Staphylococcal superantigen-carrying pathogenicity islands (SaPIs) are discrete, chromosomally integrated units of ~15 kilobases that are induced by helper phages to excise and replicate. SaPI DNA is then efficiently encapsidated in phage-like infectious particles, leading to extremely high frequencies of intra- as well as intergeneric transfer1–3. In the absence of helper phage lytic growth, the island is maintained in a quiescent prophage-like state by a global repressor, Stl, which controls expression of most of the SaPI genes4. Here we show that SaPI derepression is effected by a specific, non-essential phage protein that binds to Stl, disrupting the Stl–DNA complex and thereby initiating the excision-replication-packaging cycle of the island. Because SaPIs require phage proteins to be packaged5,6, this strategy assures that SaPIs will be transferred once induced. Several different SaPIs are induced by helper phage 80α and, in each case, the SaPI commandeers a different non-essential phage protein for its derepression. The highly specific interactions between different SaPI repressors and helper-phage-encoded antirepressors represent a remarkable evolutionary adaptation involved in pathogenicity island mobilization.

Chile has introduced sustainability goals in its electricity law in response to increased environmental awareness and the need to achieve higher levels of energy security. In northern Chile, the Atacama Desert has a large available surface with high radiation level, while the tectonic activity along the entire country testifies an ample yet unexploited geothermal resource. The novel concept of hybridizing a geothermal power plant with solar energy assistance is presented here for the particular conditions of Northern Chile. A thermodynamic model is developed to estimate the energy production in a hybrid power plant for two different configurations of solar resource use: adding peak power for a constant geothermal output, and saving geothermal resources for a constant power output. The thermodynamic model considers a single-flash geothermal plant with the addition of solar heat from a parabolic trough field. The solar heat is used to produce superheated steam and to produce additional saturated steam from the separator whenever possible. Results indicate that the energy produced by a geothermal well can be increased up to 11.6% and achieve savings of up to 10.3% in the use of geothermal resources by adding solar assistance when using the single flash geothermal technology. Moreover, the optimal mass flow rate of the geothermal plant is decreased when adding solar assistance. It is recommended to exploit solar energy together with geothermal energy wherever possible, to take advantage of each other's strengths and mutually eliminate weaknesses.