SubtiToolKit: a bioengineering kit for Bacillus subtilis and Gram-positive bacteria

Building DNA constructs of increasing complexity is key to synthetic biology. Golden Gate (GG) methods led to the creation of cloning toolkits - collections of modular standardized DNA parts hosted on hierarchic plasmids, developed for yeast, plants, Gram-negative bacteria, and human cells. However, Gram-positive bacteria have been neglected. Bacillus subtilis is a Gram-positive model organism and a workhorse in the bioindustry. Here, we present the SubtiToolKit (STK), a high-efficiency cloning toolkit for B. subtilis and Gram-positive bacteria. Its design permits DNA constructs for transcriptional units (TUs), operons, and knockin and knockout applications. The STK contains libraries of promoters, ribosome-binding site (RBSs), fluorescent proteins, protein tags, terminators, genome integration parts, a no-leakage genetic device to control the expression of toxic products during Escherichia coli assembly, and a toolbox for industrially relevant strains of Geobacillus and Parageobacillus as an example of the STK versatility for other Gram-positive bacteria and its future perspective as a reference toolkit.