The Metabolic Regulation of Sporulation and Parasporal Crystal Formation in Bacillus thuringiensis Revealed by Transcriptomics

Bacillus thuringiensis is a well-known entomopathogenic bacterium used worldwide as an environmentally compat-ible biopesticide. During sporulation, B. thuringiensis ac-cumulates a large number of parasporal crystals consist-ing of insecticidal crystal proteins (ICPs) that can account for nearly 20–30 % of the cell’s dry weight. However, the metabolic regulation mechanisms of ICP synthesis re-main to be elucidated. In this study, the combined efforts in transcriptomics and proteomics mainly uncovered the following 6 metabolic regulation mechanisms: (1) pro-teases and the amino acid metabolism (particularly, the branched-chain amino acids) became more active during sporulation; (2) stored poly--hydroxybutyrate and acet-oin, together with some low-quality substances provided considerable carbon and energy sources for sporulatio