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BACKGROUND: The relative new subspecialty 'cardio-oncology' was established to meet the growing demand for an interdisciplinary approach to the management of cancer therapy-related cardiovascular adverse events. In recent years, specialised cardio-oncology services have been implemented worldwide, which all strive to improve the cardiovascular health of cancer patients. However, limited data are currently available on the outcomes and experiences of these specialised services, and optimal strategies for cardio-oncological care have not been established. AIM: The ONCOR registry has been created for prospective data collection and evaluation of cardio-oncological care in daily practice. METHODS: Dutch hospitals using a standardised cardio-oncology care pathway are included in this national, multicentre, observational cohort study. All patients visiting these cardio-oncology services are eligible for study inclusion. Data collection at baseline consists of the (planned) cancer treatment and the cardiovascular risk profile, which are used to estimate the cardiotoxic risk. Information regarding invasive and noninvasive tests is collected during the time patients receive cardio-oncological care. Outcome data consist of the incidence of cardiovascular complications and major adverse cardiac events, and the impact of these events on the oncological treatment. DISCUSSION: Outcomes of the ONCOR registry may aid in gaining more insight into the incidence of cancer therapy-related cardiovascular complications. The registry facilitates research on mechanisms of cardiovascular complications and on diagnostic, prognostic and therapeutic strategies. In addition, it provides a platform for future (interventional) studies. Centres with cardio-oncology services that are interested in contributing to the ONCOR registry are hereby invited to participate.
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The optimal treatment strategy for asymptomatic patients with severe mitral valve regurgitation (MR) and preserved left ventricular (LV) function is challenging. This manuscript reviews the available literature on the value of left ventricular global longitudinal strain (LV-GLS) in predicting LV dysfunction after mitral valve surgery in these patients and discusses its current place in the treatment strategy. Studies were identified from Cochrane Library, SCOPUS, PubMed and Web of Science up to February 2018. The domain used was MR. The determinant was LV-GLS; other methods of deformation imaging were excluded. The examined outcome was LV dysfunction after surgery. A total of 144 articles were retrieved, of which 11 publications met the inclusion criteria, including a total of 2415 patients. Ten studies showed a significant correlation between preoperative LV-GLS and LV dysfunction postoperatively; one study reported a negative correlation. These studies suggest that LV-GLS is a predictor of LV dysfunction after surgery in asymptomatic patients with chronic MR. Hence, incorporation of LV-GLS for clinical decision-making in these patients might be of additional value. Further research is needed to confirm the role of LV-GLS in postoperative patients, and additionally in asymptomatic MR patients during a 'watchful waiting' strategy.
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Recent advances in the early detection and treatment of cancer have led to increasing numbers of cancer survivors worldwide. Nonetheless, despite major improvements in the outcome of these patients, long-term side effects of radio- and chemotherapy affect both patient survival and quality of life, independent of the oncological prognosis. Chemotherapy-related cardiac dysfunction is one of the most notorious short-term side effects of anticancer treatment, occurring in ~10% of patients. Progression to overt heart failure carries a strikingly poor prognosis with a 2-year mortality rate of 60%. Early detection of left ventricular damage by periodic monitoring and prompt initiation of heart failure treatment is key in improving cardiovascular prognosis. To meet the growing demand for a specialised interdisciplinary approach for the prevention and management of cardiovascular complications induced by cancer treatment, a new discipline termed cardio-oncology has evolved. However, an uniform, multidisciplinary approach is currently lacking in the Netherlands. This overview provides an introduction and comprehensive summary of this emerging discipline and offers a practical strategy for the outpatient management of this specific patient population.
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Chemotherapy-induced cardiomyopathy (CCMP) is a complication of chemotherapy treatment occurring in 9% of patients treated with the use of anthracyclines. Currently, risk stratification is based on clinical risk factors that do not adequately account for variable individual susceptibility. This suggests the presence of other determinants. In this case series, we describe 2 women with breast cancer who developed severe heart failure within months after chemotherapy. Genetic screening revealed truncating frameshift mutations in TTN, encoding the myofilament titin, in both women. To our knowledge, this is the 1st report of an association between truncating TTN variants and CCMP. Because truncations in TTN are the most common cause of familial and sporadic dilated cardiomyopathy, further research is needed to establish their prevalence in patients presenting with CCMP.
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Antineoplásicos/efectos adversos , Cardiomiopatías/inducido químicamente , Cardiomiopatías/genética , Conectina/genética , Variación Genética/genética , Adulto , Neoplasias de la Mama/diagnóstico por imagen , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/genética , Carcinoma Ductal/diagnóstico por imagen , Carcinoma Ductal/tratamiento farmacológico , Carcinoma Ductal/genética , Cardiomiopatías/diagnóstico por imagen , Resultado Fatal , Femenino , Humanos , Persona de Mediana EdadRESUMEN
Percutaneous MitraClip placement for treatment of severe mitral regurgitation in high surgical risk patients is a commonly performed procedure and requires a transseptal puncture to reach the left atrium. The resulting iatrogenic atrial septal defect (iASD) is not routinely closed, yet the haemodynamic and functional consequences of a persisting defect are not fully understood. Despite positive effects such as acute left atrial pressure relief, persisting iASDs are associated with negative consequences, namely significant bidirectional shunting and subsequent worse clinical outcome. Percutaneous closure of the iASD may therefore be desirable in selected cases. In this review we discuss the available literature on this matter.
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In Arctic marine bacterial communities, members of the phylum Verrucomicrobia are consistently detected, although not typically abundant, in 16S rRNA gene clone libraries and pyrotag surveys of the marine water column and in sediments. In an Arctic fjord (Smeerenburgfjord) of Svalbard, members of the Verrucomicrobia, together with Flavobacteria and smaller proportions of Alpha- and Gammaproteobacteria, constituted the most frequently detected bacterioplankton community members in 16S rRNA gene-based clone library analyses of the water column. Parallel measurements in the water column of the activities of six endo-acting polysaccharide hydrolases showed that chondroitin sulfate, laminarin, and xylan hydrolysis accounted for most of the activity. Several Verrucomicrobia water column phylotypes were affiliated with previously sequenced, glycoside hydrolase-rich genomes of individual Verrucomicrobia cells that bound fluorescently labeled laminarin and xylan and therefore constituted candidates for laminarin and xylan hydrolysis. In sediments, the bacterial community was dominated by different lineages of Verrucomicrobia, Bacteroidetes, and Proteobacteria but also included members of multiple phylum-level lineages not observed in the water column. This community hydrolyzed laminarin, xylan, chondroitin sulfate, and three additional polysaccharide substrates at high rates. Comparisons with data from the same fjord in the previous summer showed that the bacterial community in Smeerenburgfjord changed in composition, most conspicuously in the changing detection frequency of Verrucomicrobia in the water column. Nonetheless, in both years the community hydrolyzed the same polysaccharide substrates.
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Polisacáridos/metabolismo , Agua de Mar/microbiología , Verrucomicrobia/aislamiento & purificación , Verrucomicrobia/metabolismo , Regiones Árticas , Datos de Secuencia Molecular , Filogenia , Svalbard , Verrucomicrobia/clasificación , Verrucomicrobia/genéticaRESUMEN
BACKGROUND: Fluoropyrimidines (FPs) are an essential part of the majority of systemic regimens in the treatment of metastatic colorectal cancer (CRC). The use of the oral FP S-1 has been approved by the European Medicines Agency as monotherapy or in combination with oxaliplatin or irinotecan, with or without bevacizumab, for the treatment of patients with metastatic CRC in whom it is not possible to continue treatment with another FP due to hand-foot syndrome (HFS) or cardiovascular toxicity (CVT). Subsequently, this indication has been included in the 2022 ESMO guidelines for metastatic CRC. Recommendations for use in daily practice are not available. PATIENTS AND METHODS: Based on peer-reviewed published data on the use of S-1 in Western patients with metastatic CRC who switched from infusional 5-fluorouracil (5-FU) or capecitabine to S-1 for reasons of HFS or CVT, recommendations for its use were formulated by an international group of medical oncologists with expertise in the treatment of metastatic CRC and a cardio-oncologist. RESULTS: In patients who experience pain and/or functional impairment due to HFS during treatment with capecitabine or infusional 5-FU, a switch to S-1 is recommended without prior dose reduction of capecitabine/5-FU. S-1 should preferably be initiated at full dose when HFS has decreased to grade ≤1. In patients with cardiac complaints, in whom an association with capecitabine or infusional 5-FU treatment cannot be excluded, capecitabine/5-FU should be discontinued and a switch to S-1 is recommended. CONCLUSIONS: These recommendations should guide clinicians in daily practice in the treatment of patients with metastatic CRC with FP-containing regimens.
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Neoplasias del Colon , Neoplasias Colorrectales , Síndrome Mano-Pie , Humanos , Capecitabina/efectos adversos , Neoplasias Colorrectales/tratamiento farmacológico , Neoplasias Colorrectales/patología , Síndrome Mano-Pie/etiología , Síndrome Mano-Pie/tratamiento farmacológico , Fluorouracilo/efectos adversos , Irinotecán/uso terapéutico , Neoplasias del Colon/tratamiento farmacológico , Factores Inmunológicos/uso terapéuticoRESUMEN
The rapid emergence of cardio-oncology has resulted in a rapid growth of cardio-oncology programs, dedicated professional societies sections and committees, and multiple collaborative networks that emerged to amplify the access to care in this new subspecialty. However, most existing data, position statements and guidelines are limited by the lack of availability of large clinical trials to support these recommendations. Furthermore, there are significant challenges regarding proper access to cardio-oncology care and treatment, particularly in marginalized and minority populations. The emergence and evolution of personalized medicine, artificial intelligence (AI), and machine learning in medicine and in cardio-oncology provides an opportunity for a more targeted, personalized approach to cardiovascular complications of cancer treatment. The proper implementation of these new modalities may facilitate a more equitable approach to adequate and universal access to cardio-oncology care, improve health related outcomes, and enable health care systems to eliminate the digital divide. This article reviews and analyzes the current status on these important issues.
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BACKGROUND: Capecitabine- or 5-fluorouracil (5-FU)-based chemotherapy is widely used in many solid tumours, but is associated with cardiotoxicity. S-1 is a fluoropyrimidine with low rates of cardiotoxicity, but evidence regarding the safety of switching to S-1 after 5-FU- or capecitabine-associated cardiotoxicity is scarce. PATIENTS AND METHODS: This retrospective study (NCT04260269) was conducted at 13 centres in 6 countries. The primary endpoint was recurrence of cardiotoxicity after switch to S-1-based treatment due to 5-FU- or capecitabine-related cardiotoxicity: clinically meaningful if the upper boundary of the 95% confidence interval (CI; by competing risk) is not including 15%. Secondary endpoints included cardiac risk factors, diagnostic work-up, treatments, outcomes, and timelines of cardiotoxicity. RESULTS: Per protocol, 200 patients, treated between 2011 and 2020 [median age 66 years (range 19-86); 118 (59%) males], were included. Treatment intent was curative in 145 (73%). Initial cardiotoxicity was due to capecitabine (n = 170), continuous infusion 5-FU (n = 22), or bolus 5-FU (n = 8), which was administered in combination with other chemotherapy, targeted agents, or radiotherapy in 133 patients. Previous cardiovascular comorbidities were present in 99 (50%) patients. Cardiotoxic events (n = 228/200) included chest pain (n = 125), coronary syndrome/infarction (n = 69), arrhythmia (n = 22), heart failure/cardiomyopathy (n = 7), cardiac arrest (n = 4), and malignant hypertension (n = 1). Cardiotoxicity was severe or life-threatening in 112 (56%) patients and led to permanent capecitabine/5-FU discontinuation in 192 (96%). After switch to S-1, recurrent cardiotoxicity was observed in eight (4%) patients (95% CI 2.02-7.89, primary endpoint met). Events were limited to grade 1-2 and occurred at a median of 16 days (interquartile range 7-67) from therapy switch. Baseline ischemic heart disease was a risk factor for recurrent cardiotoxicity (odds ratio 6.18, 95% CI 1.36-28.11). CONCLUSION: Switching to S-1-based therapy is safe and feasible after development of cardiotoxicity on 5-FU- or capecitabine-based therapy and allows patients to continue their pivotal fluoropyrimidine-based treatment.
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Fluorouracilo , Neoplasias , Adulto , Anciano , Anciano de 80 o más Años , Capecitabina/efectos adversos , Cardiotoxicidad/etiología , Femenino , Fluorouracilo/efectos adversos , Humanos , Masculino , Persona de Mediana Edad , Neoplasias/tratamiento farmacológico , Estudios Retrospectivos , Adulto JovenRESUMEN
Heterotrophic microbial communities in seawater and sediments metabolize much of the organic carbon produced in the ocean. Although carbon cycling and preservation depend critically on the capabilities of these microbial communities, their compositions and capabilities have seldom been examined simultaneously at the same site. To compare the abilities of seawater and sedimentary microbial communities to initiate organic matter degradation, we measured the extracellular enzymatic hydrolysis rates of 10 substrates (polysaccharides and algal extracts) in surface seawater and bottom water as well as in surface and anoxic sediments of an Arctic fjord. Patterns of enzyme activities differed between seawater and sediments, not just quantitatively, in accordance with higher cell numbers in sediments, but also in their more diversified enzyme spectrum. Sedimentary microbial communities hydrolyzed all of the fluorescently labeled polysaccharide and algal extracts, in most cases at higher rates in subsurface than surface sediments. In seawater, in contrast, only 5 of the 7 polysaccharides and 2 of the 3 algal extracts were hydrolyzed, and hydrolysis rates in surface and deepwater were virtually identical. To compare bacterial communities, 16S rRNA gene clone libraries were constructed from the same seawater and sediment samples; they diverged strongly in composition. Thus, the broader enzymatic capabilities of the sedimentary microbial communities may result from the compositional differences between seawater and sedimentary microbial communities, rather than from gene expression differences among compositionally similar communities. The greater number of phylum- and subphylum-level lineages and operational taxonomic units in sediments than in seawater samples may reflect the necessity of a wider range of enzymatic capabilities and strategies to access organic matter that has already been degraded during passage through the water column. When transformations of marine organic matter are considered, differences in community composition and their different abilities to access organic matter should be taken into account.
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Sedimentos Geológicos/microbiología , Agua de Mar/microbiología , Regiones Árticas , Datos de Secuencia Molecular , Reacción en Cadena de la Polimerasa , ARN Ribosómico 16S/genética , Microbiología del AguaRESUMEN
OBJECTIVE: To establish cardiac magnetic resonance imaging (MRI) reference values for atrial adaptation to training in endurance athletes in comparison with matched non-athletes. In addition, to study the relationship of atrial size to ventricular and annular size and valvular function. DESIGN: Cross-sectional study. PARTICIPANTS: 180 healthy individuals aged 18-39 years (41% women): 60 elite endurance athletes (exercising > 18 h/week), 60 regular endurance athletes (9-18 h/ week), and 60 age and gender matched non-athletes (exercising ≤3 h/week) underwent cardiac MRI. Quantitative atrial dimensions and volumes, indexed for body surface area (BSA), were compared with ventricular and annular dimensions. Regurgitant fractions of all four valves and peak velocities of mitral and tricuspid valves were also assessed. RESULTS: BSA-corrected right and left atrial volumes and diameters were significantly larger for athletes compared with non-athletes (p<0.05-p<0.0005). Ventricular, annular and atrial ratios remained constant for all groups, suggesting balanced adaptation to exercise training. E/A ratios remained statistically unchanged in all groups. Regurgitant fractions of the four cardiac valves were all mild (≤15%) and not significantly different in athletes compared with non-athletes. CONCLUSIONS: Atrial remodelling in endurance athletes may be regarded as a balanced physiological adaptation to exercise training with preservation of valvular function.
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Adaptación Fisiológica/fisiología , Ventrículos Cardíacos/anatomía & histología , Válvula Mitral/fisiología , Deportes/fisiología , Válvula Tricúspide/fisiología , Adolescente , Adulto , Función Atrial/fisiología , Estudios Transversales , Dilatación Patológica/fisiopatología , Ecocardiografía , Femenino , Atrios Cardíacos/anatomía & histología , Humanos , Angiografía por Resonancia Magnética , Masculino , Resistencia Física/fisiología , Valores de Referencia , Tomografía Computarizada por Rayos X , Función Ventricular/fisiología , Adulto JovenRESUMEN
BACKGROUND: Left ventricular hypertrophy (LVH) is often observed in athletes, which should be differentiated from hypertrophic cardiomyopathy. The aim of the study was to explore the functional changes measured using tissue Doppler imaging (TDI) deformation analysis in athletes fulfilling LVH criteria participating in different endurance sports. METHODS: Healthy controls (n = 62, 58% men) and endurance athletes (n = 120, 62% men) aged 18-40 years were prospectively enrolled and underwent both standard echocardiography as well as TDI. Longitudinal TDI-derived strain and strain rate (SR) were calculated in the septal and posterior wall in three segments. LVH was defined as a left ventricular mass (LVM) over 132 g/m2 in men and over 109 g/m2 in women. RESULTS: Echocardiographic LVH was observed in 33 athletes (67% men). LVM was significantly increased in both athlete groups (102.6 g/m2 (SD 16.0) and 135.7 g/m2 (SD 15.9) vs 88.0 g/m2 (SD 16.5) in controls, p<0.001). Diastolic parameters were not significantly different between groups. Athletes with LVH showed no significant difference in strain and SR values in any segment of the septal or posterior wall compared with controls or those without LVH. A weak but significant correlation (also after multivariate analysis) was found for septal wall thickness and LVM in peak systolic strain (r = 0.26, p<0.01 and 0.23, p<0.01) and SR (r = 0.27, p<0.01 and 0.29, p<0.01). Nevertheless, strain and SR values were still within normal limits in all athletes. CONCLUSION: Athletes with LVH overall show normal deformation values in the left ventricle. These data suggest that a moderate reduction in regional septal deformation should not be considered as pathological when evaluating the endurance athlete with echocardiographic LVH of unknown origin.
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Hipertrofia Ventricular Izquierda/fisiopatología , Resistencia Física , Deportes/fisiología , Adolescente , Adulto , Estudios de Casos y Controles , Ecocardiografía , Femenino , Humanos , Hipertrofia Ventricular Izquierda/diagnóstico por imagen , Masculino , Resistencia Física/fisiología , Sístole , Función Ventricular Izquierda/fisiología , Remodelación Ventricular/fisiología , Adulto JovenRESUMEN
A previously unknown giant sulfur bacterium is abundant in sediments underlying the oxygen minimum zone of the Benguela Current upwelling system. The bacterium has a spherical cell that exceeds by up to 100-fold the biovolume of the largest known prokaryotes. On the basis of 16S ribosomal DNA sequence data, these bacteria are closely related to the marine filamentous sulfur bacteria Thioploca, abundant in the upwelling area off Chile and Peru. Similar to Thioploca, the giant bacteria oxidize sulfide with nitrate that is accumulated to =800 millimolar in a central vacuole.
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Bacterias/aislamiento & purificación , Bacterias/metabolismo , Sedimentos Geológicos/microbiología , Nitratos/metabolismo , Sulfuros/metabolismo , Azufre/análisis , Bacterias/clasificación , Bacterias/citología , Citoplasma/ultraestructura , Genes de ARNr , Microscopía Electrónica , Datos de Secuencia Molecular , Namibia , Nitratos/análisis , Oxidación-Reducción , Filogenia , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , Azufre/metabolismo , Terminología como Asunto , Vacuolas/química , Vacuolas/ultraestructuraRESUMEN
The number of cancer survivors has tremendously increased over the past decades as a result of aging of the population and improvements in early cancer detection and treatment. Ongoing successes in cancer treatment are expected to result in a further increase in the number of long-term survivors. However, cancer treatment can have detrimental cardiovascular side-effects that impact morbidity and mortality, reducing quality of life in cancer survivors. The spectrum of radiotherapy- and chemotherapy-induced cardiovascular disease is broad, varying from subclinical valvular dysfunction to overt congestive heart failure, and such effects may not be apparent for more than twenty years after the initial cancer treatment. Awareness of these long-term side-effects is of crucial value in the management of these patients, in order to reduce the impact of cardiovascular morbidity and mortality. This review provides a comprehensive overview of the long-term cardiovascular complications of cancer treatments (radiotherapy and chemotherapy) in adult cancer survivors.
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Supervivientes de Cáncer , Enfermedades Cardiovasculares/etiología , Antineoplásicos/efectos adversos , Antineoplásicos/uso terapéutico , Humanos , Neoplasias/tratamiento farmacológico , Neoplasias/radioterapiaRESUMEN
Crusts and chimneys composed of authigenic barite are found at methane seeps and hydrothermal vents that expel fluids rich in barium. Microbial processes have not previously been associated with barite precipitation in marine cold seep settings. Here, we report on the precipitation of barite on filaments of sulfide-oxidizing bacteria at a brine seep in the Gulf of Mexico. Barite-mineralized bacterial filaments in the interiors of authigenic barite crusts resemble filamentous sulfide-oxidizing bacteria of the genus Beggiatoa. Clone library and iTag amplicon sequencing of the 16S rRNA gene show that the barite crusts that host these filaments also preserve DNA of Candidatus Maribeggiatoa, as well as sulfate-reducing bacteria. Isotopic analyses show that the sulfur and oxygen isotope compositions of barite have lower δ(34)S and δ(18)O values than many other marine barite crusts, which is consistent with barite precipitation in an environment in which sulfide oxidation was occurring. Laboratory experiments employing isolates of sulfide-oxidizing bacteria from Gulf of Mexico seep sediments showed that under low sulfate conditions, such as those encountered in brine fluids, sulfate generated by sulfide-oxidizing bacteria fosters rapid barite precipitation localized on cell biomass, leading to the encrustation of bacteria in a manner reminiscent of our observations of barite-mineralized Beggiatoa in the Gulf of Mexico. The precipitation of barite directly on filaments of sulfide-oxidizing bacteria, and not on other benthic substrates, suggests that sulfide oxidation plays a role in barite formation at certain marine brine seeps where sulfide is oxidized to sulfate in contact with barium-rich fluids, either prior to, or during, the mixing of those fluids with sulfate-containing seawater in the vicinity of the sediment/water interface. As with many other geochemical interfaces that foster mineral precipitation, both biological and abiological processes likely contribute to the precipitation of barite at marine brine seeps such as the one studied here.
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Bacterias/genética , Bacterias/metabolismo , Sulfato de Bario/metabolismo , Sulfuros/metabolismo , Bacterias/clasificación , Bacterias/aislamiento & purificación , Beggiatoa/clasificación , Beggiatoa/genética , Beggiatoa/aislamiento & purificación , Beggiatoa/metabolismo , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , Golfo de México , Datos de Secuencia Molecular , Oxidación-Reducción , Filogenia , ARN Ribosómico 16S/genética , ARN Ribosómico 16S/metabolismo , Análisis de Secuencia de ADNRESUMEN
Filamentous sulfur bacteria of the genus Thioploca occur as dense mats on the continental shelf off the coast of Chile and Peru. Since little is known about their nitrogen, sulfur, and carbon metabolism, this study was undertaken to investigate their (eco)physiology. Thioploca is able to store internally high concentrations of sulfur globules and nitrate. It has been previously hypothesized that these large vacuolated bacteria can oxidize sulfide by reducing their internally stored nitrate. We examined this nitrate reduction by incubation experiments of washed Thioploca sheaths with trichomes in combination with 15N compounds and mass spectrometry and found that these Thioploca samples produce ammonium at a rate of 1 nmol min-1 mg of protein-1. Controls showed no significant activity. Sulfate was shown to be the end product of sulfide oxidation and was observed at a rate of 2 to 3 nmol min-1 mg of protein-1. The ammonium and sulfate production rates were not influenced by the addition of sulfide, suggesting that sulfide is first oxidized to elemental sulfur, and in a second independent step elemental sulfur is oxidized to sulfate. The average sulfide oxidation rate measured was 5 nmol min-1 mg of protein-1 and could be increased to 10.7 nmol min-1 mg of protein-1 after the trichomes were starved for 45 h. Incorporation of 14CO2 was at a rate of 0.4 to 0.8 nmol min-1 mg of protein-1, which is half the rate calculated from sulfide oxidation. [2-14C]acetate incorporation was 0.4 nmol min-1 mg of protein-1, which is equal to the CO2 fixation rate, and no 14CO2 production was detected. These results suggest that Thioploca species are facultative chemolithoautotrophs capable of mixotrophic growth. Microautoradiography confirmed that Thioploca cells assimilated the majority of the radiocarbon from [2-14C]acetate, with only a minor contribution by epibiontic bacteria present in the samples.
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The almost complete 16S rRNA sequence from Mycobacterium leprae was determined by direct sequencing of the chromosomal gene amplified by the polymerase chain reaction. The primary sequence revealed an insertion of 12 nucleotides at the 5' end of the 16S rRNA gene, which consists of an A-T stretch and appears to be unique for M. leprae. Within the mycobacteria M. leprae branches off with a group of slow-growing species comprising M. scrofulaceum, M. kansasii, M. szulgai, M. malmoense, M. intracellulare and M. avium. A systematic comparison of the nucleotide sequence resulted in the characterization of oligonucleotide probes which are highly specific for M. leprae. The probes hybridized exclusively to 16S rRNA nucleic acids from M. leprae, but not to nucleic acids from 20 cultivable fast- and slow-growing mycobacteria.
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Sondas de ADN , Mycobacterium leprae/genética , ARN Ribosómico 16S/química , Secuencia de Bases , Datos de Secuencia Molecular , FilogeniaRESUMEN
Microscopy of organic-rich, sulfidic sediment samples of marine and freshwater origin revealed filamentous, multicellular microorganisms with gliding motility. Many of these neither contained sulfur droplets such as the Beggiatoa species nor exhibited the autofluorescence of the chlorophyll-containing cyanobacteria. A frequently observed morphological type of filamentous microorganism was enriched under anoxic conditions in the dark with isobutyrate plus sulfate. Two strains of filamentous, gliding sulfate-reducing bacteria, Tokyo 01 and Jade 02, were isolated in pure cultures. Both isolates oxidized acetate and other aliphatic acids. Enzyme assays indicated that the terminal oxidation occurs via the anaerobic C(1) pathway (carbon monoxide dehydrogenase pathway). The 16S rRNA genes of the new isolates and of the two formerly described filamentous species of sulfate-reducing bacteria, Desulfonema limicola and Desulfonema magnum, were analyzed. All four strains were closely related to each other and affiliated with the delta-subclass of Proteobacteria. Another close relative was the unicellular Desulfococcus multivorans. Based on phylogenetic relationships and physiological properties, Strains Tokyo 01 and Jade 02 are assigned to a new species, Desulfonema ishimotoi. A new, fluorescently labeled oligonucleotide probe targeted against 16S rRNA was designed so that that it hybridized specifically with whole cells of Desulfonema species. Filamentous bacteria that hybridized with the same probe were detected in sediment samples and in association with the filamentous sulfur-oxidizing bacterium Thioploca in its natural habitat. We conclude that Desulfonema species constitute an ecologically significant fraction of the sulfate-reducing bacteria in organic-rich sediments and microbial mats.