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.

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 Involvement of RpoN in Regulating Bacterial Arsenite Oxidation

2012 ◽  
Vol 78 (16) ◽  
pp. 5638-5645 ◽  
Author(s):  
Yoon-Suk Kang ◽  
Brian Bothner ◽  
Christopher Rensing ◽  
Timothy R. McDermott
Keyword(s):  
Binding Site ◽  
Sigma Factor ◽  
Model Organism ◽  
Coding Region ◽  
Rt Pcr ◽  
Obvious Effect ◽  
Content Type ◽  
Definitive Evidence ◽  
Relative Contribution ◽  
Insertional Inactivation

ABSTRACTIn this study with the model organismAgrobacterium tumefaciens, we used a combination oflacZgene fusions, reverse transcriptase PCR (RT-PCR), and deletion and insertional inactivation mutations to show unambiguously that the alternative sigma factor RpoN participates in the regulation of AsIIIoxidation. A deletion mutation that removed the RpoN binding site from theaioBApromoter and anaacC3(gentamicin resistance) cassette insertional inactivation of therpoNcoding region eliminatedaioBAexpression and AsIIIoxidation, althoughrpoNexpression was not related to cell exposure to AsIII. Putative RpoN binding sites were identified throughout the genome and, as examples, included promoters foraioB,phoB1,pstS1,dctA,glnA,glnB, andflgBthat were examined by using qualitative RT-PCR andlacZreporter fusions to assess the relative contribution of RpoN to their transcription. The expressions ofaioBanddctAin the wild-type strain were considerably enhanced in cells exposed to AsIII, and both genes were silent in therpoN::aacC3mutant regardless of AsIII. The expression level ofglnAwas not influenced by AsIIIbut was reduced (but not silent) in therpoN::aacC3mutant and further reduced in the mutant under N starvation conditions. TherpoN::aacC3mutation had no obvious effect on the expression ofglnB,pstS1,phoB1, orflgB. These experiments provide definitive evidence to document the requirement of RpoN for AsIIIoxidation but also illustrate that the presence of a consensus RpoN binding site does not necessarily link the associated gene with regulation by AsIIIor by this sigma factor.

scholarly journals Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

2014 ◽  
Vol 80 (8) ◽  
pp. 2410-2416 ◽  
Author(s):  
Areen Banerjee ◽  
Ching Leang ◽  
Toshiyuki Ueki ◽  
Kelly P. Nevin ◽  
Derek R. Lovley
Keyword(s):  
Ethanol Production ◽  
Genetic Manipulation ◽  
Electron Flow ◽  
Model Organism ◽  
Inducible Expression ◽  
Carbon Flow ◽  
Wild Type ◽  
Content Type ◽  
Microbial Electrosynthesis ◽  
Clostridium Ljungdahlii

ABSTRACTThe development of tools for genetic manipulation ofClostridium ljungdahliihas increased its attractiveness as a chassis for autotrophic production of organic commodities and biofuels from syngas and microbial electrosynthesis and established it as a model organism for the study of the basic physiology of acetogenesis. In an attempt to expand the genetic toolbox forC. ljungdahlii, the possibility of adapting a lactose-inducible system for gene expression, previously reported forClostridium perfringens, was investigated. The plasmid pAH2, originally developed forC. perfringenswith agusAreporter gene, functioned as an effective lactose-inducible system inC. ljungdahlii. Lactose induction ofC. ljungdahliicontaining pB1, in which the gene for the aldehyde/alcohol dehydrogenase AdhE1 was downstream of the lactose-inducible promoter, increased expression ofadhE130-fold over the wild-type level, increasing ethanol production 1.5-fold, with a corresponding decrease in acetate production. Lactose-inducible expression ofadhE1in a strain in whichadhE1and theadhE1homologadhE2had been deleted from the chromosome restored ethanol production to levels comparable to those in the wild-type strain. Inducing expression ofadhE2similarly failed to restore ethanol production, suggesting thatadhE1is the homolog responsible for ethanol production. Lactose-inducible expression of the four heterologous genes necessary to convert acetyl coenzyme A (acetyl-CoA) to acetone diverted ca. 60% of carbon flow to acetone production during growth on fructose, and 25% of carbon flow went to acetone when carbon monoxide was the electron donor. These studies demonstrate that the lactose-inducible system described here will be useful for redirecting carbon and electron flow for the biosynthesis of products more valuable than acetate. Furthermore, this tool should aid in optimizing microbial electrosynthesis and for basic studies on the physiology of acetogenesis.

scholarly journals Direct Interspecies Electron Transfer between Geobacter metallireducens and Methanosarcina barkeri

2014 ◽  
Vol 80 (15) ◽  
pp. 4599-4605 ◽  
Author(s):  
Amelia-Elena Rotaru ◽  
Pravin Malla Shrestha ◽  
Fanghua Liu ◽  
Beatrice Markovaite ◽  
Shanshan Chen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Model Organism ◽  
Methanosarcina Barkeri ◽  
Physical Contact ◽  
Acetate Metabolism ◽  
Geobacter Metallireducens ◽  
Content Type ◽  
Direct Interspecies Electron Transfer ◽  
Interspecies Electron Transfer ◽  
Effective Form

ABSTRACTDirect interspecies electron transfer (DIET) is potentially an effective form of syntrophy in methanogenic communities, but little is known about the diversity of methanogens capable of DIET. The ability ofMethanosarcina barkerito participate in DIET was evaluated in coculture withGeobacter metallireducens. Cocultures formed aggregates that shared electrons via DIET during the stoichiometric conversion of ethanol to methane. Cocultures could not be initiated with a pilin-deficientG. metallireducensstrain, suggesting that long-range electron transfer along pili was important for DIET. Amendments of granular activated carbon permitted the pilin-deficientG. metallireducensisolates to share electrons withM. barkeri, demonstrating that this conductive material could substitute for pili in promoting DIET. WhenM. barkeriwas grown in coculture with the H2-producingPelobacter carbinolicus, incapable of DIET,M. barkeriutilized H2as an electron donor but metabolized little of the acetate thatP. carbinolicusproduced. This suggested that H2, but not electrons derived from DIET, inhibited acetate metabolism.P. carbinolicus-M. barkericocultures did not aggregate, demonstrating that, unlike DIET, close physical contact was not necessary for interspecies H2transfer.M. barkeriis the second methanogen found to accept electrons via DIET and the first methanogen known to be capable of using either H2or electrons derived from DIET for CO2reduction. Furthermore,M. barkeriis genetically tractable, making it a model organism for elucidating mechanisms by which methanogens make biological electrical connections with other cells.

scholarly journals Osmoadaptation Strategy of the Most Halophilic Fungus, Wallemia ichthyophaga, Growing Optimally at Salinities above 15% NaCl

2013 ◽  
Vol 80 (1) ◽  
pp. 247-256 ◽  
Author(s):  
Janja Zajc ◽  
Tina Kogej ◽  
Erwin A. Galinski ◽  
José Ramos ◽  
Nina Gunde-Cimerman
Keyword(s):  
Biomass Production ◽  
Osmotic Shock ◽  
Model Organism ◽  
Salinity Range ◽  
Growth Media ◽  
Optimal Salinity ◽  
Content Type ◽  
Batch Cultures ◽  
Specific Growth Rates ◽  
Optimum Salinity

ABSTRACTWallemia ichthyophagais a fungus from the ancient basidiomycetous genusWallemia(Wallemiales, Wallemiomycetes) that grows only at salinities between 10% (wt/vol) NaCl and saturated NaCl solution. This obligate halophily is unique among fungi. The main goal of this study was to determine the optimal salinity range for growth of the halophilicW. ichthyophagaand to unravel its osmoadaptation strategy. Our results showed that growth on solid growth media was extremely slow and resulted in small colonies. On the other hand, in the liquid batch cultures, the specific growth rates ofW. ichthyophagawere higher, and the biomass production increased with increasing salinities. The optimum salinity range for growth ofW. ichthyophagawas between 15 and 20% (wt/vol) NaCl. At 10% NaCl, the biomass production and the growth rate were by far the lowest among all tested salinities. Furthermore, the cell wall content in the dry biomass was extremely high at salinities above 10%. Our results also showed that glycerol was the major osmotically regulated solute, since its accumulation increased with salinity and was diminished by hypo-osmotic shock. Besides glycerol, smaller amounts of arabitol and trace amounts of mannitol were also detected. In addition,W. ichthyophagamaintained relatively small intracellular amounts of potassium and sodium at constant salinities, but during hyperosmotic shock, the amounts of both cations increased significantly. Given our results and the recent availability of the genome sequence,W. ichthyophagashould become well established as a novel model organism for studies of halophily in eukaryotes.

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 Droplet- Rather than Aerosol-Mediated Dispersion Is the Primary Mechanism of Bacterial Transmission from Contaminated Hand-Washing Sink Traps

2018 ◽  
Vol 85 (2) ◽  
Author(s):  
Shireen M. Kotay ◽  
Rodney M. Donlan ◽  
Christine Ganim ◽  
Katie Barry ◽  
Bryan E. Christensen ◽  
...  
Keyword(s):  
Patient Care ◽  
Sampling Methods ◽  
Fluorescent Protein ◽  
Model Organism ◽  
Air Sampling ◽  
Multidrug Resistant ◽  
Hand Washing ◽  
Content Type ◽  
E Coli ◽  
Green Fluorescent

ABSTRACT An alarming rise in hospital outbreaks implicating hand-washing sinks has led to widespread acknowledgment that sinks are a major reservoir of antibiotic-resistant pathogens in patient care areas. An earlier study using green fluorescent protein (GFP)-expressing Escherichia coli (GFP-E. coli) as a model organism demonstrated dispersal from drain biofilms in contaminated sinks. The present study further characterizes the dispersal of microorganisms from contaminated sinks. Replicate hand-washing sinks were inoculated with GFP-E. coli, and dispersion was measured using qualitative (settle plates) and quantitative (air sampling) methods. Dispersal caused by faucet water was captured with settle plates and air sampling methods when bacteria were present on the drain. In contrast, no dispersal was captured without or in between faucet events, amending an earlier theory that bacteria aerosolize from the P-trap and disperse. Numbers of dispersed GFP-E. coli cells diminished substantially within 30 minutes after faucet usage, suggesting that the organisms were associated with larger droplet-sized particles that are not suspended in the air for long periods. IMPORTANCE Among the possible environmental reservoirs in a patient care environment, sink drains are increasingly recognized as a potential reservoir to hospitalized patients of multidrug-resistant health care-associated pathogens. With increasing antimicrobial resistance limiting therapeutic options for patients, a better understanding of how pathogens disseminate from sink drains is urgently needed. Once this knowledge gap has decreased, interventions can be engineered to decrease or eliminate transmission from hospital sink drains to patients. The current study further defines the mechanisms of transmission for bacteria that colonize sink drains.

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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