Subcompartmentalization by cross-membranes during early growth of Streptomyces hyphae

Bacteria of the genus Streptomyces are a model system for bacterial multicellularity. Their mycelial life style involves the formation of long multinucleated hyphae during vegetative growth, with occasional cross-walls separating long compartments. Reproduction occurs by specialized aerial hyphae, which differentiate into chains of uninucleoid spores. While the tubulin-like FtsZ protein is required for the formation of all peptidoglycan-based septa in Streptomyces , canonical divisome-dependent cell division only occurs during sporulation. Here we report extensive subcompartmentalization in young vegetative hyphae of Streptomyces coelicolor , whereby 1 μm compartments are formed by nucleic acid stain-impermeable barriers. These barriers possess the permeability properties of membranes and at least some of them are cross-membranes without detectable peptidoglycan. Z-ladders form during the early growth, but cross-membrane formation does not depend on FtsZ. Thus, a new level of hyphal organization is presented involving unprecedented high-frequency compartmentalization, which changes the old dogma that Streptomyces vegetative hyphae have scarce compartmentalization. Bacteria of the genus Streptomyces form cellular filaments (hyphae) in which sporadic peptidoglycan cell walls separate multinucleate compartments. Here, Yagüe et al . show that young hyphae are further compartmentalized by cross-membranes lacking detectable peptidoglycan.