Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 21
Filtrar
1.
BJOG ; 130(1): 15-23, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36047598

RESUMO

OBJECTIVE: To test the equivalence of two doses of intravenous iron (ferric carboxymaltose) in pregnancy. DESIGN: Parallel, two-arm equivalence randomised controlled trial with an equivalence margin of 5%. SETTING: Single centre in Australia. POPULATION: 278 pregnant women with iron deficiency. METHODS: Participants received either 500 mg (n = 152) or 1000 mg (n = 126) of intravenous ferric carboxymaltose in the second or third trimester. MAIN OUTCOME MEASURES: The proportion of participants requiring additional intravenous iron (500 mg) to achieve and maintain ferritin >30 microg/L (diagnostic threshold for iron deficiency) at 4 weeks post-infusion, and at 6 weeks, and 3-, 6- and 12-months postpartum. Secondary endpoints included repeat infusion rate, iron status, birth and safety outcomes. RESULTS: The two doses were not equivalent within a 5% margin at any time point. At 4 weeks post infusion, 26/73 (36%) participants required a repeat infusion in the 500-mg group compared with 5/67 (8%) in the 1000-mg group: difference in proportions, 0.283 (95% confidence interval [CI] 0.177-0.389). Overall, participants in the 500-mg arm received twice the repeat infusion rate (0.81 [SD = 0.824] versus 0.40 [SD = 0.69], rate ratio 2.05, 95% CI 1.45-2.91). CONCLUSIONS: Administration of 1000 mg ferric carboxymaltose in pregnancy maintains iron stores and reduces the need for repeat infusions. A 500- mg dose requires ongoing monitoring to ensure adequate iron stores are reached and sustained.


Assuntos
Anemia Ferropriva , Deficiências de Ferro , Feminino , Humanos , Gravidez , Ferro , Anemia Ferropriva/tratamento farmacológico , Maltose/uso terapêutico , Compostos Férricos/uso terapêutico , Administração Intravenosa
2.
Artigo em Inglês | MEDLINE | ID: mdl-33669705

RESUMO

Exposure assessment seldom precedes the medical health checks in occupational health surveillance. In order to emphasize the interconnection between exposure assessment and medical health checks, a process model was developed. The process model aimed to guide employers and Occupational Health Service providers through the execution of occupational health surveillance. The objective of this qualitative study is to explore company representatives' experiences of the process model, in terms of feasibility and values, and to identify factors that facilitate or impede the process. Thirty-three company representatives from ten companies were interviewed. Interviews were analyzed using content analysis. The company representatives experienced that the model contributed to increased risk awareness and understanding of the exposure effects on workers' health. They valued the exposure assessments performed by an ergonomics expert, which led to the discovery of previously unidentified risks. The feasibility was facilitated by: a joint start-up meeting in which the process was planned, clear communication between the involved parties, and clarity regarding the process ownership. The findings reveal that a guiding process model is valuable for the execution of occupational health surveillance. However, the model should not only define the components included; a practical guide concerning how the process can be executed is also needed.


Assuntos
Serviços de Saúde do Trabalhador , Saúde Ocupacional , Comunicação , Mãos , Humanos , Pesquisa Qualitativa
3.
Sensors (Basel) ; 21(3)2021 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-33572815

RESUMO

Body postural allocation during daily life is important for health, and can be assessed with thigh-worn accelerometers. An algorithm based on sedentary bouts from the proprietary ActivePAL software can detect lying down from a single thigh-worn accelerometer using rotations of the thigh. However, it is not usable across brands of accelerometers. This algorithm has the potential to be refined. Aim: To refine and assess the validity of an algorithm to detect lying down from raw data of thigh-worn accelerometers. Axivity-AX3 accelerometers were placed on the thigh and upper back (reference) on adults in a development dataset (n = 50) and a validation dataset (n = 47) for 7 days. Sedentary time from the open Acti4-algorithm was used as input to the algorithm. In addition to the thigh-rotation criterion in the existing algorithm, two criteria based on standard deviation of acceleration and a time duration criterion of sedentary bouts were added. The mean difference (95% agreement-limits) between the total identified lying time/day, between the refined algorithm and the reference was +2.9 (-135,141) min in the development dataset and +6.5 (-145,159) min in the validation dataset. The refined algorithm can be used to estimate lying time in studies using different accelerometer brands.


Assuntos
Acelerometria , Comportamento Sedentário , Coxa da Perna , Adulto , Algoritmos , Feminino , Humanos , Postura
4.
Artigo em Inglês | MEDLINE | ID: mdl-32887430

RESUMO

The objective of this study protocol is to describe the development of a process model for occupational health surveillance for workers exposed to hand-intensive work (the HIW-model), and to describe the studies that will explore the model. The studies are designed to: (1) explore stakeholders' experiences of the model, and (2) explore if, and how, the model affects actions for reduction of exposure to hand-intensive work. The study protocol presents a research project that is described as two studies. The first study will explore company representatives' and ergonomists' experiences of the execution of the HIW-model and its various components concerning feasibility and values. Semi-structured interviews will constitute the data source. The second study will explore whether the execution of the HIW-model leads to work environmental changes, such as actions for reduction of exposure to hand-intensive work, and whether these potential actions are based on the ergonomist's feedback of the exposure assessment and the medical health checks. A mixed method approach will be applied, in which the data sources will be comprised of semi-structured interviews, questionnaires, and documents. The project is expected to generate knowledge regarding the values of the HIW-model. The project is anticipated to shed light on factors that facilitate or impede execution of the model from the different stakeholders' perspectives; the employer's as having the legal responsibility for the work environment, and the occupational health service consultants', being the work environment experts supporting the employers.


Assuntos
Mãos , Saúde Ocupacional , Trabalho , Humanos , Atividade Motora , Pesquisa Qualitativa
5.
BMJ Open Sport Exerc Med ; 6(1): e000874, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33408875

RESUMO

INTRODUCTION: The Prospective Physical Activity Sitting and Sleep consortium (ProPASS) is an international collaboration platform committed to harmonise thigh-worn accelerometry data. The aim of this paper is to (1) outline observational thigh-worn accelerometry studies and (2) summarise key strategic directions arising from the inaugural ProPASS meeting. METHODS: (1) We performed a systematic scoping review for observational studies of thigh-worn triaxial accelerometers in free-living adults (n≥100, 24 hours monitoring protocols). (2)Attendees of the inaugural ProPASS meeting were sent a survey focused on areas related to developing ProPASS: important terminology (Q1); accelerometry constructs (Q2); advantages and distinct contribution of the consortium (Q3); data pooling and harmonisation (Q4); data access and sharing (Q5 and Q6). RESULTS: (1) Eighty eligible articles were identified (22 primary studies; n~17 685). The accelerometers used most often were the ActivPAL3 and ActiGraph GT3X. The most commonly collected health outcomes were cardiometabolic and musculoskeletal. (2) None of the survey questions elicited the predefined 60% agreement. Survey responses recommended that ProPASS: use the term physical behaviour or movement behaviour rather than 'physical activity' for the data we are collecting (Q1); make only minor changes to ProPASS's accelerometry construct (Q2); prioritise developing standardised protocols/tools (Q4); facilitate flexible methods of data sharing and access (Q5 and Q6). CONCLUSIONS: Thigh-worn accelerometry is an emerging method of capturing movement and posture across the 24 hours cycle. In 2020, the literature is limited to 22 primary studies from high-income western countries. This work identified ProPASS's strategic directions-indicating areas where ProPASS can most benefit the field of research: use of clear terminology, refinement of the measured construct, standardised protocols/tools and flexible data sharing.

7.
Genes (Basel) ; 10(3)2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30832293

RESUMO

The unexpected lysis of a large culture of Halobacterium salinarum strain S9 was found to be caused by a novel myovirus, designated ChaoS9. Virus purification from the culture lysate revealed a homogeneous population of caudovirus-like particles. The viral genome is linear, dsDNA that is partially redundant and circularly permuted, has a unit length of 55,145 nt, a G + C% of 65.3, and has 85 predicted coding sequences (CDS) and one tRNA (Arg) gene. The left arm of the genome (0⁻28 kbp) encodes proteins similar in sequence to those from known caudoviruses and was most similar to myohaloviruses phiCh1 (host: Natrialbamagadii) and phiH1 (host: Hbt. salinarum). It carries a tail-fiber gene module similar to the invertible modules present in phiH1 and phiCh1. However, while the tail genes of ChaoS9 were similar to those of phiCh1 and phiH1, the Mcp of ChaoS9 was most similar (36% aa identity) to that of Haloarcula hispanica tailed virus 1 (HHTV-1). Provirus elements related to ChaoS9 showed most similarity to tail/assembly proteins but varied in their similarity with head/assembly proteins. The right arm (29⁻55 kbp) of ChaoS9 encoded proteins involved in DNA replication (ParA, RepH, and Orc1) but the other proteins showed little similarity to those from phiH1, phiCh1, or provirus elements, and most of them could not be assigned a function. ChaoS9 is probably best classified within the genus Myohalovirus, as it shares many characteristics with phiH1 (and phiCh1), including many similar proteins. However, the head/assembly gene region appears to have undergone a recombination event, and the inferred proteins are different to those of phiH1 and phiCh1, including the major capsid protein. This makes the taxonomic classification of ChaoS9 more ambiguous. We also report a revised genome sequence and annotation of Natrialba virus phiCh1.


Assuntos
DNA Viral/genética , Halobacterium salinarum/virologia , Myoviridae/classificação , Composição de Bases , Tamanho do Genoma , Anotação de Sequência Molecular , Myoviridae/genética , Filogenia
8.
Ann Work Expo Health ; 62(6): 689-698, 2018 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-29945157

RESUMO

Regarding prevention of neck and shoulder pain (NSP), unsupported arm elevation is one factor that should be taken into account when performing work risk assessment. Triaxial accelerometers can be used to measure arm elevation over several days but it is not possible to differentiate between supported and unsupported arm elevation from accelerometers only. Supported arm elevation is more likely to exist during sitting than standing. The aim of the study was to evaluate the use of whole workday measurements of arm elevation with accelerometers to assess potentially harmful work exposure of arm elevation, by comparing arm elevation at work with arm elevation during leisure, in a population with diverse work tasks, and to assess how the exposure parameters were modified when upper arm elevation during sitting time was excluded. The participants, 197 workers belonging to 12 occupational groups with diverse work tasks, wore triaxial accelerometers on the dominant arm, hip, and back for 1-4 days to measure arm elevation and periods of sitting. None of the groups were found to have higher exposure to arm elevation during work compared to leisure. Even though some occupations where known to have work tasks that forced them to work with elevated arms to a large extent. A high proportion of arm elevation derived from sitting time, especially so during leisure. When arm elevation during sitting time was excluded from the analysis, arm elevation was significantly higher at work than during leisure among construction workers, garbage collectors, manufacturing workers, and domestic cleaners. Together this illustrates that it is not suitable to use whole workday measurments of arm elevation with accelerometer as a sole information source when assessing the risk for NSP due to arm elevation. Information on body posture can provide relevant contextual information in exposure assessments when it is known that the potential harmful exposure is performed in standing or walking.


Assuntos
Acelerometria , Braço , Ocupações , Postura , Adulto , Estudos Transversais , Dinamarca , Feminino , Humanos , Atividades de Lazer , Masculino , Pessoa de Meia-Idade , Cervicalgia/prevenção & controle , Dor de Ombro/prevenção & controle
11.
Appl Ergon ; 62: 1-8, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28411720

RESUMO

A common way to conduct practical risk assessments is to observe a job and report the observed long term risks for musculoskeletal disorders. The aim of this study was to evaluate the inter- and intra-observer reliability of ergonomists' risk assessments without the support of an explicit risk assessment method. Twenty-one experienced ergonomists assessed the risk level (low, moderate, high risk) of eight upper body regions, as well as the global risk of 10 video recorded work tasks. Intra-observer reliability was assessed by having nine of the ergonomists repeat the procedure at least three weeks after the first assessment. The ergonomists made their risk assessment based on his/her experience and knowledge. The statistical parameters of reliability included agreement in %, kappa, linearly weighted kappa, intraclass correlation and Kendall's coefficient of concordance. The average inter-observer agreement of the global risk was 53% and the corresponding weighted kappa (Kw) was 0.32, indicating fair reliability. The intra-observer agreement was 61% and 0.41 (Kw). This study indicates that risk assessments of the upper body, without the use of an explicit observational method, have non-acceptable reliability. It is therefore recommended to use systematic risk assessment methods to a higher degree.


Assuntos
Transtornos Traumáticos Cumulativos/etiologia , Ergonomia/métodos , Observação/métodos , Variações Dependentes do Observador , Saúde Ocupacional , Adulto , Feminino , Humanos , Região Lombossacral , Masculino , Pessoa de Meia-Idade , Movimento , Sistema Musculoesquelético/lesões , Pescoço , Ocupações , Postura , Competência Profissional , Reprodutibilidade dos Testes , Medição de Risco/métodos , Extremidade Superior
12.
Ann Surg ; 264(1): 41-6, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26817624

RESUMO

OBJECTIVE: To determine if preoperative intravenous (IV) iron improves outcomes in abdominal surgery patients. SUMMARY BACKGROUND DATA: Preoperative iron deficiency anemia (IDA) occurs frequently; however if left untreated, increases the risk of blood transfusion allogeneic blood transfusion (ABT). Limited evidence supports IDA treatment with preoperative IV iron. This randomized controlled trial aimed to determine whether perioperative IV iron reduced the need for ABT. METHODS: Between August 2011 and November 2014, 72 patients with IDA were assigned to receive either IV iron or usual care. The primary endpoint was incidence of ABT. Secondary endpoints were various hemoglobin (Hb) levels, change in Hb between time points, length of stay, iron status, morbidity, mortality, and quality of life 4 weeks postsurgery. RESULTS: A 60% reduction in ABT was observed in the IV iron group compared with the usual care group (31.25% vs 12.5%). Hb values, although similar at randomization, improved by 0.8 g/dL with IV iron compared with 0.1 g/dL with usual care (P = 0.01) by the day of admission. The IV iron group had higher Hb 4 weeks after discharge compared with the usual care group (1.9 vs 0.9 g/dL, P = 0.01), and a shorter length of stay (7.0 vs 9.7 d, P = 0.026). There was no difference in discharge Hb levels, morbidity, mortality, or quality of life. CONCLUSIONS: Administration of perioperative IV iron reduces the need for blood transfusion, and is associated with a shorter hospital stay, enhanced restoration of iron stores, and a higher mean Hb concentration 4 weeks after surgery.


Assuntos
Anemia Ferropriva/tratamento farmacológico , Perda Sanguínea Cirúrgica/prevenção & controle , Compostos Férricos/administração & dosagem , Tempo de Internação , Maltose/análogos & derivados , Assistência Perioperatória , Cuidados Pós-Operatórios , Qualidade de Vida , Cavidade Abdominal/cirurgia , Idoso , Anemia Ferropriva/terapia , Transfusão de Sangue/métodos , Índice de Massa Corporal , Procedimentos Cirúrgicos do Sistema Digestório , Feminino , Seguimentos , Humanos , Injeções Intravenosas , Masculino , Maltose/administração & dosagem , Pessoa de Meia-Idade , Resultado do Tratamento
13.
Ergonomics ; 59(6): 829-39, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26538287

RESUMO

We evaluated the intra- and inter-observer reliability and criterion validity of an observation protocol, developed in an iterative process involving practicing ergonomists, for assessment of working technique during cash register work for the purpose of preventing upper extremity symptoms. Two ergonomists independently assessed 17 15-min videos of cash register work on two occasions each, as a basis for examining reliability. Criterion validity was assessed by comparing these assessments with meticulous video-based analyses by researchers. Intra-observer reliability was acceptable (i.e. proportional agreement >0.7 and kappa >0.4) for 10/10 questions. Inter-observer reliability was acceptable for only 3/10 questions. An acceptable inter-observer reliability combined with an acceptable criterion validity was obtained only for one working technique aspect, 'Quality of movements'. Thus, major elements of the cashiers' working technique could not be assessed with an acceptable accuracy from short periods of observations by one observer, such as often desired by practitioners. Practitioner Summary: We examined an observation protocol for assessing working technique in cash register work. It was feasible in use, but inter-observer reliability and criterion validity were generally not acceptable when working technique aspects were assessed from short periods of work. We recommend the protocol to be used for educational purposes only.


Assuntos
Ergonomia , Observação , Variações Dependentes do Observador , Exposição Ocupacional , Extremidade Superior , Transtornos Traumáticos Cumulativos , Estudos de Viabilidade , Feminino , Humanos , Masculino , Traumatismos Ocupacionais , Reprodutibilidade dos Testes , Gravação em Vídeo
14.
Genome Announc ; 1(2): e0009513, 2013 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-23516216

RESUMO

The genus Natronomonas contains two species, one haloalkaliphile (N. pharaonis) and one neutrophile (N. moolapensis). Here, we report the genome sequence of N. moolapensis strain 8.8.11. The overall genome properties are similar for the two species. Only the neutrophile contains bacteriorhodopsin and a membrane glycolipid.

15.
Environ Microbiol ; 15(5): 1619-33, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-22583374

RESUMO

Salt acclimation in moderately halophilic bacteria is the result of action of a grand interplay orchestrated by signals perceived from the environment. To elucidate the cellular players involved in sensing and responding to changing salinities we have determined the genome sequence of Halobacillus halophilus, a Gram-positive moderate halophilic bacterium that has a strict requirement for the anion chloride. Halobacillus halophilus synthesizes a multitude of different compatible solutes and switches its osmolyte strategy with the external salinity and growth phase. Based on the emerging genome sequence, the compatible solutes glutamate, glutamine, proline and ectoine have already been experimentally studied. The biosynthetic routes for acetyl ornithine and acetyl lysine are also delineated from the genome sequence. Halobacillus halophilus is nutritionally very versatile and most compatible solutes cannot only be produced but also used as carbon and energy sources. The genome sequence unravelled isogenes for many pathways indicating a fine regulation of metabolism. Halobacillus halophilus is unique in integrating the concept of compatible solutes with the second fundamental principle to cope with salt stress, the accumulation of molar concentrations of salt (Cl(-)) in the cytoplasm. Extremely halophilic bacteria/archaea, which exclusively rely on the salt-in strategy, have a high percentage of acidic proteins compared with non-halophiles with a low percentage. Halobacillus halophilus has an intermediate position which is consistent with its ability to integrate both principles.


Assuntos
Cloretos/metabolismo , Halobacillus/fisiologia , Salinidade , Genoma Bacteriano/genética , Halobacillus/química , Halobacillus/crescimento & desenvolvimento , Halobacillus/metabolismo , Homeostase , Proteoma , Cloreto de Sódio/metabolismo
16.
Work ; 41 Suppl 1: 663-8, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22316798

RESUMO

Checkout cashier work consists of handling a large number of items during a work shift, which implies repetitive movements of the shoulders, arms and hands/wrists, and a high work rate. The work is associated with a high prevalence of disorders in the neck and upper extremity. The concept of workstyle explains how ergonomic and psychosocial factors interact in the development of work-related upper extremity disorders. The aim of the project was to develop an instrument for the occupational health services to be used in the efforts to prevent upper extremity disorders in checkout cashier work. The instrument is based on the workstyle concept and is intended to be used as a tool to identify high-risk workstyle and needs for interventions, such as training and education. The instrument, BAsIK, consists of four parts; a questionnaire about workstyle, an observation protocol for work technique, a checklist about the design of the checkout and a questionnaire about work organization. The instrument was developed by selecting workstyle items developed for office work and adapting them to checkout cashier work, discussions with researchers and ergonomists, focus-group interviews with cashiers, observations of video recordings of cashiers, and studies of existing guidelines and checklists.


Assuntos
Comércio , Transtornos Traumáticos Cumulativos/prevenção & controle , Ergonomia/métodos , Doenças Profissionais/prevenção & controle , Saúde Ocupacional , Análise e Desempenho de Tarefas , Lista de Checagem , Transtornos Traumáticos Cumulativos/etiologia , Grupos Focais , Humanos , Entrevistas como Assunto , Doenças Profissionais/etiologia , Inquéritos e Questionários , Extremidade Superior , Gravação em Vídeo , Local de Trabalho/organização & administração
17.
PLoS One ; 6(6): e20968, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-21701686

RESUMO

BACKGROUND: Haloquadratum walsbyi commonly dominates the microbial flora of hypersaline waters. Its cells are extremely fragile squares requiring >14%(w/v) salt for growth, properties that should limit its dispersal and promote geographical isolation and divergence. To assess this, the genome sequences of two isolates recovered from sites at near maximum distance on Earth, were compared. PRINCIPAL FINDINGS: Both chromosomes are 3.1 MB in size, and 84% of each sequence was highly similar to the other (98.6% identity), comprising the core sequence. ORFs of this shared sequence were completely synteneic (conserved in genomic orientation and order), without inversion or rearrangement. Strain-specific insertions/deletions could be precisely mapped, often allowing the genetic events to be inferred. Many inferred deletions were associated with short direct repeats (4-20 bp). Deletion-coupled insertions are frequent, producing different sequences at identical positions. In cases where the inserted and deleted sequences are homologous, this leads to variant genes in a common synteneic background (as already described by others). Cas/CRISPR systems are present in C23(T) but have been lost in HBSQ001 except for a few spacer remnants. Numerous types of mobile genetic elements occur in both strains, most of which appear to be active, and with some specifically targetting others. Strain C23(T) carries two ∼6 kb plasmids that show similarity to halovirus His1 and to sequences nearby halovirus/plasmid gene clusters commonly found in haloarchaea. CONCLUSIONS: Deletion-coupled insertions show that Hqr. walsbyi evolves by uptake and precise integration of foreign DNA, probably originating from close relatives. Change is also driven by mobile genetic elements but these do not by themselves explain the atypically low gene coding density found in this species. The remarkable genome conservation despite the presence of active systems for genome rearrangement implies both an efficient global dispersal system, and a high selective fitness for this species.


Assuntos
Halobacteriaceae/genética , Genoma Arqueal/genética , Halobacteriaceae/classificação , Dados de Sequência Molecular , Filogenia , RNA Ribossômico 16S/genética
18.
Appl Environ Microbiol ; 73(2): 371-9, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17085700

RESUMO

The moderately halophilic bacterium Halobacillus halophilus carries a homologue of LuxS, a protein involved in the activated methyl cycle and the production of autoinducer-2, which mediates quorum sensing between certain species. luxS of H. halophilus is part of an operon that encodes an S-adenosylmethionine-dependent methyltransferase, a cysteine synthase, and a beta-cystathionine lyase. Expression of luxS was growth phase dependent, with maximal expression in the mid-exponential growth phase. In addition, transcription of luxS was strictly salt dependent; maximal mRNA concentrations were observed with 2.0 M NaCl in the growth medium. Chloride ions stimulated luxS transcription by a factor of three. Western blot analyses demonstrated a growth phase- and salinity-dependent production of LuxS. Moreover, cellular LuxS levels were strictly chloride dependent. Maximal accumulation of LuxS was observed at 0.5 to 1.0 M Cl(-) and depended on the salinity.


Assuntos
Bacillaceae/metabolismo , Proteínas de Bactérias/metabolismo , Liases de Carbono-Enxofre/metabolismo , Cloretos/farmacologia , Regulação Bacteriana da Expressão Gênica , Homosserina/análogos & derivados , Cloreto de Sódio/farmacologia , Sequência de Aminoácidos , Bacillaceae/genética , Bacillaceae/crescimento & desenvolvimento , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Liases de Carbono-Enxofre/química , Liases de Carbono-Enxofre/genética , Homosserina/biossíntese , Lactonas , Dados de Sequência Molecular , Transcrição Gênica
19.
J Bacteriol ; 188(19): 6808-15, 2006 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16980483

RESUMO

The moderately halophilic, chloride-dependent bacterium Halobacillus halophilus produces glutamate and glutamine as main compatible solutes at external salinities of 1.0 to 1.5 M NaCl. The routes for the biosynthesis of these solutes and their regulation were examined. The genome contains two genes potentially encoding glutamate dehydrogenases and two genes for the small subunit of a glutamate synthase, but only one gene for the large subunit. However, the expression of these genes was not salt dependent, nor were the corresponding enzymatic activities detectable in cell extracts of cells grown at different salinities. In contrast, glutamine synthetase activity was readily detectable in H. halophilus. Induction of glutamine synthetase activity was strictly salt dependent and reached a maximum at 3.0 M NaCl; chloride stimulated the production of active enzyme by about 300%. Two potential genes encoding a glutamine synthetase, glnA1 and glnA2, were identified. The expression of glnA2 but not of glnA1 was increased up to fourfold in cells adapted to high salt, indicating that GlnA2 is the glutamine synthetase involved in the synthesis of the solutes glutamate and glutamine. Furthermore, expression of glnA2 was stimulated twofold by the presence of chloride ions. Chloride exerted an even more pronounced effect on the enzymatic activity of preformed enzyme: in the absence of chloride in the assay buffer, glutamine synthetase activity was decreased by as much as 90%. These data demonstrate for the first time a regulatory role of a component of common salt, chloride, in the biosynthesis of compatible solutes.


Assuntos
Bacillaceae/metabolismo , Regulação Bacteriana da Expressão Gênica , Ácido Glutâmico/biossíntese , Glutamina/biossíntese , Bacillaceae/genética , Cloretos , DNA Bacteriano/química , DNA Bacteriano/genética , Indução Enzimática , Regulação da Expressão Gênica , Genes Bacterianos , Glutamato Desidrogenase/análise , Glutamato Desidrogenase/genética , Glutamato Sintase/análise , Glutamato Sintase/genética , Glutamato-Amônia Ligase/análise , Glutamato-Amônia Ligase/genética , Dados de Sequência Molecular , Análise de Sequência de DNA , Cloreto de Sódio
20.
BMC Genomics ; 7: 169, 2006 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-16820047

RESUMO

BACKGROUND: The square halophilic archaeon Haloquadratum walsbyi dominates NaCl-saturated and MgCl2 enriched aquatic ecosystems, which imposes a serious desiccation stress, caused by the extremely low water activity. The genome sequence was analyzed and physiological and physical experiments were carried out in order to reveal how H. walsbyi has specialized into its narrow and hostile ecological niche and found ways to cope with the desiccation stress. RESULTS: A rich repertoire of proteins involved in phosphate metabolism, phototrophic growth and extracellular protective polymers, including the largest archaeal protein (9159 amino acids), a homolog to eukaryotic mucins, are amongst the most outstanding features. A relatively low GC content (47.9%), 15-20% less than in other halophilic archaea, and one of the lowest coding densities (76.5%) known for prokaryotes might be an indication for the specialization in its unique environment CONCLUSION: Although no direct genetic indication was found that can explain how this peculiar organism retains its square shape, the genome revealed several unique adaptive traits that allow this organism to thrive in its specific and extreme niche.


Assuntos
Archaea/genética , Archaea/fisiologia , Desidratação/genética , Genoma Arqueal , Bacteriorodopsinas/metabolismo , Água Corporal , Di-Hidroxiacetona/metabolismo , Estruturas Genéticas , Modelos Biológicos , Fosfatos/metabolismo , Fosfoenolpiruvato/metabolismo , Fosfotransferases/metabolismo , Filogenia , Plasmídeos/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...