Bacillus licheniformis sigB operon encoding the general stress transcription factor σB

The general stress response of the Gram-positive soil bacterium Bacillus subtilis is controlled by the sigma(B) transcription factor. sigma(B) activity is regulated by the newly discovered partner switching mechanism of signal transduction, which integrates the two different classes of challenges which posttranslationally activate sigma(B): environmental stress and energy stress. Our investigation of a possible sigma(B) homologue in the related soil bacterium B. licheniformis had two goals. First, this study would contribute to understanding the distribution of the sigma(B) general stress system among Gram-positive bacteria. Second, a phylogenetic comparison of regulatory systems can supplement genetic and biochemical analysis by revealing conserved features that are critical for function. We report here that (1) B. licheniformis cells contain a protein that closely resembles B. subtilis sigma(B) in size and antigenic properties; (2) the level of this potential sigma(B) homologue rapidly increases following environmental or energy stress; and (3) the B. licheniformis genome encodes a homologue of the sigB general stress operon, including the sigma(B) structural gene and seven rsb regulatory genes. Based on these results, B. licheniformis possesses a general stress system likely regulated by two coupled partner switching modules that sense and integrate the two broad classes of activating stress signals. (C) 1998 Elsevier Science B.V. All rights reserved.