Cadmium (Cd) is considered a toxic heavy metal; nevertheless, its toxicity fluctuates for different organisms. Cadmium‐tolerant bacteria (CdtB) are diverse and non‐phylogenetically related. Because ...of their ecological importance these bacteria become particularly relevant when pollution occurs and where human health is impacted. The aim of this review is to show the significance, culturable diversity, metabolic detoxification mechanisms of CdtB and their current uses in several bioremediation processes applied to agricultural soils. Further discussion addressed the technological devices and the possible advantages of genetically modified CdtB for diagnostic purposes in the future.
Significance and Impact of the Study: Crop production is adversely affected by the presence of heavy metals in soils dedicated to agriculture. These metals ultimately accumulate in seeds or edible parts and enter the human food chain. The application of cadmium (Cd)‐tolerant bacteria capacities for Cd immobilization and sequestration, in combination with soil management and implementation of other agronomic practices, may reduce the Cd levels in farmlands.
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► Emphasis is put on extracting microbial growth parameters from isothermal microcalorimetry data. ► Misconceptions in the interpretation of thermograms from microbial culture are ...discussed with respect to those parameters. ► Application, advantages and drawbacks of different growth models are discussed for isothermal calorimetry data.
Over the last 10 years use of isothermal microcalorimetry in the biological and biomedical field has been a increasing. Several biomedical applications such as detection and characterization of pathogens, drug testing, parasitology, and tissue engineering have been investigated. Similarly in environmental science isothermal microcalorimetry has been shown to provide insight in soil science or in geomicrobiology. Often it is useful to convert the isothermal microcalorimetry data into biologically meaningful data such as growth rate, lag phase, or maximum growth. In this study we review not only the various approaches used for such conversion but we also carefully look at the advantages, the drawbacks and underlying assumption of each approach. Understanding of these assumptions is a critical point into applying the right model to the right portion of the microcalorimetric data.
Isothermal microcalorimetry measures the heat released or consumed by physical or chemical processes. Metabolic activity releases heat that can be measured. However the calorimetric signal can be ...difficult for new users to interpret. This paper compares microcalorimetry to other techniques and reviews its application to different fields where microbiological activity is important. We also describe different ways to analyze the data and translate it into meaningful (micro)biological equivalents. This paper aims at providing non-specialist reader the tools to understand how isothermal microcalorimetry can be used for microbiological applications.
Mineral precipitation in microbial mats may have been the key to their preservation as fossil stromatolites, potentially documenting evidence of the earliest life on Earth. Two factors that ...contribute to carbonate mineral precipitation are the saturation index (SI) and the presence of nucleation sites. Both of these can be influenced by micro‐organisms, which can either alter SI through their metabolisms, or produce and consume organic substances such as extracellular polymeric substances (EPS) that can affect nucleation. It is the balance of individual metabolisms within the mat community that determines the pH and the dissolved inorganic carbon concentration, thereby potentially increasing the alkalinity and consequently the SI. Sulfate‐reducing bacteria (SRB) are an important component of this ‘alkalinity engine.’ The activity of SRB often peaks in layers where CaCO3 precipitates, and mineral precipitation has been demonstrated in SRB cultures; however, the effect of their metabolism on the alkalinity engine and actual contribution to mineral precipitation is the subject of controversy. Here, we show through culture experiments, theoretical calculations, and geochemical modeling studies that the pH, alkalinity, and organomineralization potential will vary depending on the type of electron donor. Specifically, hydrogen and formate can increase the pH, but electron donors like lactate and ethanol, and to a lesser extent glycolate, decrease the pH. The implication of this for the lithification of mats is that the combination of processes supplying electron donors and the utilization of these compounds by SRB may be critical to promoting mineral precipitation.
The role and coexistence of oxidative stress (OS) and inflammation in type C hepatic encephalopathy (C HE) is a subject of intense debate. Under normal conditions the physiological levels of ...intracellular reactive oxygen species are controlled by the counteracting antioxidant response to maintain redox homeostasis. Our previous in-vivo1H-MRS studies revealed the longitudinal impairment of the antioxidant system (ascorbate) in a bile-duct ligation (BDL) rat model of type C HE.
Therefore, the aim of this work was to examine the course of central nervous system (CNS) OS and systemic OS, as well as to check for their co-existence with inflammation in the BDL rat model of type C HE. To this end, we implemented a multidisciplinary approach, including ex-vivo and in-vitro electron paramagnetic resonance spectroscopy (EPR) spin-trapping, which was combined with UV–Vis spectroscopy, and histological assessments. We hypothesized that OS and inflammation act synergistically in the pathophysiology of type C HE.
Our findings point to an increased CNS- and systemic-OS and inflammation over the course of type C HE progression. In particular, an increase in the CNS OS was observed as early as 2-weeks post-BDL, while the systemic OS became significant at week 6 post-BDL. The CNS EPR measurements were further validated by a substantial accumulation of 8-Oxo-2′-deoxyguanosine (Oxo-8-dG), a marker of oxidative DNA/RNA modifications on immunohistochemistry (IHC). Using IHC, we also detected increased synthesis of antioxidants, glutathione peroxidase 1 (GPX-1) and superoxide dismutases (i.e.Cu/ZnSOD (SOD1) and MnSOD (SOD2)), along with proinflammatory cytokine interleukin-6 (IL-6) in the brains of BDL rats. The presence of systemic inflammation was observed already at 2-weeks post-surgery. Thus, these results suggest that CNS OS is an early event in type C HE rat model, which seems to precede systemic OS. Finally, our results suggest that the increase in CNS OS is due to enhanced formation of intra- and extra-cellular ROS rather than due to reduced antioxidant capacity, and that OS in parallel with inflammation plays a significant role in type C HE.
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•Longitudinal tracking of both CNS and systemic oxidative stress in a rat model of type C HE using ex-vivo and in-vitro EPR spin-trapping.•Synergistic participation of CNS oxidative stress and inflammation in the progression of type C HE.•Increased oxidative stress is not due to the decline of antioxidant activity but rather to an increase in ROS production.
In modern stromatolites, mineralization results from a complex interplay between microbial metabolisms, the organic matrix, and environmental parameters. Here, we combined biogeochemical, ...mineralogical, and microscopic analyses with measurements of metabolic activity to characterize the mineralization processes and products in an emergent (<18 months) hypersaline microbial mat. While the nucleation of Mg silicates is ubiquitous in the mat, the initial formation of a Ca‐Mg carbonate lamina depends on (i) the creation of a high‐pH interface combined with a major change in properties of the exopolymeric substances at the interface of the oxygenic and anoxygenic photoautotrophic layers and (ii) the synergy between two major players of sulfur cycle, purple sulfur bacteria, and sulfate‐reducing bacteria. The repetition of this process over time combined with upward growth of the mat is a possible pathway leading to the formation of a stromatolite.
Summary
Creatine deficiency syndromes, either due to AGAT, GAMT or SLC6A8 deficiencies, lead to a complete absence, or a very strong decrease, of creatine within the brain, as measured by magnetic ...resonance spectroscopy. While the mammalian central nervous system (CNS) expresses AGAT, GAMT and SLC6A8, the lack of SLC6A8 in astrocytes around the blood–brain barrier limits the brain capacity to import creatine from the periphery, and suggests that the CNS has to rely mainly on endogenous creatine synthesis through AGAT and GAMT expression. This seems contradictory with SLC6A8 deficiency, which, despite AGAT and GAMT expression, also leads to creatine deficiency in the CNS. We present novel data showing that in cortical grey matter, AGAT and GAMT are expressed in a dissociated way: e.g. only a few cells co-express both genes. This suggests that to allow synthesis of creatine within the CNS, at least for a significant part of it, guanidinoacetate must be transported from AGAT- to GAMT-expressing cells, possibly through SLC6A8. This would explain the creatine deficiency observed in SLC6A8-deficient patients. By bringing together creatine deficiency syndromes, AGAT, GAMT and SLC6A8 distribution in CNS, as well as a synthetic view on creatine and guanidinoacetate levels in the brain, this review presents a comprehensive framework, including new hypotheses, on brain creatine metabolism and transport, both in normal conditions and in case of creatine deficiency.
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