RESUMEN
OrganiCam is a laser-induced luminescence imager and spectrometer designed for standoff organic and biosignature detection on planetary bodies. OrganiCam uses a diffused laser beam (12° cone) to cover a large area at several meters distance and records luminescence on half of its intensified detector. The diffuser can be removed to record Raman and fluorescence spectra from a small spot from 2 m standoff distance. OrganiCam's small size and light weight makes it ideal for surveying organics on planetary surfaces. We have designed and built a brassboard version of the OrganiCam instrument and performed initial tests of the system.
RESUMEN
DNA in intracellular Salmonella enterica serovar Typhimurium relaxes during growth in the acidified (pH 4-5) macrophage vacuole and DNA relaxation correlates with the upregulation of Salmonella genes involved in adaptation to the macrophage environment. Bacterial ATP levels did not increase during adaptation to acid pH unless the bacterium was deficient in MgtC, a cytoplasmic-membrane-located inhibitor of proton-driven F1 F0 ATP synthase activity. Inhibiting ATP binding by DNA gyrase and topo IV with novobiocin enhanced the effect of low pH on DNA relaxation. Bacteria expressing novobiocin-resistant (NovR ) derivatives of gyrase or topo IV also exhibited DNA relaxation at acid pH, although further relaxation with novobiocin was not seen in the strain with NovR gyrase. Thus, inhibition of the negative supercoiling activity of gyrase was the primary cause of enhanced DNA relaxation in drug-treated bacteria. The Salmonella cytosol reaches pH 5-6 in response to an external pH of 4-5: the ATP-dependent DNA supercoiling activity of purified gyrase was progressively inhibited by lowering the pH in this range, as was the ATP-dependent DNA relaxation activity of topo IV. We propose that DNA relaxation in Salmonella within macrophage is due to acid-mediated impairment of the negative supercoiling activity of gyrase.
Asunto(s)
Girasa de ADN/metabolismo , ADN Superhelicoidal/metabolismo , Salmonella typhi/genética , Inhibidores de Topoisomerasa II/metabolismo , Adaptación Fisiológica/genética , Girasa de ADN/genética , Topoisomerasa de ADN IV/genética , ADN-Topoisomerasas de Tipo I , ADN Bacteriano/genética , ADN Bacteriano/metabolismo , ADN Superhelicoidal/genética , Concentración de Iones de Hidrógeno , Novobiocina/farmacología , Conformación de Ácido Nucleico , Salmonella typhi/metabolismo , Salmonella typhimurium/genética , Estrés Fisiológico/genéticaRESUMEN
The evolution of new gene networks is a primary source of genetic innovation that allows bacteria to explore and exploit new niches, including pathogenic interactions with host organisms. For example, the archetypal DNA binding protein, OmpR, is identical between Salmonella Typhimurium serovar Typhimurium and Escherichia coli, but regulatory specialization has resulted in different environmental triggers of OmpR expression and largely divergent OmpR regulons. Specifically, ompR mRNA and OmpR protein levels are elevated by acid pH in S. Typhimurium but not in E. coli. This differential expression pattern is due to differences in the promoter regions of the ompR genes and the E. coli ompR orthologue can be made acid-inducible by introduction of the appropriate sequences from S. Typhimurium. The OmpR regulon in S. Typhimurium overlaps that of E. coli at only 15 genes and includes many horizontally acquired genes (including virulence genes) that E. coli does not have. We found that OmpR binds to its genomic targets in higher abundance when the DNA is relaxed, something that occurs in S. Typhimurium as a result of acid stress and which is a requirement for optimal expression of its virulence genes. The genomic targets of OmpR do not share a strong nucleotide sequence consensus: we propose that the ability of OmpR to recruit additional genes to its regulon arises from its modest requirements for specificity in its DNA targets with its preference for relaxed DNA allowing it to cooperate with DNA-topology-based allostery to modulate transcription in response to acid stress.
Asunto(s)
Proteínas Bacterianas/genética , Escherichia coli/genética , Evolución Molecular , Salmonella typhimurium/genética , Estrés Fisiológico/genética , Transactivadores/genética , Proteínas Bacterianas/metabolismo , Secuencia de Bases , Proteínas de Unión al ADN/genética , Escherichia coli/metabolismo , Escherichia coli/patogenicidad , Regulación Bacteriana de la Expresión Génica , Operón/genética , Regiones Promotoras Genéticas , Regulón , Salmonella typhimurium/metabolismo , Salmonella typhimurium/patogenicidad , Transactivadores/metabolismoRESUMEN
The nucleoid-associated protein FIS is a global regulator of gene expression and chromosome structure in Escherichia coli and Salmonella enterica. Despite the importance of FIS for infection and intracellular invasion, very little is known about the regulation of S. enterica fis expression. Under standard laboratory growth conditions, fis is highly expressed during rapid growth but is then silenced as growth slows. However, if cells are cultured in non-aerated conditions, fis expression is sustained during stationary phase. This led us to test whether the redox-sensing transcription factors ArcA and FNR regulate S. enterica fis. Deletion of FNR had no detectable effect, whereas deletion of ArcA had the unexpected effect of further elevating fis expression in stationary phase. ArcA required RpoS for induction of fis expression, suggesting that ArcA indirectly affects fis expression. Other putative regulators were found to play diverse roles: FIS acted directly as an auto-repressor (as expected), whereas CRP had little direct effect on fis expression. Deleting regions of the fis promoter led to the discovery of a novel anaerobically-induced transcription start site (Pfis-2) upstream of the primary transcription start site (Pfis-1). Promoter truncation also revealed that the shortest functional fis promoter was incapable of sustained expression. Moreover, fis expression was observed to correlate directly with DNA supercoiling in non-aerated conditions. Thus, the full-length S. enterica fis promoter region may act as a topological switch that is sensitive to stress-induced duplex destabilisation and up-regulates expression in non-aerated conditions.
Asunto(s)
Factor Proteico para Inverción de Estimulación/genética , Regulación Bacteriana de la Expresión Génica , Oxígeno/metabolismo , Regiones Promotoras Genéticas , Salmonella typhimurium/genética , Proteínas de la Membrana Bacteriana Externa/metabolismo , Secuencia de Bases , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/genética , Factor Proteico para Inverción de Estimulación/química , Factor Proteico para Inverción de Estimulación/metabolismo , Orden Génico , Datos de Secuencia Molecular , Mutación , Secuencias Reguladoras de Ácidos Nucleicos , Proteínas Represoras/metabolismo , Salmonella typhimurium/metabolismo , Alineación de Secuencia , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
To determine clinical and sociodemographic factors that are associated with major neuropsychiatric illnesses among brain tumor patients, we administered a modified version of the Brief Patient Health Questionnaire and a demographic data form to 363 adult neuro-oncology patients. Responses were analyzed to assess for associations between demographic variables, clinical variables, and symptoms consistent with diagnoses of generalized anxiety disorder and/or depression. Multivariate logistic regression analyses showed that female gender was associated with the presence of symptoms of anxiety, depression, and combined anxiety and depression. Lower WHO tumor grade classifications, lower education level, and a history of psychiatric illness also emerged as important predictors of symptoms consistent with anxiety and/or depression. Marital status and presence of past/current medical illness trended toward being significantly associated with depression alone. Patient use of psychiatric medication was not associated with any study variables. Results of the present study suggest several hypotheses to test with neuro-oncology patients in further longitudinal analyses, which would benefit from the inclusion of a wider range of neuropsychiatric symptoms in conjunction with neurocognitive and functional impairment variables.
