SigB, an alternative sigma factor of the myxobacterium Stigmatella aurantiaca, is synthesized during development and heat shock

ZMBH, Zentrum für Molekulare Biologie der Universität Heidelberg, Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany 1 Author for correspondence: Hans U. Schairer. Tel: +49 6221 546880/30. Fax: +49 6221 545893. e-mail: hus{at}zmbh.uni-heidelberg.de Alternative sigma factors have been detected in the myxobacterium Stigmatella aurantiaca during indole-induced sporulation, fruiting body formation and heat shock using an antiserum raised against sigma factor SigB. The time course of sigB gene expression was analysed by RT-PCR and by determining ß-galactosidase activity during development in a merodiploid strain that harboured a sigB – lacZ fusion gene. Inactivation of the sigB gene by insertion of the neo gene resulted in the loss of one sigma factor as shown by Western analysis. Neither fruiting body formation nor sporulation, nor the production of possible SigB targets, such as DnaK, GroEL or HspA, were affected. Keywords: myxobacteria, developmental biology, Western analysis The GenBank accession number for the SigE sequence reported in this paper is AF023661 . a Present address: Gesellschaft für Biotechnologische Forschung GBF, Mascheroder Weg 1, D-38124 Braunschweig, Germany. b B. Silakowski and S. Müller contributed equally to this work. c Present address: Praxis Dr Dr Greiner, Mollstraße 49a, D-68165 Mannheim, Germany.