Cell polarity and the control of apical growth in Streptomyces

Streptomyces cells grow by building cell wall at one pole - the hyphal tip. Although analogous to hyphal growth in fungi, this is achieved in a prokaryote, without any of the well-known eukaryotic cell polarity proteins, and it is also unique among bacterial cases of cell polarity. Further, polar growth of Streptomyces and the related mycobacteria and corynebacteria is independent of the MreB cytoskeleton and involves a number of coiled-coil proteins, including the polarity determinant DivIVA. Recent progress sheds light on targeting of DivIVA to hyphal tips and highlight protein phosphorylation in the regulation of actinobacterial growth. Furthermore, cell polarity affects not only cell envelope biogenesis in Streptomyces, but apparently also assembly of fimbriae, conjugation and migration of nucleoids.