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Role of phosphate transport system component PstB1 in phosphate internalization by Nostoc punctiforme

journal contribution
posted on 2016-01-01, 00:00 authored by Lee Hudek, Dasun Premachandra, Wesley Webster, Lambert BrauLambert Brau
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

History

Journal

Applied and Environmental Microbiology

Volume

82

Issue

21

Pagination

6344 - 6356

Publisher

AMER SOC MICROBIOLOGY

Location

United States

ISSN

0099-2240

eISSN

1098-5336

Language

English

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2016, American Society for Microbiology