Alkaline phosphatase production of Bacillus subtilis

A pho regulon promoter induced under sporulation conditions

Sporulation-induced alkaline phosphatases (APases) of Bacillus subtilis require the products of the sporulation stage-0 genes and certain stage-II genes, including the spoIIA operon, for induction. Mutations in either sapA or sapB bypass this requirement [Piggot and Taylor, J. Gen. Microbiol. 10 (1977) 69-80], resulting in APase production in a spoIIA sapA or spoIIA sapB strain, under sporulation conditions. B. subtilis has multiple structural genes encoding APases, which are induced either by phosphate starvation or during sporulation, or under both conditions. We report studies designed to determine which APase(s) were being expressed in the sap mutants, and from which promoters. phoB (formerly phoAIII), one of the structural genes encoding an APase in B. subtilis, is expressed under both sporulation and phosphate starvation conditions, but from separate promoters [Chesnut et al., Mol. Microbiol. 5 (1991) 2181-2190]. The spoIIA sapA and spoIIA sapB strains express phoB under sporulation conditions. Interestingly, the expression of phoB during sporulation was from Pv, the phosphate starvation-inducible promoter of phoB, rather than from Ps, the sporulation-specific promoter. Since the induction of phosphate starvation-inducible promoters during phosphate limitation requires the phoPR operon [Miki et al., Genetics 52 (1965) 1093-1100], we asked if the phoPR products were involved in regulating Pv expression under sporulation conditions. The phoPR genes are transcribed under sporulation conditions, regulated by sapA and sapB under sporulation conditions, and required for expression from Pv under sporulation conditions.

The Bacillus subtilis 168 alkaline phosphatase III gene: impact of a phoAIII mutation on total alkaline phosphatase synthesis

The first alkaline phosphatase (APase) structural gene mutant of Bacillus subtilis 168 was constructed by using a clone identified by hybridization to a synthetic degenerative oligonucleotide. The design of the probe was based on the first 29 amino acids of the sequenced mature APase III protein, which had been isolated from the secreted fraction of vegetative, phosphate-starved cells. DNA sequencing of the clone revealed the first 80 amino acids of the APase III protein, including a typical procaryotic signal sequence of 32 amino acids preceding the start of the mature protein. The 29 amino acids encoded by the predicted open reading frame immediately following the signal sequence are identical to the first 29 amino acids of the sequenced mature protein. This region shows 80% identity to strand A of the beta sheet that is very well conserved in Escherichia coli and mammalian APases. A phoAIII structural mutant was constructed by insertional mutagenesis with a fragment internal to the coding region. The effects of this mutation on APase production in B. subtilis 168 were analyzed under both phosphate starvation and sporulation conditions. The mutation in APase III reduced the total vegetative APase specific activity by approximately 40% and sporulation APase specific activity by approximately 45%. An APase protein was isolated from sporulating cells at stage III and was identified as APase III by protein sequencing of the amino terminus and by its absence in the phoAIII mutant. The APase III gene has been mapped to approximately 50 degrees on the B. subtilis chromosome.

Factors influencing the activity of cellular alkaline phosphatase during growth and sporulation of Bacillus cereus

Alkaline phosphatase (EC 3.1.3.1) is synthesized in media with a low phosphate concentration (0.37 mM of total and 19 microM of inorganic phosphate, respectively) already during the exponential phase of growth of Bacillus cereus. The enzyme is repressed by higher phosphate concentrations (3.7 mM) during the whole growth period; during sporogenesis the enzyme activity in cells slightly increases even under these conditions. During growth the enzyme is not secreted into the medium, a minor amount being released after cessation of growth. The enzyme activity can be increased by adding Zn2+ ions (10 microM). When during growth without phosphate the pH of the medium decreases below 5.0, the enzyme activity temporarily decreases and growth is slowed down, followed by a subsequent increase of the enzyme activity. In this case the onset of sporulation is also delayed.

Localization of alkaline phosphatase in Streptomyces noursei

Alkaline phosphatase activity appeared in Streptomyces noursei strain IMET 43,716 when cultures were shifted to phosphate limitation. By using p-nitrophenylphosphate as substrate, the activity detected at pH 9.4 was cell-bound, as long as young mycelia were studied. Supernatant fluids of the cultures were only active, if partial mycelial lysis had taken place after incubation for several days under the influence of shear forces. After cytochemical staining the phosphatase reaction products were microscopically visible as grains distributed rather homogeneously within the hyphal lumen. The frequency of grains was correlated to the rate of nourseothricin production. Electron microscopy of thin sections showed the phosphatase reaction products to be only present in the cytoplasm.

Secondary metabolism: regulation by phosphate and trace elements

Secondary metabolism and cellular differentiation occur within a range of concentrations of phosphate and, in specific taxonomic groups, of zinc, manganese, and/or iron that is much narrower than that permittee for primary metabolism. Possible molecular sites of action of the four elements are reviewed.

Repression of sporulation in Bacillus subtilis by L-malate

L-Malate repressed sporulation in the wild-type strain of Bacillus subtilis. When 75 mM L-malate was added to the growth medium at the time of inoculation, the appearance of heat-resistant spores was delayed 6 to 8 h. The synthesis of extracellular serine protease, alkaline phosphatase, glucose dehydrogenase, and dipicolinic acid was similarly delayed. Sporulation was not repressed when malate was added to the culture at t4 or later. A mutant was selected for ability to sporulate in the presence of malate. This strain could also sporulate in the presence of glucose. The malate-resistant mutant grew poorly with malate as sole carbon source, although it possessed an intact citric acid cycle, and it showed increased levels of malic enzyme. This indicates a defect in the metabolism of malate in the mutant. A mutant lacking malate dehydrogenase activity was also able to sporulate in the presence of malate. A model for the regulation of sporulation by malate is presented and discussed. Citric acid cycle intermediates other than malate did not affect sporulation. In contrast to previous results, sporulation of certain citric acid cycle mutants could be greatly increased or completely restored by the addition of intermediates after the enzymatic block. The results indicate that the failure of citric acid cycle mutants to sporulate can be adequately explained by lack of energy and lack of glutamate.