Accumulation of uranium by basidiomycetes

Accumulation of uranium by basidiomycetes was examined. Of 46 species of basidiomycetes tested, extremely high abilities to accumulate uranium were found in Favolus arcularis, Inonotus mikadoi and Tricholoma conglobatum. All basidiomycetes tested took up uranium far more readily than other heavy metals from a solution containing seven metals. T. conglobatum accumulated uranium more readily than thorium from a solution containing both uranium and thorium. The ability of heavy metal accumulation by T. conglobatum varied with the culture stage; cells cultured for 4 days had the highest affinity and selectivity for uranium. The immobilized T. conglobatum cells adsorbed uranium almost quantitatively and almost all uranium adsorbed was desorbed with 1 M Na₂CO₃. The immobilized cells can be used repeatedly for the process of uranium adsorption-desorption. Correspondence to: T. Sakaguchi     

Recovery of uranium by immobilized microorganisms

Summary Some attempts were made to recover uranium from sea and fresh water using immobilized Streptomyces viridochromogenes and Chlorella regularis cells. The cells immobilized in polyacrylamide gel have the most favorable features for uranium recovery; high adsorption ability, good mechanical properties, and applicability in a column system. The adsorption of uranium by the immobilized cells is not affected by the pH values between 4 and 9. These results show that uranium adsorption becomes independent of pH after immobilization. The amounts of uranium adsorbed by the immobilized cells increased linearly with temperature, suggesting that the adsorption of uranium by the immobilized cells is an endothermic reaction. The immobilized cells can recover uranium almost quantitatively from both fresh and sea water containing uranium, and almost all uranium adsorbed is desorbed with a solution of Na₂CO₃. Thus the immobilized cells of Streptomyces and Chlorella can be used repeatedly in adsorption-desorption process.Studies on the Accumulation of Heavy Metal Elements in Biological Systems. XXI     

Accumulation of gold by microorganisms

Thirty species of microorganisms (8 bacteria, 9 actinomycetes, 8 fungi and 5 yeasts) were screened for maximal gold accumulation. Extremely high abilities to accumulate gold from a solution containing hydrogen tetrachloroaurate(III) were found in bacterial strains, such as Escherichia coli and Pseudomonas maltophilia. Most of the actinomycetes, fungi and yeasts had lower ability to accumulate gold than bacteria. Some microorganisms could accumulate similar amounts of gold from a solution containing sodium gold(I) thiomalate as those from gold(III) solution. However, most microorganisms tested accumulated far lesser amounts of gold from a solution containing sodium dicyanoaurate(I) than from the other two gold solutions. The accumulation of gold from the solution containing hydrogen tetrachloroaurate(III) by Pseudomonas maltophilia was very rapid, was affected by the pH of the solution, and obeyed the Langmuir adsorption isotherm. Pseudomonas maltophilia cells immobilized in polyacrylamide gel adsorbed gold effectively from the solution containing hydrogen tetrachloroaurate(III). The gold adsorbed on the cells was easily desorbed with 0.1 M thiourea solution. The immobilized Pseudomonas cells could be used repeatedly in the adsorption–desorption cycle using 0.1 M thiourea solution as desorbent.     

Biosorption and recycling of gold using various microorganisms

In order to obtain basic information on the biosorption and recycling of gold from aqueous systems using microbial cells, the biosorption of gold by various microorganisms was investigated. Of 75 strains of microorganisms tested (25 bacteria, 19 actinomycetes, 17 fungi and 14 yeasts), high abilities of gold biosorption from a solution containing hydrogen tetrachloroaurate (III) were found in some gram-negative bacterial strains, such as Acinetobacter calcoaceticus, Erwinia herbicola, Pseudomonas aeruginosa, and P. maltophilia. Most of the gram-positive bacteria, actinomycetes, fungi and yeasts had a lower ability for gold biosorption than gram-negative bacteria. On the other hand, all of the microorganisms tested adsorbed far smaller amounts of gold from a solution containing gold dicyanoaurate (I). The biosorption of gold from a solution containing hydrogen tetrachloroaurate (III) using P. maltophilia having a high adsorbing ability for gold was very rapid and was affected by the pH of the solution, external gold concentration, and cell amounts. P. maltophilia cells immobilized with polyacrylamide gel also have a high ability for gold biosorption. The gold adsorbed on the immobilized cells is easily desorbed with 0.1 M thiourea solution. The immobilized P. maltophilia cells can be used repeatedly in biosorption-desorption cycles.     

Mercury bioremediation by mercury accumulating Enterobacter sp. cells and its alginate immobilized application

The effective microbial remediation of the mercury necessitates the mercury to be trapped within the cells without being recycled back to the environment. The study describes a mercury bioaccumulating strain of Enterobacter sp., which remediated mercury from the medium simultaneous to its growth. The transmission electron micrographs and electron dispersive X-ray analysis revealed the accumulation of remediated mercury as nano-size particles in the cytoplasm as well as on the cell wall. The Enterobacter sp. in the present work was able to accumulate mercury, without being engineered in its native form. The possibility of recovering the accumulated mercury from the cells is also indicated. The applicability of the alginate immobilized cells in removing mercury from synthetic and complex industrial effluent in a batch mode was amply demonstrated. The initial load of 7.3 mg l⁻¹ mercury in the industrial effluent was completely removed in 72 h. The cells immobilized in calcium alginate were similarly effective in the complete removal of 5 mg l⁻¹ HgCl₂ of mercury from the synthetic effluent in less than 72 h. The immobilized cells could be reused for multiple cycles.     

Hyperparasitism of Streptomyces albus on a Destructive Mycoparasite Nectria inventa

Using scanning electron microscopy, Streptomyces albus was proved to be a hyperparasite of Nectria inventa, itself a well-known mycoparasite on many fungi. The hyperparasite had no apparent antagonistic activity against N. inventa, but did have intense tropic response toward it. Upon contact with the host, the hyperparasite grew along, and formed appressorium-like structures on the host hyphae. The parasitism that led to the eventual collapse of the host cells was not necessarily accompanied by actual hyphal penetration. The hyperparasite could, however, readily penetrate the host hyphae, and its hyphae were frequently found inside the host hyphae.     

Yeasts and filamentous fungi carried by the gynes of leaf-cutting ants

Insect-associated microbes exhibit a wide range of interactions with their hosts. One example of such interactions is the insect-driven dispersal of microorganisms, which plays an essential role in the ecology of several microbes. To study dispersal of microorganisms by leaf-cutting ants (Formicidae: Attini), we applied culture-dependent methods to identify the filamentous fungi and yeasts found in two different body parts of leaf-cutting ant gynes: the exoskeleton and the infrabuccal pocket. The gynes use the latter structure to store a pellet of the ants’ symbiotic fungus during nest founding. Many filamentous fungi (n = 142) and yeasts (n = 19) were isolated from the gynes’ exoskeleton. In contrast, only seven filamentous fungi and three yeasts isolates were recovered from the infrabuccal pellets, suggesting an efficient mechanism utilized by the gynes to prevent contamination of the symbiotic fungus inoculum. The genus Cladosporium prevailed (78%) among filamentous fungi whereas Aureobasidium, Candida and Cryptococcus prevailed among yeasts associated with gynes. Interestingly, Escovopsis, a specialized fungal pathogen of the leaf-cutting ant-fungus symbiosis, was not isolated from the body parts or from infrabuccal pellets of any gynes sampled. Our results suggest that gynes of the leaf-cutter ants Atta laevigata and A. capiguara do not vertically transmit any particular species of yeasts or filamentous fungi during the foundation of a new nest. Instead, fungi found in association with gynes have a cosmopolitan distribution, suggesting they are probably acquired from the environment and passively dispersed during nest foundation. The possible role of these fungi for the attine ant–microbial symbiosis is discussed.     

Microbiological Asymmetric Hydroxylation of 7-Carboxybicyclo[2.2.1]heptane and hept-2-ene and Their Methyl Esters Giving Potentially Useful Chiral Synthons for Cyclopentanoids

One hundred and nineteen strains of microorganisms (yeasts, bacteria, actinomycetes and fungi) were screened as to the hydroxylation of bicyclo[2.2.1]heptane-7-carboxylic acid, bicyclo[2.2.1]hept-2-ene-7-syn-carboxylic acid, and their methyl esters. Several species belonging to the genera, Bacillus, Streptomyces, Penicillium, Aspergillus, Absidia, Beauveria, Cunninghamella, Drechslera, Mucor and Chaetomium, were found to asymmetrically hydroxylate some or all of the substrates. Bacillus thuringiensis and Aspergillus awamori were the most effective microorganisms for obtaining the chiral products, (lR)-2-hydroxy acids or esters, with enantiomeric purities of 75~90% e.e., which are potential intermediates for (?)-methyl jasmonate or natural prostaglandins.     

Safety and regulation of yeasts used for biocontrol or biopreservation in the food or feed chain

Yeasts have been important components of spontaneous fermentations in food and beverage processing for millennia. More recently, the potential of utilising antagonistic yeasts, e.g. Pichia anomala and Candida spp., for post-harvest biological control of spoilage fungi during storage of plant-derived produce (‘biopreservation’) has been clearly demonstrated. Although some yeast species are among the safest microorganisms known, several have been reported in opportunistic infections in humans, including P. anomala and bakers’ yeast, Saccharomyces cerevisiae. More research is needed about the dominant pathogenicity and virulence factors in opportunistic yeasts, and whether increased utilisation of biopreservative yeasts in general could contribute to an increased prevalence of yeast infections. The regulatory situation for yeasts used in post-harvest biocontrol is complex and the few products that have reached the market are mainly registered as biological pesticides. The qualified presumption of safety (QPS) approach to safety assessments of microorganisms intentionally added to food or feed, recently launched by the European Food Safety Authority, can lead to more efficient evaluations of new products containing microbial species with a sufficient body of knowledge or long-term experience on their safety. P. anomala is one of several yeast species that have been given QPS status, although the status is restricted to use of this yeast for enzyme and metabolite production purposes. With regard to authorisation of new biopreservative yeasts, we recommend that the possibility to regulate microorganisms for food biopreservation as food additives be considered.     

Neutralization of acidified water by use of Rhizopus delemar immobilized with a cellulose membrane

To solve serious environmental problems caused by the acidification of pond and lake water by acid rain, remediation methods must be used to keep water pH values neutral. In this study, a microbial method to neutralize acidified water was developed. The neutralization activities of 30 strains of bacteria, yeasts and fungi were measured with a medium adjusted to pH 3.0. Because fungi showed high neutralization properties, the Rhizopus delemar fungus was used to study the characteristics of acidified water neutralization. When R. delemar cells were cultured in a media acidified with nitric, sulfuric and hydrochloric acids, the cells neutralized acids by secreting basic compounds including ammonia. The cells also assimilated nitric acid. R. delemar was used to neutralize pond water adjusted to pH 4.0 with nitric acid. R. delemar cells increased the pH value of pond water from 4.0 to around 7.0 within 2 days, although indigenous microorganisms had not been able to neutralize the same pond water. In this study, R. delemar immobilized in a cellulose tube neutralized acidified water repeatedly by the draw-fill method.     

The effect of long-term preservation of bacterial cells immobilized in poly(vinyl alcohol) cryogel on their viability and biosynthesis of target metabolites

The effect of cell storage at ?18°C for 18–24 months on reproductive capacity was investigated for various microorganisms (gram-positive and gram-negative bacteria, yeasts, and filamentous fungi) immobilized in poly(vinyl alcohol) cryogel. To examine the viability of immobilized cells after defrosting, the bioluminescent method of intracellular ATP determination was used. A high level of metabolic activity of immobilized cells after various periods of storage was recorded for Streptomyces anulatus, Rhizopus oryzae, and Escherichia coli, which are producers of the antibiotic aurantin, L(+)-lactic acid, and the recombinant enzyme organophosphate hydrolase, respectively. It was shown that the initial concentration of immobilized cells in cryogel granules plays an important role in the survival of Str. anulatus and Pseudomonas putida after 1.5 years of storage. It was found that, after slow defrosting in the storage medium at 5°C for 18 h of immobilized cells of the yeast Saccharomyces cerevisiae that had been stored for nine months, the number of reproductive cells increased due to the formation of ascospores.     

Monitoring of Microbial Degraders in Manned Space Stations

Samples of microorganisms from the surface of constructions of Mir Space Station (Mir SS) were taken and examined after 13 years of operation. The following microorganisms were isolated and identified: 12 fungal species belonging to the genera Penicillium, Aspergillus, Cladosporium, and Aureobasidium; 3 yeast species belonging to the genera Debaryomyces, Candida, and Rhodotorula; and 4 bacterial species belonging to the genera Bacillus, Myxococcus, and Rhodococcus. The predominant species in all samples was Penicillium chrisogenum. It was shown that the fungi isolated could damage polymers and induce corrosion of aluminum-magnesium alloys. We commenced a study of microbial degraders on constructions of the Russian section of the International Space Station (RS ISS). Twenty-six species of fungi, bacteria, yeasts, and actinomycetes, known as active biodegraders, were identified in three sample sets taken at intervals. We founded a collection of microorganisms surviving throughout space flights. This collection can be used to test spacecraft production materials, in order to determine their resistance to biodegradation.__________Translated from Prikladnaya Biokhimiya i Mikrobiologiya, Vol. 41, No. 4, 2005, pp. 435–443.Original Russian Text Copyright © 2005 by Alekhova, Aleksandrova, Novozhilova, Lysak, Zagustina, Bezborodov.     

Screening,Isolation, and Some Properties of Microbial Cell Flocculants

Nineteen out of 214 strains of microorganisms including moulds, bacteria, actinomycetes and yeasts, which were selected from the culture collection of our laboratory were found to produce the substances which flocculate Saccharomyces cerevisiae AJ4005 (baker’s yeast). Among them are Aspergillus sojae, Anixiella reticulata, Geotrichum candidum, Eupenicillium crustaceus, Circinella sydowi, Monascus anka, Sordaria fimicola, Pseudomonas fluorescens, Staphylococcus aureus, Corynebacterium brevicale, Brevibacterium insectiphilum, Streptomyces vinaceus.

The flocculants in the culture broth of these microorganisms precipitated readily by addition of acetone, and flocculated various microorganisms nonspecifically. The flocculant produced by Asp. sojae AJ7002 sedimented activated sludge well.     

Yeasts and fungi in excrements of the sand hill snail,Theba pisana

Eight microbial species were isolated and identified from excrements of the sand hill snail,Theba pisana, viz. 3 filamentous fungi, 3 basidiomycetous yeasts and 2 yeast-like ascomycetous fungi.     

Microbial symbiotes of the ambrosia beetleXyloterinus politus

Progression in the understanding of the microecology of ambrosia beetles and their associated microorganisms is briefly reviewed. Between the 1840s and the early 1960s the concept of one ambrosial fungus per ambrosia beetle was emphasized. Some subsequent research has supported the view that each ambrosia beetle plus several associated microorganisms constitute a highly co-evolved symbiotic community. It was hypothesized in this study that such a community of symbiotic microbial species, not just one ambrosial fungus, is actively cultivated and perpetuated by the ambrosia beetleXyloterinus politus. Experimental results indicated that bacteria, yeasts, a yeastlike fungus, and ambrosial fungi compose such a symbiotic microbial complex in association withX. politus. The microecology of the ectosymbiotic microorganisms in relation to this insect is discussed.     

Screening for microorganisms performing the stereoselective reduction of α-formyl-esters

Summary 107 Microorganisms selected from 26 genera belonging to bacteria, actinomycetes, fungi and yeasts were screened for their ability to reduce -formyl-esters stereoselectively. Eighteen strains have been found which were able to reduce at least one of 5 substrates tested with an optical purity of more than 85% ee. The best strains were Candida humicola, Aspergillus petrakii, Streptomyces hydrogenans and Streptomyces griseus. The dependence of the enantioselectivity of the reduction on the group of microorganisms and on the substituents of the formyl-esters is discussed.     

Ecological aspects of microorganisms inhabiting uranium mill tailings

Numbers and types of microorganisms in uranium mill tailings were determined using culturing techniques.Arthrobacter were found to be the predominant microorganism inhabiting the sandy tailings, whereasBacillus and fungi predominated in the slime tailings. Sulfate-reducing bacteria, capable of leaching radium, were isolated in low numbers from tailings samples but were isolated in significantly high numbers from topsoil in contact with the tailings. The results are placed in the context of the magnitude of uranium mill tailings in the United States, the hazards posed by the tailings, and how such hazards could be enhanced or diminished by microbial activities. Patterns in the composition of the microbial population are evaluated with respect to the ecological variables that influence microbial growth.     

Effects and modes of action of live yeasts in the rumen

Live yeasts (Saccharomyces cerevisiae) are more and more widely used as feed additives for ruminants. They are considered as allochtonous microorganisms in the rumen environment, however, distributed daily to dairy cows or beef cattle they can survive in the digestive tract and interact with autochtonous microbial populations. The positive effects of yeast cells have been mainly demonstrated on growth and activity of fibre-degrading bacteria and fungi, on stabilisation of rumen pH and prevention of lactate accumulation, on ruminal microbial colonization and on the set up of fermentative processes during the pre-weaning period. Modes of action of yeast probiotics depend on their viability and stability in the rumen ecosystem. Up to now, the main modes of action identified are the supply of growth factors to rumen microorganisms, oxygen scavenging inducing more favourable conditions for the anaerobic communities, and nutritional competition with autochtonous ruminal species. Presented at the Second Probiotic Conference, Košice, 15–19 September 2004, Slovakia.     

Microbial degradation of phenol and phenolic derivatives

Phenol and its derivatives are one of the largest groups of environmental pollutants due to their presence in many industrial effluents and broad application as antibacterial and antifungal agents. A number of microbial species possess enzyme systems that are applicable for the decomposition of various aliphatic and aromatic toxic compounds. Intensive efforts to screen species with high‐degradation activity are needed to study their capabilities of degrading phenol and phenolic derivatives. Most of the current research has been directed at the isolation and study of microbial species of potential ecological significance. In this review, some of the best achievements in degrading phenolic compounds by bacteria and yeasts are presented, which draws attention to the high efficiency of strains of Pseudomonas, Candida tropicalis, Trichosporon cutaneum, etc. The unique ability of fungi to maintain their degradation potential under conditions unfavorable for other microorganisms is outstanding. Mathematical models of the microbial biodegradation dynamics of single and mixed aromatic compounds, which direct to the benefit of the processes studied in optimization of modern environmental biotechnology are also presented.     

Yeasts in an industrial malting ecosystem

The malting ecosystem consists of two components: the germinating cereal grains and the complex microbial community. Yeasts and yeast-like fungi are an important part of this ecosystem, but the composition and the effects of this microbial group have been largely unknown. In this study we surveyed the development of yeasts and yeast-like fungi in four industrial scale malting processes. A total of 136 malting process samples were collected and examined for the presence of yeasts growing at 15, 25 and 37°C. More than 700 colonies were isolated and characterized. The isolates were discriminated by PCR-fingerprinting with microsatellite primer (M13). Yeasts representing different fingerprint types were identified by sequence analysis of the D1/D2 domain of the 26S rRNA gene. Furthermore, identified yeasts were screened for the production of α-amylase, β-glucanase, cellulase and xylanase. A numerous and diverse yeast community consisting of both ascomycetous (25) and basidiomycetous (18) species was detected in the various stages of the malting process. The most frequently isolated ascomycetous yeasts belonged to the genera Candida, Clavispora, Galactomyces, Hanseniaspora, Issatchenkia, Pichia, Saccharomyces and Williopsis and the basidiomycetous yeasts to Bulleromyces, Filobasidium, Cryptococcus, Rhodotorula, Sporobolomyces and Trichosporon. In addition, two ascomycetous yeast-like fungi (black yeasts) belonging to the genera Aureobasidium and Exophiala were commonly detected. Yeasts and yeast-like fungi produced extracellular hydrolytic enzymes with a potentially positive contribution to the malt enzyme spectrum. Knowledge of the microbial diversity provides a basis for microflora management and understanding of the role of microbes in the cereal germination process.