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      Role of Phosphate Transport System Component PstB1 in Phosphate Internalization by Nostoc punctiforme

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          ABSTRACT

          In bacteria, limited phosphate availability promotes the synthesis of active uptake systems, such as the Pst phosphate transport system. To understand the mechanisms that facilitate phosphate accumulation in the cyanobacterium Nostoc punctiforme, phosphate transport systems were identified, revealing a redundancy of Pst phosphate uptake systems that exists across three distinct operons. Four separate PstB system components were identified. pstB1 was determined to be a suitable target for creating phenotypic mutations that could result in the accumulation of excessive levels of phosphate through its overexpression or in a reduction of the capacity to accumulate phosphate through its deletion. Using quantitative real-time PCR (qPCR), it was determined that pstB1 mRNA levels increased significantly over 64 h in cells cultured in 0 mM added phosphate and decreased significantly in cells exposed to high (12.8 mM) phosphate concentrations compared to the level in cells cultured under normal (0.8 mM) conditions. Possible compensation for the loss of PstB1 was observed when pstB2, pstB3, and pstB4 mRNA levels increased, particularly in cells starved of phosphate. The overexpression of pstB1 increased phosphate uptake by N. punctiforme and was shown to functionally complement the loss of PstB in E. coli PstB knockout (PstB ) mutants. The knockout of pstB1 in N. punctiforme did not have a significant effect on cellular phosphate accumulation or growth for the most part, which is attributed to the compensation for the loss of PstB1 by alterations in the pstB2, pstB3, and pstB4 mRNA levels. This study provides novel in vivo evidence that PstB1 plays a functional role in phosphate uptake in N. punctiforme.

          IMPORTANCE Cyanobacteria have been evolving over 3.5 billion years and have become highly adept at growing under limiting nutrient levels. Phosphate is crucial for the survival and prosperity of all organisms. In bacteria, limited phosphate availability promotes the synthesis of active uptake systems. The Pst phosphate transport system is one such system, responsible for the internalization of phosphate when cells are in phosphate-limited environments. Our investigations reveal the presence of multiple Pst phosphate uptake systems that exist across three distinct operons in Nostoc punctiforme and functionally characterize the role of the gene product PstB1 as being crucial for the maintenance of phosphate accumulation. We demonstrate that the genes pstB2, pstB3, and pstB4 show alterations in expression to compensate for the deletion of pstB1. The overall outcomes of this work provide insights as to the complex transport mechanisms that exist in cyanobacteria like N. punctiforme, allowing them to thrive in low-phosphate environments.

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          Author and article information

          Contributors
          Role: Editor
          Journal
          Appl Environ Microbiol
          Appl. Environ. Microbiol
          aem
          aem
          AEM
          Applied and Environmental Microbiology
          American Society for Microbiology (1752 N St., N.W., Washington, DC )
          0099-2240
          1098-5336
          19 August 2016
          14 October 2016
          1 November 2016
          : 82
          : 21
          : 6344-6356
          Affiliations
          [a ]Centre for Regional and Rural Futures, Faculty of Science Engineering and Built Environment, Deakin University, Burwood, Victoria, Australia
          [b ]Centre for Cellular and Molecular Biology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria, Australia
          Chinese Academy of Sciences
          Author notes
          Address correspondence to L. Bräu, lambert.brau@ 123456deakin.edu.au .

          Citation Hudek L, Premachandra D, Webster WAJ, Bräu L. 2016. Role of phosphate transport system component PstB1 in phosphate internalization by Nostoc punctiforme. Appl Environ Microbiol 82:6344–6356. doi: 10.1128/AEM.01336-16.

          Article
          PMC5066351 PMC5066351 5066351 01336-16
          10.1128/AEM.01336-16
          5066351
          27542935
          f4381619-5d53-43fe-b7ed-6ba6ee58b473
          Copyright © 2016, American Society for Microbiology. All Rights Reserved.
          History
          : 17 May 2016
          : 11 August 2016
          Page count
          Figures: 10, Tables: 2, Equations: 0, References: 47, Pages: 13, Words: 10152
          Funding
          This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
          Categories
          Environmental Microbiology

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