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Inorganic polyphosphate in Dictyostelium discoideum: influence on development, sporulation, and predation

Haiyu Zhang1, María R Gómez-García, Michael R W Brown

  • 1Department of Biochemistry, Stanford University School of Medicine, Stanford, CA 94305-5307, USA.

Proceedings of the National Academy of Sciences of the United States of America
|February 11, 2005
PubMed

Insights

Dictyostelium discoideum requires inorganic polyphosphate (poly P) for development and bacterial predation. Mutants lacking the poly P kinase (PPK1) gene show impaired development and reduced phagocytosis, highlighting poly P

Area of Science:

  • Cellular biology
  • Microbiology
  • Biochemistry

Background:

  • Dictyostelium discoideum is a social amoeba crucial for studying eukaryotic development and cell signaling.
  • Inorganic polyphosphate (poly P) is a vital biopolymer involved in various cellular processes, including development and energy storage.
  • Polyphosphate kinase (PPK1) is the primary enzyme responsible for poly P synthesis in bacteria, with homologs present in eukaryotes.

Purpose of the Study:

  • To investigate the role of the Dictyostelium discoideum polyphosphate kinase homolog (DdPPK1) in the organism's development and nutritional predation.
  • To determine the impact of DdPPK1 deficiency on poly P levels and associated cellular functions.

Main Methods:

  • Generation and characterization of D. discoideum DdPPK1 mutants.
  • Assessment of poly P levels in wild-type and mutant strains.
  • Evaluation of developmental phenotypes, including fruiting body formation and spore germination.
  • Analysis of bacterial predation efficiency using plaque assays and phagocytosis experiments with Klebsiella aerogenes.

Main Results:

  • DdPPK1 mutants exhibited significantly reduced poly P levels compared to wild-type D. discoideum.
  • Mutants displayed developmental defects, forming smaller fruiting bodies with fewer spores.
  • Phagocytosis and bacterial clearance were impaired in DdPPK1 mutants, indicating a role in predation.
  • The study also observed that bacterial PPK1 is important for prey survival against D. discoideum predation.

Conclusions:

  • Polyphosphate and its synthesizing enzyme DdPPK1 are essential for Dictyostelium discoideum development and efficient bacterial predation.
  • Poly P plays a critical role in phagocytosis and bacterial killing by D. discoideum.
  • The findings suggest a dual role for poly P in the predator-prey relationship, impacting both the slime mold and its bacterial targets.

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