title: Apparent phosphate retrieval system in Bacillus cereus.
abstract: Bacillus cereus secretes three different phospholipases C. We studied the effect of Pi levels in the growth medium on the production of these exoenzymes. Production of both phosphatidylcholine-preferring phospholipase C and sphingomyelinase C was repressed by Pi in the growth medium, whereas production of phosphatidylinositol phospholipase C was unaffected. We also found that B. cereus secretes a phosphate-repressed alkaline phosphatase activity. Together with a previously reported highly efficient, active uptake system for Pi, these three phosphate-repressed exoenzyme activities seem to be part of a phosphate retrieval mechanism that operates under growth-limiting concentrations of Pi. In natural soil systems, which are the natural habitats of B. cereus, the scarcity of Pi is the major growth-limiting factor. A phosphate-repressed metalloprotease activity was also detected in culture supernatants of B. cereus. It is unclear whether this exoenzyme activity also participates in the proposed phosphate-scavenging system.
authors.affiliation: Department of Biochemistry, University of Tromsø, Norway.
authors.forename: P H
authors.initials: PH
authors.lastname: Guddal
authors.forename: T
authors.initials: T
authors.lastname: Johansen
authors.forename: K
authors.initials: K
authors.lastname: Schulstad
authors.forename: C
authors.initials: C
authors.lastname: Little
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D001409:Bacillus cereus / Q000201:enzymology / Q000378:metabolism*; D005110:Extracellular Space / Q000201:enzymology; D010447:Peptide Hydrolases / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D010710:Phosphates; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D000469:Alkaline Phosphatase; D010738:Type C Phospholipases; D013108:Sphingomyelin Phosphodiesterase; D010447:Peptide Hydrolases