The katX gene of Bacillus subtilis is under dual control of sigma(B) and sigma(F)

The gene katX, which encodes a catalase in Bacillus subtilis, is transcribe d by E sigma(F) in the pre-spore. This catalase is responsible for the resi stance to hydrogen peroxide shown by germinating and outgrowing spores. We demonstrated that katX is also a sigma(B)-dependent general stress gene, si nce it is strongly induced by heat, salt and ethanol stress, as well as by energy depletion. The -10 and -35 sequences of the sigma(B)- and sigma(F)-d ependent promoters of katX overlap, and the transcriptional start points us ed by E sigma(B) and E sigma(F) differ by only one nucleotide. Our results indicate that the level of KatX level in outgrowing spores depends mainly o n E sigma(F), because sigB mutants show normal KatX activity in dormant and outgrowing spores, katX mutants also develop the non-specific resistance t o oxidative stress that is typical of glucose-starved cells. Therefore, the physiological role of sigma(B)-dependent katX expression remains obscure. The results indicate an overlap between the sigma(B) regulon and the sigma( F) regulon, and the physiological implications of this overlap are discusse d.