Identification of two novel highly inducible promoters from Bacillus licheniformis by screening transcriptomic data

Bacillus licheniformis TCCC11148 is an important industrial strain used to produce alkaline protease. In this study, the transcriptome of B. licheniformis TCCC11148 was analyzed by high throughput RNA sequencing (RNA-Seq) to identify genes that are expressed differentially in the different phases were detected using RNA-Seq. In total, 440 differentially expressed genes between the 12 h and 48 h groups were identified, including 267 up- and 173 downregulated genes. Additionally, 198 differentially expressed genes were identified in the 48 h vs. the 60 h group, including 182 up- and 16 downregulated genes. To screen for novel inducible promoters, an alkaline protease reporter gene was used to test 24 promoters from 66 candidate genes with obviously higher expression levels (RPKM values) than the control group based on the transcriptome data of B. licheniformis in different phases. Gene 707, related to coenzyme transport and metabolism, and gene 1004, related to posttranslational modification were identified as likely having inducible promoters. The expression level of recombinant strains with reporter genes under the control of promoters p707 and p1004 were 8 times higher than that of the control group. This study contributes a method for finding useful inducible promoters for industrial use based on transcriptomic data.