Modern antifouling coatings use heavy metals and toxic organic molecules to prevent biofouling, the undesirable growth of marine organisms on man-made substrata. In an ongoing survey of deep-sea microorganisms aimed at finding low toxic antifouling metabolites, an actinomycete bacterium was isolated from the Pacific sediment at the depth of about 5000 m. The bacterium was closely related to Streptomyces fungicidicus (99% similarity) according to 16S ribosomal RNA sequence information. The spent culture medium of this bacterium inhibited barnacle larval attachment. Bioassay-guided fractionation was employed to isolate antifouling compounds. The ethyl acetate extract was fractionated by using an open silica gel column. Active fractions were further purified on a HPLC C 18 column., and cyclo-(L-Leu-L-Val) were isolated for the first time from a deep sea bacterium, and the structures of the compounds were elucidated by nuclear magnetic resonance spectroscopy and mass spectrometry. The pure diketopiperazines were tested for antilarval activity using the barnacle Balanus amphitrite. Effective concentrations that inhibited 50% larval attachment (EC 50 ) after 24 h ranged from 0.10 -0.27 mM. The data suggest that diketopiperazines and other compounds from deep-sea bacteria may be used as novel antifoulants.

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This study investigated the effect of UV-A and B (UVR) on larval settlement of the polychaete Hydroides elegans through their influence on biofilms. Multispecies biofilms were treated with 3 doses of UVR (10, ) at 2 environmentally realistic irradiance levels (4 and 2 W m -2 ) in the laboratory, and their ability to induce the settlement of H. elegans larvae was then examined in both laboratory and field conditions. For the field experiment, only 10 and 80 KJ m -2 doses under 4 W m -2 were used. In addition, this study evaluated the effects of UVR on monospecies bacterial biofilms and then their ability to induce larval settlement in the laboratory. Results demonstrated that the ability of multispecies biofilms to trigger larval settlement could be compromised as a result of enhanced UVR exposure. Although larval settlement on multispecies biofilms treated with the lowest UV dose (at both irradiance levels) was at the same level as that of the control, the exposure of biofilms to the highest dose significantly reduced their larval settlement triggering ability. Furthermore, UVR treatments decreased the percentage of metabolically active bacterial cells in monospecies biofilms; the effect increased with increasing UV dose. Larval settlement response to monospecies biofilms decreased with increasing UV dose, suggesting that the bacterial metabolic activity in biofilms is essential for the biofilms to have an inductive effect on larval settlement. This study suggests that enhanced UVR, which might occur due to ozone depletion, may have a significant effect on the larval settlement of H. elegans by affecting a biofilm's inductive cues. KEY WORDS: Hydroides elegans · Larval settlement · Biofilms · Ultraviolet radiation Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 304: [155][156][157][158][159][160][161][162][163][164][165][166] 2005 induce larval settlement. Consequently, biofilms play a key role in determining the recruitment success of invertebrates. The precise interactions among environmental conditions, biofilm dynamics and larval settlement, however, have been poorly investigated (Lau et al. 2005).Among all the potential environmental factors, ultraviolet radiation (UVR, 280 to 400 nm) is considered one of the most important variables in marine ecosystems. Although the ozone layer in the atmosphere filters out most of the biologically destructive UVR, depletion of ozone due to anthropogenic pollution results in an increase in short-wavelength UVR that reaches the earth's surface (Smith et al. 1992). This enhanced UVR causes significant unfavorable effects in marine ecosystems, as both UV-B (280 to 315 nm) and UV-A (315 to 400 nm) can penetrate to significant depths (Kirt 1994, Conde et al. 2000. For example, previous studies documented the negative effects of UVR on phytoplankton (e.g. Santas et al. 1998, Helbling et al. 2001 and references therein), bacterioplankton (e.g. Helbling et al. 1995, Jeffrey et al. 1996, Kaiser & Herndl 1997, Gustavson e...

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This study examined the attachment response of Balanus amphitrite larvae to bacteriadominated biofilms originating from 4 sites of varying environmental conditions in the intertidal region of subtropical Hong Kong waters and during 2 seasons (winter and summer), under both laboratory and field conditions. Using multiple fingerprinting techniques (terminal restriction fragment length polymorphism, denaturing gradient gel electrophoresis and fluorescence in situ hybridization), we observed differences in the bacterial community composition of biofilms originating from the 4 sites. These biofilm samples were used to study the linkage between spatial changes in bacterial communities of biofilms and larval choice at the time of attachment. It was hypothesized that cyprids can distinguish biofilms originating from habitats that support higher recruitment. Both laboratory and field multiple-choice bioassays demonstrated that cyprids preferred to attach on biofilms originating from habitats where recruitment, juvenile growth and survival were the highest, thereby accepting the hypothesis proposed. This study did not identify particular bacterial species or groups in biofilms that attract or inhibit larval attachment, but we could correlate site-specific variations in bacterial community composition with larval choice, whereas bacterial abundance in biofilms was less important in this regard. Overall, this study highlights the significance of site-specific variation in biofilms on larval recruitment and demonstrated the discriminative behavior of barnacle larvae to biofilms originating from contrasting environments in the intertidal region. Thus, attachment cues from biofilms may also play a significant role in generating spatial variation in larval recruitment. KEY WORDS: Balanus amphitrite · Biofilms · Larval attachment · Bacterial community · Barnacle recruitment Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 333: [229][230][231][232][233][234][235][236][237][238][239][240][241][242] 2007 phosis (reviewed by Rittschof et al. 1998). Biofilms exist on virtually all hard substrata, and are agglomerates of macromolecules, bacteria, diatoms, protozoans and fungi (Decho 2000). They also serve as an important cue for larval attachment (reviewed by Holmström & Kjelleberg 1994, Wieczorek & Todd 1998, Maki et al. 2000, Hadfield & Paul 2001, Steinberg et al. 2001. Among different biofilm components, bacteria are primarily responsible for larval attachment, particularly for barnacles (e.g. Maki et al. 1990, Wieczorek et al. 1995. Thus, numerous studies have examined the interaction between the bacterial component of the biofilm and larval attachment (see Qian et al. 2003 and references therein). These studies revealed that barnacle larval response (i.e. attachment induction or inhibition) is primarily determined by the abundance and community composition of bacteria in biofilms. For example, barnacle larvae can distinguish between biofilms of varying composition and pr...

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Multi-species natural microbial biofilms have been identified as sources of cues to induce larval attachment of a broad range of sessile marine invertebrates. However, the chemical identities of the cues originating from these films have not been fully characterized. In this study, we isolated and characterized 2 compounds from natural biofilms that induced the larval attachment of the polychaete Hydroides elegans. Biofilms were developed on Petri dishes in seawater in the field for 6 d, collected from the Petri dishes using cotton buds, and extracted using a combination of polar and non-polar solvents. The non-polar fraction was inductive to larval attachment and was thus further fractionated using HPLC. Bioassay-guided fractionation was used to locate the active compounds that were then structurally characterized by using nuclear magnetic resonance (NMR) spectroscopy. Two inductive compounds were identified, a hydrocarbon (6, 9-heptadecadiene) and a fatty acid (12-octadecenoic acid), which are the first chemical cues inductive to larval attachment of marine invertebrates isolated from natural biofilms.