Cell surface acid-base properties of the cyanobacterium Synechococcus: Influences of nitrogen source, growth phase and N:P ratios
File(s)Liu et al 2016.pdf (1.35 MB)
Accepted version
Author(s)
Type
Journal Article
Abstract
The distribution of many trace metals in the oceans is controlled by biological uptake. Recently, Liu et al. (2015) demonstrated the propensity for a marine cyanobacterium to adsorb cadmium from seawater, suggesting that cell surface reactivity might also play an important role in the cycling of metals in the oceans. However, it remains unclear how variations in cyanobacterial growth rates and nutrient supply might affect the chemical properties of their cellular surfaces. In this study we used potentiometric titrations and Fourier Transform Infrared (FT-IR) spectrometry to profile the key metabolic changes and surface chemical responses of a Synechococcus strain, PCC 7002, during different growth regimes. This included testing various nitrogen (N) to phosphorous (P) ratios (both nitrogen and phosphorous dependent), nitrogen sources (nitrate, ammonium and urea) and growth stages (exponential, stationary, and death phase). FT-IR spectroscopy showed that varying the growth substrates on which Synechococcus cells were cultured resulted in differences in either the type or abundance of cellular exudates produced or a change in the cell wall components. Potentiometric titration data were modeled using three distinct proton binding sites, with resulting pKa values for cells of the various growth conditions in the ranges of 4.96-5.51 (pKa1), 6.67-7.42 (pKa2) and 8.13-9.95 (pKa3). According to previous spectroscopic studies, these pKa ranges are consistent with carboxyl, phosphoryl, and amine groups, respectively. Comparisons between the titration data (for the cell surface) and FT-IR spectra (for the average cellular changes) generally indicate (1) that the nitrogen source is a greater determinant of ligand concentration than growth phase, and (2) that phosphorus limitation has a greater impact on Synechococcus cellular and extracellular properties than does nitrogen limitation. Taken together, these techniques indicate that nutritional quality during cell growth can noticeably influence the expression of cell surface ligands and their measurable densities. Given that cell surface charge ultimately affects metal adsorption, our results suggest that the cycling of metals by Synechococcus cells in the oceans may vary regionally.
Date Issued
2016-05-21
Date Acceptance
2016-05-11
Citation
Geochimica et Cosmochimica Acta, 2016, 187, pp.179-194
ISSN
1872-9533
Publisher
Elsevier
Start Page
179
End Page
194
Journal / Book Title
Geochimica et Cosmochimica Acta
Volume
187
Copyright Statement
© 2016 Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Subjects
Science & Technology
Physical Sciences
Geochemistry & Geophysics
Synechococcus
Marine cyanobacteria
FTIR
Potentiometric titrations
Cell surface reactivity
Nitrogen and phosphate limitation
BACILLUS-SUBTILIS CELLS
SP STRAIN PCC-6803
ESCHERICHIA-COLI
BACTERIAL SURFACES
FTIR SPECTROSCOPY
FUNCTIONAL-GROUPS
AGMENELLUM-QUADRUPLICATUM
POTENTIOMETRIC TITRATION
INFRARED-SPECTROSCOPY
RAMAN-SPECTROSCOPY
0402 Geochemistry
0403 Geology
Publication Status
Published