[Synthesis of heat shock proteins following amino acid or oxygen limitation in Bacillus subtilis relA+ and relA strains].

Some of the presumable heat shock proteins will be produced in Bacillus subtilis in response to different environmental conditions, e.g. heat shock, amino acid limitation or oxygen limitation. During amino acid limitation or during oxygen limitation the relA+ strain is able of synthesizing this set of proteins but the relA strain is not. We suggest that the accelerated rate of the synthesis of some heat shock proteins depends on the induction of the stringent response because the (p)ppGpp production does not occur in the relA strain during amino acid or oxygen limitation. On the other hand the relA strain can produce heat shock proteins under heat stress. Therefore different mechanisms must be responsible for the expression of this set of genes during heat and other stress stimuli. It can be supposed that in B. subtilis the (p)ppGpp-dependent stringent control is a central defense reaction against different adverse environmental conditions and furthermore, that the synthesis of "stress" proteins as an essential component of the stringent response is part of a general adaptation mechanism under non-growing conditions.