Synechocystis sp. PCC 6803 Requires the Bidirectional Hydrogenase to Metabolize Glucose and Arginine Under Oxic Conditions

The cyanobacterium Synechocystis sp.PCC 6803 possesses a bidirectional NiFe-hydrogenase, HoxEFUYH. It functions to produce hydrogen under dark, fermentative conditions and photoproduces hydrogen when dark-adapted cells are illuminated. Unexpectedly, we found that the deletion of the large subunit of the hydrogenase (HoxH) in Synechocystis leads to an inability to grow on arginine and glucose under continuous light in the presence of oxygen. This is surprising, as the hydrogenase is an oxygen-sensitive enzyme. In wild-type (WT) cells, thylakoid membranes largely disappeared, cyanophycin accumulated, and the plastoquinone (PQ) pool was highly reduced, whereas ΔhoxH cells entered a dormant-like state and neither consumed glucose nor arginine at comparable rates to the WT. Hydrogen production was not traceable in the WT under these conditions. We tested and could show that the hydrogenase does not work as an oxidase on arginine and glucose but has an impact on the redox states of photosynthetic complexes in the presence of oxygen. It acts as an electron valve as an immediate response to the supply of arginine and glucose but supports the input of electrons from arginine and glucose oxidation into the photosynthetic electron chain in the long run, possibly via the NDH-1 complex. Despite the data presented in this study, the latter scenario requires further proof. The exact role of the hydrogenase in the presence of arginine and glucose remains unresolved. In addition, a unique feature of the hydrogenase is its ability to shift electrons between NAD(H), NADP(H), ferredoxin, and flavodoxin, which was recently shown in vitro and might be required for fine-tuning. Taken together, our data show that Synechocystis depends on the hydrogenase to metabolize organic carbon and nitrogen in the presence of oxygen, which might be an explanation for its prevalence in aerobic cyanobacteria

Monitoring and adaptation of service-oriented systems with goal and variability models

Variability modelling and service-orientation are important approaches for achieving both flexibility and adaptability required by stakeholders of software systems. In this paper, we present the MAESoS approach that utilizes goal and variability models to support runtime monitoring and adaptation of service-oriented systems. We illustrate our approach using two scenarios and present a tool architecture that integrates a monitoring tool and an existing tool for defining and executing variability models.Postprint (published version

CELL-SELEX: Novel Perspectives of Aptamer-Based Therapeutics

Aptamers, single stranded DNA or RNA molecules, generated by a method called SELEX (systematic evolution of ligands by exponential enrichment) have been widely used in various biomedical applications. The newly developed Cell-SELEX (cell based-SELEX) targeting whole living cells has raised great expectations for cancer biology, -therapy and regenerative medicine. Combining nanobiotechnology with aptamers, this technology opens the way to more sophisticated applications in molecular diagnosis. This paper gives a review of recent developments in SELEX technologies and new applications of aptamers

Monitoring and adaptation of service-oriented systems with goal and variability models

Variability modelling and service-orientation are important approaches for achieving both flexibility and adaptability required by stakeholders of software systems. In this paper, we present the MAESoS approach that utilizes goal and variability models to support runtime monitoring and adaptation of service-oriented systems. We illustrate our approach using two scenarios and present a tool architecture that integrates a monitoring tool and an existing tool for defining and executing variability models

Field modeling of carbon monoxide production in vitiated compartment fires

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Synechocystis sp. PCC 6803 Requires the Bidirectional Hydrogenase to Metabolize Glucose and Arginine Under Oxic Conditions

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Monitoring and adaptation of service-oriented systems with goal and variability models

Variability modelling and service-orientation are important approaches for achieving both flexibility and adaptability required by stakeholders of software systems. In this paper, we present the MAESoS approach that utilizes goal and variability models to support runtime monitoring and adaptation of service-oriented systems. We illustrate our approach using two scenarios and present a tool architecture that integrates a monitoring tool and an existing tool for defining and executing variability models

Goal-driven adaptation of service-based systems from runtime monitoring data

Service-based systems need to provide flexibility to adapt both to evolving requirements from multiple, often conflicting, ephemeral and unknown stakeholders, as well as to changes in the runtime behavior of their component services. Goal-oriented models allow representing the requirements of the system whilst keeping information about alternatives. We present the MAESoS approach which uses i* diagrams to identify quality of service requirements over services. The alternatives are extracted and kept in a variability model. A monitoring infrastructure identifies changes in runtime behavior that can propagate up to the level of stakeholder goals and trigger the required adaptations. We illustrate the approach with a scenario of use.Peer Reviewe

Modelling the mechanisms of glucose transport through cell membrane of aspergillus niger in submerged citric acid fermennation processess

Data from batch fermentations of citric acid producing Aspergillus niger cultures in shake flasks, loop and stirred tank bioreactors, were used to construct diffusion models for the transport of glucose. It was found that the mediated diffusion model does not reflect the relationship between the observed uptake rate and glucose concentration, nor for the lack of sensitivity to citrate. This is due in part of the low value of Km in relation to the actual substrate concentration, which means that the carriers are saturated until the end of the process. The membrane barriers must be strongly inhibited under the standard production conditions. Instead, the simple diffusion model fits all the observed data and it explains the relationship between the specific uptake rate and the concentration of glucose, which should not exist under carrier-saturated conditions. This may account for the overproduction or organic acids under the specific process conditions. The simple nature of this mechanism also explains the similarity of the uptake relationships from different sources, despite the use of different growing conditions