All vectors use the strong promoter preceding the groESL operon of Bacillus subtilis fused to the lac operator allowing their induction by addition of IPTG. While the background level of expression of these expression cassettes is very low in the absence of the inducer, an induction factor of about 1,300 was measured using the bgaB reporter gene. The amount of recombinant protein produced after addition of IPTG may represent 10 and 13%, respectively, of the total cellular protein. High level secretion of amyQ α-amylase and cellulase A and B of Clostridium thermocellum was demonstrated. An efficient Shine-Dalgarno sequence as well as a multiple cloning site (BamH I, Xba I, AatII, SmaI) were also inserted. To obtain secretion of recombinant proteins, the coding region for the signal peptide of the amyQ gene encoding an α-amylase was fused to the SD sequence of pHT01, thereby constructing pHT43.

pHT01是一种大肠杆菌-枯草芽孢杆菌穿梭质粒的表达载体，可以在枯草芽孢杆菌中高效表达重组外源蛋白。载体基于强σA-依赖性启动子的枯草杆菌groE操纵子，通过添加lac操纵子改造成为一种高效可控的（IPTG诱导的）启动子。