The Phosin PptA Plays a Negative Role in the Regulation of Antibiotic Production in <i>Streptomyces lividans</i>
In <i>Streptomyces</i>, antibiotic biosynthesis is triggered in phosphate limitation that is usually correlated with energetic stress. Polyphosphates constitute an important reservoir of phosphate and energy and a better understanding of their role in the regulation of antibiotic biosynt...
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| Main Authors: | , , , , , , , , , , , , |
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MDPI AG,
2021-03-01T00:00:00Z.
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| Summary: | In <i>Streptomyces</i>, antibiotic biosynthesis is triggered in phosphate limitation that is usually correlated with energetic stress. Polyphosphates constitute an important reservoir of phosphate and energy and a better understanding of their role in the regulation of antibiotic biosynthesis is of crucial importance. We previously characterized a gene, <i>SLI_4384/ppk</i>, encoding a polyphosphate kinase, whose disruption greatly enhanced the weak antibiotic production of <i>Streptomyces lividans</i>. In the condition of energetic stress, Ppk utilizes polyP as phosphate and energy donor, to generate ATP from ADP. In this paper, we established that <i>ppk</i> is co-transcribed with its two downstream genes, <i>SLI_4383</i>, encoding a phosin called PptA possessing a CHAD domain constituting a polyphosphate binding module and <i>SLI_4382</i> encoding a nudix hydrolase. The expression of the <i>ppk/pptA/SLI_4382</i> operon was shown to be under the positive control of the two-component system PhoR/PhoP and thus mainly expressed in condition of phosphate limitation. However, <i>pptA and SLI_4382</i> can also be transcribed alone from their own promoter. The deletion of <i>pptA</i> resulted into earlier and stronger actinorhodin production and lower lipid content than the disruption of <i>ppk</i>, whereas the deletion of <i>SLI_4382</i> had no obvious phenotypical consequences. The disruption of <i>ppk</i> was shown to have a polar effect on the expression of <i>pptA</i>, suggesting that the phenotype of the <i>ppk</i> mutant might be linked, at least in part, to the weak expression of <i>pptA</i> in this strain. Interestingly, the expression of <i>phoR/phoP</i> and that of the genes of the <i>pho</i> regulon involved in phosphate supply or saving were strongly up-regulated in <i>pptA</i> and <i>ppk</i> mutants, revealing that both mutants suffer from phosphate stress. Considering the presence of a polyphosphate binding module in PptA, but absence of similarities between PptA and known exo-polyphosphatases, we proposed that PptA constitutes an accessory factor for exopolyphosphatases or general phosphatases involved in the degradation of polyphosphates into phosphate. |
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| Item Description: | 10.3390/antibiotics10030325 2079-6382 |