scholarly journals Geochemical Niches of Iron-Oxidizing Acidophiles in Acidic Coal Mine Drainage

2014 ◽  
Vol 81 (4) ◽  
pp. 1242-1250 ◽  
Author(s):  
Daniel S. Jones ◽  
Courtney Kohl ◽  
Christen Grettenberger ◽  
Lance N. Larson ◽  
William D. Burgos ◽  
...  
Keyword(s):  
Mine Drainage ◽  
Stream Water ◽  
Subsequent Treatment ◽  
Ecological Niches ◽  
Content Type ◽  
Somerset County ◽  
Dissolved Iron ◽  
Geochemical Parameters ◽  
Low Levels ◽  
Red Eyes

ABSTRACTA legacy of coal mining in the Appalachians has provided a unique opportunity to study the ecological niches of iron-oxidizing microorganisms. Mine-impacted, anoxic groundwater with high dissolved-metal concentrations emerges at springs and seeps associated with iron oxide mounds and deposits. These deposits are colonized by iron-oxidizing microorganisms that in some cases efficiently remove most of the dissolved iron at low pH, making subsequent treatment of the polluted stream water less expensive. We used full-cycle rRNA methods to describe the composition of sediment communities at two geochemically similar acidic discharges, Upper and Lower Red Eyes in Somerset County, PA, USA. The dominant microorganisms at both discharges were acidophilicGallionella-like organisms, “Ferrovum” spp., andAcidithiobacillusspp.ArchaeaandLeptospirillumspp. accounted for less than 2% of cells. The distribution of microorganisms at the two sites could be best explained by a combination of iron(II) concentration and pH. Populations of theGallionella-like organisms were restricted to locations with pH >3 and iron(II) concentration of >4 mM, whileAcidithiobacillusspp. were restricted to pH <3 and iron(II) concentration of <4 mM.Ferrovumspp. were present at low levels in most samples but dominated sediment communities at pH <3 and iron(II) concentration of >4 mM. Our findings offer a predictive framework that could prove useful for describing the distribution of microorganisms in acid mine drainage, based on readily accessible geochemical parameters.

scholarly journals Correlating Microbial Diversity Patterns with Geochemistry in an Extreme and Heterogeneous Environment of Mine Tailings

2014 ◽  
Vol 80 (12) ◽  
pp. 3677-3686 ◽  
Author(s):  
Jun Liu ◽  
Zheng-Shuang Hua ◽  
Lin-Xing Chen ◽  
Jia-Liang Kuang ◽  
Sheng-Jin Li ◽  
...  
Keyword(s):  
Microbial Diversity ◽  
Community Composition ◽  
Environmental Conditions ◽  
Mine Tailings ◽  
Large Scale ◽  
Hot Springs ◽  
Mine Drainage ◽  
Rrna Gene ◽  
Content Type ◽  
Geochemical Parameters

ABSTRACTRecent molecular surveys have advanced our understanding of the forces shaping the large-scale ecological distribution of microbes in Earth's extreme habitats, such as hot springs and acid mine drainage. However, few investigations have attempted dense spatial analyses of specific sites to resolve the local diversity of these extraordinary organisms and how communities are shaped by the harsh environmental conditions found there. We have applied a 16S rRNA gene-targeted 454 pyrosequencing approach to explore the phylogenetic differentiation among 90 microbial communities from a massive copper tailing impoundment generating acidic drainage and coupled these variations in community composition with geochemical parameters to reveal ecological interactions in this extreme environment. Our data showed that the overall microbial diversity estimates and relative abundances of most of the dominant lineages were significantly correlated with pH, with the simplest assemblages occurring under extremely acidic conditions and more diverse assemblages associated with neutral pHs. The consistent shifts in community composition along the pH gradient indicated that different taxa were involved in the different acidification stages of the mine tailings. Moreover, the effect of pH in shaping phylogenetic structure within specific lineages was also clearly evident, although the phylogenetic differentiations within theAlphaproteobacteria,Deltaproteobacteria, andFirmicuteswere attributed to variations in ferric and ferrous iron concentrations. Application of the microbial assemblage prediction model further supported pH as the major factor driving community structure and demonstrated that several of the major lineages are readily predictable. Together, these results suggest that pH is primarily responsible for structuring whole communities in the extreme and heterogeneous mine tailings, although the diverse microbial taxa may respond differently to various environmental conditions.

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

The effects of contaminated sediments of the Blesbok Spruit near Witbank on water quality and the toxicity thereof to Daphnia pulex

1999 ◽  
Vol 39 (10-11) ◽  
pp. 173-176 ◽  
Author(s):  
Liesl Hill ◽  
Sebastian Jooste
Keyword(s):  
Surface Water ◽  
Mine Drainage ◽  
Interstitial Water ◽  
Stream Water ◽  
Daphnia Pulex ◽  
Contaminated Sediments ◽  
Toxicity Tests ◽  
Major Route ◽  
Acute Toxicity Tests ◽  
Route Of Exposure

With the increasing focus on environmental issues, the objective of this study is to evaluate the potential impact of contaminated sediments of the Blesbok Spruit near Witbank - which receives acid mine drainage (AMD) inter alia - on biota. Direct transfer of chemicals from sediments to organisms is considered to be a major route of exposure for many species, and therefore focusing attention on sediment contamination and highlighting the fact that sediments are an important resource. Acute toxicity tests were performed on Daphnia pulex using both extracted sediment interstitial water and surface water. Chemical analyses were also performed on the sediment, interstitial water and surface water samples. The toxicity results suggest that metal toxicity adds significantly to the toxicity of the stream water which is enhanced by the effect of pH. The pH of the stream and interstitial water was consistently below 4.5.

When do job insecure employees adapt to change?

2019 ◽  
Vol 25 (3) ◽  
pp. 271-286 ◽  
Author(s):  
Kristi N. Lavigne ◽  
Victoria L. Whitaker ◽  
Dustin K. Jundt ◽  
Mindy K. Shoss
Keyword(s):  
Job Insecurity ◽  
Small Sample ◽  
Adaptive Performance ◽  
Work Behaviors ◽  
Content Type ◽  
Work Tasks ◽  
Main Effect ◽  
Low Levels ◽  
The Impact ◽  
The Relationship

Purpose The purpose of this paper is to examine the relationship between job insecurity and adaptive performance (AP), contingent on changes to core work tasks, which we position as a situational cue to employees regarding important work behaviors. Design/methodology/approach Employees and their supervisors were invited to participate in the study. Supervisors were asked to provide ratings of employees’ AP and changes to core tasks; employees reported on job insecurity. Findings As predicted, changes to core tasks moderated the relationship between job insecurity and AP. Job insecurity was negatively related to AP for those experiencing low levels of change, but was not related to AP for those experiencing high levels of change. Counter to expectations, no main effect of job insecurity was found. Research limitations/implications This study employed a fairly small sample of workers from two organizations, which could limit generalizability. Practical implications The study identifies changes to core tasks as a boundary condition for the job insecurity–AP relationship. Findings suggest that organizations may not observe deleterious consequences of job insecurity on AP when changes to core tasks are high. Originality/value Few researchers have examined boundary conditions of the impact of job insecurity on AP. Furthermore, inconsistent findings regarding the link between job insecurity and AP have emerged. This study fills the gap and expands upon previous research by examining changes to core tasks as a condition under which job insecurity does not pose an issue for AP.

Employee emotional displays in the extended service encounter

2019 ◽  
Vol 31 (1) ◽  
pp. 115-136 ◽  
Author(s):  
Magnus Soderlund ◽  
Hanna Berg
Keyword(s):  
Marketing Communications ◽  
Emotional Expressions ◽  
Service Firms ◽  
Still Images ◽  
Content Type ◽  
Emotional Displays ◽  
Service Setting ◽  
Low Levels ◽  
The Impact ◽  
Practical Implications

Purpose The purpose of this paper is to examine the impact of happiness expressed by service firm employees when they are depicted in marketing communications materials, such as printed ads and videos. Design/methodology/approach Two experiments were conducted in a fitness service setting, in which employee display of happiness was manipulated (low vs high). Findings Both experiments showed that expressions of high levels of happiness produced a more positive attitude toward the service employee than expressions of low levels of happiness. Moreover, the impact of the expression of happiness on the evaluation of the employee was mediated by several variables, which suggests that the influence of depicted employees’ emotional expressions can take several routes. Practical implications The results imply that service firms should not only be mindful about which specific employee they select for appearing in marketing communications materials, they should also pay attention to the emotional displays of selected employees. Originality/value The present study contributes to previous research by assessing a set of potential mediators to explain why displays of happiness influence consumers, and by examining these effects in a marketing communications setting in which the customer is exposed to still images or video-based representations of the employee. The present study also focuses explicitly on happiness rather than on smiles.

scholarly journals Coordination of K+Transporters in Neurospora: TRK1 Is Scarce and Constitutive, while HAK1 Is Abundant and Highly Regulated

2013 ◽  
Vol 12 (5) ◽  
pp. 684-696 ◽  
Author(s):  
Alberto Rivetta ◽  
Kenneth E. Allen ◽  
Carolyn W. Slayman ◽  
Clifford L. Slayman
Keyword(s):  
Atp Hydrolysis ◽  
Model Organism ◽  
Carbon Starvation ◽  
Transmembrane Helices ◽  
Content Type ◽  
Biochemical Genetic ◽  
Low Levels ◽  
Electrophysiological Characterization ◽  
Low K ◽  
Potassium Limitation

ABSTRACTFungi, plants, and bacteria accumulate potassium via two distinct molecular machines not directly coupled to ATP hydrolysis. The first, designated TRK, HKT, or KTR, has eight transmembrane helices and is folded like known potassium channels, while the second, designated HAK, KT, or KUP, has 12 transmembrane helices and resembles MFS class proteins. One of each type functions in the model organismNeurospora crassa, where both are readily accessible for biochemical, genetic, and electrophysiological characterization. We have now determined the operating balance between Trk1p and Hak1p under several important conditions, including potassium limitation and carbon starvation. Growth measurements, epitope tagging, and quantitative Western blotting have shown the geneHAK1to be much more highly regulated than isTRK1. This conclusion follows from three experimental results: (i) Trk1p is expressed constitutively but at low levels, and it is barely sensitive to extracellular [K+] and/or the coexpression ofHAK1; (ii) Hak1p is abundant but is markedly depressed by elevated extracellular concentrations of K+and by coexpression ofTRK1; and (iii) Carbon starvation slowly enhances Hak1p expression and depresses Trk1p expression, yielding steady-state Hak1p:Trk1p ratios of ∼500:1,viz., 10- to 50-fold larger than that in K+- and carbon-replete cells. Additionally, it appears that both potassium transporters can adjust kinetically to sustained low-K+stress by means of progressively increasing transporter affinity for extracellular K+. The underlying observations are (iv) that K+influx via Trk1p remains nearly constant at ∼9 mM/h when extracellular K+is progressively depleted below 0.05 mM and (v) that K+influx via Hak1p remains at ∼3 mM/h when extracellular K+is depleted below 0.1 mM.

Resolution of brain edema in severe brain injury at controlled high and low intracranial pressures

1984 ◽  
Vol 61 (4) ◽  
pp. 707-712 ◽  
Author(s):  
Meihong Cao ◽  
He Lisheng ◽  
Sun Shouzheng
Keyword(s):  
Cerebrospinal Fluid ◽  
Brain Injury ◽  
Brain Edema ◽  
External Ventricular Drainage ◽  
Blue Dye ◽  
Severe Brain Injury ◽  
Content Type ◽  
Intracranial Pressures ◽  
Low Levels ◽  
Cerebrospinal Fluid Protein

✓ A series of 87 patients with severe brain injury were studied. Intracranial pressure (ICP) monitoring and external ventricular drainage were used to control ICP at high and low levels. Clearance of ytterbium-169-labeled diethylenetriaminepentaacetic acid (169Yb-DTPA), Evans blue dye, and ventricular cerebrospinal fluid protein was measured at the two ICP levels over consecutive periods of 4 hours to confirm clearance of brain edema. The results support the hypothesis that brain edema is in part absorbed in the cerebrospinal fluid via transventricular flow.

Directional predictability between returns and volume in cryptocurrencies markets

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Panos Fousekis ◽  
Vasilis Grigoriadis
Keyword(s):  
High Volume ◽  
Stationary Time Series ◽  
Temporal Association ◽  
Informational Efficiency ◽  
Content Type ◽  
Low Levels ◽  
The Cross ◽  
Trading Volumes ◽  
Directional Predictability ◽  
The Empirical Analysis

Purpose This paper aims to identify and quantify directional predictability between returns and volume in major cryptocurrencies markets. Design/methodology/approach The empirical analysis relies on the cross-quantilogram approach that allows one to assess the temporal (lag-lead) association between two stationary time series at different parts of their joint distribution. The data are daily prices and trading volumes from four markets (Bitcoin, Ethereum, Ripple and Litecoin). Findings Extreme returns either positive or negative tend to lead high volume levels. Low levels of trading activity have in general no information content about future returns; high levels, however, tend to precede extreme positive returns. Originality/value This is the first work that uses the cross-quantilogram approach to assess the temporal association between returns and volume in cryptocurrencies markets. The findings provide new insights about the informational efficiency of these markets and the traders’ strategies.

scholarly journals RNA Sequencing-Based Transcriptional Overview of Xerotolerance inCronobacter sakazakiiSP291

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Shabarinath Srikumar ◽  
Yu Cao ◽  
Qiongqiong Yan ◽  
Koenraad Van Hoorde ◽  
Scott Nguyen ◽  
...  
Keyword(s):  
Infant Formula ◽  
Mortality Rates ◽  
Secondary Response ◽  
Ecological Niches ◽  
Infant Food ◽  
Powdered Infant Formula ◽  
Cronobacter Sakazakii ◽  
Rna Seq ◽  
Production Environment ◽  
Content Type

ABSTRACTCronobacter sakazakiiis a xerotolerant neonatal pathogen epidemiologically linked to powdered infant food formula, often resulting in high mortality rates. Here, we used transcriptome sequencing (RNA-seq) to provide transcriptional insights into the survival ofC. sakazakiiin desiccated conditions. Our RNA-seq data show that about 22% of the totalC. sakazakiigenes were significantly upregulated and 9% were downregulated during desiccation survival. When reverse transcription-quantitative PCR (qRT-PCR) was used to validate the RNA-seq data, we found that the primary desiccation response was gradually downregulated during the tested 4 hours of desiccation, while the secondary response remained constitutively upregulated. The 4-hour desiccation tolerance ofC. sakazakiiwas dependent on the immediate microenvironment surrounding the bacterial cell. The removal of Trypticase soy broth (TSB) salts and the introduction of sterile infant formula residues in the microenvironment enhanced the desiccation survival ofC. sakazakiiSP291. The trehalose biosynthetic pathway encoded byotsAandotsB, a prominent secondary bacterial desiccation response, was highly upregulated in desiccatedC. sakazakii.C. sakazakiiSP291 ΔotsABwas significantly inhibited compared with the isogenic wild type in an 8-hour desiccation survival assay, confirming the physiological importance of trehalose in desiccation survival. Overall, we provide a comprehensive RNA-seq-based transcriptional overview along with confirmation of the phenotypic importance of trehalose metabolism inCronobacter sakazakiiduring desiccation.IMPORTANCECronobacter sakazakiiis a pathogen of importance to neonatal health and is known to persist in dry food matrices, such as powdered infant formula (PIF) and its associated production environment. When infections are reported in neonates, mortality rates can be high. The success of this bacterium in surviving these low-moisture environments suggests thatCronobacterspecies can respond to a variety of environmental signals. Therefore, understanding those signals that aid the persistence of this pathogen in these ecological niches is an important step toward the development of strategies to reduce the risk of contamination of PIF. This research led to the identification of candidate genes that play a role in the persistence of this pathogen in desiccated conditions and, thereby, serve as a model target to design future strategies to mitigate PIF-associated survival ofC. sakazakii.

Comparing retail formats in an emerging market

2014 ◽  
Vol 6 (1) ◽  
pp. 48-69 ◽  
Author(s):  
Gordhan K. Saini ◽  
Arvind Sahay
Keyword(s):  
Purchase Intention ◽  
Emerging Market ◽  
Retail Store ◽  
Policy Implications ◽  
Content Type ◽  
Consumer Responses ◽  
Consumer Purchase Intention ◽  
Low Levels ◽  
Low Price Guarantee ◽  
Retail Formats

Purpose – This study aims to examine the importance of credit and low price guarantee (LPG) on consumer purchase intention across types of retail store formats in an emerging market context. Design/methodology/approach – A 2 (kirana/modern retail)×2 (high/low LPG)×2 (credit/no credit) experimental design was used for this study. A sample of 200 respondents was asked about their purchase intention for a newly introduced hypothetical toothpaste brand and six hypotheses were tested. Findings – Findings show that credit and level of LPG determine consumer's purchase intention across store formats. The presence of credit and high LPG increases the purchase intention; however, relatively importance of these two varies by type of store. The absence of credit at kirana store definitely reduces the buying intention, while same is not true for modern retail store, where level of LPG is more important than the credit. Interestingly, buyer is likely to discount high LPG for a month's credit offered by a kirana store. Practical implications – The study can help practitioners and scholars to understand consumer responses to credit and LPG in buying decisions, and subsequently in designing a better product offer at a particular store format in emerging markets. Originality/value – Important insights are provided about the consumer behavior resulting from the presence or absence of credit and high or low levels of LPG in an emerging market context. The study also has public policy implications in a country where FDI in retail is a hotly debated topic.

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