VAAM-Jahrestagung 2012 18.–21. März in Tübingen

171OTP153Transcriptional regulation of the operon encoding the stressresponsivesigma factor SigH and its anti-sigma factor RshA, andcontrol of SigH regulatory network in CorynebacteriumglutamicumT. Busche* 1 , R. Šilar 2 , M. Pimanová 2 , M. Pátek 2 , J. Kalinowski 21 Universität Bielefeld, Centrum für Biotechnologie (CeBiTec), Institut fürGenomforschung und Systembiologie, Bielefeld, Germany2 AS CR, v.v.i., Institute of Microbiology, Prague, Czech RepublicExpression of genes in Corynebacterium glutamicum, a Gram-positivenon-pathogenic bacterium used mainly for industrial production of aminoacids, is regulated by seven different sigma factors of RNA polymerase,including stress-responsive SigH. According to the C. glutamicum genomesequence, the SigH-dependent transcription may be controlled by antisigmafactor encoded by the rshA gene. The aim of the study was toanalyze transcriptional regulation of thesigHandrshAgenes, prove thefunction of rshA, determine the genes of the SigH regulon and propose amodel describing the role of SigH and RshA in oxidative and heat stressresponses.Transcription analysis revealed that the sigH gene and anti-sigma rshAgene are cotranscribed from four sigH housekeeping promoters in C.glutamicum. In addition, a SigH-controlled rshA promoter was found todrive separate transcription of the rshA gene. To test if transcription ofSigH-controlled genes is increased in the absence of the anti-sigma factorrshA gene under standard growth conditions, a C. glutamicumr shAdeletion strain was constructed and used for genome-wide transcriptionprofiling. In total, 83 genes organized in 61 putative transcriptional units,including those which were previously detected using sigH deletionstrains, exhibited increased transcription in the rshA deletion mutant incomparison to the wildtype strain. The genes encoding proteins related todisulphide stress response, heat stress proteins, components of the SOSresponseto DNA damage and proteasome components were the mostapparent upregulated gene groups. Potential SigH-dependent promotersupstream of the identified genes were found by transcription startdetermination and by sequence analysis.The rshA gene codes for an anti-sigma factor controlling function of thestress-responsive sigma factor SigH in C. glutamicum. Transcription ofrshA from a SigH-dependent promoter may serve to quickly shutdown theSigH-dependent stress response after the cells have passed the stresscondition. We propose here a model of regulation of oxidative and heatstress response including the redox homeostasis by SigH, RshA andthioredioxin system. The updated consensus sequence of SigH-controlledpromoters was derived from the 45 promoters of the genes belonging tothe SigH regulon.OTP154Nanoflagellate diversity during the iron fertilizationexperiment LOHAFEXS. Thiele* 1 , C. Wolf 2 , I. Schulz 2 , B. Fuchs 1 , P. Assmy 3 , R. Amann 11 The Max Planck Institute for Marine Microbiology, Bremen, Germany2 Alfred Wegener Institut, Research Group Bioscience, Bremerhaven, Germany3 Norwegian Polar Institute, Tromsø, NorwayAccording to the iron hypothesis of J. Martin, vast parts of the ocean arenutrient rich but iron limited. Therefore, fertilization of these areas withiron sulfate, in order to create algae blooms, was considered as a method ofCO 2 sequestration. The main aim of the study was the investigation ofside-effects of such events to the ecosystem. Since investigations of thebacterial community discovered a strongly top down controlled system,investigation of the next larger organism, the eukaryotic plankton < 20m,may help to shed light into the black box of biological carbon pump. The