The signal-based relationship between marine bacteria and the green seaweed Ulva

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The green seaweed Ulva reproduces by production of vast numbers of motile swimming zoospores. These zoospores test available surfaces for their suitability before committing to an irreversible attachment. Once attached, the zoospores grow and developed into a mature plant. Ulva is an extremely problematic biofouling alga, and there is considerable interest in how the alga chooses surfaces for selection, grows and develops. Of great interest is the role bacteria play in the life cycle of Ulva. We have shown that zoospores tap into bacterial communication systems to aid them in their surface selection; zoospores preferentially settle on bacterial biofilms producing small diffusible signal molecules. In addition, bacteria are known to be important for the growth and morphological development of Ulva. Plantlets where bacteria have been removed do not exhibit normal morphology, and growth is often stunted. The aim of this project is to examine the relationship between bacteria and Ulva, focusing on the hypothesis that the signal-producing bacteria that are targeted during zoospore settlement are those required for healthy growth into a mature plant. We will identify bacteria and bacterially-derived cues used by Ulva for settlement, and establish if these have any effect on growth and development. The effect of bacteria and their signal molecules on sporulation will also be examined.