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

Alternative sigma factors have been detected in the myxobacterium Stigmatel la aurantiaca during indole-induced sporulation, fruiting body formation an d 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,be ta -galactosidase activity during development in a merodiploid strain that harboured a sigB-lacZ fusion gene. Inactivation of the sigB gene by inserti on of the neo gene resulted in the loss of one sigma factor as shown by Wes tern analysis. Neither fruiting body formation nor sporulation, nor the pro duction of possible SigB targets, such as DnaK, GroEL or HspA, were affecte d.