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ENVIRONMENTAL EFFECTS ON EXOPOLYMER PRODUCTION BY MARINE BENTHIC DIATOMS: DYNAMICS, CHANGES IN COMPOSITION, AND PATHWAYS OF PRODUCTION1

Underwood, Graham JC and Boulcott, Matthew and Raines, Christine A and Waldron, Keith (2004) 'ENVIRONMENTAL EFFECTS ON EXOPOLYMER PRODUCTION BY MARINE BENTHIC DIATOMS: DYNAMICS, CHANGES IN COMPOSITION, AND PATHWAYS OF PRODUCTION1.' Journal of Phycology, 40 (2). pp. 293-304. ISSN 0022-3646

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Abstract

Marine benthic diatoms excrete large quantities of extracellular polymeric substances (EPS), both as a function of their motility system and as a response to environmental conditions. Diatom EPS consists predominantly of carbohydrate-rich polymers and is important in the ecology of cells living on marine sediments. Production rates, production pathways, and monosaccharide composition of water-soluble (colloidal) carbohydrates, EPS, and intracellular storage carbohydrate (glucans) were investigated in the epipelic (mud-inhabiting) diatoms Cylindrotheca closterium (Ehrenburg), Navicula perminta (Grün.) in Van Heurck, and Amphora exigua Greg. under a range of experimental conditions simulating aspects of the natural environment. Cellular rates of colloidal carbohydrate, EPS, and glucan production were significantly higher during nutrient-replete compared with nutrient-limited growth for all three species. The proportion of EPS in the extracellular carbohydrate pool increased significantly (to 44%-69%) as cells became nutrient limited. Cylindrotheca closterium produced two types of EPS differing in sugar composition and production patterns. Nutrient-replete cells produced a complex EPS containing rhamnose, fucose, xylose, mannose, galactose, glucose, and uronic acids. Nutrient-limited cells produced an additional EPS containing mannose, galactose, glucose, and uronic acids. Both EPS types were produced under illuminated and darkened conditions. 14C-labeling revealed immediate production of 14C-glucan and significant increases in 14C-EPS between 3 and 4 h after addition of label. The glucan synthesis inhibitor 2,6-dichlorobenzonitrile significantly reduced 14C-colloidal carbohydrate and 14C-EPS. The glucanase inhibitor P-nitrophenyl β-D-glucopyranoside resulted in accumulation of glucan within cells and lowered rates of 14C-colloidal and 14C-EPS production. Cycloheximide prevented glucan catabolism, but glucan production and EPS synthesis were unaffected.

Item Type: Article
Uncontrolled Keywords: benthic diatoms; epipelic; EPS; exopolymers; glucans; monosaccharide composition; mucilage production; uronic acids
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health
Faculty of Science and Health > Life Sciences, School of
SWORD Depositor: Elements
Depositing User: Elements
Date Deposited: 01 Sep 2015 08:37
Last Modified: 15 Jan 2022 00:18
URI: http://repository.essex.ac.uk/id/eprint/14739

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