Interference with the germination and growth of U lva zoospores by quorum‐sensing molecules from U lva ‐associated epiphytic bacteria

Abstract

Summary U lva zoospores preferentially settle on N ‐acylhomoserine lactone ( AHL ) producing marine bacterial biofilms. To investigate whether AHL signal molecules also affect the success and rate of zoospore germination in addition to zoospore attraction, the epiphytic bacteria associated with mature U lva linza were characterized and bacterial isolates representative of this community tested for the ability to produce AHLs . Two of these AHL ‐producing isolates, S ulfitobacter spp. 376 and S hewanella spp. 79, were transformed with plasmids expressing the B acillus spp. AHL lactonase gene aii A to generate AHL ‐deficient variants. The germination and growth of U . linza zoospores was studied in the presence of these AHL ‐deficient strains and their AHL ‐producing counterparts. This revealed that the AHLs produced by S ulfitobacter spp. and S hewanella spp. or the bacterial products they regulate have a negative impact on both zoospore germination and the early growth of the U lva germling. Further experiments with E scherichia coli biofilms expressing recombinant AHL synthases and synthetic AHLs provide data to demonstrate that zoospores germinated and grown in the absence of AHLs were significantly longer than those germinated in the presence of AHLs . These results reveal an additional role for AHLs per se in the interactive relationships between marine bacteria and U lva zoospores.

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