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INTRODUCTION: Follicular lymphoma is a common non-Hodgkin lymphoma that can start in a diverse array of tissues throughout the body. While the majority of patients may be able to live many years with this disease, cure remains very difficult to achieve. OBJECTIVE: We sought to investigate the impact of follicular lymphoma primary disease site in early-stage disease on patient outcomes using a large national database. METHODS: Baseline demographic and disease data for patients diagnosed with follicular lymphoma from 2000-2015 was identified and extracted from the NCI Surveillance, Epidemiology, and End Results (SEER) database. Primary disease sites were grouped into one of two cohorts: nodal disease (lymph nodes and spleen) and extranodal disease (everything else). Analysis was performed using summary statistics, Kaplan-Meier method, and Cox-proportional hazards models for univariate and multivariate analysis. RESULTS: A total of 13,400 patients were included in the final analysis and the majority were non-Hispanic white (81%), with stage I (63%), and nodal FL (79%). Median overall survival for nodal disease was 15.1 years [95% CI (14.6-15.6)] while median overall survival for extranodal disease was 15.8 years [95% CI (14.9-16.3)]. Overall survival was slightly better for patients with extranodal disease [HR = 0.89, 95% CI (0.84-0.96); p-value = 0.00012]. This finding remained consistent after controlling for age and race [HR = 0.84, 95% CI (0.79-0.90); p-value <0.0001]. CONCLUSIONS: The primary site of involvement by early-stage follicular lymphoma may have an impact on patient outcomes and warrants further investigation.
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BACKGROUND: Patients in the intensive care unit (ICU) often experience extended periods of immobility. Following hospital discharge, many face impaired mobility and never return to their baseline function. Although the benefits of physical and occupational rehabilitation are well established in non-ICU patients, a paucity of work describes effective practices to alleviate ICU-related declines in mobility. OBJECTIVE: To assess how rehabilitation with physical and occupational therapy (PT-OT) during ICU stays affects patients' mobility, self-care, and length of hospital stay. DESIGN: Retrospective cohort study. SETTING: Inpatient ICU. PARTICIPANTS: A total of 6628 adult patients who received physical rehabilitation across multiple sites (Arizona, Florida, Minnesota, and Wisconsin) of a single institution between January 2018 and December 2021. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Descriptive statistics, linear regression models, and gradient boosting machine methods were used to determine the relationship between the amount of PT-OT received and outcomes of hospital length of stay (LOS), Activity Measure for Post-Acute Care Daily Activity and Basic Mobility scores. RESULTS: The 6628 patients who met inclusion criteria received an average (median) of 23 (range: 1-89) minutes of PT-OT per day. Regression analyses showed each additional 10 minutes of PT-OT per day was associated with a 1.0% (95% confidence interval [CI]: 0.41-1.66, p < .001) higher final Basic Mobility score, a 1.8% (95% CI: 1.30%-2.34%, p < .001) higher final Daily Activity score, and a 1.2-day (95% CI: -1.28 to -1.09, p < .001) lower hospital LOS. One-dimensional partial dependence plots revealed an exponential decrease in predicted LOS as minutes of PT-OT received increased. CONCLUSION: Higher rehabilitation minutes provided to patients in the ICU may reduce the LOS and improve patients' functional outcomes at discharge. The benefits of rehabilitation increased with increasing amounts of time of therapy received.
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Terapia Ocupacional , Adulto , Humanos , Tempo de Internação , Estudos Retrospectivos , Unidades de Terapia Intensiva , HospitaisRESUMO
Stress and psychiatric disorders have been independently associated with disruption of the maternal and offspring microbiome and with increased risk of the offspring developing psychiatric disorders, both in clinical studies and in preclinical studies. However, the role of the microbiome in mediating the effect of prenatal stress on offspring behavior is unclear. While preclinical studies have identified several key mechanisms, clinical studies focusing on mechanisms are limited. In this review, we discuss 3 specific mechanisms by which the microbiome could mediate the effects of prenatal stress: 1) altered production of short-chain fatty acids; 2) disruptions in TH17 (T helper 17) cell differentiation, leading to maternal and fetal immune activation; and 3) perturbation of intestinal and microbial tryptophan metabolism and serotonergic signaling. Finally, we review the existing clinical literature focusing on these mechanisms and highlight the need for additional mechanistic clinical research to better understand the role of the microbiome in the context of prenatal stress.
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Transtornos Mentais , Microbiota , Efeitos Tardios da Exposição Pré-Natal , Gravidez , Feminino , Humanos , Transtornos Mentais/etiologiaRESUMO
INTRODUCTION: Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) is a rare, highly heterogeneous group of mature T-cell neoplasms that historically has been associated with poor outcomes. We sought to investigate the influence of primary disease site on PTCL-NOS outcomes using a large national cancer registry. METHODS: Baseline clinical and demographic data including primary organ of involvement and Ann Arbor disease stage were extracted from the SEER database. Patients were grouped into nine organ system groups and compared to nodal disease acting as a control. Cox regression models were utilized for adjusted survival analyses. RESULTS: A total of 3095 patients were identified in the SEER database and included in the final analysis. The median age was 61 and a majority of patients were male (60%) and identified as non-Hispanic white (68%). A plurality of patients had stage IV disease (32%). Lymph nodes and spleen were the most common primary disease sites (67%), while central nervous system was the least common (1%). Patients with early-stage PTCL-NOS of the gastrointestinal/genitourinary systems had worse overall survival [HR = 1.97 (1.50-2.59); p < 0.001] and lymphoma-specific survival [HR = 1.74 (1.26-2.40); p < 0.001] which was statistically significant even after adjusting for other variables. Early-stage PTCL-NOS of the central nervous system also had worse overall survival [HR = 1.90 (1.11-3.27); p = 0.020] and lymphoma-specific survival [HR = 2.11 (1.17-3.80); p = 0.013]. Early-stage PTCL-NOS of the skin had better overall survival [HR = 0.54 (0.42-0.68); p < 0.001] and lymphoma-specific survival [HR = 0.388 (0.28-0.53); p < 0.001] which was statistically significant even after adjustments. CONCLUSION: Our findings suggest an association between primary organ involved by PTCL-NOS and both overall and lymphoma-specific survival even after adjusting for common variables. These results warrant validation in future prospective studies.
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Linfoma de Células T Periférico , Humanos , Masculino , Feminino , Pessoa de Meia-Idade , Prognóstico , Linfonodos/patologia , Estudos ProspectivosRESUMO
The extracellular matrix (ECM) is a dynamic structure of molecules that can be divided into six different categories and are collectively called the matrisome. The ECM plays pivotal roles in physiological processes in many tissues, including the nervous system. Intriguingly, alterations in ECM molecules/pathways are associated with painful human conditions and murine pain models. Nevertheless, mechanistic insight into the interplay of normal or defective ECM and pain is largely lacking. The goal of this study was to integrate bulk, single-cell, and spatial RNA sequencing (RNAseq) datasets to investigate the expression and cellular origin of matrisome genes in male and female murine and human dorsal root ganglia (DRG). Bulk RNAseq showed that about 65% of all matrisome genes were expressed in both murine and human DRG, with proportionally more core matrisome genes (glycoproteins, collagens, and proteoglycans) expressed compared to matrisome-associated genes (ECM-affiliated genes, ECM regulators, and secreted factors). Single cell RNAseq on male murine DRG revealed the cellular origin of matrisome expression. Core matrisome genes, especially collagens, were expressed by fibroblasts whereas matrisome-associated genes were primarily expressed by neurons. Cell-cell communication network analysis with CellChat software predicted an important role for collagen signaling pathways in connecting vascular cell types and nociceptors in murine tissue, which we confirmed by analysis of spatial transcriptomic data from human DRG. RNAscope in situ hybridization and immunohistochemistry demonstrated expression of collagens in fibroblasts surrounding nociceptors in male and female human DRG. Finally, comparing human neuropathic pain samples with non-pain samples also showed differential expression of matrisome genes produced by both fibroblasts and by nociceptors. This study supports the idea that the DRG matrisome may contribute to neuronal signaling in both mouse and human, and that dysregulation of matrisome genes is associated with neuropathic pain.
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Unmyelinated non-peptidergic nociceptors (NP afferents) arborise in lamina II of the spinal cord and receive GABAergic axoaxonic synapses, which mediate presynaptic inhibition. However, until now the source of this axoaxonic synaptic input was not known. Here we provide evidence that it originates from a population of inhibitory calretinin-expressing interneurons (iCRs), which correspond to lamina II islet cells. The NP afferents can be assigned to 3 functionally distinct classes (NP1-3). NP1 afferents have been implicated in pathological pain states, while NP2 and NP3 afferents also function as pruritoceptors. Our findings suggest that all 3 of these afferent types innervate iCRs and receive axoaxonic synapses from them, providing feedback inhibition of NP input. The iCRs also form axodendritic synapses, and their targets include cells that are themselves innervated by the NP afferents, thus allowing for feedforward inhibition. The iCRs are therefore ideally placed to control the input from non-peptidergic nociceptors and pruritoceptors to other dorsal horn neurons, and thus represent a potential therapeutic target for the treatment of chronic pain and itch.
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Nociceptores , Medula Espinal , Animais , Camundongos , Calbindina 2 , Células do Corno Posterior , Medula Espinal/fisiologia , SinapsesRESUMO
Dendritic spine remodeling in the dorsal horn is associated with many chronic pain models. Li et al. demonstrate that Tiam1 links Rac1-mediated spine changes to NMDA receptor activity to promote behavioral signs of chronic pain in rodents.
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Dor Crônica , Receptores de N-Metil-D-Aspartato , Humanos , Receptores de N-Metil-D-Aspartato/metabolismo , Espinhas Dendríticas/metabolismo , Transdução de Sinais , Neurônios/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismoRESUMO
Unmyelinated non-peptidergic nociceptors (NP afferents) arborise in lamina II of the spinal cord and receive GABAergic axoaxonic synapses, which mediate presynaptic inhibition. However, until now the source of this axoaxonic synaptic input was not known. Here we provide evidence that it originates from a population of inhibitory calretinin-expressing interneurons (iCRs), which correspond to lamina II islet cells. The NP afferents can be assigned to 3 functionally distinct classes (NP1-3). NP1 afferents have been implicated in pathological pain states, while NP2 and NP3 afferents also function as pruritoceptors. Our findings suggest that all 3 of these afferent types innervate iCRs and receive axoaxonic synapses from them, providing feedback inhibition of NP input. The iCRs also form axodendritic synapses, and their targets include cells that are themselves innervated by the NP afferents, thus allowing for feedforward inhibition. The iCRs are therefore ideally placed to control the input from non-peptidergic nociceptors and pruritoceptors to other dorsal horn neurons, and thus represent a potential therapeutic target for the treatment of chronic pain and itch.
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Animals can use a variety of sources of information to learn about local predation threats, including the behavior of conspecifics. Socially-acquired information about predation risk has been demonstrated in a variety of fish species, so the phenomenon is likely taxonomically widespread. Threespine stickleback fish are a geographically widespread species that encounters a variety of native and introduced predators throughout its range; as such, learning to recognize predators may be an important component of survival. We assessed whether laboratory-bred, predator-naïve stickleback could learn to fear the odor of a live rainbow trout by first observing videos of conspecifics exhibiting antipredator responses in the presence of trout odor. We found that this is not the case: following one conditioning trial in which trout odor was paired with videos of frightened conspecifics, stickleback did not exhibit an increase in antipredator behavior (e.g., a decrease in activity or an increase in hiding) in the presence of trout odor. Although there is evidence that stickleback use social information to find foraging patches, it does not appear that they do the same to learn about predation threat, at least in the context of our experimental conditions.
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Oncorhynchus mykiss , Smegmamorpha , Animais , Sinais (Psicologia) , Comportamento Predatório , Aprendizagem , Smegmamorpha/fisiologiaRESUMO
BACKGROUND: The purpose of this study is to undertake a comprehensive systematic review to describe multilevel factors (barriers and facilitators) that may influence the implementation of low-dose chest computed tomography for lung cancer screening in the United States. METHODS: Systematic literature searches were performed using 6 online databases and citation indexes for peer-reviewed studies, for articles published from 2013 to 2021. Studies were classified into 3 perspectives, based on the study's unit of analysis: system, health-care provider, and patient. Barriers and facilitators identified for each study included in our final review were then coded and categorized using the Consolidate Framework for Implementation Research domains. RESULTS: At the system level, the 2 most common constructs were external policy and incentives and executing the implementation process. At the provider level, the most common constructs were evidence strength and quality of the intervention characteristics, patient needs and resources, implementation climate, and an individual's knowledge and beliefs about the intervention. At the patient level, the most common constructs were patient needs and resources, individual's knowledge and beliefs about the intervention, and engaging in the implementation process. These constructs can act as facilitators or barriers to lung cancer screening implementation. CONCLUSIONS: Applying the Consolidate Framework for Implementation Research domains and constructs to understand and specify factors facilitating uptake of lung cancer screening as well as cataloging the lessons learned from previous efforts helps inform the development and implementation processes of lung cancer screening programs in the community setting. REGISTRATION: PROSPERO, CRD42021247677.
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Detecção Precoce de Câncer , Neoplasias Pulmonares , Humanos , Pessoal de Saúde , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/prevenção & controleRESUMO
Neurons located in dorsal root ganglia (DRG) are crucial for transmitting peripheral sensations such as proprioception, touch, temperature, and nociception to the spinal cord before propagating these signals to higher brain structures. To date, difficulty in identifying modality-specific DRG neurons has limited our ability to study specific populations in detail. As the calcium-binding protein parvalbumin (PV) is a neurochemical marker for proprioceptive DRG cells we used a transgenic mouse line expressing green fluorescent protein (GFP) in PV positive DRGs, to study the functional and molecular properties of putative proprioceptive neurons. Immunolabeled DRGs showed a 100% overlap between GFP positive (GFP+) and PV positive cells, confirming the PVeGFP mouse accurately labeled PV neurons. Targeted patch-clamp recording from isolated GFP+ and GFP negative (GFP-) neurons showed the passive membrane properties of the two groups were similar, however, their active properties differed markedly. All GFP+ neurons fired a single spike in response to sustained current injection and their action potentials (APs) had faster rise times, lower thresholds and shorter half widths. A hyperpolarization-activated current (Ih) was observed in all GFP+ neurons but was infrequently noted in the GFP- population (100% vs. 11%). For GFP+ neurons, Ih activation rates varied markedly, suggesting differences in the underlying hyperpolarization-activated cyclic nucleotide-gated channel (HCN) subunit expression responsible for the current kinetics. Furthermore, quantitative polymerase chain reaction (qPCR) showed the HCN subunits 2, 1, and 4 mRNA (in that order) was more abundant in GFP+ neurons, while HCN 3 was more highly expressed in GFP- neurons. Likewise, immunolabeling confirmed HCN 1, 2, and 4 protein expression in GFP+ neurons. In summary, certain functional properties of GFP+ and GFP- cells differ markedly, providing evidence for modality-specific signaling between the two groups. However, the GFP+ DRG population demonstrates considerable internal heterogeneity when hyperpolarization-activated cyclic nucleotide-gated channel (HCN channel) properties and subunit expression are considered. We propose this heterogeneity reflects the existence of different peripheral receptors such as tendon organs, muscle spindles or mechanoreceptors in the putative proprioceptive neuron population.
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Nociceptive information is relayed through the spinal cord dorsal horn, a critical area in sensory processing. The neuronal circuits in this region that underpin sensory perception must be clarified to better understand how dysfunction can lead to pathological pain. This study used an optogenetic approach to selectively activate spinal interneurons that express the calcium-binding protein calretinin (CR). We show that these interneurons form an interconnected network that can initiate and sustain enhanced excitatory signaling, and directly relay signals to lamina I projection neurons. Photoactivation of CR interneurons in vivo resulted in a significant nocifensive behavior that was morphine sensitive, caused a conditioned place aversion, and was enhanced by spared nerve injury. Furthermore, halorhodopsin-mediated inhibition of these interneurons elevated sensory thresholds. Our results suggest that dorsal horn circuits that involve excitatory CR neurons are important for the generation and amplification of pain and identify these interneurons as a future analgesic target.
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Calbindina 2/genética , Interneurônios/metabolismo , Neuralgia/fisiopatologia , Neurônios/metabolismo , Corno Dorsal da Medula Espinal/metabolismo , Analgésicos Opioides/farmacologia , Animais , Calbindina 2/metabolismo , Modelos Animais de Doenças , Expressão Gênica , Halorrodopsinas/genética , Halorrodopsinas/metabolismo , Interneurônios/efeitos dos fármacos , Interneurônios/patologia , Camundongos , Camundongos Transgênicos , Morfina/farmacologia , Rede Nervosa/efeitos dos fármacos , Rede Nervosa/metabolismo , Rede Nervosa/patologia , Neuralgia/tratamento farmacológico , Neuralgia/genética , Neuralgia/metabolismo , Neurônios/efeitos dos fármacos , Neurônios/patologia , Optogenética/métodos , Limiar da Dor/efeitos dos fármacos , Técnicas de Patch-Clamp , Estimulação Luminosa , Corno Dorsal da Medula Espinal/efeitos dos fármacos , Corno Dorsal da Medula Espinal/patologia , Técnicas de Cultura de Tecidos , TransgenesRESUMO
Around 75% of neurons in laminae I-II of the mouse dorsal horn are excitatory interneurons, and these are required for normal pain perception. We have shown that four largely non-overlapping excitatory interneuron populations can be defined by expression of the neuropeptides neurotensin, neurokinin B (NKB), gastrin-releasing peptide (GRP) and substance P. In addition, we recently identified a population of excitatory interneurons in glabrous skin territory that express dynorphin. The calcium-binding protein calretinin is present in many excitatory neurons in this region, but we know little about its relation to these neuropeptide markers. Here we show that calretinin is differentially expressed, being present in the majority of substance P-, GRP- and NKB-expressing cells, but not in the neurotensin or dynorphin cells. Calretinin-positive cells have been implicated in detection of noxious mechanical stimuli, but are not required for tactile allodynia after neuropathic pain. Our findings are therefore consistent with the suggestion that neuropathic allodynia involves the neurotensin and/or dynorphin excitatory interneuron populations. Around a quarter of inhibitory interneurons in lamina I-II contain calretinin, and recent transcriptomic studies suggest that these co-express substance P. We confirm this, by showing that inhibitory Cre-expressing cells in a Tac1Cre knock-in mouse are calretinin-immunoreactive. Interestingly, there is evidence that these cells express low levels of peptidylglycine alpha-amidating monooxygenase, an enzyme required for maturation of neuropeptides. This may explain our previous finding that although the substance P precursor preprotachykinin A can be detected in some inhibitory interneurons, very few inhibitory axonal boutons are immunoreactive for substance P.
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Calbindina 2/metabolismo , Interneurônios/metabolismo , Medula Espinal/metabolismo , Animais , Expressão Gênica , Imuno-Histoquímica , Interneurônios/citologia , Masculino , Camundongos Transgênicos , Microscopia Confocal , Medula Espinal/citologiaRESUMO
We conducted an in-person survey of New York City (NYC) pharmacies to assess the availability, accessibility, and price of the over-the-counter, rapid HIV self-test kit. NYC pharmacies were stratified into high, moderate and low morbidity neighborhoods by the HIV diagnosis rate of the neighborhood in which the pharmacy was located. A random sample of 500 pharmacies was taken [250 from high morbidity neighborhoods (HighMN) and 250 from low morbidity neighborhoods (LowMN)]. Pharmacies were excluded if: closed during survey, non-retail, or >10 min walk from subway. Project staff visited pharmacies to determine kit availability (in pharmacy on day of survey), accessibility (not locked/behind counter), and price (marked on shelf/product). Of 361 pharmacies (161 LowMN; 200 HighMN), kits were available in 27 % and accessible in 10 %; there was no difference by neighborhood. Kits were most often kept behind the pharmacy counter; this was more common in HighMN than in LowMN. Kits were kept solely behind the pharmacy counter in 52 %. Median price was US $42.99 without variability across neighborhoods. The rapid HIV self-test had limited availability and access in retail pharmacies. The high median price measured suggests that cost remained a barrier.
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Custos e Análise de Custo , Triagem e Testes Direto ao Consumidor/provisão & distribuição , Infecções por HIV/diagnóstico , Acessibilidade aos Serviços de Saúde , Farmácias , Kit de Reagentes para Diagnóstico/provisão & distribuição , Características de Residência , Triagem e Testes Direto ao Consumidor/economia , Humanos , Programas de Rastreamento , Cidade de Nova Iorque , Kit de Reagentes para Diagnóstico/economiaRESUMO
BACKGROUND: There are limited prospective data on the relative safety of very early mobilization of stroke patients after intravenous recombinant tissue plasminogen activator (IV rtPA) in stroke patients. We hypothesized that very early patient mobilization within 24 hours after IV rtPA administration for acute ischemic stroke would be safe and feasible. METHODS: The study was a prospective observational safety and feasibility study involving very early mobilization of stroke patients by physical therapy/occupational therapy within 24 hours after IV rtPA administration for treatment of ischemic stroke. A premobilization safety checklist was completed before mobilization to ensure hemodynamic stability. We assessed adverse safety events, including changes in patient symptoms, changes in vital signs, and bleeding complications. RESULTS: Eighteen patients were enrolled in the study, and informed consent was obtained. One hundred percent of patients were evaluated with a premobilization safety checklist; 72.2% (13 of 18) were mobilized without any adverse event. Eighty-nine percent (42 of 47) of mobilization activities were tolerated without an adverse response. One patient was orthostatic, and 1 patient had transient worsening of hemiparesis. No patient had intracranial bleeding or permanent worsening of neurologic deficits. CONCLUSIONS: Very early mobilization within 24 hours of ischemic stroke for patients who receive IV rtPA appears to be relatively safe and feasible in most patients. Patients who are mobilized within 24 hours of IV rtPA require detailed neurologic and vital sign monitoring.
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Isquemia Encefálica/tratamento farmacológico , Fibrinolíticos/uso terapêutico , Acidente Vascular Cerebral/tratamento farmacológico , Terapia Trombolítica , Ativador de Plasminogênio Tecidual/uso terapêutico , Adulto , Idoso , Idoso de 80 Anos ou mais , Deambulação Precoce , Feminino , Fibrinolíticos/administração & dosagem , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Ativador de Plasminogênio Tecidual/administração & dosagem , Resultado do TratamentoRESUMO
The acidic polysaccharide succinoglycan produced by the nitrogen-fixing rhizobial symbiont Sinorhizobium meliloti 1021 is required for this bacterium to invade the host plant Medicago truncatula and to efficiently invade the host plant M. sativa (alfalfa). The ß-glucanase enzyme encoded by exoK has previously been demonstrated to cleave succinoglycan and participate in producing the low molecular weight form of this polysaccharide. Here, we show that exoK is required for efficient S. meliloti invasion of both M. truncatula and alfalfa. Deletion mutants of exoK have a substantial reduction in symbiotic productivity on both of these plant hosts. Insertion mutants of exoK have an even less productive symbiosis than the deletion mutants with the host M. truncatula that is caused by a secondary effect of the insertion itself, and may be due to a polar effect on the expression of the downstream exoLAMON genes.
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Glicosídeo Hidrolases/genética , Medicago sativa/microbiologia , Medicago truncatula/microbiologia , Sinorhizobium meliloti/enzimologia , Simbiose , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biomassa , Teste de Complementação Genética , Glicosídeo Hidrolases/metabolismo , Mutação , Fixação de Nitrogênio , Fenótipo , Nodulação , Raízes de Plantas/microbiologia , Brotos de Planta/microbiologia , Polissacarídeos Bacterianos/metabolismo , Proteínas Recombinantes de Fusão , Sinorhizobium meliloti/genética , Sinorhizobium meliloti/fisiologiaRESUMO
BACKGROUND: We have used the genomic data in the Integrated Microbial Genomes system of the Department of Energy's Joint Genome Institute to make predictions about rhizobial open reading frames that play a role in nodulation of host plants. The genomic data was screened by searching for ORFs conserved in α-proteobacterial rhizobia, but not conserved in closely-related non-nitrogen-fixing α-proteobacteria. RESULTS: Using this approach, we identified many genes known to be involved in nodulation or nitrogen fixation, as well as several new candidate genes. We knocked out selected new genes and assayed for the presence of nodulation phenotypes and/or nodule-specific expression. One of these genes, SMc00911, is strongly expressed by bacterial cells within host plant nodules, but is expressed minimally by free-living bacterial cells. A strain carrying an insertion mutation in SMc00911 is not defective in the symbiosis with host plants, but in contrast to expectations, this mutant strain is able to out-compete the S. meliloti 1021 wild type strain for nodule occupancy in co-inoculation experiments. The SMc00911 ORF is predicted to encode a "SodM-like" (superoxide dismutase-like) protein containing a rhodanese sulfurtransferase domain at the N-terminus and a chromate-resistance superfamily domain at the C-terminus. Several other ORFs (SMb20360, SMc01562, SMc01266, SMc03964, and the SMc01424-22 operon) identified in the screen are expressed at a moderate level by bacteria within nodules, but not by free-living bacteria. CONCLUSIONS: Based on the analysis of ORFs identified in this study, we conclude that this comparative genomics approach can identify rhizobial genes involved in the nitrogen-fixing symbiosis with host plants, although none of the newly identified genes were found to be essential for this process.