Project description:The aim of this study was to understand how autotrophic (CO2-fixing) bacteria balance the different needs for substrate assimilation, growth functions, and resilience in order to thrive in their environment.To this end, the proteome of the model chemolithoautotroph Ralstonia eutropha a.k.a. Cupriavidus necator was studied in different environmental conditions (four limiting substrates, and five different growth rates). Cupriavidus was cultivated in substrate-limited chemostats with fructose, formate, succinate and ammonium limitation to obtain steady state cell samples. The dilution rate/growth rate was increased step-wise from 0.05 to 0.25 1/h in 0.05 steps. Protein quantity was determined by LC-MS, and enzyme utilization was investigated by resource balance analysis modeling.
Project description:Background: The uncontrolled and widespread use of (nano)silver compounds has led to the increased release of these compounds into the environment, raising concerns about their negative impact on ecosystems. Concomitantly, silver resistance determinants are widely spread among environmental and clinically relevant bacteria although the underlying mechanisms are not yet fully understood. Results: In this study, we show that Cupriavidus metallidurans is able to adapt to toxic silver concentrations and explicate the genetic circuit responsible for this adaptation. None of the known silver resistant determinants present in C. metallidurans are involved in the adapted response. Instead, increased silver resistance is achieved by the concerted action of a two-component system AgrR-AgrS, previously not associated with metal resistance, and two intrinsically disordered proteins PrsQ1 and PrsQ2. Both belong to an unique group of small, uncharacterized, extracellular proteins restricted to the genera Cupriavidus and Ralstonia. This system seems to be much more efficient as it gives C. metallidurans the ability to withstand much higher silver concentrations. The latter could be facilitated by the accumulation of silver ions and the formation of silver nanoparticles. Conclusions: Detailed knowledge and exploitation of this protein family could result in novel routes for metal nanoparticle formation and metal processing relevant for biotechnical and biomedical applications.
