Biohydrogen is a clean and renewable form of hydrogen, which can be produced by photosynthetic bacteria in outdoor large-scale photobioreactors using sunlight. In this study, the transcriptional response of Rhodobacter capsulatus to cold (4 °C) and heat (42 °C) stress was studied using microarrays. Bacteria were grown in 30/2 acetate/glutamate medium at 30 °C for 48 h under continuous illumination. Then, cold and heat stresses were applied for two and six hours. Growth and hydrogen production were impaired under both stress conditions. Microarray chips for R. capsulatus were custom designed by Affymetrix (GeneChip®. TR_RCH2a520699F). The numbers of significantly changed genes were 328 and 293 out of 3685 genes under cold and heat stress, respectively. Our results indicate that temperature stress greatly affects the hydrogen production metabolisms of R. capsulatus. Specifically, the expression of genes that participate in nitrogen metabolism, photosynthesis and the electron transport system were induced by cold stress, while decreased by heat stress. Heat stress also resulted in down regulation of genes related to cell envelope, transporter and binding proteins. Transcriptome analysis and physiological results were consistent with each other. The results presented here may aid clarification of the genetic mechanisms for hydrogen production in purple non-sulfur (PNS) bacteria under temperature stress.

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Objective: The growth of plants during recovery period after freezing stress is more important for winter cereals to survive frost. However, little research has been done on physio-biochemical changes in response to recovery or rewarming conditions in cereals. In this study, the changes in oxidative stress intensities and antioxidant enzyme activities were thus examined under cold acclimation (CA), short-term freezing stress (F) and rewarming (R) conditions in barley cultivars differing in cold tolerance in order to assess the changes in Reactive Oxygen Species (ROS) scavenging system.Methods: Electrolyte leakage, Fv/Fm ratio (quantum efficiency of PSII), the contents of hydrogen peroxide (HResults: A corresponding increase in the free proline content and activities of APX and GR, the levels of Fv/Fm ratio, electrolyte leakage and the contents of MDA and HConclusion: Lower amount of H