Limits...
Roseobacticides: small molecule modulators of an algal-bacterial symbiosis.

Seyedsayamdost MR, Carr G, Kolter R, Clardy J - J. Am. Chem. Soc. (2011)

Bottom Line: A recent study of Phaeobacter gallaeciensis, a member of the large roseobacter clade of α-proteobacteria, and Emiliania huxleyi, a prominent member of the microphytoplankton found in large algal blooms, revealed that an algal senescence signal produced by E. huxleyi elicits the production of novel algaecides, the roseobacticides, from the bacterial symbiont.Structures of the new family members arise from variable substituents at the C3 and C7 positions of the roseobacticide core as the diversifying elements and suggest that the roseobacticides result from modifications and combinations of aromatic amino acids.Together these studies support a model in which algal senescence converts a mutualistic bacterial symbiont into an opportunistic parasite of its hosts.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States.

ABSTRACT
Marine bacteria and microalgae engage in dynamic symbioses mediated by small molecules. A recent study of Phaeobacter gallaeciensis, a member of the large roseobacter clade of α-proteobacteria, and Emiliania huxleyi, a prominent member of the microphytoplankton found in large algal blooms, revealed that an algal senescence signal produced by E. huxleyi elicits the production of novel algaecides, the roseobacticides, from the bacterial symbiont. In this report, the generality of these findings are examined by expanding the number of potential elicitors. This expansion led to the identification of nine new members of the roseobacticide family, rare bacterial troponoids, which provide insights into both their biological roles and their biosynthesis. The qualitative and quantitative changes in the levels of roseobacticides induced by the additional elicitors and the elicitors' varied efficiencies support the concept of host-targeted roseobacticide production. Structures of the new family members arise from variable substituents at the C3 and C7 positions of the roseobacticide core as the diversifying elements and suggest that the roseobacticides result from modifications and combinations of aromatic amino acids. Together these studies support a model in which algal senescence converts a mutualistic bacterial symbiont into an opportunistic parasite of its hosts.

Show MeSH
Dose–response analysis for three elicitors of roseobacticide production in P. gallaeciensis BS107. The amount of 2 is plotted as a function of the concentrations of pCA (7), sinapic acid (8), or ferulic acid (9), and the data fit to eq 1, yielding an EC50 of 0.16 ± 0.02 mM (9) and 0.43 ± 0.03 (8). The data for 7 are from ref (2), where a value of 0.79 ± 0.03 was determined. For each elicitor, the maximal amount of 2 was normalized to 100%. Each point is the average of two independent measurements; error bars represent standard deviation about the mean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211371&req=5

fig3: Dose–response analysis for three elicitors of roseobacticide production in P. gallaeciensis BS107. The amount of 2 is plotted as a function of the concentrations of pCA (7), sinapic acid (8), or ferulic acid (9), and the data fit to eq 1, yielding an EC50 of 0.16 ± 0.02 mM (9) and 0.43 ± 0.03 (8). The data for 7 are from ref (2), where a value of 0.79 ± 0.03 was determined. For each elicitor, the maximal amount of 2 was normalized to 100%. Each point is the average of two independent measurements; error bars represent standard deviation about the mean.

Mentions: To find optimal conditions for roseobacticide production, a dose-response analysis was carried out with each of the main elicitors. P. gallaeciensis BS107 was incubated with varying concentrations of the elicitor, and roseobacticide B production was quantified using HPLC-ESI-MS. The analysis previously indicated a half-maximal effective concentration (EC50) of 0.79 ± 0.03 mM with pCA.(2) With 8 and 9, we obtained EC50 values of 0.43 ± 0.03 and 0.16 ± 0.02 mM, respectively, indicating that these are more potent elicitors of roseobacticide B production in P. gallaeciensis BS107 (Figure 3). Each elicitor also shows quantitative changes in the levels of roseobacticide B produced, which may have implications for the interaction of P. gallaeciensis BS107 with its algal hosts (see below).


Roseobacticides: small molecule modulators of an algal-bacterial symbiosis.

Seyedsayamdost MR, Carr G, Kolter R, Clardy J - J. Am. Chem. Soc. (2011)

Dose–response analysis for three elicitors of roseobacticide production in P. gallaeciensis BS107. The amount of 2 is plotted as a function of the concentrations of pCA (7), sinapic acid (8), or ferulic acid (9), and the data fit to eq 1, yielding an EC50 of 0.16 ± 0.02 mM (9) and 0.43 ± 0.03 (8). The data for 7 are from ref (2), where a value of 0.79 ± 0.03 was determined. For each elicitor, the maximal amount of 2 was normalized to 100%. Each point is the average of two independent measurements; error bars represent standard deviation about the mean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211371&req=5

fig3: Dose–response analysis for three elicitors of roseobacticide production in P. gallaeciensis BS107. The amount of 2 is plotted as a function of the concentrations of pCA (7), sinapic acid (8), or ferulic acid (9), and the data fit to eq 1, yielding an EC50 of 0.16 ± 0.02 mM (9) and 0.43 ± 0.03 (8). The data for 7 are from ref (2), where a value of 0.79 ± 0.03 was determined. For each elicitor, the maximal amount of 2 was normalized to 100%. Each point is the average of two independent measurements; error bars represent standard deviation about the mean.
Mentions: To find optimal conditions for roseobacticide production, a dose-response analysis was carried out with each of the main elicitors. P. gallaeciensis BS107 was incubated with varying concentrations of the elicitor, and roseobacticide B production was quantified using HPLC-ESI-MS. The analysis previously indicated a half-maximal effective concentration (EC50) of 0.79 ± 0.03 mM with pCA.(2) With 8 and 9, we obtained EC50 values of 0.43 ± 0.03 and 0.16 ± 0.02 mM, respectively, indicating that these are more potent elicitors of roseobacticide B production in P. gallaeciensis BS107 (Figure 3). Each elicitor also shows quantitative changes in the levels of roseobacticide B produced, which may have implications for the interaction of P. gallaeciensis BS107 with its algal hosts (see below).

Bottom Line: A recent study of Phaeobacter gallaeciensis, a member of the large roseobacter clade of α-proteobacteria, and Emiliania huxleyi, a prominent member of the microphytoplankton found in large algal blooms, revealed that an algal senescence signal produced by E. huxleyi elicits the production of novel algaecides, the roseobacticides, from the bacterial symbiont.Structures of the new family members arise from variable substituents at the C3 and C7 positions of the roseobacticide core as the diversifying elements and suggest that the roseobacticides result from modifications and combinations of aromatic amino acids.Together these studies support a model in which algal senescence converts a mutualistic bacterial symbiont into an opportunistic parasite of its hosts.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, United States.

ABSTRACT
Marine bacteria and microalgae engage in dynamic symbioses mediated by small molecules. A recent study of Phaeobacter gallaeciensis, a member of the large roseobacter clade of α-proteobacteria, and Emiliania huxleyi, a prominent member of the microphytoplankton found in large algal blooms, revealed that an algal senescence signal produced by E. huxleyi elicits the production of novel algaecides, the roseobacticides, from the bacterial symbiont. In this report, the generality of these findings are examined by expanding the number of potential elicitors. This expansion led to the identification of nine new members of the roseobacticide family, rare bacterial troponoids, which provide insights into both their biological roles and their biosynthesis. The qualitative and quantitative changes in the levels of roseobacticides induced by the additional elicitors and the elicitors' varied efficiencies support the concept of host-targeted roseobacticide production. Structures of the new family members arise from variable substituents at the C3 and C7 positions of the roseobacticide core as the diversifying elements and suggest that the roseobacticides result from modifications and combinations of aromatic amino acids. Together these studies support a model in which algal senescence converts a mutualistic bacterial symbiont into an opportunistic parasite of its hosts.

Show MeSH