Diatom-derived carbohydrates as factors affecting bacterial community composition in estuarine sediments

Haynes, K., Hofmann, T. A., Smith, C. J. , Ball, A. S., Underwood, G. J. C. and Osborn, A. M. (2007) Diatom-derived carbohydrates as factors affecting bacterial community composition in estuarine sediments. Applied and Environmental Microbiology, 73 (19). pp. 6112-6124. ISSN 0099-2240

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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 β-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 β-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 β-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 γ-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. Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Keywords:Bacteria, Carbohydrates, Estuaries, Glycoproteins, Organic carbon, RNA, Sediments, Bacterial community, Compositional shifts, Heterotrophic activity, Treatment-specific shifts, Biofilms, beta glucosidase, carbohydrate derivative, glycoprotein, polysaccharide, RNA 16S, bacterium, biodegradation, biofilm, carbohydrate, community composition, diatom, enzyme activity, estuarine sediment, genetic analysis, microbial community, primary production, relative abundance, RNA, Acinetobacter, article, bacterial flora, carbohydrate metabolism, enzyme specificity, estuary, Gammaproteobacteria, microbial degradation, microcosm, nonhuman, polymerase chain reaction, restriction fragment length polymorphism, RNA sequence, sediment, Animals, Diatoms, DNA, Bacterial, DNA, Ribosomal, Geologic Sediments, Polymorphism, Restriction Fragment Length, Polysaccharides, RNA, Ribosomal, 16S, Seawater, Substrate Specificity, Acinetobacter, Bacillariophyta, Bacteria (microorganisms)
Subjects:C Biological Sciences > C180 Ecology
C Biological Sciences > C500 Microbiology
Divisions:College of Science > School of Life Sciences
ID Code:8950
Deposited On:22 Apr 2013 09:46

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