scholarly journals Phenotypic Analysis Reveals that the 2010 Haiti Cholera Epidemic Is Linked to a Hypervirulent Strain

2016 ◽  
Vol 84 (9) ◽  
pp. 2473-2481 ◽  
Author(s):  
Karla J. F. Satchell ◽  
Christopher J. Jones ◽  
Jennifer Wong ◽  
Jessica Queen ◽  
Shivani Agarwal ◽  
...  
Keyword(s):  
Phylogenetic Analyses ◽  
Event Analysis ◽  
Phenotypic Analysis ◽  
Genetic Event ◽  
Content Type ◽  
Virulence Potential ◽  
Selection For ◽  
El Tor ◽  
Early Isolate ◽  
Over Time

Vibrio choleraeO1 El Tor strains have been responsible for pandemic cholera since 1961. These strains have evolved over time, spreading globally in three separate waves. Wave 3 is caused by altered El Tor (AET) variant strains, which include the strain with the signaturectxB7allele that was introduced in 2010 into Haiti, where it caused a devastating epidemic. In this study, we used phenotypic analysis to compare an early isolate from the Haiti epidemic to wave 1 El Tor isolates commonly used for research. It is demonstrated that the Haiti isolate has increased production of cholera toxin (CT) and hemolysin, increased motility, and a reduced ability to form biofilms. This strain also outcompetes common wave 1 El Tor isolates for colonization of infant mice, indicating that it has increased virulence. Monitoring of CT production and motility in additional wave 3 isolates revealed that this phenotypic variation likely evolved over time rather than in a single genetic event. Analysis of available whole-genome sequences and phylogenetic analyses suggested that increased virulence arose from positive selection for mutations found in known and putative regulatory genes, includinghnsandvieA, diguanylate cyclase genes, and genes belonging to thelysRandgntRregulatory families. Overall, the studies presented here revealed thatV. choleraevirulence potential can evolve and that the currently prevalent wave 3 AET strains are both phenotypically distinct from and more virulent than many El Tor isolates.

scholarly journals Whole-Genome Sequencing and Phenotypic Analysis of Bacillus subtilis Mutants following Evolution under Conditions of Relaxed Selection for Sporulation

2011 ◽  
Vol 77 (19) ◽  
pp. 6867-6877 ◽  
Author(s):  
Christopher T. Brown ◽  
Laura K. Fishwick ◽  
Binna M. Chokshi ◽  
Marissa A. Cuff ◽  
Jay M. Jackson ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Chromosomal Rearrangements ◽  
Whole Genome ◽  
Nucleotide Polymorphisms ◽  
Relaxed Selection ◽  
Phenotypic Analysis ◽  
Competitive Fitness ◽  
Content Type ◽  
Intergenic Regions ◽  
Selection For

ABSTRACTLittle is known about how genetic variation at the nucleotide level contributes to competitive fitness within species. During a 6,000-generation study ofBacillus subtilisevolved under relaxed selection for sporulation, a new strain, designated WN716, emerged with significantly different colony and cell morphologies; loss of sporulation, competence, acetoin production, and motility; multiple auxotrophies; and increased competitive fitness (H. Maughan and W. L. Nicholson, Appl. Environ. Microbiol.77:4105–4118, 2011). The genome of WN716 was analyzed by OpGen optical mapping, whole-genome 454 pyrosequencing, and the CLC Genomics Workbench. No large chromosomal rearrangements were found; however, 34 single-nucleotide polymorphisms (SNPs) and +1 frameshifts were identified in WN716 that resulted in amino acid changes in coding sequences of annotated genes, and 11 SNPs were located in intergenic regions. Several classes of genes were affected, including biosynthetic pathways, sporulation, competence, and DNA repair. In several cases, attempts were made to link observed phenotypes of WN716 with the discovered mutations, with various degrees of success. For example, a +1 frameshift was identified at codon 13 ofsigW, the product of which (SigW) controls a regulon of genes involved in resistance to bacteriocins and membrane-damaging antibiotics. Consistent with this finding, WN716 exhibited sensitivity to fosfomycin and to a bacteriocin produced byB. subtilissubsp.spizizeniiand exhibited downregulation of SigW-dependent genes on a transcriptional microarray, consistent with WN716 carrying a knockout ofsigW. The results suggest that propagation ofB. subtilisfor less than 2,000 generations in a nutrient-rich environment where sporulation is suppressed led to rapid initiation of genomic erosion.

Chromobacterium vaccinii sp. nov., isolated from native and cultivated cranberry (Vaccinium macrocarpon Ait.) bogs and irrigation ponds

2013 ◽  
Vol 63 (Pt_5) ◽  
pp. 1840-1846 ◽  
Author(s):  
Scott D. Soby ◽  
Sudhindra R. Gadagkar ◽  
Cristina Contreras ◽  
Frank L. Caruso
Keyword(s):  
Type Species ◽  
Phylogenetic Analyses ◽  
Vaccinium Macrocarpon ◽  
Rrna Gene ◽  
The Novel ◽  
Phenotypic Analysis ◽  
Separate Species ◽  
Content Type ◽  
Link Type ◽  
Kalmia Angustifolia

A large number of Gram-negative, motile, mesophilic, violacein-producing bacteria were isolated from the soils and roots of Vaccinium macrocarpon Ait. and Kalmia angustifolia L. plants and from irrigation ponds associated with wild and cultivated cranberry bogs in Massachusetts, USA. Phylogenetic analyses of 16S rRNA gene sequences placed these isolates in a clade with Chromobacterium species, but the specialized environment from which they were isolated, their low genomic DNA relatedness with Chromobacterium violaceum ATCC 12472T and C. subtsugae PRAA4-1T, significant differences in fatty acid composition and colony morphology indicate that the cranberry and Kalmia isolates comprise a separate species of Chromobacterium , for which the name Chromobacterium vaccinii sp. nov. is proposed. Strain MWU205T ( = ATCC BAA-2314T  = DSM 25150T) is proposed as the type strain for the novel species. Phenotypic analysis of 26 independent isolates of C. vaccinii sp. nov. indicates that, despite close geographical and biological proximity, there is considerable metabolic diversity among individuals within the population.

scholarly journals Fitness Consequences ofPlasmodium falciparum pfmdr1Polymorphisms Inferred fromEx VivoCulture of Ugandan Parasites

2013 ◽  
Vol 57 (9) ◽  
pp. 4245-4251 ◽  
Author(s):  
Edwin Ochong ◽  
Patrick K. Tumwebaze ◽  
Oswald Byaruhanga ◽  
Bryan Greenhouse ◽  
Philip J. Rosenthal
Keyword(s):  
Wild Type ◽  
Complex Interplay ◽  
Content Type ◽  
Fitness Consequences ◽  
Ofplasmodium Falciparum ◽  
Stable Mutant ◽  
Selection For ◽  
Insight Into ◽  
Over Time ◽  
Selection Of

ABSTRACTPolymorphisms in thePlasmodium falciparummultidrug resistance 1 (pfmdr1) gene impact sensitivity to multiple antimalarials. In Africa, polymorphisms at N86Y and D1246Y are common and have various impacts on sensitivity to different drugs. To gain insight into the fitness consequences of these polymorphisms, we cultured parasites isolated from children with malaria in Tororo, Uganda, where the multiplicity of infection is high, and used pyrosequencing to follow polymorphism prevalences in culture over time. Of 71 cultures, parasites in 69 were successfully analyzed at N86Y and parasites in 68 were successfully analyzed at D1246Y over 3 to 36 days of culture. For position 86, the sequences of 39/69 (56.5%) parasites remained stable (>90% prevalence over 2 to 17 time points), with 82.1% of these being stable for the 86Y mutation. For position 1246, the sequences of 31/68 (45.6%) parasites remained stable, with 64.5% of these being stable for the wild-type D1246 sequence (P= 0.0002 for comparison of stable mutant genotypes for the two alleles). Defining allele selection as a ≥15% change in prevalence between the first and last samples assessed, for position 86, 11 samples showed selection, with selection toward 86Y occurring in 72.7% of alleles; for position 1246, 14 samples showed selection, with selection toward D1246 occurring in 64.3% of alleles (P= 0.11 for comparison of selection of mutations at the two alleles). Among the 7 samples with selection at both alleles, 5 showed selection for both 86Y and D1246. Overall, consistent trends in the direction of selection were seen, although differences were not statistically significant. Our results suggest fitness advantages for parasites with thepfmdr186Y mutation and wild-type D1246, highlighting the complex interplay between drug resistance and fitness in malaria parasites. (This study has been registered at ClinicalTrials.gov under registration no. NCT00948896 and NCT00993031.)

scholarly journals Characterization of RarA, a Novel AraC Family Multidrug Resistance Regulator in Klebsiella pneumoniae

2012 ◽  
Vol 56 (8) ◽  
pp. 4450-4458 ◽  
Author(s):  
Mark Veleba ◽  
Paul G. Higgins ◽  
Gerardo Gonzalez ◽  
Harald Seifert ◽  
Thamarai Schneiders
Keyword(s):  
Multidrug Resistance ◽  
Klebsiella Pneumoniae ◽  
Efflux Pump ◽  
Content Type ◽  
Resistance Phenotype ◽  
Serratia Proteamaculans ◽  
Virulence Potential ◽  
Article Type ◽  
Acrab Efflux Pump

ABSTRACTTranscriptional regulators, such as SoxS, RamA, MarA, and Rob, which upregulate the AcrAB efflux pump, have been shown to be associated with multidrug resistance in clinically relevant Gram-negative bacteria. In addition to the multidrug resistance phenotype, these regulators have also been shown to play a role in the cellular metabolism and possibly the virulence potential of microbial cells. As such, the increased expression of these proteins is likely to cause pleiotropic phenotypes.Klebsiella pneumoniaeis a major nosocomial pathogen which can express the SoxS, MarA, Rob, and RamA proteins, and the accompanying paper shows that the increased transcription oframAis associated with tigecycline resistance (M. Veleba and T. Schneiders, Antimicrob. Agents Chemother. 56:4466–4467, 2012). Bioinformatic analyses of the availableKlebsiellagenome sequences show that an additional AraC-type regulator is encoded chromosomally. In this work, we characterize this novel AraC-type regulator, hereby called RarA (Regulator of antibiotic resistance A), which is encoded inK. pneumoniae,Enterobactersp. 638,Serratia proteamaculans568, andEnterobacter cloacae. We show that the overexpression ofrarAresults in a multidrug resistance phenotype which requires a functional AcrAB efflux pump but is independent of the other AraC regulators. Quantitative real-time PCR experiments show thatrarA(MGH 78578 KPN_02968) and its neighboring efflux pump operonoqxAB(KPN_02969_02970) are consistently upregulated in clinical isolates collected from various geographical locations (Chile, Turkey, and Germany). Our results suggest thatrarAoverexpression upregulates theoqxABefflux pump. Additionally, it appears thatoqxR, encoding a GntR-type regulator adjacent to theoqxABoperon, is able to downregulate the expression of theoqxABefflux pump, where OqxR complementation resulted in reductions to olaquindox MICs.

scholarly journals Rough diamonds in emerging markets: legacy, competitiveness, and sustained high performance

2019 ◽  
Vol 26 (3) ◽  
pp. 363-386
Author(s):  
Seung Ho Park ◽  
Gerardo R. Ungson
Keyword(s):  
Human Capital ◽  
Emerging Markets ◽  
High Performance ◽  
Core Competencies ◽  
Market Potential ◽  
Government Support ◽  
Screening Tests ◽  
Institutional Voids ◽  
Content Type ◽  
Over Time

Purpose The purpose of this paper is to uncover the underlying drivers of sustained high performing companies based on a field study of 127 companies in Brazilian, Russian, Indian and Chinese (BRIC) and Association of Southeast Asian Nations (ASEAN) emerging markets. Understanding these companies provides a complementary way of appraising the growth, development and transformation of emerging markets. The authors synthesize the findings in an overarching framework that covers six strategies for building and sustaining legacy that leads to the succession of intergenerational wealth over time: overcoming institutional voids, inclusive markets, deepening localization, nurturing government support, building core competencies and harnessing human capital. The authors relate these strategies to different levels of development using Prahalad and Hart’s BOP framework. Design/methodology/approach This study examines the underlying drivers of sustained high-performance companies based on field studies from an initial set of 105,260 BRIC companies and close to 500 companies in ASEAN. The methods employed four screening tests to arrive at a selection of the highest-performing firms: 70 firms in the BRIC nations and 58 firms from ASEAN. Following the selection, the authors constructed cases using primary interviews and secondary data, with the assistance of Ernst & Young and with academic colleagues in Manila. These studies were originally conducted in two separate time periods and reported accordingly. This paper synthesizes the findings of these two studies to arrive at an extended integrative framework. Findings From the cases, the authors examine six strategies for building and sustaining legacy that lead to high performance over time: overcoming institutional voids, creating inclusive markets, deepening localization, nurturing government support, building core competencies and harnessing human capital. To address the evolving state of institutional voids in these countries, the authors employ similar methods to hypothesize the placement of these strategies in the context of the world economic pyramid, initially formulated as the “bottom of the pyramid” framework. Originality/value This paper synthesizes and extends the authors’ previous works by proposing the concept of legacy to describe the emergence and succession of local exemplary firms in emerging markets. This study aims to complement extant measures of nation-growth based primarily on GDP. The paper also extends the literature on institutional voids in shifting the focus from the mix of voids to their evolving state. Altogether, the paper provides a complementary narrative on assessing the market potential of emerging markets by adopting several categories of performance.

scholarly journals Beyond agency and stewardship theory: shareholder–manager relationships and governance structures in family firms

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ann Sophie K. Löhde ◽  
Giovanna Campopiano ◽  
Andrea Calabrò
Keyword(s):  
Social Exchange ◽  
Family Business ◽  
Social Exchange Theory ◽  
Family Firms ◽  
Governance Structure ◽  
Managerial Behavior ◽  
Exchange System ◽  
Content Type ◽  
The One ◽  
Over Time

PurposeChallenging the static view of family business governance, we propose a model of owner–manager relationships derived from the configurational analysis of managerial behavior and change in governance structure.Design/methodology/approachStemming from social exchange theory and building on the 4C model proposed by Miller and Le Breton-Miller (2005), we consider the evolving owner–manager relationship in four main configurations. On the one hand, we account for family businesses shifting from a generalized to a restricted exchange system, and vice versa, according to whether a family manager misbehaves in a stewardship-oriented governance structure or a nonfamily manager succeeds in building a trusting relationship in an agency-oriented governance structure. On the other hand, we consider that family firms will strengthen a generalized exchange system, rather than a restricted one, according to whether a family manager contributes to the stewardship-oriented culture in the business or a nonfamily manager proves to be driven by extrinsic rewards. Four scenarios are analyzed in terms of the managerial behavior and governance structure that characterize the phases of the relationship between owners and managers.FindingsVarious factors trigger managerial behavior, making the firm deviate from or further build on what is assumed by stewardship and agency theories (i.e. proorganizational versus opportunistic behavior, respectively), which determine the governance structure over time. Workplace deviance, asymmetric altruism and patriarchy on the one hand, and proorganizational behavior, relationship building and long-term commitment on the other, are found to determine how the manager behaves and thus characterize the owner's reactions in terms of governance mechanisms. This enables us to present a dynamic view of governance structures, which adapt to the actual attitudes and behaviors of employed managers.Research limitations/implicationsAs time is a relevant dimension affecting individual behavior and triggering change in an organization, one must consider family business governance as being dynamic in nature. Moreover, it is not family membership that determines the most appropriate governance structure but the owner–manager relationship that evolves over time, thus contributing to the 4C model.Originality/valueThe proposed model integrates social exchange theory and the 4C model to predict changes in governance structure, as summarized in the final framework we propose.

scholarly journals Enhancing Terpene Yield from Sugars via Novel Routes to 1-Deoxy-d-Xylulose 5-Phosphate

2014 ◽  
Vol 81 (1) ◽  
pp. 130-138 ◽  
Author(s):  
James Kirby ◽  
Minobu Nishimoto ◽  
Ruthie W. N. Chow ◽  
Edward E. K. Baidoo ◽  
George Wang ◽  
...  
Keyword(s):  
Bacterial Species ◽  
Xylose Reductase ◽  
Pentose Phosphate ◽  
Terpene Biosynthesis ◽  
Content Type ◽  
E Coli ◽  
Pathway Expression ◽  
Terpene Synthesis ◽  
Selection For

ABSTRACTTerpene synthesis in the majority of bacterial species, together with plant plastids, takes place via the 1-deoxy-d-xylulose 5-phosphate (DXP) pathway. The first step of this pathway involves the condensation of pyruvate and glyceraldehyde 3-phosphate by DXP synthase (Dxs), with one-sixth of the carbon lost as CO2. A hypothetical novel route from a pentose phosphate to DXP (nDXP) could enable a more direct pathway from C5sugars to terpenes and also circumvent regulatory mechanisms that control Dxs, but there is no enzyme known that can convert a sugar into its 1-deoxy equivalent. Employing a selection for complementation of adxsdeletion inEscherichia coligrown on xylose as the sole carbon source, we uncovered two candidate nDXP genes. Complementation was achieved either via overexpression of the wild-typeE. coliyajOgene, annotated as a putative xylose reductase, or via various mutations in the nativeribBgene.In vitroanalysis performed with purified YajO and mutant RibB proteins revealed that DXP was synthesized in both cases from ribulose 5-phosphate (Ru5P). We demonstrate the utility of these genes for microbial terpene biosynthesis by engineering the DXP pathway inE. colifor production of the sesquiterpene bisabolene, a candidate biodiesel. To further improve flux into the pathway from Ru5P, nDXP enzymes were expressed as fusions to DXP reductase (Dxr), the second enzyme in the DXP pathway. Expression of a Dxr-RibB(G108S) fusion improved bisabolene titers more than 4-fold and alleviated accumulation of intracellular DXP.

Changes in commitment to change among leaders in home help services

2015 ◽  
Vol 28 (3) ◽  
pp. 216-227 ◽  
Author(s):  
Kristina Westerberg ◽  
Susanne Tafvelin
Keyword(s):  
Organizational Change ◽  
Structured Interviews ◽  
Change Initiatives ◽  
Commitment To Change ◽  
Content Type ◽  
Team Meetings ◽  
Home Help ◽  
Home Help Services ◽  
One Year ◽  
Over Time

Purpose – The purpose of the this study was to explore the development of commitment to change among leaders in the home help services during organizational change and to study this development in relation to workload and stress. During organizational change initiatives, commitment to change among leaders is important to ensure the implementation of the change. However, little is known of development of commitment of change over time. Design/methodology/approach – The study used a qualitative design with semi-structured interviews with ten leaders by the time an organizational change initiative was launched and follow-up one year later. Thematic content analysis was used to analyze the interviews. Findings – Commitment to change is not static, but seems to develop over time and during organizational change. At the first interview, leaders had a varied pattern reflecting different dimensions of commitment to change. One year later, the differences between leaders’ commitment to change was less obvious. Differences in commitment to change had no apparent relationship with workload or stress. Research limitations/implications – The data were collected from one organization, and the number of participants were small which could affect the results on workload and stress in relation to commitment to change. Practical implications – It is important to support leaders during organizational change initiatives to maintain their commitment. One way to accomplish this is to use management team meetings to monitor how leaders perceive their situation. Originality/value – Qualitative, longitudinal and leader studies on commitment to change are all unusual, and taken together, this study shows new aspects of commitment.

scholarly journals Nesterenkonia alkaliphila sp. nov., an alkaliphilic, halotolerant actinobacteria isolated from the western Pacific Ocean

2015 ◽  
Vol 65 (Pt_2) ◽  
pp. 516-521 ◽  
Author(s):  
Gaiyun Zhang ◽  
Yubian Zhang ◽  
Xijie Yin ◽  
Shuang Wang
Keyword(s):  
Pacific Ocean ◽  
Type Species ◽  
Sequence Similarity ◽  
Phylogenetic Analyses ◽  
Western Pacific ◽  
Rrna Gene ◽  
Western Pacific Ocean ◽  
Content Type ◽  
Link Type ◽  
The Western Pacific

A Gram-staining-positive, aerobic, motile and non-spore-forming actinobacteria, designated strain F10T, was isolated from a deep-sea sediment of the western Pacific Ocean. Phylogenetic and phenotypic properties of the organism supported that it belonged to the genus Nesterenkonia . Strain F10T shared highest 16S rRNA gene sequence similarity of 96.8 % with Nesterenkonia aethiopica DSM 17733T, followed by Nesterenkonia xinjiangensis YIM 70097T (96.7 %) and Nesterenkonia alba CAAS 252T (96.6 %). The organism grew at 4–50 °C, at pH 7.0–12.0 and in the presence of 0–12 % (w/v) NaCl, with optimal growth occurring at 40 °C, at pH 9.0 and in the presence of 1 % (w/v) NaCl. The peptidoglycan type was A4(alpha), l-Lys–Gly–l-Glu. The polar lipid profile of strain F10T consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, two unknown glycolipids and two unknown lipids. The isolate contained MK-9 (92 %) and MK-8 (5.8 %) as the major components of the menaquinone system, and anteiso-C17 : 0 (50.9 %) and anteiso-C15 : 0 (29.8 %) as the predominant fatty acids. The G+C content of the genomic DNA of strain F10T was 66.2 mol%. Based on phenotypic, genotypic and phylogenetic analyses, strain F10T represents a novel species of the genus Nesterenkonia for which the name Nesterenkonia alkaliphila sp. nov. is proposed. The type strain is F10T ( = LMG 28112T = CGMCC 1.12781T = JCM 19766T = MCCC 1A09946T).

Sign in / Sign up

Export Citation Format

Share Document