1,720,984 research outputs found
Tunable photoluminescence properties of selenium nanoparticles: biogenic versus chemogenic synthesis
Full text linkVarious technological and biomedical applications
rely on the ability of materials to emit light (photoluminescence
[PL]), and, among them, metal nanoparticles
(NPs) and semi-conductor Quantum Dots (QDs) represent
ideal candidates as sensing probes and imaging tools, portraying
better PL features than conventional organic dyes.
However,theknowledgeofPLbehaviorofsemiconductorNPs
– i.e., selenium; SeNPs – is still in its infancy, especially for
those synthesized by microorganisms. Considering the
essential role played by biogenic SeNPs as antimicrobial,
anticancer, and antioxidant agents, or food supplements,
their PL properties must be explored to take full advantage of
them as eco-friendly and versatile tools. Here, PL features of
SeNPs produced by the Se-tolerant Stenotrophomonasmaltophilia
SeITE02 strain, compared with chemogenic ones, are
investigated, highlighting the PL dependency on the NP size.
Indeed, PL emission shifted from indigo-blue (emission
wavelength λem 400–450 nm) to green-yellow (λem 480–
570 nm) and orange-red (λem 580–700 nm) for small (ca.
50 nm) and big (ca. 100 nm) SeNPs respectively, revealing the
versatility of an environmental bacterial isolate to synthesize
diverse PL probes. Besides, biogenic SeNPs show PL lifetime
comparable to those of the most used fluorophores, supporting
their potential application as markers for (bio)imaging
Interaction of Rhodococcus with Metals and Biotechnological Applications
No full textIn studies of environmental stresses caused by metals, Rhodococcus species are routinely identified as part of a beneficial microbial rhizosphere community. These bacterial strains, inhabiting diverse ecological niches, possess a variety of enzymatic activities to carry out relevant biodegradation reactions, such as degradation of organic pollutants in some cases using them for both carbon and energy. In this context, most Rhodococcus strains have been found to have very high levels of metal resistance. Thus, these microorganisms are not only capable of metabolizing various organic pollutants in the presence of co-contaminating heavy metals, but they can also bioadsorb and/or bioconvert various metals and metalloids [metal(loid)s]. Indeed, some Rhodococcus exploit these metal(loid) compounds to generate biogenic nanoscale materials of intriguing physical-chemical properties, which can find applications in biotechnology.
This book chapter has the focus in overviewing the biotechnological relevance of the Rhodococcus genus relationship with metal(loid)s, the bioprocesses elicited by these microorganisms in handling metal(loid)s’ toxicity, and the importance of these actinomycetes in the context of the bioremediation and bionanotechnology fields
Biotechnology of Rhodococcus for the production of valuable compounds
Full text linkBacteria belonging to Rhodococcus genus represent ideal candidates for microbial biotechnology applications because of their
metabolic versatility, ability to degrade a wide range of organic compounds, and resistance to various stress conditions, such as
metal toxicity, desiccation, and high concentration of organic solvents. Rhodococcus spp. strains have also peculiar biosynthetic
activities that contribute to their strong persistence in harsh and contaminated environments and provide them a competitive
advantage over other microorganisms. This review is focused on the metabolic features of Rhodococcus genus and their potential
use in biotechnology strategies for the production of compounds with environmental, industrial, and medical relevance such as
biosurfactants, bioflocculants, carotenoids, triacylglycerols, polyhydroxyalkanoate, siderophores, antimicrobials, and metalbased
nanostructures. These biosynthetic capacities can also be exploited to obtain high value-added products from low-cost
substrates (industrial wastes and contaminants), offering the possibility to efficiently recover valuable resources and providing
possible waste disposal solutions. Rhodococcus spp. strains have also recently been pointed out as a source of novel bioactive
molecules highlighting the need to extend the knowledge on biosynthetic capacities of members of this genus and their potential
utilization in the framework of bioeconomy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Selenium and tellurium nanomaterials
No full textmajor advantages, drawbacks as weOver the last 40 years, the rapid and exponential growth of nanotechnology led to the development of vari- ous synthesis methodologies to generate nanomaterials different in size, shape and composition to be applied in various fields. In particular, nanostructures composed of Selenium (Se) or Tellurium (Te) have attracted in- creasing interest, due to their intermediate nature between metallic and non-metallic elements, being defined as metalloids. Indeed, this key shared feature of Se and Te allows us the use of their compounds in a variety of applications fields, such as for manufacturing photocells, photographic exposure meters, piezoelectric devices, and thermoelectric materials, to name a few. Considering also that the chemical-physical properties of ele- ments result to be much more emphasized when they are assembled at the nanoscale range, huge efforts have been made to develop highly effective synthesis methods to generate Se- or Te-nanomaterials. In this context, the present book chapter will explore the most used chemical and/or physical methods exploited to gener- ate different morphologies of metalloid-nanostructures, focusing also the attention on thell as the safety related to these synthetic procedures
The actinomycete Kitasatospora sp. SeTe27, subjected to adaptive laboratory evolution (ALE) in the presence of selenite, varies its cellular morphology, redox stability, and tolerance to the toxic oxyanion
Full text linkThe effects of oxyanions selenite (SeO32−) in soils are of high concern in ecotoxicology and microbiology as they can react with mineral particles and microorganisms. This study investigated the evolution of the actinomycete Kitasatospora sp. SeTe27 in response to selenite. To this aim, we used the Adaptive Laboratory Evolution (ALE) technique, an experimental approach that mimics natural evolution and enhances microbial fitness for specific growth conditions. The original strain (wild type; WT) isolated from uncontaminated soil gave us a unique model system as it has never encountered the oxidative damage generated by the prooxidant nature of selenite. The WT strain exhibited a good basal level of selenite tolerance, although its growth and oxyanion removal capacity were limited compared to other environmental isolates. Based on these premises, the WT and the ALE strains, the latter isolated at the end of the laboratory evolution procedure, were compared. While both bacterial strains had similar fatty acid profiles, only WT cells exhibited hyphae aggregation and extensively produced membrane-like vesicles when grown in the presence of selenite (challenged conditions). Conversely, ALE selenite-grown cells showed morphological adaptation responses similar to the WT strain under unchallenged conditions, demonstrating the ALE strain improved resilience against selenite toxicity. Whole-genome sequencing revealed specific missense mutations in genes associated with anion transport and primary and secondary metabolisms in the ALE variant. These results were interpreted to show that some energy-demanding processes are attenuated in the ALE strain, prioritizing selenite bioprocessing to guarantee cell survival in the presence of selenite. The present study indicates some crucial points for adapting Kitasatospora sp. SeTe27 to selenite oxidative stress to best deal with selenium pollution. Moreover, the importance of exploring non-conventional bacterial genera, like Kitasatospora, for biotechnological applications is emphasized
The DNA cytosine methylome revealed two methylation motifs in the upstream regions of genes related to morphological and physiological differentiation in Streptomyces coelicolor A(3)2 M145
Full text linkDNA methylation is an epigenetic modification detected in both prokaryotic and eukaryotic genomic DNAs. In bacteria, the importance of 5-methylcytosine (m5C) in gene expression has been less investigated than in eukaryotic systems. Through dot-blot analysis employing m5C antibodies against chromosomal DNA, we have previously demonstrated that m5C influences the differentiation of Streptomyces coelicolor A(3)2 M145 in solid sporulating and liquid non-sporulating complex media. Here, we mapped the methylated cytosines of the M145 strain growing in the defined Maltose Glutamate (MG) liquid medium. Sequencing of the M145 genome after bisulfite treatment (BS-sequencing) evidenced 3360 methylated cytosines and the two methylation motifs, GGCmCGG and GCCmCG, in the upstream regions of 321 genes. Besides, the role of cytosine methylation was investigated using the hypo-methylating agent 5'-aza-2'-deoxycytidine (5-aza-dC) in S. coelicolor cultures, demonstrating that m5C affects both growth and antibiotic biosynthesis. Finally, quantitative reverse-transcription polymerase-chain-reaction (RT-qPCR) analysis of genes containing the methylation motifs in the upstream regions showed that 5-aza-dC treatment influenced their transcriptional levels and those of the regulatory genes for two antibiotics. To the best of our knowledge, this is the first study that reports the cytosine methylome of S. coelicolor M145, supporting the crucial role ascribed to cytosine methylation in controlling bacterial gene expression
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Rhodococcus aetherivorans BCP1 as cell factory for the production of intracellular tellurium nanorods under aerobic conditions
Full text linkBackground: Tellurite (TeO32-) is recognized as a toxic oxyanion to living organisms. However, mainly anaerobic or facultative-anaerobic microorganisms are able to tolerate and convert TeO32- into the less toxic and available form of elemental Tellurium (Te0), producing Te-deposits or Te-nanostructures. The use of TeO32--reducing bacteria can lead to the decontamination of polluted environments and the development of "green-synthesis" methods for the production of nanomaterials. In this study, the tolerance and the consumption of TeO32- have been investigated, along with the production and characterization of Te-nanorods by Rhodococcus aetherivorans BCP1 grown under aerobic conditions. Results: Aerobically grown BCP1 cells showed high tolerance towards TeO32- with a minimal inhibitory concentration (MIC) of 2800μg/mL (11.2mM). TeO32- consumption has been evaluated exposing the BCP1 strain to either 100 or 500μg/mL of K2TeO3 (unconditioned growth) or after re-inoculation in fresh medium with new addition of K2TeO3 (conditioned growth). A complete consumption of TeO32- at 100μg/mL was observed under both growth conditions, although conditioned cells showed higher consumption rate. Unconditioned and conditioned BCP1 cells partially consumed TeO32- at 500μg/mL. However, a greater TeO32- consumption was observed with conditioned cells. The production of intracellular, not aggregated and rod-shaped Te-nanostructures (TeNRs) was observed as a consequence of TeO32- reduction. Extracted TeNRs appear to be embedded in an organic surrounding material, as suggested by the chemical-physical characterization. Moreover, we observed longer TeNRs depending on either the concentration of precursor (100 or 500μg/mL of K2TeO3) or the growth conditions (unconditioned or conditioned grown cells). Conclusions:Rhodococcus aetherivorans BCP1 is able to tolerate high concentrations of TeO32- during its growth under aerobic conditions. Moreover, compared to unconditioned BCP1 cells, TeO32- conditioned cells showed a higher oxyanion consumption rate (for 100μg/mL of K2TeO3) or to consume greater amount of TeO32- (for 500μg/mL of K2TeO3). TeO32- consumption by BCP1 cells led to the production of intracellular and not aggregated TeNRs embedded in an organic surrounding material. The high resistance of BCP1 to TeO32- along with its ability to produce Te-nanostructures supports the application of this microorganism as a possible eco-friendly nanofactory
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