Impairment of benthic diatom adhesion and photosynthetic activity by allelopathic compounds from a green alga: involvement of free fatty acids?

• Published in: Environmental science and pollution research international 2015-09, Vol.22 (18), p.13669-13680
• Main Authors: Allen, Joey L., Ten-Hage, Loïc, Leflaive, Joséphine
• Format: Article
• Language: English
• Subjects: Adhesion; Algae; Allelopathy; Aquatic plants; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Bacillariophyceae; Bioassays; Biodiversity and Ecology; Biofilms; Cell Adhesion; Cell adhesion & migration; Cell culture; Chemical interactions; Chlorophyta - chemistry; Coastal environments; Culture media; Cyanobacteria; Diatoms - drug effects; Diatoms - physiology; Earth and Environmental Science; Ecology, environment; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental Sciences; Fatty acids; Fatty Acids, Nonesterified; Filamentous microorganisms; Fractionation; Freshwater microorganisms; Kinases; Life Sciences; Liquid chromatography; Microbial activity; Microbial Ecology of the Continental and Coastal Environments; Microenvironments; Microorganisms; Morphology; Nitric oxide; Pheromones - pharmacology; Photosynthesis; Phototrophic microorganisms; Plankton; Uronema confervicolum; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-014-3873-9

The role of chemical interactions in shaping microbial communities has raised increasing interest over the last decade. Many benthic microorganisms are known to develop chemical strategies to overcome competitors, but the real importance of chemical interactions within freshwater biofilm remains unknown. This study focused on the biological and chemical mechanisms of an interaction involving two benthic microorganisms, an allelopathic filamentous green alga, Uronema confervicolum , and a common diatom, Fistulifera saprophila . Our results showed that functions critical for benthic phototrophic microorganisms were inhibited by U. confervicolum extracts. Growth, cell motility, adhesion, and photosynthetic activity were impaired at extract concentrations ranging between 5 and 20 μg ml −1 . The adhesion inhibition was mediated by intracellular nitric oxide (NO) induction. A bioassay-guided fractionation of the extract with HPLC helped to identify two C18 fatty acids present in the growth-inhibiting fractions: linoleic (LA) and α-linolenic (LNA) acids. These compounds represented 77 % of the total free fatty acids of U. confervicolum and were present in the culture medium (1.45 μg l −1 in total). Both could inhibit the diatom growth at concentrations higher than 0.25 μg ml −1 , but had no effect on cell adhesion. The discrepancy between the effective concentrations of fatty acids and the concentration found in culture medium may be explained by the presence of high-concentration microenvironments. The compounds involved in adhesion inhibition remain to be identified. Though further experiments with complex biofilms are needed, our results suggest that U. confervicolum may participate to the control of biofilm composition by inhibiting diatom adhesion.