Reentrant DNA shells tune polyphosphate condensate size.

The ancient, inorganic biopolymer polyphosphate (polyP) occurs in all three domains of life and affects myriad cellular processes. An intriguing feature of polyP is its frequent proximity to chromatin, and in the case of many bacteria, its occurrence in the form of magnesium-enriched condensates embedded in the nucleoid, particularly in response to stress. The physical basis of the interaction between polyP and DNA, two fundamental anionic biopolymers, and the resulting effects on the organization of both the nucleoid and polyP condensates remain poorly understood. Given the essential role of magnesium ions in the coordination of polymeric phosphate species, we hypothesized that a minimal system of polyP, magnesium ions, and DNA (polyP-Mg