Abstract
Filamentous actinobacteria such as Streptomyces undergo two distinct modes of cell division, leading to partitioning of growing hyphae into multicellular compartments via cross-walls, and to septation and release of unicellular spores. Specific determinants for cross-wall formation and the importance of hyphal compartmentalization for Streptomyces development are largely unknown. Here we show that SepX, an actinobacterial-specific protein, is crucial for both cell division modes in Streptomyces venezuelae. Importantly, we find that sepX-deficient mutants grow without cross-walls and that this substantially impairs the fitness of colonies and the coordinated progression through the developmental life cycle. Protein interaction studies and live-cell imaging suggest that SepX contributes to the stabilization of the divisome, a mechanism that also requires the dynamin-like protein DynB. Thus, our work identifies an important determinant for cell division in Streptomyces that is required for cellular development and sporulation.
Highlights
Filamentous actinobacteria such as Streptomyces undergo two distinct modes of cell division, leading to partitioning of growing hyphae into multicellular compartments via cross-walls, and to septation and release of unicellular spores
We further demonstrate that SepX plays an important role in sporulation-specific cell division via direct interaction with the bacterial dynamin-like protein DynB, which was previously shown to contribute to Z-ring stability
Using chromatin immunoprecipitation (ChIP)-seq in concert with microarray transcriptional profiling, we previously revealed the WhiAB-mediated activation of several genes encoding core members of the bacterial division machinery, including ftsW, ftsK and ftsZ
Summary
Filamentous actinobacteria such as Streptomyces undergo two distinct modes of cell division, leading to partitioning of growing hyphae into multicellular compartments via cross-walls, and to septation and release of unicellular spores. In filamentous growing organisms, such as the abundant soil bacteria of the genus Streptomyces, two functionally distinct modes of cell division exist, cross-wall formation in vegetative hyphae and sporulation in aerial hyphae (Fig. 1a). Sporulation-specific cell division results in the formation of ladder-like arrays of division septa that are structurally distinct from cross-walls, and which lead to cell fission and the release of unigenomic spores[1]. Additional factors have been identified that associate with the divisome and/or contribute to the efficient assembly and stability of Z-rings These proteins include the actinobacterialspecific protein SsgB, which has been reported to mark future sporulation-septation sites[8], SepF, which is likely to function as a membrane anchor for FtsZ9–11, SepH, which stimulates FtsZ filament assembly[12], the two dynamin-like proteins DynA and
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