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Applied and Environmental Microbiology, October 2007, p. 6112-6124, Vol. 73, No. 19
0099-2240/07/$08.00+0     doi:10.1128/AEM.00551-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Diatom-Derived Carbohydrates as Factors Affecting Bacterial Community Composition in Estuarine Sediments{triangledown}

Kelly Haynes,1 Tanja A. Hofmann,1 Cindy J. Smith,1 Andrew S. Ball,1,{dagger} Graham J. C. Underwood,1 and A. Mark Osborn1,2*

Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, United Kingdom,1 Department of Animal and Plant Sciences, The University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom2

Received 9 March 2007/ Accepted 26 July 2007

Microphytobenthic biofilms in estuaries, dominated by epipelic diatoms, are sites of high primary productivity. These diatoms exude large quantities of extracellular polymeric substances (EPS) comprising polysaccharides and glycoproteins, providing a substantial pool of organic carbon available to heterotrophs within the sediment. In this study, sediment slurry microcosms were enriched with either colloidal carbohydrates or colloidal EPS (cEPS) or left unamended. Over 10 days, the fate of these carbohydrates and changes in ß-glucosidase activity were monitored. Terminal restriction fragment length polymorphism (T-RFLP), DNA sequencing, and quantitative PCR (Q-PCR) analysis of 16S rRNA sequences were used to determine whether sediment bacterial communities exhibited compositional shifts in response to the different available carbon sources. Initial heterotrophic activity led to reductions in carbohydrate concentrations in all three microcosms from day 0 to day 2, with some increases in ß-glucosidase activity. During this period, treatment-specific shifts in bacterial community composition were not observed. However, by days 4 and 10, the bacterial community in the cEPS-enriched sediment diverged from those in colloid-enriched and unamended sediments, with Q-PCR analysis showing elevated bacterial numbers in the cEPS-enriched sediment at day 4. Community shifts were attributed to changes in cEPS concentrations and increased ß-glucosidase activity. T-RFLP and sequencing analyses suggested that this shift was not due to a total community response but rather to large increases in the relative abundance of members of the {gamma}-proteobacteria, particularly Acinetobacter-related bacteria. These experiments suggest that taxon- and substrate-specific responses within the bacterial community are involved in the degradation of diatom-derived extracellular carbohydrates.

* Corresponding author. Mailing address: Department of Animal and Plant Sciences, The University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom. Phone: 44 (0114) 22 24626. Fax: 44 (0114) 22 20002. E-mail: A.M.Osborn{at}sheffield.ac.uk

{triangledown} Published ahead of print on 3 August 2007.

{dagger} Present address: School of Biological Sciences, Flinders University of South Australia, Adelaide, GPO Box 2100, Adelaide, SA 5001, Australia.

Applied and Environmental Microbiology, October 2007, p. 6112-6124, Vol. 73, No. 19
0099-2240/07/$08.00+0     doi:10.1128/AEM.00551-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Bruckner, C. G., Bahulikar, R., Rahalkar, M., Schink, B., Kroth, P. G. (2008). Bacteria Associated with Benthic Diatoms from Lake Constance: Phylogeny and Influences on Diatom Growth and Secretion of Extracellular Polymeric Substances. Appl. Environ. Microbiol. 74: 7740-7749 [Abstract] [Full Text]  


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