A. Petersohn et al., Identification and transcriptional analysis of new members of the sigma(B)regulon in Bacillus subtilis, MICROBIO-UK, 145, 1999, pp. 869-880
Bacillus subtilis responds to various stimuli (heat, ethanol and salt stres
s, energy starvation) with the induction of general stress proteins (GSPs).
Most of them belong to the stress and stationary-phase regulon controlled
by the alternative sigma factor sigma(B). The majority of sigma(B)-dependen
t proteins are thought to provide a precautionary general stress resistance
in stressed or starved cells. In this report, the identification and trans
criptional analysis of nine new members of the sigma(B) regulon are describ
ed. The biochemical function was not determined for any of the proteins enc
oded by the nine new sigma(B)-dependent stress genes, however, similarities
to proteins in the databases allowed a distinction between proteins with p
utative (i-iv) and unknown (v) function. The putative functions of BmrU, Yc
dF, YdaD, YdaP, YhdN and YocK underline the suggested protective role of si
gma(B)-dependent GSPs and also elucidate new areas where sigma(B) might pla
y an important role. (i) The finding that the bmrUR operon is under sigma(B
) control indicates that the elimination of multidrug compounds might be a
new function in multiple stress resistance. (ii) YcdF and YdaD resemble NAD
(P)-dependent dehydrogenases. Both proteins could be involved in the genera
tion of NAD(P)H and therefore in the maintenance of the intracellular redox
balance under stress. (iii) The ydaP gene might belong to the increasing n
umber of sigma(B)-dependent genes whose orthologues are under the control o
f sigma(S) in Escherichia coli, indicating that both regulons may fulfil si
milar functions. (iv) YhdN shows weak similarities to potassium ion channel
proteins and YocK shows resemblance to the DnaK suppressor protein DksA. (
v) Three new sigma(B)-dependent genes (ydaE, ydaG and yfkM) encoding protei
ns with still unknown functions were also described. Further analyses of co
rresponding mutants might allow a first prediction of their function within
the framework of the general stress regulon.