scholarly journals Bradyrhizobium diazoefficiens USDA110 Nodulation of Aeschynomene afraspera Is Associated with Atypical Terminal Bacteroid Differentiation and Suboptimal Symbiotic Efficiency

mSystems ◽  
2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Quentin Nicoud ◽  
Florian Lamouche ◽  
Anaïs Chaumeret ◽  
Thierry Balliau ◽  
Romain Le Bars ◽  
...  
Keyword(s):  
Host Plants ◽  
Terminal Differentiation ◽  
Symbiotic Interaction ◽  
New Host ◽  
Symbiotic Efficiency ◽  
Content Type ◽  
Legume Plants ◽  
Main Input ◽  
High Level ◽  
Full Activation

ABSTRACT Legume plants can form root organs called nodules where they house intracellular symbiotic rhizobium bacteria. Within nodule cells, rhizobia differentiate into bacteroids, which fix nitrogen for the benefit of the plant. Depending on the combination of host plants and rhizobial strains, the output of rhizobium-legume interactions varies from nonfixing associations to symbioses that are highly beneficial for the plant. Bradyrhizobium diazoefficiens USDA110 was isolated as a soybean symbiont, but it can also establish a functional symbiotic interaction with Aeschynomene afraspera. In contrast to soybean, A. afraspera triggers terminal bacteroid differentiation, a process involving bacterial cell elongation, polyploidy, and increased membrane permeability, leading to a loss of bacterial viability while plants increase their symbiotic benefit. A combination of plant metabolomics, bacterial proteomics, and transcriptomics along with cytological analyses were used to study the physiology of USDA110 bacteroids in these two host plants. We show that USDA110 establishes a poorly efficient symbiosis with A. afraspera despite the full activation of the bacterial symbiotic program. We found molecular signatures of high levels of stress in A. afraspera bacteroids, whereas those of terminal bacteroid differentiation were only partially activated. Finally, we show that in A. afraspera, USDA110 bacteroids undergo atypical terminal differentiation hallmarked by the disconnection of the canonical features of this process. This study pinpoints how a rhizobium strain can adapt its physiology to a new host and cope with terminal differentiation when it did not coevolve with such a host. IMPORTANCE Legume-rhizobium symbiosis is a major ecological process in the nitrogen cycle, responsible for the main input of fixed nitrogen into the biosphere. The efficiency of this symbiosis relies on the coevolution of the partners. Some, but not all, legume plants optimize their return on investment in the symbiosis by imposing on their microsymbionts a terminal differentiation program that increases their symbiotic efficiency but imposes a high level of stress and drastically reduces their viability. We combined multi-omics with physiological analyses to show that the symbiotic couple formed by Bradyrhizobium diazoefficiens USDA110 and Aeschynomene afraspera, in which the host and symbiont did not evolve together, is functional but displays a low symbiotic efficiency associated with a disconnection of terminal bacteroid differentiation features.

scholarly journals Bradyrhizobium diazoefficiens USDA110 nodulation of Aeschynomene afraspera is associated with atypical terminal bacteroid differentiation and suboptimal symbiotic efficiency

2020 ◽  
Author(s):  
Quentin Nicoud ◽  
Florian Lamouche ◽  
Anaïs Chaumeret ◽  
Thierry Balliau ◽  
Romain Le Bars ◽  
...  
Keyword(s):  
Host Plants ◽  
Terminal Differentiation ◽  
Fixed Nitrogen ◽  
Symbiotic Interaction ◽  
New Host ◽  
Symbiotic Efficiency ◽  
Legume Plants ◽  
Main Input ◽  
High Level ◽  
Full Activation

AbstractLegume plants can form root organs called nodules where they house intracellular symbiotic rhizobium bacteria. Within nodule cells, rhizobia differentiate into bacteroids, which fix nitrogen for the benefit of the plant. Depending on the combination of host plants and rhizobial strains, the output of rhizobium-legume interactions is varying from non-fixing associations to symbioses that are highly beneficial for the plant. Bradyrhizobium diazoefficiens USDA110 was isolated as a soybean symbiont but it can also establish a functional symbiotic interaction with Aeschynomene afraspera. In contrast to soybean, A. afraspera triggers terminal bacteroid differentiation, a process involving bacterial cell elongation, polyploidy and membrane permeability leading to loss of bacterial viability while plants increase their symbiotic benefit. A combination of plant metabolomics, bacterial proteomics and transcriptomics along with cytological analyses was used to study the physiology of USDA110 bacteroids in these two host plants. We show that USDA110 establish a poorly efficient symbiosis with A. afraspera, despite the full activation of the bacterial symbiotic program. We found molecular signatures of high level of stress in A. afraspera bacteroids whereas those of terminal bacteroid differentiation were only partially activated. Finally, we show that in A. afraspera, USDA110 bacteroids undergo an atypical terminal differentiation hallmarked by the disconnection of the canonical features of this process. This study pinpoints how a rhizobium strain can adapt its physiology to a new host and cope with terminal differentiation when it did not co-evolve with such a host.ImportanceLegume-rhizobium symbiosis is a major ecological process in the nitrogen cycle, responsible for the main input of fixed nitrogen in the biosphere. The efficiency of this symbiosis relies on the coevolution of the partners. Some legume plants, but not all, optimize their return-on-investment in the symbiosis by imposing on their microsymbionts a terminal differentiation program that increases their symbiotic efficiency but imposes a high level of stress and drastically reduce their viability. We combined multi-omics with physiological analyses to show that the non-natural symbiotic couple formed by Bradyrhizobium diazoefficiens USDA110 and Aeschynomene afraspera is functional but displays a low symbiotic efficiency associated to a disconnection of terminal bacteroid differentiation features.

scholarly journals Mutations in fbiD (Rv2983) as a Novel Determinant of Resistance to Pretomanid and Delamanid in Mycobacterium tuberculosis

2020 ◽  
Vol 65 (1) ◽  
pp. e01948-20
Author(s):  
Dalin Rifat ◽  
Si-Yang Li ◽  
Thomas Ioerger ◽  
Keshav Shah ◽  
Jean-Philippe Lanoix ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Clinical Evidence ◽  
Clinical Samples ◽  
Loss Of Function ◽  
Wild Type ◽  
Content Type ◽  
Solid Media ◽  
High Level ◽  
Level Resistance

ABSTRACTThe nitroimidazole prodrugs delamanid and pretomanid comprise one of only two new antimicrobial classes approved to treat tuberculosis (TB) in 50 years. Prior in vitro studies suggest a relatively low barrier to nitroimidazole resistance in Mycobacterium tuberculosis, but clinical evidence is limited to date. We selected pretomanid-resistant M. tuberculosis mutants in two mouse models of TB using a range of pretomanid doses. The frequency of spontaneous resistance was approximately 10−5 CFU. Whole-genome sequencing of 161 resistant isolates from 47 mice revealed 99 unique mutations, of which 91% occurred in 1 of 5 genes previously associated with nitroimidazole activation and resistance, namely, fbiC (56%), fbiA (15%), ddn (12%), fgd (4%), and fbiB (4%). Nearly all mutations were unique to a single mouse and not previously identified. The remaining 9% of resistant mutants harbored mutations in Rv2983 (fbiD), a gene not previously associated with nitroimidazole resistance but recently shown to be a guanylyltransferase necessary for cofactor F420 synthesis. Most mutants exhibited high-level resistance to pretomanid and delamanid, although Rv2983 and fbiB mutants exhibited high-level pretomanid resistance but relatively small changes in delamanid susceptibility. Complementing an Rv2983 mutant with wild-type Rv2983 restored susceptibility to pretomanid and delamanid. By quantifying intracellular F420 and its precursor Fo in overexpressing and loss-of-function mutants, we provide further evidence that Rv2983 is necessary for F420 biosynthesis. Finally, Rv2983 mutants and other F420H2-deficient mutants displayed hypersusceptibility to some antibiotics and to concentrations of malachite green found in solid media used to isolate and propagate mycobacteria from clinical samples.

scholarly journals Understanding employee turnover in humanitarian organizations

2016 ◽  
Vol 48 (4) ◽  
pp. 208-214 ◽  
Author(s):  
Rameshwar Dubey ◽  
Angappa Gunasekaran ◽  
Nezih Altay ◽  
Stephen J Childe ◽  
Thanos Papadopoulos
Keyword(s):  
Employee Turnover ◽  
Factor Loading ◽  
Personal Factors ◽  
Related Factors ◽  
Content Type ◽  
Factors Affecting ◽  
Work Related ◽  
Humanitarian Organizations ◽  
Using Data ◽  
High Level

Purpose – At a time when the number and seriousness of disasters seems to be increasing, humanitarian organizations find that besides their challenging work they are faced with problems caused by a high level of turnover of staff. The paper aims to discuss these issues. Design/methodology/approach – Based on the 24 variables leading to employee turnover identified by Cotton and Tuttle (1986) the authors analyse the work-related, external and personal factors affecting employee turnover in humanitarian organizations, using a survey of members of the Indian National Institute of Disaster Management. Findings – Results indicated that the three factors are present. Of the external factors, only employment perception had a factor loading over 0.7; of the work-related factors, all were significant; of the personal factors, biographical information, marital status, number of dependants, aptitude and ability and intelligence had the highest loadings. It was also shown that behavioural intentions and net expectation were not significant. Originality/value – Only a few studies reported on employee turnover and its reasons are not well understood in the context of humanitarian organizations. To address this need, the aim of this paper is to explore the personal reasons impacting employee turnover in humanitarian organizations. In the study the authors have adopted 24 variables used in Cotton and Tuttle (1986) and classified into constructs to explain turnover, and further tested the model using data gathered from humanitarian organizations.

scholarly journals Whole-Genome Phylogenomic Heterogeneity of Neisseria gonorrhoeae Isolates with Decreased Cephalosporin Susceptibility Collected in Canada between 1989 and 2013

2014 ◽  
Vol 53 (1) ◽  
pp. 191-200 ◽  
Author(s):  
Walter Demczuk ◽  
Tarah Lynch ◽  
Irene Martin ◽  
Gary Van Domselaar ◽  
Morag Graham ◽  
...  
Keyword(s):  
Neisseria Gonorrhoeae ◽  
Large Scale ◽  
Epidemiological Studies ◽  
23S Rrna ◽  
Genome Comparison ◽  
Whole Genome ◽  
Content Type ◽  
Genomic Epidemiology ◽  
High Level ◽  
Sequence Types

A large-scale, whole-genome comparison of CanadianNeisseria gonorrhoeaeisolates with high-level cephalosporin MICs was used to demonstrate a genomic epidemiology approach to investigate strain relatedness and dynamics. Although current typing methods have been very successful in tracing short-chain transmission of gonorrheal disease, investigating the temporal evolutionary relationships and geographical dissemination of highly clonal lineages requires enhanced resolution only available through whole-genome sequencing (WGS). Phylogenomic cluster analysis grouped 169 Canadian strains into 12 distinct clades. While someN. gonorrhoeaemultiantigen sequence types (NG-MAST) agreed with specific phylogenomic clades or subclades, other sequence types (ST) and closely related groups of ST were widely distributed among clades. Decreased susceptibility to extended-spectrum cephalosporins (ESC-DS) emerged among a group of diverse strains in Canada during the 1990s with a variety of nonmosaicpenAalleles, followed in 2000/2001 with thepenAmosaic X allele and then in 2007 with ST1407 strains with thepenAmosaic XXXIV allele. Five genetically distinct ESC-DS lineages were associated withpenAmosaic X, XXXV, and XXXIV alleles and nonmosaic XII and XIII alleles. ESC-DS with coresistance to azithromycin was observed in 5 strains with 23S rRNA C2599T or A2143G mutations. As the costs associated with WGS decline and analysis tools are streamlined, WGS can provide a more thorough understanding of strain dynamics, facilitate epidemiological studies to better resolve social networks, and improve surveillance to optimize treatment for gonorrheal infections.

Living in the end times: a short course addressing end of life issues for older people in an English parish church setting

2015 ◽  
Vol 19 (3) ◽  
pp. 140-149 ◽  
Author(s):  
Joanna Collicutt
Keyword(s):  
Older People ◽  
End Of Life ◽  
Group Dynamics ◽  
Death And Dying ◽  
Community Context ◽  
Content Type ◽  
End Of Life Issues ◽  
End Times ◽  
High Level ◽  
High Degree

Purpose – The purpose of this paper is to report a pilot study that evaluated an innovative practice in a faith community context designed to help older people live well at the end of life and prepare for death. Design/methodology/approach – A simple audit of the intervention using a contemporaneous journal kept by the author, and a follow up questionnaire completed by participants. Findings – Rich findings on the process are reported. These indicate a high degree of engagement by participants, the establishment of a high degree of group intimacy and trust, a high level of articulation of wisdom, the emergence of significant anxiety in some isolated cases, and the use made of tea and cake to manage the transition between the existentially demanding nature of the discussions and normal life. The outcome indicated very high levels of appreciation and increased confidence in relation to issues of death and dying. Practical implications – The findings of the pilot have been used to inform training of clergy in the principles of working in this area (e.g. in ways of managing group dynamics and anxiety, pacing, tuning in to archetypes and the natural symbols that people use to talk about death and dying, self-care and supervision of the programme leader/facilitator). Originality/value – The paper adds to knowledge in terms of an in depth description of processes at work in a group of older people working on spiritual and practical issues in relation to death, and offers ideas for supporting older people in this process, some of which are specific to the Christian tradition, and some of which are more widely applicable to people of all faiths and none. It gives a specific worked example of what “spiritual care” in this area might look like.

Flexible contracting in project business

2015 ◽  
Vol 8 (1) ◽  
pp. 92-106 ◽  
Author(s):  
Jaakko Kujala ◽  
Soili Nystén-Haarala ◽  
Jouko Nuottila
Keyword(s):  
Oral Communication ◽  
Underlying Assumption ◽  
Content Type ◽  
Iterative Development ◽  
Flexible Adaptation ◽  
Contracting Process ◽  
High Level ◽  
Project Lifecycle ◽  
Project Contract ◽  
Formal Contract

Purpose – The purpose of this paper is to increase the understanding of the main challenges of the contracting process and project contracts in the context of project business characterized by a high level of complexity and uncertainty. The authors argue that understanding contracting as a flexible process and as a business tool will contribute to creating more value in projects which are implemented in constantly changing circumstances or which require gradual and iterative development. Design/methodology/approach – This is a conceptual paper with illustrative examples from the software industry. Findings – A prevailing approach for both managing contracts and the contracting process focuses on careful planning and drafting of contracts that protect each party in the case of conflicts and disagreements. The underlying assumption is that all activities can be planned and documented in a formal contract. According to this approach, the contracting process is seen only as a bargaining negotiation and the project contract as a detailed agreement of the responsibilities and safeguarding clauses to protect one’s position in the event of conflicts and failures. However, in the context of project business characterized by complexity and uncertainty, there is a need for flexible project contracts. The authors suggest that there are two fundamentally different approaches to implementing flexibility in both the contracting process and the project contract: postponing the decision until there is adequate information for decision making or making decisions that allow flexible adaptation to changes during the project lifecycle. Practical implications – The authors suggest that organizations in project business should pay closer attention to how contracts are formed and how flexibility is introduced to projects. Organizations are encouraged to see contracts as a business tool, not as rigid documents which are taken into use in case something goes wrong. Originality/value – This paper contributes to the understanding of how to adapt the contracting process to overcome challenges related to uncertainty, especially during the early phases of the project lifecycle. The authors provide a novel perspective on contracting as a process that extends over the lifecycle of a project and on the project contract as an agreement between parties formed during the contracting process. This perspective includes formal contract documents as well as various other documents, oral communication, commitments, actions and incidents.

Evaluation of brain-stem dysfunction following severe fluid-percussion head injury to the cat

1991 ◽  
Vol 74 (2) ◽  
pp. 270-277 ◽  
Author(s):  
Katsuji Shima ◽  
Anthony Marmarou
Keyword(s):  
Brain Stem ◽  
Content Type ◽  
Fluid Percussion ◽  
Fluid Percussion Injury ◽  
Brain Stem Injury ◽  
Group 2 ◽  
High Level ◽  
Subarachnoid Hemorrhages ◽  
Fine Print ◽  
Group 1

✓ The degree of brain-stem dysfunction associated with high-level fluid-percussion injury (3.0 to 3.8 atm) was investigated in anesthetized cats. Measurements were made of the animals' intracranial pressure (ICP), pressure-volume index (PVI), far-field brain-stem auditory evoked responses (BAER's), and cerebral blood flow (CBF). The animals were classified into two groups based on the severity of neuropathological damage to the brain stem after trauma: Group 1 had mild intraparenchymal and subarachnoid hemorrhages and Group 2 had severe intraparenchymal and subarachnoid hemorrhages. The ICP values in Group 1 were insignificantly lower than those in Group 2, while the PVI values in Group 2 were clearly lower (p < 0.05). Immediately after the injury, peaks II, III, and IV of the BAER's demonstrated a transitory and marked suppression. One Group 1 and two Group 2 animals showed the disappearance of peak V. In Group 1, the latencies of peak II, III, and IV gradually increased until 60 to 150 minutes postinjury, then returned to 95% of baseline value at 8 hours; however, the animals in Group 2 showed poor recovery of latencies. Two hours after brain injury, the CBF decreased to 40% of the preinjury measurement in both groups (p < 0.001). In contrast to Group 2, the CBF in Group 1 returned to 86.8% of the preinjury measurement by 8 hours following the injury. Changes in PVI, BAER, and CBF correlated well with the degree of brain-stem injury following severe head injury'- These data indicate that high-level fluid-percussion injury (> 3.0 atm) is predominantly a model of brain-stem injury.

scholarly journals ArmA Methyltransferase in a Monophasic Salmonella enterica Isolate from Food

2011 ◽  
Vol 55 (11) ◽  
pp. 5262-5266 ◽  
Author(s):  
Sophie A. Granier ◽  
Laura Hidalgo ◽  
Alvaro San Millan ◽  
Jose Antonio Escudero ◽  
Belen Gutierrez ◽  
...  
Keyword(s):  
16S Rrna ◽  
Salmonella Enterica ◽  
Multidrug Resistant ◽  
Broad Host Range ◽  
En Bloc ◽  
Content Type ◽  
Route Of Transmission ◽  
Amoxicillin Clavulanate ◽  
High Level ◽  
Level Resistance

ABSTRACTThe 16S rRNA methyltransferase ArmA is a worldwide emerging determinant that confers high-level resistance to most clinically relevant aminoglycosides. We report here the identification and characterization of a multidrug-resistantSalmonella entericasubspecies I.4,12:i:− isolate recovered from chicken meat sampled in a supermarket on February 2009 in La Reunion, a French island in the Indian Ocean. Susceptibility testing showed an unusually high-level resistance to gentamicin, as well as to ampicillin, expanded-spectrum cephalosporins and amoxicillin-clavulanate. Molecular analysis of the 16S rRNA methyltransferases revealed presence of thearmAgene, together withblaTEM-1,blaCMY-2, andblaCTX-M-3. All of these genes could be transferreden blocthrough conjugation intoEscherichia coliat a frequency of 10−5CFU/donor. Replicon typing and S1 pulsed-field gel electrophoresis revealed that thearmAgene was borne on an ∼150-kb broad-host-range IncP plasmid, pB1010. To elucidate howarmAhad integrated in pB1010, a PCR mapping strategy was developed for Tn1548, the genetic platform forarmA.The gene was embedded in a Tn1548-like structure, albeit with a deletion of the macrolide resistance genes, and an IS26was inserted within themelgene. To our knowledge, this is the first report of ArmA methyltransferase in food, showing a novel route of transmission for this resistance determinant. Further surveillance in food-borne bacteria will be crucial to determine the role of food in the spread of 16S rRNA methyltransferase genes worldwide.

Board demographic diversity, firm performance and strategic change

2014 ◽  
Vol 37 (12) ◽  
pp. 1110-1136 ◽  
Author(s):  
Daniel Kipkirong Tarus ◽  
Federico Aime
Keyword(s):  
Firm Performance ◽  
Fixed Effects ◽  
Strategic Change ◽  
Secondary Data ◽  
Developed Countries ◽  
Outcome Variable ◽  
Demographic Diversity ◽  
Content Type ◽  
Fixed Effects Regression ◽  
High Level

Purpose – The purpose of this study is to examine the effect of boards’ demographic diversity on firms’ strategic change and the interaction effect of firm performance. Design/methodology/approach – This paper used secondary data derived from publicly listed firms in Kenya during 2002-2010 and analyzed the data using fixed effects regression model to test the effect of board demographic and strategic change, while moderated regression analysis was used to test the moderating effect of firm performance. Findings – The results partially supported board demographic diversity–strategic change hypothesis. In particular, results indicate that age diversity produces less strategic change, while functional diversity is associated with greater levels of strategic change. The moderated regression results do not support our general logic that high firm performance enhances board demographic diversity–strategic change relationship. In effect, the results reveal that at high level of firm performance, board demographic diversity produces less strategic change. Originality/value – Despite few studies that have examined board demographic diversity and firm performance, this paper introduces strategic change as an outcome variable. This paper also explores the moderating role of firm performance in board demographic diversity–strategic change relationship, and finally, the study uses Kenyan dataset which in itself is unique because most governance and strategy research uses data from developed countries.

Sign in / Sign up

Export Citation Format

Share Document