Isolation of sulfonosphingolipids from the rosette-inducing bacterium Zobellia uliginosa and evaluation of their rosette-inducing activity.

The choanoflagellate transitions from unicellular to multicellular forms in the presence of bacterial signaling molecules, such as sulfonosphingolipids (RIFs). We set out to characterize the abundance of RIF-like molecules within five different Bacteroidetes strains belonging to different genera. While four strains exhibited similar sulfonosphingolipid profiles with sulfobacin A as the dominant feature, the composition in differed distinctively. Targeted isolation yielded four sulfonosphingolipids, including the previously reported flavocristamide A. While none of the sulfonosphingolipids induced rosette formation, a negative impact on choanoflagellate growth and cell density was observed. In contrast, supernatant extracts of depleted in sulfonosphingolipid-like features provoked rosette formation in indicating for the presence of yet another morphogenic compound class.