BACILLUS-LICHENIFORMIS SIGB OPERON ENCODING THE GENERAL STRESS TRANSCRIPTION FACTOR SIGMA(B)

The general stress response of the Gram-positive soil bacterium Bacill us subtilis is controlled by the sigma(B) transcription factor. sigma( B) activity is regulated by the newly discovered partner switching mec hanism of signal transduction, which integrates the two different clas ses of challenges which posttranslationally activate sigma(B): environ mental stress and energy stress. Our investigation of a possible sigma (B) homologue in the related soil bacterium B. licheniformis had two g oals. First, this study would contribute to understanding the distribu tion of the sigma(B) general stress system among Gram-positive bacteri a. Second, a phylogenetic comparison of regulatory systems can supplem ent genetic and biochemical analysis by revealing conserved features t hat are critical for function. We report here that (1) B. licheniformi s cells contain a protein that closely resembles B. subtilis sigma(B) in size and antigenic properties; (2) the level of this potential sigm a(B) homologue rapidly increases following environmental or energy str ess; and (3) the B. licheniformis genome encodes a homologue of the si gB general stress operon, including the sigma(B) structural gene and s even rsb regulatory genes. Based on these results, B. licheniformis po ssesses a general stress system likely regulated by two coupled partne r switching modules that sense and integrate the two broad classes of activating stress signals. (C) 1998 Elsevier Science B.V. All rights r eserved.