39 research outputs found
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Interspecies acetate transfer influences the extent of anaerobic benzoate degradation by syntrophic consortia
Benzoate degradation by an anaerobic, syntrophic bacterium, strain SB, in coculture with Desulfovibrio strain G-11 reached a threshold value which depended on the amount of acetate added, and ranged from about 2.5 to 29.9 {mu}M. Increasing acetate concentrations also uncompetitively inhibited benzoate degradation. The apparent V{sub max} and K{sub m} for benzoate degradation decreased with increasing acetate concentration, but the benzoate degradation capacity (V{sub max}/K{sub m}) of cell suspensions remained comparable. The addition of an acetate-using bacterium to cocultures after the threshold was reached resulted in the degradation of benzoate to below the detection limit. Mathematical simulations showed that the benzoate threshold was not predicted by the inhibitory effect of acetate on benzoate degradation kinetics. With nitrate instead of sulfate as the terminal electron acceptor, no benzoate threshold was observed in the presence of 20 mM acetate even though the degradation capacity was lower with nitrate than with sulfate. When strain SB was grown with a hydrogen-using partner that had a 5-fold lower hydrogen utilization capacity, a 5 to 9-fold lower the benzoate degradation capacity was observed compared to SB/G-11 cocultures. The Gibb`s free energy for benzoate degradation was less negative in cell suspensions with threshold compared to those without threshold. These studies showed that the threshold was not a function of the inhibition of benzoate degradation capacity by acetate, or the toxicity of the undissociated form of acetate. Rather a critical or minimal Gibb`s free energy may exist where thermodynamic constraints preclude further benzoate degradation
Breaking the Cyber Kill Chain by Modelling Resource Costs
To combat cybercrime, a clearer understanding of the attacks and the offenders is necessary. When there is little available data about attack incidents, which is usually the case for new technology, one can make estimations about the necessary investments an offender would need to compromise the system. The next step would be to implement measures that increase these costs to a level that makes the attack unattractive. Our research method follows the principles of design science, where cycles of research activities are used to create artefacts intended to solve real-world problems. Our artefacts are an approach for creating a resource costs model (RCM) and an accompanying modelling tool implemented as a web application. These are used to find the required attacker resources at each stage of the cyber kill chain. End user feedback show that structured visualisation of the required resources raises the awareness of the cyberthreat. This approach has its strength and provides best accuracy with specific attacks, but is more limited when there are many possible attack vectors of different types