Exopolysaccharides produced by bacteria isolated from the pelagic Southern Ocean - Role in Fe binding, chemical reactivity, and bioavailability

Hassler, CS; Alasonati, E; Mancuso Nichols, CA; Slaveykova, VI

Exopolysaccharides produced by bacteria isolated from the pelagic Southern Ocean - Role in Fe binding, chemical reactivity, and bioavailability

Hassler, CS Alasonati, E Mancuso Nichols, CA Slaveykova, VI

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Publication Type:: Journal Article
Citation:: Marine Chemistry, 2011, 123 (1-4), pp. 88 - 98
Issue Date:: 2011-01-20

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Field	Value	Language
dc.contributor.author	Hassler, CS	en_US
dc.contributor.author	Alasonati, E	en_US
dc.contributor.author	Mancuso Nichols, CA	en_US
dc.contributor.author	Slaveykova, VI	en_US
dc.date.issued	2011-01-20	en_US
dc.identifier.citation	Marine Chemistry, 2011, 123 (1-4), pp. 88 - 98	en_US
dc.identifier.issn	0304-4203	en_US
dc.identifier.uri	http://hdl.handle.net/10453/18063
dc.description.abstract	As a result of ubiquitous excretion by micro-organisms, extracellular polymeric substances are reported in high concentrations in marine systems. The majority of this material is exopolysaccharide (EPS). Despite previous studies showing that EPS can affect carbon as well as trace metal cycling, little is known about the effect on Fe - a critical nutrient limiting primary productivity in up to 40% of the ocean. Here, we have characterised an EPS purified from bacteria isolated from the pelagic Southern Ocean (Pseudoalteromonas sp.) and investigated its role in Fe chemical speciation, solubility, as well as bioavailability for two keystone Southern Ocean phytoplankton strains. This EPS has an average molecular weight of 4.6MDa, exhibiting mainly -OH, COO- and -NH2 functional groups. An asymmetrical flow field-flow fractionation coupled online with UV-spectrophotometer, differential refractive index, and multiangle laser light scattering (aFlFFF-UV-DRI-MALS) demonstrates that this EPS is polydisperse with three, not well resolved, size populations having molar masses in the range from 0.57 to 15.8MDa. Fe was exclusively associated with the medium size fraction of this EPS and was the most abundant trace metal with 2.2nM Fe per nM EPS. Only a third of this Fe was chemically labile, and the strength of Fe-EPS complexes increased with equilibration time. 1nM EPS is efficient to retain Fe in solution, mainly in the colloidal phase (0.02-0.2μm). Fe bound to the EPS was highly bioavailable (25% as much as for inorganic Fe). Due to combined effect of EPS on Fe solubility and bioavailability, it can increase the residence time of bioavailable Fe in the euphotic zone, therefore possibly sustaining and controlling primary productivity in sensitive oceanic regions, such as the Southern Ocean. © 2010 Elsevier B.V.	en_US
dc.relation.ispartof	Marine Chemistry	en_US
dc.relation.isbasedon	10.1016/j.marchem.2010.10.003	en_US
dc.subject.classification	Oceanography	en_US
dc.title	Exopolysaccharides produced by bacteria isolated from the pelagic Southern Ocean - Role in Fe binding, chemical reactivity, and bioavailability	en_US
dc.type	Journal Article
utslib.citation.volume	1-4	en_US
utslib.citation.volume	123	en_US
utslib.for	040501 Biological Oceanography	en_US
utslib.for	0399 Other Chemical Sciences	en_US
utslib.for	0402 Geochemistry	en_US
utslib.for	0405 Oceanography	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
utslib.copyright.status	closed_access
pubs.issue	1-4	en_US
pubs.publication-status	Published	en_US
pubs.volume	123	en_US

Abstract:

As a result of ubiquitous excretion by micro-organisms, extracellular polymeric substances are reported in high concentrations in marine systems. The majority of this material is exopolysaccharide (EPS). Despite previous studies showing that EPS can affect carbon as well as trace metal cycling, little is known about the effect on Fe - a critical nutrient limiting primary productivity in up to 40% of the ocean. Here, we have characterised an EPS purified from bacteria isolated from the pelagic Southern Ocean (Pseudoalteromonas sp.) and investigated its role in Fe chemical speciation, solubility, as well as bioavailability for two keystone Southern Ocean phytoplankton strains. This EPS has an average molecular weight of 4.6MDa, exhibiting mainly -OH, COO- and -NH2 functional groups. An asymmetrical flow field-flow fractionation coupled online with UV-spectrophotometer, differential refractive index, and multiangle laser light scattering (aFlFFF-UV-DRI-MALS) demonstrates that this EPS is polydisperse with three, not well resolved, size populations having molar masses in the range from 0.57 to 15.8MDa. Fe was exclusively associated with the medium size fraction of this EPS and was the most abundant trace metal with 2.2nM Fe per nM EPS. Only a third of this Fe was chemically labile, and the strength of Fe-EPS complexes increased with equilibration time. 1nM EPS is efficient to retain Fe in solution, mainly in the colloidal phase (0.02-0.2μm). Fe bound to the EPS was highly bioavailable (25% as much as for inorganic Fe). Due to combined effect of EPS on Fe solubility and bioavailability, it can increase the residence time of bioavailable Fe in the euphotic zone, therefore possibly sustaining and controlling primary productivity in sensitive oceanic regions, such as the Southern Ocean. © 2010 Elsevier B.V.

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http://hdl.handle.net/10453/18063