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The inhibitory effect of biofilms produced by wild bacterial isolates to the larval settlement of the fouling ascidia Ciona intestinalis and Pyura praeputialis Manuel
Zapata Fernando
Silva Yery
Luza Marcela
Wilkens Carlos
Riquelme* *Corresponding author Financial support: Chilean National Fund for Promotion of Scientific and Technological Development (FONDEF) project Nº DO1I1166. Keywords: antifouling extracts, ascidian bioassays, bacterial biofilms, Ciona intestinalis, marine biofouling, natural antifoulants, Pyura praeputialis.
Ciona
intestinalis
and Pyura praeputialis are an important fouling organism
on both natural and artificial substrates. Mainly, C. intestinalis
produces serious operational difficulties in diverse aquaculture centres,
for example in The main objective of the present study was to search for indigenous marine bacteria occurring in biofilms which exerted inhibitory activity on the settlement of larvae of the tunicates common in the fouling of A. purpuratus culture systems. A long term goal of this work was to concentrate natural antifouling materials produced by bacteria in a way that they could be employed in fouling prevention without toxic side effects for the organisms in culture.
A total of 73 film-forming bacterial strains were isolated (Table 1). The assays with living bacterial films showed that 20% of the strains had inhibitory effects on the settlement of C .intestinalis larvae; strong inhibition was indicated when 50% or more of the larvae present failed to settle in the plates. The
approximate molecular size bacterial antifouling compounds was determined
using dialysis by fractionation from bacterial strains Nil-LEM and
HA by dialysis against sterile distilled water for 12 hrs at Furthermore the characterization of active fractions was carry out, separation of extracellular products fractions using high pressure liquid chromatography (HPLC). The antifouling compounds can be incorporated into the matrix at concentrations higher than those in the natural environment without altering the physical characteristics of the settlement surface (Henrikson and Pawlik, 1995). This technique is valuable for assaying the antifouling effects of secondary metabolites produced by marine organisms (Henrikson and Pawlik, 1998). PhytagelTM was chosen for the present study due to its stability when compared with other potentially useful polymers. Our results suggest that the bacterial inhibitory substances are thermostable, proteic or peptidic substance of less than 3500 Da in MW; this agrees with Holmström and Kjelleberg (1999) and Egan et al. (2001) that low molecular weight peptides or proteins inhibited the settlement of bacteria, fungi, microalgae, algal spores, and invertebrates. The present study is part of the beginning effort to find natural products which in the future will fulfil emerging needs for antifouling products which repel classically damaging invertebrates.
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