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Functional characterisation of the pst1 and pst2 gene clusters in Synechocystis sp. PCC6803
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Pitt, Frances Diana (2010) Functional characterisation of the pst1 and pst2 gene clusters in Synechocystis sp. PCC6803. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b2491649~S15
Abstract
Cyanobacteria are common components of the bacterioplankton in
freshwater environments, where they play a key role as primary producers. Growth is
limited by the availability of nutrients, particularly phosphate (Pi), and yet many
species persist and flourish in environments with an unpredictable and constantly
fluctuating supply of Pi. Genome analysis of the freshwater cyanobacterium
Synechocystis sp. PCC6803 has identified that the membrane-bound transporter
components of its Pho regulon consist of two high affinity (Pi) ABC transporters
with multiple associated phosphate binding proteins (PBP), features in contrast to
virtually all other known bacteria. Whilst the occurrence of duplicate ABC
transporter mechanisms has been widely reported in freshwater cyanobacteria there
are still very few reports that demonstrate the functional significance of individual,
and apparently redundant, components of these ABC transporter systems.
In previous work, disruption of one of the PBPs in Synechocystis sp.
PCC6803, pstS1 (sll0680) led to an impairment in the expression of specific genes
of the Pho regulon during Pi-deplete growth. This phenotype was not observed
when the PBP from the second transporter was disrupted suggesting that each
transporter could be functionally distinct. In this study 32Pi radiotracer uptake
experiments using pst1 and pst2 deletion mutants showed Pst1 acts as a low
affinity, high velocity transporter (Ks 3.7 ± 0.7 μM, Vmax 31.18 ± 3.96 fmol cell-1
min-1) and Pst2 a high affinity, low velocity system (Ks 0.07± 0.01 μM, Vmax 0.88 ±
0.11 fmol cell-1 min-1). Analysis of (qPCR) gene expression profiles and alkaline
phosphatase activity also revealed how regulation of transporter abundance
controls the nature of the Pi stress signal transduced by the SphS-SphR two
component system. These Pi ABC transporters thus exhibit key differences in both
their kinetic and regulatory properties, revealing a new strategy for the acquisition
of phosphate that has potential implications for our understanding of the ecological
success of this key microbial group.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QR Microbiology | ||||
Library of Congress Subject Headings (LCSH): | Cyanobacteria -- Physiology, Cyanobacteria -- Genetics, Phosphates | ||||
Official Date: | September 2010 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Biological Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Scanlan, David J., 1963- | ||||
Extent: | xxi, 209 leaves : ill., charts | ||||
Language: | eng |
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