L. Baillie et al., THE EXPRESSION OF THE PROTECTIVE ANTIGEN OF BACILLUS-ANTHRACIS IN BACILLUS-SUBTILIS, Journal of applied microbiology, 84(5), 1998, pp. 741-746
The expression of Bacillus anthracis protective antigen (PA) in B. sub
tilis from the pag gene in pPA101-1 was explored in different genetic
backgrounds in an attempt to identify opportunities to maximize expres
sion. Introduction of AtxA, which positively regulates PA expression i
n B. anthracis did not improve expression levels in the protease-defic
ient strain WB600. Plasmid pPA101-1 was found to carry a deletion whic
h created a new fusion point between vector and insert sequence, and w
hich removed part of the AtxA binding site. The deletion map have occu
rred as a consequence of recombination between TCTAT sequences within
both the vector and insert. Host mutations could influence expression;
PA levels from pPA101-1 are threefold higher in a ccpA mutant than in
an otherwise isogenic parent, and eightfold higher in an abrB mutant.
These data demonstrate that the introduction of mutations affecting c
atabolite repression and growth phase regulation results in an increas
e in the yield of PA in this host-vector system. Combining these mutat
ions with a multiply protease-negative background could potentially al
low further improvements in PA yield.