Defence Chemistry Modulation by Light and Temperature Shifts and the Resulting Effects on Associated Epibacteria of Fucus vesiculosus

Abstract

The goals of this study were (1) to investigate whether Fucus vesiculosus regulates the production of its antifouling defence chemicals against epibacteria in response to light limitation and temperature shifts and (2) to investigate if different surface concentrations of defence compounds shape epibacterial communities. F. vesiculosus was incubated in indoor mesocosms at five different temperature conditions (5 to 25°C) and in outdoor mesocosms under six differently reduced sunlight conditions (0 to 100%), respectively. Algal surface concentrations of previously identified antifouling compounds - dimethylsulphopropionate (DMSP), fucoxanthin and proline – were determined and the bacterial community composition was characterized by in-depth sequencing of the 16S-rRNA gene. Altogether, the effect of different treatment levels upon defence compound concentrations was limited. Under all conditions DMSP alone appeared to be sufficiently concentrated to warrant for at least a partial inhibitory action against epibiotic bacteria of F. vesiculosus. In contrast, proline and fucoxanthin rarely reached the necessary concentration ranges for self-contained inhibition. Nonetheless, in both experiments along with the direct influence of temperature and light, all three compounds apparently affected the overall bacterial community composition associated with F. vesiculosus since tendencies for insensitivity towards all three compounds were observed among bacterial taxa that typically dominate those communities. Given that the concentrations of at least one of the compounds (in most cases DMSP) were always high enough to inhibit bacterial settlement, we conclude that the capacity of F. vesiculosus for such defence will hardly be compromised by shading or warming to temperatures up to 25°C.

Temporal covariation of epibacterial community and surface metabolome in the Mediterranean seaweed holobiont Taonia atomaria

“…In the particular case of algae, proline and DMSP have been detected at the surface of the brown alga F. vesiculosus and it has been demonstrated that these compounds had antibacterial properties at natural concentrations (Saha et al ., ). More particularly, DMSP content was high at 20°C and then decreased at 25°C and was globally higher under dark conditions (Saha et al ., ). In previous works dealing with total extracts of several macroalgae, it has been demonstrated that DMSP content increased with irradiance and decreased with temperature, with such variations being in accordance with the roles of DMSP as an antioxidant or cryoprotectant (Karsten et al ., ; Lyons et al ., ).…”

Rapid adaptation to controlling new microbial epibionts in the invaded range promotes invasiveness of an exotic seaweed

“…qualitative control (admission of some strains and repellence of others) (Saha et al . ). Both protective (Weinberger, Hoppe & Friedlander ) and detrimental (Weinberger, Friedlander & Gunkel ; Largo, Fukami et al .…”

Response of foundation macrophytes to near‐natural simulated marine heatwaves

“…Thus, the absence of an effect of heatwaves may not be surprising, at least with respect to net defence strength. The antibacterial net defence of F. vesiculosus is a product of several active metabolites, with some of them being up‐ or down‐regulated when temperature changes (Saha et al, ). Despite maintained antibacterial defence, epibacterial abundance on the surface of adult algae was significantly reduced in 1HW.…”

“…stress tolerance, abundance of energy reserves, etc.) defence activity may be increased (Saha & Wahl, ), remain unaltered with increasing threat (Saha et al, ) or be decreased in cases of resource limitation (Sudatti, Fujii, Rodrigues, Turra, & Pereira, ). Specific components of the defence mechanism may also be impaired due to temperature stress (Weinberger et al, ).…”