Effects of small abalone, Haliotis diversicolor, pedal mucus on bacterial growth, attachment, biofilm formation and community structure

Pedal mucus is important for locomotion, protection and signal transmission in the Gastropoda. It also provides nutrients and a habitat for microbes. In this study, we examined the effects of pedal mucus and the mucus trail of the small abalone, Haliotis diversicolor, on bacterial growth, attachment, biofilm formation and community structure. The results showed that pedal mucus enhanced the growth of bacteria, and that more opportunistic pathogens attached to a substrate covered with pedal mucus (for Vibrio alginolyticus, the cell density was up to 5 times higher than on a clean substrate). During microplate assay, when pedal mucus was added as the sole nutrient source, V. alginolyticus formed a biofilm, but few cells grew on the bottom of the wells if no mucus was added. Under flow-cell culture conditions, differently structured biofilms were formed in the clean and pedal mucus conditioned glass slides. The mucus trail induced a heterogeneous biofilm with cell clusters. Moreover, pedal mucus could support much more CFUs than the clean substrates. Using denatured gradient gel electrophoresis comparison of the bacterial community on a clean substrate and in the mucus trail, we found several specific species in the latter. At least one species, Klebsiella pneumoniae, is potentially harmful to the small abalone. In summary, the pedal mucus of Haliotis diversicolor enriched bacterial occurrence, including some pathogens, which deserves to be considered in high density culture conditions.