Browsing by Subject "PH"

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  • Pathak, Lakshmi; Singh, Vineeta; Niwas, Ram; Osama, Khwaja; Khan, Saif; Haque, Shafiul; Tripathi, C. K. M.; Mishra, B. N. (2015)
    Cholesterol oxidase (COD) is a bi-functional FAD-containing oxidoreductase which catalyzes the oxidation of cholesterol into 4-cholesten-3-one. The wider biological functions and clinical applications of COD have urged the screening, isolation and characterization of newer microbes from diverse habitats as a source of COD and optimization and over-production of COD for various uses. The practicability of statistical/artificial intelligence techniques, such as response surface methodology (RSM), artificial neural network (ANN) and genetic algorithm (GA) have been tested to optimize the medium composition for the production of COD from novel strain Streptomyces sp. NCIM5500. All experiments were performed according to the five factor central composite design (CCD) and the generated data was analysed using RSM and ANN. GA was employed to optimize the models generated by RSM and ANN. Based upon the predicted COD concentration, the model developed with ANN was found to be superior to the model developed with RSM. The RSM-GA approach predicted maximum of 6.283 U/mL COD production, whereas the ANN-GA approach predicted a maximum of 9.93 U/mL COD concentration. The optimum concentrations of the medium variables predicted through ANN-GA approach were: 1.431 g/50 mL soybean, 1.389 g/50 mL maltose, 0.029 g/50 mL MgSO4, 0.45 g/50 mL NaCl and 2.235 ml/50 mL glycerol. The experimental COD concentration was concurrent with the GA predicted yield and led to 9.75 U/mL COD production, which was nearly two times higher than the yield (4.2 U/mL) obtained with the un-optimized medium. This is the very first time we are reporting the statistical versus artificial intelligence based modeling and optimization of COD production by Streptomyces sp. NCIM 5500.
  • Ren, Hao; Yang, Peng; Winnik, Francoise M. (2020)
    Azo dyes, such as azobenzene, are able to convert absorbed light into motion or deformation on the macroscopic scale on the basis of their remarkable ability to undergo repeatedly and in 100% yield reversibletrans-to-cisphotoisomerization. Current needs for multiresponsive and fast photoswitches have led to the development of heteroaryl azo dyes, such as azopyridine. This remarkable azo compound combines the photoresponse of the azo chromophore with the chemistry of the pyridine ring, in particular its responsiveness to changes in pH and its ability to form hydrogen- and halogen-bonds. This mini-review summarizes key features of the photoisomerization of polymer-tethered azopyridine in aqueous media and describes a few recent research accomplishments in emerging areas that have benefited of the fast thermalcis-to-transrelaxation characteristics of azopyridinium or H-bonded azopyridine. It also discusses the effects of the photoisomerization of azopyridine on the thermoresponsive properties of azopyridine-tethered heat-sensitive polymers. Overall, azopyridine is a highly versatile actuator to consider when designing photo/multiresponsive polymeric materials.
  • Sun, Hui; Santalahti, Minna; Pumpanen, Jukka; Köster, Kajar; Berninger, Frank; Raffaello, Tommaso; Asiegbu, Fred O.; Heinonsalo, Jussi (2016)
    Soil microbial responses to fire are likely to change over the course of forest recovery. Investigations on long-term changes in bacterial dynamics following fire are rare. We characterized the soil bacterial communities across three different times post fire in a 2 to 152-year fire chronosequence by Illumina MiSeq sequencing, coupled with a functional gene array (GeoChip). The results showed that the bacterial diversity did not differ between the recently and older burned areas, suggesting a concomitant recovery in the bacterial diversity after fire. The differences in bacterial communities over time were mainly driven by the rare operational taxonomic units (OTUs <0.1%). Proteobacteria (39%), Acidobacteria (34%) and Actinobacteria (17%) were the most abundant phyla across all sites. Genes involved in C and N cycling pathways were present in all sites showing high redundancy in the gene profiles. However, hierarchical cluster analysis using gene signal intensity revealed that the sites with different fire histories formed separate clusters, suggesting potential differences in maintaining essential biogeochemical soil processes. Soil temperature, pH and water contents were the most important factors in shaping the bacterial community structures and function. This study provides functional insight on the impact of fire disturbance on soil bacterial community.
  • Syrjänen, Leo; Valanne, Susanna; Kuuslahti, Marianne; Tuomela, Tea; Sriram, Ashwin; Sanz, Alberto; Jacobs, Howard T.; Rämet, Mika; Parkkila, Seppo (2015)
    Background: Carbonic anhydrases (CAs, EC 4.2.1.1) are ubiquitous enzymes that catalyze the reversible hydration reaction of carbon dioxide. CAs are present as six structurally divergent enzyme families: alpha, beta, gamma, delta, zeta and eta. beta-CAs have a wide distribution across different species including invertebrates. Previously, we showed that Drosophila melanogaster beta-CA is a highly active mitochondrial enzyme. In this study, we investigated the function of Drosophila beta-CA by silencing the expression of the beta-CA gene using UAS/GAL4-based RNA interference (RNAi) in Drosophila in vivo. Results: Crossing beta-CA RNAi lines over ubiquitous Actin driver flies did not produce any viable progeny, indicating that beta-CA expression is required for fly development. RNAi silencing of beta-CA ubiquitously in adult flies did not affect their survival rate or function of mitochondrial electron transport chain. Importantly, beta-CA RNAi led to impaired reproduction. All beta-CA knockdown females were sterile, and produced few or no eggs. Whole ovaries of knockdown females looked normal but upon cadherin staining, there was an apparent functional defect in migration of border cells, which are considered essential for normal fertilization. Conclusions: These results indicate that although Drosophila beta-CA is dispensable for survival of adult flies, it is essential for female fertility.
  • Suetake, Mizuki; Nakano, Yuriko; Furuki, Genki; Ikehara, Ryohei; Komiya, Tatsuki; Kurihara, Eitaro; Morooka, Kazuya; Yamasaki, Shinya; Ohnuki, Toshihiko; Horie, Kenji; Takehara, Mami; Law, Gareth T.W.; Bower, William; Grambow, Bernd; Ewing, Rodney C.; Utsunomiya, Satoshi (2019)
    To understand the chemical durability of highly radioactive cesium-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant in March 2011, we have, for the first time, performed systematic dissolution experiments with CsMPs isolated from Fukushima soils (one sample with 108 Bq and one sample with 57.8 Bq of Cs-137) using three types of solutions: simulated lung fluid, ultrapure water, and artificial sea water, at 25 and 37 degrees C for 1-63 days. The Cs-137 was released rapidly within three days and then steady-state dissolution was achieved for each solution type. The steady-state Cs-137 release rate at 25 degrees C was determined to be 4.7 x 10(3), 1.3 x 10(3), and 1.3 x 10(3) Bq . m(-2)s(-1) for simulated lung fluid, ultrapure water, and artificial sea water, respectively. This indicates that the simulated lung fluid promotes the dissolution of CsMPs. The dissolution of CsMPs is similar to that of Si-based glass and is affected by the surface moisture conditions. In addition, the Cs release from the CsMPs is constrained by the rate-limiting dissolution of silicate matrix. Based on our results, CsMPs with similar to 2 Bq, which can be potentially inhaled and deposited in the alveolar region, are completely dissolved after >35 years. Further, CsMPs could remain in the environment for several decades; as such, CsMPs are important factors contributing to the long-term impacts of radioactive Cs in the environment. (C) 2019 Elsevier Ltd. All rights reserved.
  • Tenca, Andrea; de Bortoli, Nicola; Mauro, Aurelio; Frazzoni, Marzio; Savarino, Edoardo; Massironi, Sara; Russo, Salvatore; Bertani, Lorenzo; Marchi, Santino; Penagini, Roberto (2017)
    Background: The factors influencing new markers of gastro-esophageal reflux disease detected by impedance-pH monitoring - mean nocturnal baseline impedance (MNBI) and post-reflux swallow-induced peristaltic wave (PSPW) index - need to be evaluated. Aim: To compare endoscopy-negative heartburn with chronic autoimmune atrophic gastritis (CAAG). Materials and methods: 24 patients with CAAG, 25 with non-erosive reflux disease (NERD) and 25 with functional heartburn (FH) were included. In all patients the main impedance-pH monitoring parameters were calculated. Results: CAAG and NERD patients had a number of reflux events (non-acid ones being more common among the former group) which was higher than that found in FH (p <0.001). MNBI decreased progressively in FH (> 3000 Ohm), CAAG (> 2000 Ohm) and NERD (<1000 Ohm) patients (p = 0.0046). The PSPW index was similar between CAAG and NERD patients but significantly lower in comparison to FH (p <0.0001). Conclusion: Patients with CAAG have evidence of non-acid reflux based on the high number of reflux events and confirmed by low values of MNBI and PSPW index. MNBI is a strong marker of acid/non-acid reflux-induced mucosal damage, whereas the PSPW index can reliably discriminate patients with reflux from those with FH, independently of the acidity of refluxate. (C) 2017 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.
  • Kouzi, Afamia; Puranen, Matti; Kontro, Merja H. (2020)
    Biogas production from sewage sludge volatile solids (VS) by anaerobic digestion slows down towards the end of the process, among inhibitory factors being pH increase upon ammonia accumulation, poorly digestible biomaterials, and high fixed solid (FS) content. The possibility of concentrating the digested sludge VS (41.7-56.6% on a dry weight basis) by surface and bottom layer separation with biogas post-production was studied. Furthermore, the potential to recycle concentrated VS and digested sludge back to the process after adjusting pH 7.0 to optimal for biogas-producing microbes and after acid, alkali, thermal, and sonolytic treatments was examined. In general, pH 7.0 control alone improved biogas production from the recycled digested sludge the most. An equally good improvement in biogas production was achieved by recycling the digested sludge, which had been heated until ammonia had evaporated and the pH dropped to 7.0 (1-2 h, 75 degrees C), and at the same time, VS was degraded. The biogas production from the sonicated and recycled sludge was almost as good as from the pH-adjusted, or heat-treated recycled sludge. After the acid and base treatments of the digested sludge, the recycled sludge yielded often the lowest biogas volume, as the added chemicals increased the FS concentration, which proved to be a more important inhibitory factor than poorly degradable VS. The high FS content significantly reduced the benefits of the treatments. By separating the surface and bottom layers with biogas post-production, the surface layer of VS was concentrated to 51.6-61.8%, while different compositions of the layers affected the biogas production.
  • Pernu, Noora; Keto-Timonen, Riikka; Lindström, Miia; Korkeala, Hannu (2020)
    Clostridium botulinum is a significant food safety concern due to its ability to produce highly potent neurotoxin and resistant endospores. Vegetarian sausages have become a popular source of plant protein and alternative for meat products. While vegetarian sausages have not been linked to botulism, numerous outbreaks due to preserved vegetables suggest a frequent occurrence of C. botulinum spores in the raw material. The product formulation of vegetarian sausages involves limited NaCl and preservatives, and shelf-lives may be several months. The safety of vegetarian sausages thus relies mainly on heat treatment and chilled storage. The main food safety concern is C. botulinum Group II that can grow and produce toxin at refrigeration temperatures. Here we show a high overall prevalence (32%) of C. botulinum in 74 samples of vegetarian sausages from seven producers. Both Groups I and II strains and genes for neurotoxin types A, B, E and F were detected in the products. The highest cell counts (1200 spores/kg) were observed for C. botulinum Group II in products with remaining shelf-lives of 6 months at the time of purchase. We conclude that vacuum-packaged vegetarian sausage products frequently contain C. botulinum spores and may possess a high risk of C. botulinum growth and toxin production. Chilled storage below 3°C and thorough reheating before consumption are warranted.
  • Greis, M; Seppa, L; Venalainen, E. R; Lyytikainen, A; Tuorila, H (2018)
    Abstract The impact of iodized table salt on the sensory quality of wheat bread, bologna sausage and pickled cucumber was studied. Table salt (NaCl) content of the products was 1.7, 1.2 and 1.7 g/100 g, respectively. Iodine, added as potassium iodide (KI), was incorporated at levels 0, 25, 50 and 100 mg per kg table salt. Odor, flavor, appearance, and texture were evaluated using deviation from reference descriptive analysis (12 panelists, 4 replicates). Each sample was rated against the non-iodized reference sample (0 mg iodine). The retention of iodine during processing and storage was determined chemically. The iodine level 25 mg/kg, corresponding to current recommendations, did not cause sensory changes in tested products. In sausage, 50 and 100 mg/kg levels were associated with minor changes in texture and color. The maximum retention of iodine was 83% for bread, 98% for sausage, and 51% for cucumber. We did not find any sensory obstacle to using iodized table salt in industrial food production. Due to loss in manufacturing and inadequate intakes, iodine additions higher than currently recommended should be considered.
  • Bach, Lennart T.; Taucher, Jan; Boxhammer, Tim; Ludwig, Andrea; Achterberg, Eric P.; Alguero-Muniz, Maria; Anderson, Leif G.; Bellworthy, Jessica; Buedenbender, Jan; Czerny, Jan; Ericson, Ylva; Esposito, Mario; Fischer, Matthias; Haunost, Mathias; Hellemann, Dana; Horn, Henriette G.; Hornick, Thomas; Meyer, Jana; Sswat, Michael; Zark, Maren; Riebesell, Ulf; Kristineberg KOSMOS Consortium (2016)
    Every year, the oceans absorb about 30% of anthropogenic carbon dioxide (CO2) leading to a re-equilibration of the marine carbonate system and decreasing seawater pH. Today, there is increasing awareness that these changes-summarized by the term ocean acidification (OA)-could differentially affect the competitive ability of marine organisms, thereby provoking a restructuring of marine ecosystems and biogeochemical element cycles. In winter 2013, we deployed ten pelagic mesocosms in the Gullmar Fjord at the Swedish west coast in order to study the effect of OA on plankton ecology and biogeochemistry under close to natural conditions. Five of the ten mesocosms were left unperturbed and served as controls (similar to 380 mu atm pCO(2)), whereas the others were enriched with CO2-saturated water to simulate realistic end-of-the-century carbonate chemistry conditions (mu 760 mu atm pCO(2)). We ran the experiment for 113 days which allowed us to study the influence of high CO2 on an entire winter-to-summer plankton succession and to investigate the potential of some plankton organisms for evolutionary adaptation to OA in their natural environment. This paper is the first in a PLOS collection and provides a detailed overview on the experimental design, important events, and the key complexities of such a "long-term mesocosm" approach. Furthermore, we analyzed whether simulated end-of-the-century carbonate chemistry conditions could lead to a significant restructuring of the plankton community in the course of the succession. At the level of detail analyzed in this overview paper we found that CO2-induced differences in plankton community composition were non-detectable during most of the succession except for a period where a phytoplankton bloom was fueled by remineralized nutrients. These results indicate: (1) Long-term studies with pelagic ecosystems are necessary to uncover OA-sensitive stages of succession. (2) Plankton communities fueled by regenerated nutrients may be more responsive to changing carbonate chemistry than those having access to high inorganic nutrient concentrations and may deserve particular attention in future studies.
  • Carstensen, Jacob; Chierici, Melissa; Gustafsson, Bo G.; Gustafsson, Erik (2018)
    Coastal pH and total alkalinity are regulated by a diverse range of local processes superimposed on global trends of warming and ocean acidification, yet few studies have investigated the relative importance of different processes for coastal acidification. We describe long-term (1972-2016) and seasonal trends in the carbonate system of three Danish coastal systems demonstrating that hydrological modification, changes in nutrient inputs from land, and presence/absence of calcifiers can drastically alter carbonate chemistry. Total alkalinity was mainly governed by conservative mixing of freshwater (0.73-5.17mmolkg(-1)) with outer boundary concentrations (similar to 2-2.4mmolkg(-1)), modulated seasonally and spatially (similar to 0.1-0.2mmolkg(-1)) by calcifiers. Nitrate assimilation by primary production, denitrification, and sulfate reduction increased total alkalinity by almost 0.6mmolkg(-1) in the most eutrophic system during a period without calcifiers. Trends in pH ranged from -0.0088year(-1) to 0.021year(-1), the more extreme of these mainly driven by salinity changes in a sluice-controlled lagoon. Temperature increased 0.05 degrees Cyr(-1) across all three systems, which directly accounted for a pH decrease of 0.0008year(-1). Accounting for mixing, salinity, and temperature effects on dissociation and solubility constants, the resulting pH decline (0.0040year(-1)) was about twice the ocean trend, emphasizing the effect of nutrient management on primary production and coastal acidification. Coastal pCO(2) increased similar to 4 times more rapidly than ocean rates, enhancing CO2 emissions to the atmosphere. Indeed, coastal systems undergo more drastic changes than the ocean and coastal acidification trends are substantially enhanced from nutrient reductions to address coastal eutrophication.
  • Kickova, Eva; Salmaso, Stefano; Mastrotto, Francesca; Caliceti, Paolo; Urtti, Arto (2021)
    Posterior segment eye diseases are mostly related to retinal pathologies that require pharmacological treatments by invasive intravitreal injections. Reduction of frequent intravitreal administrations may be accomplished with delivery systems that provide sustained drug release. Pullulan-dexamethasone conjugates were developed to achieve prolonged intravitreal drug release. Accordingly, dexamethasone was conjugated to similar to 67 kDa pullulan through hydrazone bond, which was previously found to be slowly cleavable in the vitreous. Dynamic light scattering and transmission electron microscopy showed that the pullulan-dexamethasone containing 1:20 drug/glucose unit molar ratio (10% w/w dexamethasone) self-assembled into nanoparticles of 461 +/- 30 nm and 402 +/- 66 nm, respectively. The particles were fairly stable over 6 weeks in physiological buffer at 4, 25 and 37 degrees C, while in homogenized vitreous at 37 degrees C, the colloidal assemblies underwent size increase over time. The drug was released slowly in the vitreous and rapidly at pH 5.0 mimicking lysosomal conditions: 50% of the drug was released in about 2 weeks in the vitreous, and in 2 days at pH 5.0. In vitro studies with retinal pigment epithelial cell line (ARPE-19) showed no toxicity of the conjugates in the cells. Flow cytometry and confocal microscopy showed cellular association of the nanoparticles and intracellular endosomal localization. Overall, pullulan conjugates showed interesting features that may enable their successful use in intravitreal drug delivery.
  • Tiainen, Tony; Lobanova, Marina; Karjalainen, Erno; Tenhu, Heikki; Hietala, Sami (2020)
    Nanodiamonds (NDs) can considerably improve the mechanical and thermal properties of polymeric composites. However, the tendency of NDs to aggregate limits the potential of these non-toxic, mechanically- and chemically-robust nanofillers. In this work, tough, flexible, and stimuli-responsive polyelectrolyte films composed of cross-linked poly(butyl acrylate-co-dimethylaminoethyl methacrylate) (P(BA-co-DMAEMA)) were prepared by photopolymerization. The effects of the added carboxylate-functionalized NDs on their mechanical and stimuli-responsive properties were studied. When the negatively charged NDs were added to the polymerization media directly, the mechanical properties of the films changed only slightly, because of the uneven distribution of the aggregated NDs in the films. In order to disperse and distribute the NDs more evenly, a prepolymerized polycation block copolymer complexing agent was used during the photopolymerization process. This approach improved the mechanical properties of the films and enhanced their thermally-induced, reversible phase-transition behavior.
  • Jansson, Anna; Lischka, Silke; Boxhammer, Tim; Schulz, Kai G.; Norkko, Joanna (2016)
    Anthropogenic carbon dioxide (CO2) emissions are causing severe changes in the global inorganic carbon balance of the oceans. Associated ocean acidification is expected to pose a major threat to marine ecosystems worldwide, and it is also expected to be amplified in the Baltic Sea where the system is already exposed to relatively large natural seasonal and diel pH fluctuations. We studied the responses of larvae of the benthic key species Macoma balthica to a range of future CO2 scenarios using six similar to 55 m(3) mesocosms encompassing the entire pelagic community. The mesocosms were deployed in the northern Baltic Sea in June 2012. We focused on the survival, growth and subsequent settlement process of Macoma balthica when exposed to different levels of future CO2. The size and time to settlement of M. balthica increased along the CO2 gradient, suggesting a developmental delay. With ongoing climate change, both the frequency and extent of regularly occurring high CO2 conditions are likely to increase, and a permanent pH decrease will likely occur. The strong impact of increasing CO2 levels on early-stage bivalves is alarming as these stages are crucial for sustaining viable populations, and a failure in their recruitment would ultimately lead to negative effects on the population.
  • Nordström, Tommy; Zhenyu, Gao; Andersson, Leif C.; Åkerman, Karl E. O. (2020)
    Self-renewing neural stem cells and progenitor cells are cell populations that generate radial glial cells and neurons through asymmetric division. Regulation of intracellular pH in stem cells with high metabolic activity is critical for both cell signaling and proliferation. We have recently found that a S0859-inhibitable electrogenic Na+/HCO3- co-transporter (NBCe1, Slc4a4), is the primary pH(i) regulatory mechanism in stem cell-derived radial glial-like cells. Here we show, by using the voltage-sensitive fluorescent dye DiBAC 4(3) and BCECF, a pH-sensitive dye, that an antioxidant, tannic acid (100 mu M), can inhibit potassium- and calcium-dependent rapid changes in membrane potential and NBCe1 mediated pH i regulation in brain-derived glial-like cells in vitro. Furthermore, neural stem cell differentiation and neurosphere formation (proliferation) were completely inhibited by tannic acid. The present study provides evidence that tannic acid is a natural inhibitor of NBCe1. It is tempting to speculate that tannic acid or related compounds that inhibits NBCe1-mediated pH(i) regulation in glial-like cells may also have bearing on the treatment of glial neoplasms. NeuroReport 31: 57-63 Copyright (c) 2019 The Author(s). Published by Wolters Kluwer Health, Inc.
  • Adamczyk, Bartosz; Simon, Judy; Kitunen, Veikko; Adamczyk, Sylwia; Smolander, Aino (2017)
    Tannins, an abundant group of plant secondary compounds, raise interest in different fields of science, owing to their unique chemical characteristics. In chemical ecology, tannins play a crucial role in plant defense against pathogens, herbivores, and changing environmental conditions. In the food industry and in medicine, tannins are important because of their proven positive effect on human health and disease treatment, Such wide interests fueled studies on tannin chemistry, especially on their flagship ability to precipitate proteins. In this Review, we expand the basic knowledge on tannin chemistry to the newest insights from the field. We focus especially on tannin reactions with different non-protein organic N compounds, as well as the complex interactions of tannins with enzymes, resulting in either an increase or decrease in enzyme activity.
  • Niinikoski-Fusswinkel, Paula; Purkamo, Lotta; Karhu, Juha (2020)
    This study examines the effect of poly-aluminium chloride (PACl) pre-treatment on the biological purification process taking place during managed aquifer recharge (MAR). PACl treatment is used in waste and surface water treatment to remove organic material. PACl can decrease the organic carbon contents of water significantly. However, aluminium is toxic to microbes, which may be detrimental when the PACl treatment is followed by infiltration into an aquifer (MAR). In this study the effect of pre-treatment with PACl on the water purification process in MAR was examined, by using sediment from a MAR site in four test columns. Two columns were filled with PACl-treated water, and the remaining ones with river water without PACl. The residence time of water in the columns was raised from direct sampling gradually to 64 days. Among the parameters monitored were the pH of the water, microbial activity and the decomposition of dissolved organic carbon (DOC). The results showed active decomposition in all columns. Decomposition of organic matter, and the amount of living/active microbial cells, was marginally higher in the untreated water, which could imply a better functioning MAR system. However, this may also be due to higher DOC starting concentration.
  • Malkamäki, Aapo; Meunier, Brigitte; Reidelbach, Marco; Rich, Peter R.; Sharma, Vivek (2019)
    Cytochrome c oxidases (CcOs) in the respiratory chains of mitochondria and bacteria are primary consumers of molecular oxygen, converting it to water with the concomitant pumping of protons across the membrane to establish a proton electrochemical gradient. Despite a relatively well understood proton pumping mechanism of bacterial CcOs, the role of the H channel in mitochondrial forms of CcO remains debated. Here, we used site-directed mutagenesis to modify a central residue of the lower span of the H channel, Q413, in the genetically tractable yeast Saccharomyces cerevisiae. Exchange of Q413 to several different amino acids showed no effect on rates and efficiencies of respiratory cell growth, and redox potential measurements indicated minimal electrostatic interaction between the 413 locus and the nearest redox active component heme a. These findings clearly exclude a primary role of this section of the H channel in proton pumping in yeast CcO. In agreement with the experimental data, atomistic molecular dynamics simulations and continuum electrostatic calculations on wildtype and mutant yeast CcOs highlight potential bottlenecks in proton transfer through this route. Our data highlight the preference for neutral residues in the 413 locus, precluding sufficient hydration for formation of a proton conducting wire.
  • Qin, Huayu; Wang, Shang; Feng, Kai; He, Zhili; Virta, Marko P. J.; Hou, Weiguo; Dong, Hailiang; Deng, Ye (2019)
    Sulfate reduction is an important biogeochemical process in the ecosphere; however, the major taxa of sulfate reducers have not been fully identified. Here, we used epicPCR (Emulsion, Paired Isolation, and Concatenation PCR) technology to identify the phylogeny of sulfate-reducing prokaryotes (SRP) in sediments from Tibetan Plateau saline lakes. A total of 12,519 OTUs and 883 SRP-OTUs were detected in ten lakes by sequencing of 16S rRNA gene PCR amplicons and epicPCR products of fused 16S rRNA plus dsrB gene, respectively, with Proteobacteria, Firmicutes, and Bacteroidetes being the dominant phyla in both datasets. The 120 highly abundant SRP-OTUs (>1% in at least one sample) were affiliated with 17 described phyla, only 7 of which are widely recognized as SRP phyla. The majority of OTUs from both the whole microbial communities and the SRPs were not detected in more than one specific lake, suggesting high levels of endemism. The -diversity of the entire microbial community and SRP sub-community showed significant positive correlations. The pH value and mean water temperature of the month prior to sampling were the environmental determinants for the whole microbial community, while the mean water temperature and total nitrogen were the major environmental drivers for the SRP sub-community. This study revealed there are still many undocumented SRP in Tibetan saline lakes, many of which could be endemic and adapted to specific environmental conditions.