were also found, their cell sheaths accumulated ferric iron salts. In the Staropustynskie lakes, various morphotypes of iron bacteria formed clusters in the microaerobic zone. In Lake Svetloyar the chemocline was located at a depth of 16 m, outside the photic zone, and the conditions were unfavorable for APB growth. In the studied lakes, heterotrophic aerobic bacteria played the main role in the aerobic oxidation of sulfur compounds in the chemocline zone.

Scarce research into the secondary metabolites of the fungi Pseudogymnoascus spp. has shown a hidden biosynthetic potential for biologically active compounds. This work investigated the biosynthesis of secondary metabolites by two Pseudogymnoascus fungal strains, VKM F-4518 and VKM F-4519, isolated from the surface soil layer of the Kolyma Lowland, Russia, in the Arctic. In these strains, 16-membered trilactone macrolides, (+)-macrosphelides A and B, were identified using 1D and 2D NMR, UHRMS, and optical rotation data. In the fungi of this genus, these metabolites were found for the first time. The studied strains are highly active producers of macrosphelide A, which is being considered as a promising agent for the cure of cancer. Using the antiSMASH secondary metabolite analysis tool, we found that the genome of strain VKM F-4518 contained 32 of the biosynthetic clusters of the secondary metabolite genes (BGC) and that of VKM F-4519 had 17 BGCs. Based on the comparison of the cluster of macrotriolide genes from the fungus Paraphaeosphaeria sporulosa, we found the complete supposed cluster BGCs of macrosphelides in the genomes of two Pseudogymnoascus strains using the BLAST+ program.

The presented review is based on scientific microbiological articles and patents in the field of biomining valuable metals. The main attention is paid to publications of the last two decades, which illustrate some shifts in objects of interest and modern trends both in general and applied microbiology. The review demonstrates that microbial bioleaching continues to develop actively, despite various problems in its industrial application. The previous classic trends in the microbial bioleaching persist and remain unchanged, including (i) the search for and selection of new effective species and strains and (ii) technical optimization of the bioleaching process. Moreover, new trends were formed during the last decades with an emphasis on the phylogeny of leaching microbiota and on genomes of the leaching microorganisms. This area of genomics provides new, interesting information and forms a basis for the subsequent construction of new leaching strains. For example, this review mentions some changed strains with increased resistance to toxic compounds. Additionally, the review considers some problems of bioleaching valuable metals from toxic arsenopyrite.

— Microscopic fungi form and excrete numerous and diverse secondary metabolites, including pigments of various colors, which may be used as an alternative to chemical and plant colorants used in industry. Azaphilone compounds, first discovered in fungi of the genus Monascus , are among the promising classes of fungal pigments . The review analyzes the publications on formation of azaphilone-type pigments in Monascus fungi, as well as in Talaromyces and Aspergillus cavernicola . Brief information is provided concerning the antimicrobial, antitumor, anti-inflammatory, and hypolipidemic activities of azaphilone pigments. Possible strategies for increasing the efficiency of the production process and directed synthesis of yellow, orange, and red pigments and their derivatives are discussed. In general, the review provides for assessment of the role of azaphilone pigments, as well as of the prospects and ways to expand their production for use as natural dyes in various fields.

Acid metal bioleaching is common and classical for nickel recovery from the sulfide refractory ores: various microorganisms can oxidize sulfides as energetic substrates. Silicate nickel ores are widespread in the world but their bioleaching is more problematic because silicates cannot serve as energetic substrates. Meanwhile iron in the silicate nickel ores presents a significant part and can be used by some acidophilic autotrophic microorganisms for the ore destruction. In model experiments, we studied application of acidophilic autotrophic sulfur-/ iron-oxidizing bacteria Acidithiobacillus ferrooxidans VKM B-3655 for the nickel recovery from the nickel-bearing silicate ore with high content of iron. The strain was selected by its ability of iron oxidation and resistance to arsenic which also presented in the ore. We also evaluated possibility to stimulate the bioleaching with formate as additional energetic substrates or with persulfate for increasing the medium redox. It was shown that low concentrations of sodium formate (0.3%) and persulfate (0.1%) stimulated growth of A. ferrooxidans while higher persulfate concentration (1.0%) stimulated the ore bioleaching.

For many years, medical microbiology and food microbiology have been the most studied areas of microbial biology [...]

The leaching of hydrometallurgical metals from the ores of sulfide deposits is associated with the formation of acid mine drainage (AMD), which, in turn, provokes the acidification of mining areas. Mine drainage (MD) is a special ecological niche with natural selection formed by the low pH of the environment and the toxicity of the leached metals. Microbial communities of the MD are a good model for changes in bacterial composition under changing conditions. We have investigated the changes in the microbiota composition of MD samples taken from the Shanuch sulfide copper–nickel deposit (Kamchatka, Russia). Changes in the bacterial composition of the community are artificially provoked by transferring the initial microbiota (inoculum) to six media of different chemical compositions. The selected media provide various scenarios for possible changes in the microbiota under simulated changes in the chemical composition. Molecular analysis shows that the original MD community includes representatives of 13 genera in which strict acidophilic bacteria represent <20% of the clones. Organic additives in media provoke the dominance of heterotrophic bacteria only in one case. In general, model experiments reveal significant changes in the composition of autotrophic bacteria leaching metal, both at the species level and at the level of strains: the diversity of bacteria decreases and the analysis reveals fewer strains.

Hydrometallurgical mining of valuable and non-ferrous metals is traditionally accompanied by a large-scale pollution of the territories with sulfuric acid. This pollution is the global problem and requires the significant remediation costs. There are known some attempts to replace sulfuric and other strong inorganic acids with organic acids which could be easier utilized under natural conditions. However, this approach proved to be ineffective due to the weak leaching effect of organic acids. In our experiments on chemical leaching, we investigated leaching of nickel from low-grade silicate ores with a mixture of organic acids and persulfate. Organic acids ensured both the acidic reaction of the leaching solution while persulfate provided a short-term formation of persulfuric (peroxysulphuric) acid, which is the stronger leaching agent than sulfuric acid. In whole, experimental results showed that metal leaching can be intensified with application of organic acids.

Autotrophic acidophilic bacteria Acidithiobacillus ferrooxidans is a model species for studying metal bioleaching from low-grade sulfide ores and concentrates. Arsenopyrite gold-bearing concentrates are refractory and often processed using biohydrometallurgical approaches; therefore, it is important to develop methods to improve arsenopyrite bioleaching. In the present work, we have studied the possibility of improving arsenopyrite concentrate bioleaching by the strain of A. ferrooxidans. For this purpose, we have analyzed the genome of the strain A. ferrooxidans TFBk to reveal the genes potentially important in the bioleaching process. Genes determining resistance to arsenic, as well genes involved in the utilization of C1-compounds and resistance to oxidative stress, were revealed. Therefore, the possibility of increasing the rate of arsenopyrite concentrate bioleaching using C1-compounds (methanol and formate) was studied. Formate was able to increase both the biomass yield of the strain A. ferrooxidans TFBk as well as the bioleaching rate. In addition, the effect of redox potential increase by means of the addition of sodium persulfate in the medium on arsenopyrite concentrate bioleaching was studied. It was shown that the addition of 0.1% sodium persulfate stimulated strain growth, while a higher concentration inhibited it. Despite this, the rate of concentrate bioleaching increased in the presence of 0.5–1.0% of persulfate, which may be explained by the interactions of added oxidizer with concentrate components.

Enargite (Cu3AsS4) and arsenopyrite (FeAsS) are the most abundant arsenic containing sulfide minerals in the world. The existence of arsenic can significantly deteriorate the processes of mineral processing and extractive metallurgy, and also definitely cause environmental contamination due to the arsenic release. Hence, the arsenic removal from these two kinds of sulfide minerals is extremely important. However, most of the review articles only focus on arsenic removal from wastes. In this paper, the main arsenic removal methods from enargite and arsenopyrite have been summarized and discussed, mainly including roasting, oxidative dissolution (acidic condition, alkaline condition, pressure oxidation and biooxidation) and selective dissolution.

There are various groups of bacteria which receive energy from oxidation of inorganic sulfur compounds. Some of them produce elemental sulfur as an intermediate product and deposit it outside their cells. The group “sulfur bacteria” was described by their ability to produce intracellular sulfur inclusions. Traditionally, calculations of the released energy considered effect of the bacterial sulfide oxidation but never considered energy of the S-polymerization from monoatomic S to 8 atoms ring which is also essential (262.9 kJ). Till present, no biochemical reactions are known which could use energy of this eight atoms ring formation process. Thus, it is proposed that the intracellular sulfur inclusions can provide a lasting heating content of the cells as an additional advantage for the sulfur bacteria.