The Bacillus subtilis htpG gene is not involved in thermal stress management

To study the influence of the htpG gene on thermal stress management in Bac illus subtilis, two different kinds of htpG mutation were constructed. Tn o ne case, the gene was inactivated by insertion of a cat cassette in to the coding region; htpG was thus found to be Iron-essential. In the second case , the htpG gene was fused to a xylose-dependent promoter, allowing expressi on of the gene to be controlled. In the absence of HtpG protein, recovery o f cells from a heat shock at 53 degrees C was retarded, and this delay coul d be eliminated by overproduction of HtpG. While htpG is not involved in th e development of induced thermotolerance, DnaK and GroE proteins are absolu tely required. Overproduction of class I heat-shock proteins prior to shift ing cells to a lethal temperature is important but not sufficient for the d evelopment of intrinsic thermotolerance. It could be shown that the HtpG pr otein does not act as a cellular thermometer in B. subtilis.