Abstract
Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis (Bt) are spore-forming members of the Bacillus cereus group. Spores of B. cereus group species are encircled by exosporium, which is composed of an external hair-like nap and a paracrystalline basal layer. Despite the extensive studies on the structure of the exosporium-related proteins, little is known about the transcription and regulation of exosporium gene expression in the B. cereus group. Herein, we studied the regulation of several exosporium-related genes in Bt. A SigK consensus sequence is present upstream of genes encoding hair-like nap proteins (bclA and bclB), basal layer proteins (bxpA, bxpB, cotB, and exsY ), and inosine hydrolase (iunH). Mutation of sigK decreased the transcriptional activities of all these genes, indicating that the transcription of these genes is controlled by SigK. Furthermore, mutation of gerE decreased the transcriptional activities of bclB, bxpB, cotB, and iunH but increased the expression of bxpA, and GerE binds to the promoters of bclB, bxpB, cotB, bxpA, and iunH. These results suggest that GerE directly regulates the transcription of these genes, increasing the expression of bclB, bxpB, cotB, and iunH and decreasing that of bxpA. These findings provide insight into the exosporium assembly process at the transcriptional level.
Highlights
The genus Bacillus encompasses species capable of forming highly resistant dormant endospores as a response to harsh environmental conditions
We identified 17 exosporium homologous genes with known functions in B. cereus and B. anthracis in Bacillus thuringiensis (Bt) HD73 (Table 1) comprising genes encoding the hair-like nap proteins, basal layer proteins, and enzymes
Unlike the coat that constitutes the outermost layer of the mature B. subtilis spore[6], the B. cereus group species are encircled by the exosporium[5]
Summary
The genus Bacillus encompasses species capable of forming highly resistant dormant endospores as a response to harsh environmental conditions. The exosporium is separated from the spore coat by a region known as the interspace and is the final layer of the spore to be assembled[9,10,11,12] It is composed of an external hair-like nap and a paracrystalline basal layer and contains approximately 20 different proteins[13,14,15], which are deposited around the spore in a progressive encasement process[9,10,11]. GerE is a small DNA-binding protein that is both an activator and a repressor in the mother cell that regulates the transcription of many genes involved in spore coat synthesis and assembly in the late stages of sporulation and germination[30,31,32]. The appearance of GerE switches off the expression of some genes that had been activated by SigK31
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
