Use of inhibitors for coastal bacteria and phytoplankton: Application to nitrogen uptake measurement |
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| Authors: | Aurore Trottet Eric Fouilland Christophe Leboulanger Elodie Lanouguère Marc Bouvy |
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| Institution: | 1. Laboratoire Ecologie des Systèmes Marins Côtiers, UMR 5119 ECOSYM (Université Montpellier 2-CNRS -IRD– IFREMER, Université Montpellier 1), France;2. Station Marine de l’Environnement Littoral, 2 rue des Chantiers, 34200 Sète, France;3. Université Montpellier 2, Place E. Bataillon, CC 093, 34095 Montpellier, France |
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| Abstract: | For several decades, prokaryotic and eukaryotic inhibitors have been used to exclude bacteria from microalgal cultures and for investigating prey-predator relationships. Recently there has been considerable interest in using specific inhibitors for studying the interactions between bacteria and phytoplankton, by selective repression of either organism’s activity. The effectiveness of chemical inhibitors must be tested before applying them to natural communities to partition metabolic activities between functional groups. Six different antibiotics selected from the most commonly reported in the literature were tested, at concentrations varying from 12.5 to 100 mg L−1, for their effect on bacterial growth and functional diversity of natural communities from Mediterranean coastal waters. Penicillin and streptomycin each at a final concentration of 100 mg L−1 significantly reduced bacterial growth within 2 h. There was a greater impact on bacterial functional diversity when both antibiotics were mixed together. This mixture did not have any significant effect on the growth of selected cultured phytoplankton strains, whereas the eukaryote inhibitor cycloheximide at 100 mg L−1 reduced growth within 2 h of incubation. The penicillin–streptomycin mixture and cycloheximide alone successfully partitioned NH4+ and NO3− uptake between bacteria and phytoplankton bi-weekly sampled in a coastal lagoon in Autumn, where bacterial contribution to total NH4+ and NO3− uptake averaged 46 and 41%, respectively. The use of specific inhibitors may be a valuable method for studying interactions, such as competition and mutualism, or lack of interaction between the different components of microbial communities and could be used to study their relative importance in biogeochemical fluxes. |
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| Keywords: | antibiotics Mediterranean coastal waters phytoplankton bacterioplankton interactions Thau Lagoon |
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