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The effects of copper on the microbial community of a coral reef sponge
Author(s) -
Webster Nicole S.,
Webb Richard I.,
Ridd Michael J.,
Hill Russell T.,
Negri Andrew P.
Publication year - 2001
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1046/j.1462-2920.2001.00155.x
Subject(s) - biology , sponge , bacteria , symbiotic bacteria , terminal restriction fragment length polymorphism , microorganism , coral reef , symbiosis , zoology , restriction fragment length polymorphism , microbiology and biotechnology , ecology , botany , biochemistry , polymerase chain reaction , gene , genetics
Marine sponges often harbour communities of symbiotic microorganisms that fulfil necessary functions for the well‐being of their hosts. Microbial communities associated with the sponge Rhopaloeides odorabile were used as bioindicators for sublethal cupric ion (Cu 2+ ) stress. A combined strategy incorporating molecular, cultivation and electron microscopy techniques was adopted to monitor changes in microbial diversity. The total density of sponge‐associated bacteria and counts of the predominant cultivated symbiont (α‐proteobacterium strain NW001) were significantly reduced in response to Cu 2+ concentrations of 1.7 µg l −1 and above after 14 days of exposure. The number of operational taxonomic units (OTUs) detected by restriction fragment length polymorphism (RFLP) decreased by 64% in sponges exposed to 223 µg l −1 Cu 2+ for 48 h and by 46% in sponges exposed to 19.4 µg l −1 Cu 2+ for 14 days. Electron microscopy was used to identify 17 predominant bacterial morphotypes, composing 47% of the total observed cells in control sponges. A reduction in the proportion of these morphotypes to 25% of observed cells was evident in sponges exposed to a Cu 2+ concentration of 19.4 µg l −1 . Although the abundance of most morphotypes decreased under Cu 2+ stress, three morphotypes were not reduced in numbers and a single morphotype actually increased in abundance. Bacterial numbers, as detected using fluorescence in situ hybridization (FISH), decreased significantly after 48 h exposure to 19.4 µg l −1 Cu 2+ . Archaea, which are normally prolific in R. odorabile , were not detected after exposure to a Cu 2+ concentration of 19.4 µg l −1 for 14 days, indicating that many of the microorganisms associated with R. odorabile are sensitive to free copper. Sponges exposed to a Cu 2+ concentration of 223 µg l −1 became highly necrosed after 48 h and accumulated 142 ± 18 mg kg −1 copper, whereas sponges exposed to 19.4 µg l −1 Cu 2+ accumulated 306 ± 15 mg kg −1 copper after 14 days without apoptosis or mortality. Not only do sponges have potential for monitoring elevated concentrations of heavy metals but also examining changes in their microbial symbionts is a novel and sensitive bioindicator for the assessment of pollution on important microbial communities.