The green alga Dicytosphaeria ocellata and its organic extracts alter natural bacterial biofilm communities

Abstract

Surfaces immersed in the marine environment are under intense fouling pressure by a number of invertebrates and algae. The regulation of this fouling can often be attributed to the bacterial biofilm that quickly develops on the surface of any available substratum in the ocean. The bacterial community composition on the surface of the green alga Dictyosphaeria ocellata was investigated and compared to those found on two other green algae, Batophora oerstedii and Cladophoropsis macromeres, and on a reference surface from three sites along the Florida Keys. Although the bacterial community composition of D. ocellata was not consistent across the sites, it was significantly different from the other algae and the reference surface at two of the three sites tested. Methanol extracts of D. ocellata significantly affected the abundance of bacteria and composition of the bacterial community on Phytagel™ plates when compared to solvent controls, suggesting that the alga regulates the bacterial community by producing active metabolites.

Keywords:

• biofilm
• Dictyosphaeria ocellata
• denaturing gradient gel electrophoresis
• siphonous green macroalgae
• marine bacteria
• antifouling

Acknowledgements

The authors would like to thank Dr Valerie Paul for her advice during this project. This research was funded by the International Leibniz Research School, a member of the JSMC. Field studies were made possible by a graduate student fellowship from The Link Foundation. GP acknowledges support by a Lichtenberg Professorship of the Volkswagen Foundation. This is contribution #847 from the Smithsonian Marine Station at Fort Pierce.