Showing papers in "Geomicrobiology Journal in 2017"
TL;DR: A review of the use of MICP for soil improvement can be found in this article, where the authors discuss the treatment process including the primary components involved and major affecting factors, as well as the potential advantages and limitations.
Abstract: Biocementation is a recently developed new branch in geotechnical engineering that deals with the application of microbiological activity to improve the engineering properties of soils. One of the most commonly adopted processes to achieve soil biocementation is through microbially induced calcite precipitation (MICP). This technique utilizes the metabolic pathways of bacteria to form calcite (CaCO3) that binds the soil particles together, leading to increased soil strength and stiffness. This paper presents a review of the use of MICP for soil improvement and discusses the treatment process including the primary components involved and major affecting factors. Envisioned applications, potential advantages and limitations of MICP for soil improvement are also presented and discussed. Finally, the primary challenges that lay ahead for the future research (i.e. treatment optimization, upscaling for in situ implementation and self-healing of biotreated soils) are briefly discussed.
295 citations
TL;DR: In this paper, the potential for inducing carbonate precipitation in soil via bacterial denitrification using bench-scale experiments with the facultative anaerobe Pseudomonas denitrificans was evaluated.
Abstract: Microbially induced carbonate precipitation (MICP) and associated biogas production may provide sustainable means of mitigating a number of geotechnical challenges associated with granular soils. MICP can induce interparticle soil cementation, mineral precipitation in soil pore space and/or biogas production to address geotechnical problems such as slope instability, soil erosion and scour, seepage of levees and cutoff walls, low bearing capacity of shallow foundations, and earthquake-induced liquefaction and settlement. Microbial denitrification has potential for improving the mechanical and hydraulic properties of soils because it promotes precipitation of calcium carbonate (CaCO3) and produces nitrogen (N2) gas without generating toxic by-products. We evaluated the potential for inducing carbonate precipitation in soil via bacterial denitrification using bench-scale experiments with the facultative anaerobe Pseudomonas denitrificans. Bench-scale experiments were conducted (1) without calcium in...
97 citations
TL;DR: Three KSB strains showed the best K mineral solubilizing ability and they were identified as Mesorhizobium sp.
Abstract: More than 90% of potassium (K) in soil exists in forms of insoluble silicate minerals and cannot be directly utilized by plants. K-solubilizing bacteria (KSB) can improve soil fertility and plant growth as biofertilizers by decomposing silicate minerals and releasing insoluble K into soluble forms. The objectives of this study were to isolate and characterize KSB from rape rhizospheric soil and to evaluate their effects on ryegrass growth. In this study, 16 cultivable potential KSB were isolated from rape rhizosphere at first. Then, quantitative analysis revealed that three KSB strains, named S-15, S-17 and S-18, showed the best K mineral solubilizing ability and they were identified as Mesorhizobium sp., Paenibacillus sp. and Arthrobacter sp. Inoculating the three strains into available K limit soil increased available K content significantly. The result of the pot experiment revealed that the three strains increased ryegrass growth vigor, biomass yield and K uptake to different degrees in availa...
71 citations
TL;DR: This study clearly indicates that use of PSB, and organic amendments with insoluble RP could be a promising management strategy to enhance P availability in soil pool and improve plant growth in intensive cropping systems.
Abstract: Phosphate solubilizing bacteria (PSB) play a significant role in plant P nutrition by their effect on soil P dynamics and their subsequent ability to make P available to plants via solubilization and mineralization processes. This study aimed to evaluate the effect of separate and combined use of indigenous PSB, poultry manure (PM) and compost on solubilization and mineralization of rock phosphate (RP) and their subsequent effect on growth and P accumulation of maize (Zea mays L.). A group of fifty seven bacteria were isolated from the rhizosphere/rhizoplane of maize that had been grown in soils collected from varying altitudes (655–2,576 m) of the mountain region of Rawalakot, Azad Jammu and Kashmir, Pakistan. After screening, the capacity of eleven isolates to solubilize mineral phosphate was quantitatively evaluated using insoluble Ca3(PO4)2 in culture medium as a time course study through spectrometer. The growth hormone producing (IAA) capacity of the isolates was also determined. Furthermore...
56 citations
TL;DR: All of the isolates of O20 strain were capable of producing industrially valuable enzymes based on screening and most of them could produce at least two of these enzymes.
Abstract: In this study, the isolation, identification and characterization of the thermophilic bacteria from different hot springs in Turkey were carried out by conventional (morphological, physiological and biochemical tests) and molecular methods (fatty acid methyl esters, GTG5-PCR and 16S rRNA sequencing). These thermophilic bacteria were then tested for their capability to produce enzymes such as lipase, protease, amylase and cellulase. O20 strain is a novel species according to identification studies. All of its isolates were capable of producing industrially valuable enzymes based on screening. In fact, most of them could produce at least two of these enzymes.
55 citations
TL;DR: In this article, the authors investigated the effects of several factors including concentration of bacteria, chemical reactants, temperature, and pH on precipitation of calcium carbonate and found that after 7 and 14 days of curing, the compressive strength of silty clay soil samples increased steadily as pH increased from 5 to 9.
Abstract: Some microorganisms such as Sporoscarcina pasteurii precipitate calcium carbonate and are suitable for biocementation. This study aimed to investigate the effects of several factors including concentration of bacteria, chemical reactants, temperature, and pH on precipitation of calcium carbonate. The results showed that after 7 and 14 days of curing, the compressive strength of silty clay soil samples increased steadily as pH increased from 5 to 9. It was observed that pH plays an important role in biocementation. The highest compressive strength (i.e. 92 kPa) was observed when the soil was treated with 50 ml of bacterial solution after 14 days of curing. In addition, it was observed that the highest compressive strength of samples was achieved when the temperature was 40°C.
43 citations
TL;DR: In this paper, the culturable heterotrophic bacterial community present on two metal-loid-contaminated sites in the Northern Portugal w.r.t. heavy metal contaminated soils are investigated.
Abstract: Heavy metal–contaminated soils are a serious environmental problem. Herein, the culturable heterotrophic bacterial community present on two metal(loid)-contaminated sites in the Northern Portugal w...
42 citations
TL;DR: The isolation, molecular identification and screening of manganese (Mn) solubilizing fungal strains from low-grade Mn mine tailings are reported, indicating the role of fungi in biotransformation of insoluble Mn oxide.
Abstract: The present investigation reports the isolation, molecular identification and screening of manganese (Mn) solubilizing fungal strains from low-grade Mn mine tailings. Six morphologically distinct Mn solubilizing fungal strains were isolated on MnO2-supplemented agar plates with Mn concentration of 0.1% (w/v). The biochemical characterization of the isolated fungal strains was carried out. The molecular identification by internal transcribed spacer (ITS) sequencing identified the strains as Aspergillus terreus, Aspergillus oryzae, Penicillium sp., Penicillium sp., Penicillium daleae and Penicillium sp. with GenBank accession numbers KP309809, KP309810, KP309811, KP309812, KP309813 and KP309814, respectively. The ability of the isolated fungal strains to tolerate and solubilize Mn was investigated by subculturing them on Mn-supplemented plates with concentration ranging from 0.1 to 0.5% (w/v). Mn solubilizing ability of the fungal isolates is possibly due to the mycelia production of biogenerated or...
41 citations
TL;DR: An approach for applying biocementation in situ, by combining the surface percolation of nutrients and cementation solution (urea/CaCl2) with in situ cultivation of indigenous soil urease positive microorganisms under non-sterile conditions is proposed.
Abstract: The use of biocementation via microbially induced carbonate precipitation (MICP) for improving the mechanical properties of weak soils in the laboratory has gained increased attention in recent years. This study proposes an approach for applying biocementation in situ, by combining the surface percolation of nutrients and cementation solution (urea/CaCl2) with in situ cultivation of indigenous soil urease positive microorganisms under non-sterile conditions. The enrichment of indigenous ureolytic soil bacteria was firstly tested in batch reactors. Using selective conditions (i.e., pH of 10 and urea concentrations of 0.17 M), highly active ureolytic microorganisms were enriched from four diverse soil samples under both oxygen-limited (anoxic) and oxygen-free (strictly anaerobic) conditions, providing final urease activities of more than 10 and 5 U/mL, respectively. The enrichment of indigenous ureolytic soil microorganisms was secondly tested in pure silica sand columns (300 and 1000 mm) for biocem...
39 citations
TL;DR: Response surface methodology analysis demonstrated that strain H117 had the capability to utilize bicarbonate and sodium acetate as a carbon source under anaerobic conditions, and could perform both autotrophic and heterotrophic denitrification in the medium.
Abstract: Strain H117 was isolated from the Tang Yu reservoir. Based on the phylogenetic characteristics, strain H117, which was identified as Pseudomonas sp. strain H117, had the capability to utilize bicarbonate and sodium acetate as a carbon source under anaerobic conditions. Furthermore, the strain could grow on both autotrophic and heterotrophic media, and could perform both autotrophic and heterotrophic denitrification in the medium. Response surface methodology analysis demonstrated that the maximum degradation ratio of nitrate-occurred under the following conditions in the autotrophic medium: initial pH of 6.00, C/N ratio of 4.68 and temperature of 31.33°C. The maximum degradation ratio of nitrate occurred under the following conditions in the heterotrophic medium: initial pH of 6.16, C/N ratio of 8.23 and temperature of 28.48°C. Finally, the denitrification performance of strain H117 was evaluated under the optimum conditions. These results suggest that strain H117 has potential applications for th...
38 citations
TL;DR: The isolation, identification and molecular characterization of indigenous manganese (Mn) solubilizing acidophilic bacterial strains from mine water samples from Odisha, India are reported.
Abstract: The study of the microbial ecology in extreme acidic environments has provided an important foundation for the development of mineral biotechnology. The present investigation reports the isolation, identification and molecular characterization of indigenous manganese (Mn) solubilizing acidophilic bacterial strains from mine water samples from Odisha, India. Four morphologically distinct bacterial strains showing visible growth on Mn-supplemented plates of varying pH were isolated and identified. Mn solubilizing ability of the isolates was tested by growing them on Mn-supplemented agar plates. The appearance of lightening around the growing colonies of all the isolates demonstrated their Mn solubilizing ability in the medium. 16 S rRNA sequencing was carried out and the bacterial isolates were taxonomically classified as Enterobacter sp. AMSB1, Bacillus cereus AMSB3, Bacillus nealsonii AMSB4 and Staphylococcus hominis AMSB5. The evolutionary timeline was studied by constructing neighbor-joining phy...
TL;DR: To simulate the precipitation process of microbial limestone at the offshore of the ancient ocean, different calcites induced by Synechocystis sp.
Abstract: In order to simulate the precipitation process of microbial limestone at the offshore of the ancient ocean, different calcites induced by Synechocystis sp. PCC6803 in culture media with low Mg/Ca r...
TL;DR: The results support the idea that sulfur and sulfate reducing bacteria contribute to Fe-reduction in the upper centimeters of both sediments.
Abstract: In many marine surface sediments, the reduction of manganese (Mn) and iron (Fe) oxides is obscured by sulfate reduction, which is regarded as the predominant anaerobic microbial respiration process...
TL;DR: Canonical correspondence analysis indicated that pH, S, and Fe concentration gradients were the most important factors in structuring the river microbial community and a scheme explaining the biogeochemical Fe and S cycling is advanced.
Abstract: Indigenous Fe- and S-metabolizing bacteria play important roles both in the formation and the natural attenuation of acid mine drainage (AMD). Due to its low pH and Fe-S-rich waters, a river located in the Dabaoshan Mine area provides an ideal opportunity to study indigenous Fe- and S-metabolizing microbial communities and their roles in biogeochemical Fe and S cycling. In this work, water and sediment samples were collected from the river for physicochemical, mineralogical, and microbiological analyses. Illumina MiSeq sequencing indicated higher species richness in the sediment than in the water. Sequencing also found that Fe- and S-metabolizing bacteria were the dominant microorganisms in the heavily and moderately contaminated areas. Fe- and S-metabolizing bacteria found in the water were aerobes or facultative anaerobes, including Acidithiobacillus, Acidiphilium, Thiomonas, Gallionella, and Leptospirillum. Fe- and S-metabolizing bacteria found in the sediment belong to microaerobes, facultativ...
TL;DR: In this paper, the interaction of two model heterotrophic bacteria, soil Pseudomonas aureofaciens and aquatic P. reactans, with peat and Sphagnum moss leachates from the permafrost region under controlled laboratory conditions in nutrient-free media was studied.
Abstract: The respiration of dissolved organic matter (DOM) by aerobic heterotrophic bacterioplankton in boreal surface waters is one of the major factors that regulate CO2 exchange of lakes and rivers with the atmosphere in arctic and subarctic zones. The DOM that originates from topsoil leaching and vegetation degradation is brought to the lakes by surface flow and is subjected to coagulation and degradation by heterotrophic bacteria, which are well-established processes in the majority of boreal aquatic settings. The behavior of colloids and organic complexes of trace metals during this process is virtually unknown. In this work, we studied the interaction of two model heterotrophic bacteria, soil Pseudomonas aureofaciens and aquatic Pseudomonas reactans, with peat and Sphagnum moss leachates from the permafrost region under controlled laboratory conditions in nutrient-free media. The moss leachate was the better substrate for bacterial survival, with P. reactans exhibiting an order of magnitude higher l...
TL;DR: The results of the X-ray powder diffraction (XRD) analysis of the minerals revealed that the preferred orientation and lattice distortion were characteristic of struvite crystals as mentioned in this paper.
Abstract: The biomineralization of struvites is becoming a very popular research subject. In this study, struvite crystals were precipitated and characterized in the presence of the bacterial Leclercia adcarboxglata strain JLS1 that was isolated from a typical dolostone sample. The JLS1 strain was identified as L. adcarboxglata using physiological and biochemical identification methods and by 16S rDNA phylogenetic analysis. The minerals obtained from the culture medium using experimental samples inoculated with L. adcarboxglata JLS1 were not found in the control samples without the bacteria. The experimentally derived minerals were determined to be pure struvites that exhibited primarily a uniform, prismatic-shaped morphology of various sizes. The results of the X-Ray Powder Diffraction (XRD) analysis of the minerals revealed that the preferred orientation and lattice distortion were characteristic of struvite crystals. In the experiments conducted using the L. adcarboxglata it was also found that the phosp...
TL;DR: Protocol E developed from Yeates et al. protocol has been found to be best in terms of DNA yield, DNA purity and bacterial diversity depiction associated with boron–sulfur rich sediment of high elevation hot springs.
Abstract: Extraction of good-quality metagenomic DNA from extreme environments is quite challenging, particularly from high elevation hot spring sediments. Low microbial load, high humic acid content and other contaminants complicate the process of extraction of metagenomic DNA from hot spring sediments. In the present study, efficacy of five manual DNA extraction protocols with modifications has been evaluated for metagenomic DNA extraction from boron–sulfur rich high elevation Puga hot spring sediments. Best suited protocol was identified based on the cell lysis efficiency, DNA yield, humic acid content, PCR reproducibility and representation of bacterial diversity. Quantity as well as quality of crude metagenomic DNA differed remarkably between various protocols used and were not pure enough to give PCR amplification using 16S rRNA bacterial and archaeal primers. Crude metagenomic DNA extracted using five different DNA extraction protocols was purified using spin column based purification method. Even af...
TL;DR: The authors examined the mineralogical effect on community structure in the aquifer ecosystem by using a four-year in situ colonization experiment with igneous minerals and glasses in Integrated Ocean Drilling Program Hole 1301A on the Juan de Fuca Ridge.
Abstract: Volcanic ocean crust contains a global chemosynthetic microbial ecosystem that impacts ocean productivity, seawater chemistry and geochemical cycling. We examined the mineralogical effect on community structure in the aquifer ecosystem by using a four-year in situ colonization experiment with igneous minerals and glasses in Integrated Ocean Drilling Program Hole 1301A on the Juan de Fuca Ridge. Microbial community analysis and scanning electron microscopy revealed that olivine phases and iron-bearing minerals bore communities that were distinct from iron-poor phases. Communities were dominated by Archaeoglobaceae, Clostridia, Thermosipho, Desulforudis and OP1 lineages. Our results suggest that mineralogy determines microbial composition in the subseafloor aquifer ecosystem.
TL;DR: Two yeast isolates (KSY-29 and KSY-33) showed an ability to solubilize potassium by inducing clear zones around their colonies by releasing K of muscovite in broth culture, which resulted in significant increases in plant height, root and shoot dry weights as well as K uptakes by shoots and roots maize plants occurred through the inoculation with these isolates.
Abstract: Thirty-five yeast strains were isolated from soil samples that were collected from different locations in Upper Egypt. The purified isolates were screened for the release potassium from mica on Aleksandrov agar medium. Two yeast isolates (KSY-29 and KSY-33) showed an ability to solubilize potassium by inducing clear zones around their colonies. They were identified as Pichia anomala and Rhodotorula glutinis, respectively, based on PCR analysis of the ITSI-26S region that was amplified by NL1/NL4 species-specific primers. The amount of K released from muscovite mica in the broth culture of the yeast isolates was measured after 5, 10, 15 and 20 days of the incubation at 25°C. Both yeast isolates were very effective in releasing K of muscovite in broth culture, recording 8.11–13.21 μg/ml that were released from muscovite mica after 20 days of incubation. The inoculation of maize (Zea maize) plants with these yeast isolates under different K levels (25, 50 and 100% of recommended dose of potassium, RD...
TL;DR: The results showed that AOA outnumber ammonia-oxidizing bacteria (AOB) by up to four orders of magnitude in cave sediments, and data suggest that despite the alkaline conditions within the cave, the low NH3 concentrations measured continue to favor growth of AOA over AOB populations.
Abstract: Nitrification represents one of the key steps in the global nitrogen cycle. While originally considered an exclusive metabolic capability of bacteria, the identification of the Thaumarchaeota revealed that ammonia-oxidizing archaea (AOA) are also important contributors to this process, particularly in acidic environments. Nonetheless, the relative contribution of AOA to global nitrification remains difficult to ascertain, particularly in underexplored neutrophilic and alkalinophilic terrestrial systems. In this study we examined the contribution of AOA to nitrification within alkaline (pH 8.3–8.7) cave environments using quantitative PCR, crenarchaeol lipid identification and measurement of potential nitrification rates. Our results showed that AOA outnumber ammonia-oxidizing bacteria (AOB) by up to four orders of magnitude in cave sediments. The dominance of Thaumarchaeota in the archaeal communities was confirmed by both archaeal 16S rRNA gene clone library and membrane lipid analyses, while pot...
TL;DR: Predicted functional analysis in both the hot springs were found to be affiliated with carbohydrate, amino acids, energy, vitamins and cofactor, nucleotide, membrane transport metabolic pathways, and the genes involved in them, although their intensity of occurrence was varying as analyzed through PICRUSt and Tax4Fun probably due to physicochemical parameters prevailing around each hot spring.
Abstract: Odisha (East India) is home to several hot springs, of which Atri and Taptapani are the two with variation in temperature and located in the Mahanadi geothermal province having altitude 120 and 1800 ft., respectively, above sea level. Average temperature of Atri hot spring is as higher as 58 ± 5°C as compared to 48 ± 5°C of Taptapani. In-depth analysis of the microbial diversity of these hot springs through 16S rRNA deep sequencing analysis, targeting V3 region was performed using Illumina bar-coded sequencing platform. Existence of higher microbial diversity in Atri hot spring (1662 OTUs; 2708 species) as compared to Taptapani (1561 Operational Taxonomic Units [OTUs]; 2045 species) is supported by higher value of diversity indices for Atri (6.24, Shannon; 0.95, Simpson) than Taptapani (4.03, Shannon; 0.79, Simpson), probably due to favorable influence of environmental parameters around it. Irrespective of the four databases (GREENGENE, M5RNA, Ribosomal Database Project [RDP], and Small Subunit [S...
TL;DR: Biotic crusts from the Early Pleistocene Rumena Cave in NW Sicily have been analyzed from a geomicrobiological point of view as mentioned in this paper, and they consist largely of scleractinians and of subordina...
Abstract: Biotic crusts occurring in the Early Pleistocene Rumena Cave, in NW Sicily, have been analyzed from a geomicrobiological point of view. The crusts consist largely of scleractinians and of subordina...
TL;DR: In this article, weathering experiments of calcium-montmorillonite were conducted using Paenibacillus sp. strain SB-6 for 70 days and the results indicated that the Si4+, Al3+, Ca2+ and Na+ concentrations in the medium of the biotic experiments were evidently higher than those of the abiotic experiments, and that Paengacillus could help the transformation of partial montmorillonites into an illite-montorillonite mixed-layer.
Abstract: Investigation of the weathering of silicate minerals is helpful to understand the process of soil development, cycling of nutrient elements, and potential applications in fixation of carbon dioxide from the atmosphere through carbonate precipitation. In this study, weathering experiments of calcium-montmorillonite were conducted using Paenibacillus sp. strain SB-6 for 70 days. The results indicated that the Si4+, Al3+, Ca2+ and Na+ concentrations in the medium of the biotic experiments were evidently higher than those of the abiotic experiments, and that Paenibacillus sp. could help the transformation of partial montmorillonite into an illite–montmorillonite mixed-layer. In the process of illitization, K+ went into the interlayer of montmorillonite and hydrated Ca2+ and Na+ released from it. In the late stage of the experiments, the Ca2+ released from montmorillonite combined with carbonate ions generated by the bacterial metabolism, forming calcite.
TL;DR: In this article, the authors used the model dissimilatory iron-reducing bacterium (DIRB) Geobacter sulfurreducens to study Fe(III)-oxide vs. Fe(II)-phyllosilicate reduction in a range of subsurface materials.
Abstract: Dissimilatory microbial reduction of solid-phase Fe(III)-oxides and Fe(III)-bearing phyllosilicates (Fe(III)-phyllosilicates) is an important process in anoxic soils, sediments and subsurface materials. Although various studies have documented the relative extent of microbial reduction of single-phase Fe(III)-oxides and Fe(III)-phyllosilicates, detailed information is not available on interaction between these two processes in situations where both phases are available for microbial reduction. The goal of this research was to use the model dissimilatory iron-reducing bacterium (DIRB) Geobacter sulfurreducens to study Fe(III)-oxide vs. Fe(III)-phyllosilicate reduction in a range of subsurface materials and Fe(III)-oxide stripped versions of the materials. Low-temperature (12 K) Mossbauer spectroscopy was used to infer changes in the relative abundances of Fe(III)-oxide, Fe(III)-phyllosilicate, and phyllosilicate-associated Fe(II) (Fe(II) phyllosilicate). A Fe partitioning model was employed to anal...
TL;DR: Multivariate analysis showed that As bioavailability in soil was an important driver affecting microbial diversity, and biomass assessed by EL-FAMEs and qPCR generally decreased under higher bioavailable As, as well as enzyme activities and C substrate utilization.
Abstract: Microbial genetic, structural and functional diversity was assessed in response to arsenic (As) pollution in a former gold mine soil. Ester-linked fatty acid methyl ester (EL-FAME), quantitative PCR (qPCR), denaturating gradient gel electrophoresis (DGGE), enzyme activities and MicroResp techniques were used.Multivariate analysis showed that As bioavailability in soil was an important driver affecting microbial diversity. Microbial biomass assessed by EL-FAMEs and qPCR generally decreased under higher bioavailable As, as well as enzyme activities and C substrate utilization. Conversely, actinomycetes and fungal biomass increased along with total As content suggesting the selection of more resistant species.
TL;DR: In this article, the authors evaluated the impact of fly ash on selected microbiological properties of soils in the vicinity of an electric power plant and revealed the stimulation of dehydrogenases activity (DHA) and microbial respiration (RESP).
Abstract: The goal of this study was to evaluate the impact of alkaline fly ash on selected microbiological properties of soils in the vicinity of an electric power plant. The specific objectives were as follows: firstly, to determine the metabolic activity and functional diversity of soils, such as biological indicators of acidic soil; secondly, to compare the changes in microbial diversity indicators based on the distance from dumping site of fly ash located in the vicinity of electric power plant; thirdly, to determine the metabolic profile pattern in soils with different pH levels. The study revealed the stimulation of dehydrogenases activity (DHA) and microbial respiration (RESP) by fly ash. It contributed to the increase in metabolic profile expressed as community-level physiological profile differences. The enrichment of fly ash affected the soil microbial characteristics. The values of DHA and RESP decreased with increasing distance from the emission source, whereas the number of utilized substrates...
TL;DR: In this article, the composition of microbial communitie is studied in soil microorganisms living in close contact with minerals play key roles in the biogeochemical cycling of elements, soil formation, and plant nutrition.
Abstract: Soil microorganisms living in close contact with minerals play key roles in the biogeochemical cycling of elements, soil formation, and plant nutrition. Yet, the composition of microbial communitie ...
TL;DR: In this paper, a series of sterile control experiments without bacteria were run simultaneously, and the results demonstrated that the quantity of precipitate in the biotic experiments increased gradually with the incubation time; precipitate was not obtained in the abiotic experiments.
Abstract: To better understand the mechanism of formation of carbonate minerals by microbes, culture experiments with Arthrobacter sp. strain MF-2 were carried out using M2 medium without carbonate ions for 50 days. A series of sterile control experiments without bacteria were run simultaneously. During the incubation, cell density, the quantity of precipitate, the extracellular polysaccharide (EPS) content, the activity of carbonic anhydrase (CA), the low molecular weight organic acid concentration, the pH, the electrical conductivity, and the Ca2+ and Mg2+ concentrations of the medium were determined. The morphologies of the precipitated carbonates were observed using scanning electron microscopy, and their mineral species were determined by X-ray diffraction. The results demonstrated that the quantity of precipitate in the biotic experiments increased gradually with the incubation time; precipitate was not obtained in the abiotic experiments. The average precipitation rate correlated positively with the ...
TL;DR: In this article, Bacteria resistant to As(III), As(V), Cr, Cr, Co, Cu, Cd, Hg, Ni, Pb, Se, and Zn were isolated from the wastewater treatment plant of Kasur, Pakistan.
Abstract: Industrial progress has resulted in threatening concentrations of toxic metals in various areas of the world. Bioremediation is an economical alternative to chemical methods. Bacteria resistant to As(III), As(V), Cr, Co, Cu, Cd, Hg, Ni, Pb, Se, and Zn were isolated from the wastewater treatment plant of Kasur, Pakistan. Highest resistance against all metals was exhibited by MX-1, MX-3, MX-4, and MX-5. The isolates possessed dual ability to oxidize as well as to reduce As. Highest As(V) reduction (454 µM) was exhibited by MX-1, while most As(III) oxidation was shown by MX-3 (170 µM). The isolates were also capable of reducing Cr(VI), and maximum Cr(VI) reduction (500 µM) was exhibited by MX-3. Transformation of DH5α with MX-1 plasmid showed that resistance genes for As(III), As(V), Cr, Cd, Se, Hg, and Ni were plasmid borne, while in case of MX-3, resistance genes for As(III), As(V), Co, Cu, Se, Pb, Zn, and Ni were present on plasmid. MX-1 and MX-3 were also positive for auxin production (37 and 32....
TL;DR: Substantial increase in isolate densities at the undercanopy habitats, especially in the interdune depression with higher substrate stability raising the accumulation of OM, highlights the role of shrubs as “islands of fertility” for microfungal communities at NRS.
Abstract: We examined the depthwise distribution of microfungi through 0–40 cm of sandy profiles under bare surface and different shrub species at the Nizzana research site (NRS) in the Negev Desert, Israel. A total of 125 species from 61 genera were isolated using the soil dilution plate method. At the topsoil of all profiles melanin-containing species with large multicellular conidia predominated. In the middle depths at the majority of the profiles, mesic group of microfungi, Penicillium spp. substantially increased in abundance. Density of microfungal isolates decreased with depth under shrubs and did not substantially vary in the nonshaded profiles, highly positively correlating with electrical conductivity and organic matter (OM) content. Substantial increase in isolate densities at the undercanopy habitats, especially in the interdune depression with higher substrate stability raising the accumulation of OM, highlights the role of shrubs as “islands of fertility” for microfungal communities at NRS.