The Red Queen hypothesis proposes that coevolution of interacting species (such as hosts and parasites) should drive molecular evolution through continual natural selection for adaptation and counter-adaptation 1-3 . Although the divergence observed at some host-resistance 4-6 and parasiteinfectivity 7-9 genes is consistent with this, the long time periods typically required to study coevolution have so far prevented any direct empirical test. Here we show, using experimental populations of the bacterium Pseudomonas fluorescens SBW25 and its viral parasite, phage Φ2 (refs 10, 11), that the rate of molecular evolution in the phage was far higher when both bacterium and phage coevolved with each other than when phage evolved against a constant host genotype. Coevolution also resulted in far greater genetic divergence between replicate populations, which was correlated with the range of hosts that coevolved phage were able to infect. Consistent with this, the most rapidly evolving phage genes under coevolution were those involved in host infection. These results demonstrate, at both the genomic and phenotypic level, that antagonistic coevolution is a cause of rapid and divergent evolution, and is likely to be a major driver of evolutionary change within species.

Abstract. The role of ecological processes in the evolution of social traits is increasingly recognized. Here, we explore, using a general theoretical model and experiments with bacteria, the joint effects of disturbance frequency and resource supply on the evolution of cooperative biofilm formation. Our results demonstrate that cooperation tends to peak at intermediate frequencies of disturbance but that the peak shifts toward progressively higher frequencies of disturbance as resource supply increases. This appears to arise due to increased growth rates at higher levels of resource supply, which allows cooperators to more rapidly exceed the density threshold above which cooperation is beneficial following catastrophic disturbance. These findings demonstrate for the first time the importance of interactions between ecological processes in the evolution of public-goods cooperation and suggest that cooperation can be favored by selection across a wide range of ecological conditions.

Abstract:Organic bioelectronics forms the basis of conductive polymer tools with great potential for application in biomedical science and medicine. It is a rapidly growing field of both academic and industrial interest since conductive polymers bridge the gap between electronics and biology by being electronically and ionically conductive. This feature can be employed in numerous ways by choosing the right polyelectrolyte system and tuning its properties towards the intended application. This review highlights how active organic bioelectronic surfaces can be used to control cell attachment and release as well as to trigger cell signaling by means of electrical, chemical or mechanical actuation. Furthermore, we report on the unique properties of conductive polymers that make them outstanding materials for labeled or label-free biosensors. Techniques for electronically controlled ion transport in organic bioelectronic devices are introduced, and examples are provided to illustrate their use in self-regulated medical devices. Organic bioelectronics have great potential to become a primary platform in future bioelectronics. We therefore introduce current applications that will aid in the development of advanced in vitro systems for biomedical science and of automated systems for applications in neuroscience, cell biology and infection biology. Considering this broad spectrum of applications, organic bioelectronics could lead to timely detection of disease, and facilitate the use of remote and personalized medicine. As such, organic bioelectronics might contribute to efficient healthcare and reduced hospitalization times for patients. OPEN ACCESSElectronics 2015, 4 880

Biofouling is a major problem caused by bacteria colonizing abiotic surfaces, such as medical devices. Biofilms are formed as the bacterial metabolism adapts to an attached growth state. We studied whether bacterial metabolism, hence biofilm formation, can be modulated in electrochemically active surfaces using the conducting conjugated polymer poly(3,4-ethylenedioxythiophene) (PEDOT). We fabricated composites of PEDOT doped with either heparin, dodecyl benzene sulfonate or chloride, and identified the fabrication parameters so that the electrochemical redox state is the main distinct factor influencing biofilm growth. PEDOT surfaces fitted into a custom-designed culturing device allowed for redox switching in Salmonella cultures, leading to oxidized or reduced electrodes. Similarly large biofilm growth was found on the oxidized anodes and on conventional polyester. In contrast, biofilm was significantly decreased (52–58%) on the reduced cathodes. Quantification of electrochromism in unswitched conducting polymer surfaces revealed a bacteria-driven electrochemical reduction of PEDOT. As a result, unswitched PEDOT acquired an analogous electrochemical state to the externally reduced cathode, explaining the similarly decreased biofilm growth on reduced cathodes and unswitched surfaces. Collectively, our findings reveal two opposing effects affecting biofilm formation. While the oxidized PEDOT anode constitutes a renewable electron sink that promotes biofilm growth, reduction of PEDOT by a power source or by bacteria largely suppresses biofilm formation. Modulating bacterial metabolism using the redox state of electroactive surfaces constitutes an unexplored method with applications spanning from antifouling coatings and microbial fuel cells to the study of the role of bacterial respiration during infection.