Extracellular sugar phosphates are assimilated by Streptomyces in a PhoP-dependent manner

Abstract

Filamentous microorganisms of the bacterial genus Streptomyces have a complex life cycle that includes physiological and morphological differentiations. It is now fairly well accepted that lysis of Streptomyces vegetative mycelium induced by programmed cell death (PCD) provides the required nutritive sources for the bacterium to erect spore-forming aerial hyphae. However, little is known regarding cellular compounds released during PCD and the contribution of these molecules to the feeding of surviving cells in order to allow them to reach the late stages of the developmental program. In this work we assessed the effect of extracellular sugar phosphates (that are likely to be released in the environment upon cell lysis) on the differentiation processes. We demonstrated that the supply of phosphorylated sugars, under inorganic phosphate limitation, delays the occurrence of the second round of PCD, blocks streptomycetes life cycle at the vegetative state and inhibits antibiotic production. The mechanism by which sugar phosphates affect development was shown to involve genes of the Pho regulon that are under the positive control of the two component system PhoR/PhoP. Indeed, the inactivation of the response regulator phoP of Streptomyces lividans prevented the 'sugar phosphate effect' whereas the S. lividans ppk (polyphosphate kinase) deletion mutant, known to overexpress the Pho regulon, presented an enhanced response to phosphorylated sugars.