Glucose-Resistant Sporulation in Bacillus subtilis crsA47 Mutants Does Not Depend on Promoter Switching at the spo0A Gene

Abstract

We have found that sporulation in Bacillus subtilis crsA47 mutants does not require the H -dependent promoter of the spo0A gene. This implies that the glucose-resistant sporulation phenotype of this strain is not related to the switch from the vegetative-stage A -dependent promoter to the H -dependent promoter at the spo0A gene.The Bacillus subtilis response regulator Spo0A is at the center of a complex signal transduction network that controls entry into the developmental pathway for endospore formation. The spo0A gene has two promoters that are differentially regulated, spo0Apv and spo0Aps. The spo0Apv promoter is weakly expressed during vegetative growth and is transcribed by RNA polymerase containing the major vegetative-phase sigma factor, A (4). spo0Aps is induced during the initial stages of sporulation and requires both RNA polymerase containing the alternate sigma factor, H , and phosphorylated Spo0A (Spo0AϳP) for expression (20,23). As the spo0Aps promoter is activated, transcription from the spo0Apv promoter normally declines due to repression by Spo0AϳP; thus, there is a promoter switch. The activation of the spo0Aps promoter during sporulation has been reported to be required for the accumulation of sufficient Spo0AϳP to fully activate the transcription of stage II sporulation genes (5,13,22,23).In wild-type B. subtilis, the spo0A promoter switch has been shown to be repressed by excess glucose (26), which blocks sporulation at an early stage (3,11,21,25). One of the mutations that lead to glucose-resistant sporulation, crsA47 (4, 24), alters the gene for the major vegetative-stage sigma factor, A

Repeated triggering of sporulation in Bacillus subtilis selects against a protein that affects the timing of cell division

“…Of the poly(glycerol phosphate) subunits of WTA, B25% are glycosylated (Archibald et al, 1969;D'Elia et al, 2006;Silhavy et al, 2010). A logical explanation for increased fitness by loss of tagE would be economical; it would save a considerable amount of glucose from being incorporated in the cell wall (Dixon and Spiegelman, 2002). However, isolates of evolved stJS03 and stJS03 tagE::spec did not display significantly different logarithmic growth rates, although different growth dynamics may apply under the fluctuating culturing conditions.…”

“…Initiation of sporulation to spore maturation lasts B7 h (Hilbert and Piggot, 2004); thus, sporulation is initiated in part of the population before glucose is depleted. From these data we assume that 1 mM of glucose is consumed within B1 h (albeit dependent on biomass and portion of metabolically active cells) and that sporulation is by then induced in part of the population (Dixon and Spiegelman, 2002). A time frame of 4 h between glucose additions was chosen, so that sporulation would be initiated, while part of the vegetative cells should be able to survive this starvation episode in order to achieve selection pressure on the 'decision' to sporulate.…”

“…It is fair to assume that this system also affects the development of phenotypes that have evolved for the purpose of surviving adverse times. So far, it is not fully understood how B. subtilis coordinates sporulation by nutrient-limitation sensing (Dixon and Spiegelman, 2002;Maughan and Nicholson, 2004;Eswaramoorthy et al, 2011) and we propose a role for UDP-glucose in this process. Interestingly, sigV, a mutated gene in EvoR2, is expressed upon deletion of ugtP (Matsuoka et al, 2011), an enzyme that exerts its function upon binding UDP-glucose.…”