Novel auto-induction expression systems with high expression strength
and wide induction initiation in Bacillus subtilis
Abstract
The low expression strength and fixed induction initiation have always
been the main obstacle for applying the bacterial quorum sensing (QS)
system to protein production. As a typical QS system in Bacillus
subtilis, ComQXPA activates the promoter PsrfA using ComX and ComA as
the auto-inducer and promoter activator, respectively. This study
developed a series of novel auto-induction expression systems in B.
subtilis WB600 based on ComQXPA using super-folder green fluorescent
protein as the reporter. First, the -35 region of PsrfA was replaced by
the corresponding conserved sequence of σA-dependent promoters, yielding
P1 with an 85% enhanced expression strength. Second, by conducting a
semi-rational design within the spacer between -35 and -15 regions of in
P1, we generated the ComQXPA promoter PS1E, the expression strength of
which is 8.22-fold higher than that of PsrfA. Based on PS1E, we finally
obtained three types of auto-induction expression systems with the
induction initiations ranging from 1.5 h to 9.5 h by optimizing the
combination of the promoters for ComX and ComA. By using the
auto-induction expression systems, the yield of Bacillus deramificans
pullulanase in B. subtilis reached 80.2 U/mL, 0.36-fold higher than the
strongest constitutive promoter P566. With the diversity in dynamic
features, the novel auto-induction expression systems provide great
potential for improving protein expression and metabolite production in
B. subtilis.