Composition and density of bacterial biofilms determine larval settlement of the polychaete Hydroides elegans

Abstract

Larvae of the polychaete worm Hydroides elegans settle and metamorphose in response to marine biofilms. Phylogenetic relationships among 4 marine-biofilm bacterial species identified by 16S rDNA sequences were not predictive of their inductive capacity. Two bacterial species separated by a genetic distance of 30% shared the greatest capacity for inducing metamorphosis in H. elegans. Two bacterial strains with only a 3% divergence in 16S rRNA gene sequences were very different; one strain induced metamorphosis strongly while the other one did not. The percent of larvae that metamorphosed correlated positively with bacterial density in either natural biofilms or biofilms composed of a single bacterial species. When results of tests across 4 bacterial species were compared, the most inductive bacterial species was effective in much lower biofilm densities than weakly or non-inductive bacteria. Evidence presented here indicates that the cue that triggers settlement and metamorphosis in larvae of H. elegans is not unique to a single bacterial taxon and is likely to be an insoluble, surface-bound material. KEY WORDS: Biofilm bacteria · Larval settlement · Metamorphosis · Hydroides elegansResale or republication not permitted without written consent of the publisher

Larvae of Pocillopora damicornis (Anthozoa) settle and metamorphose in response to surface-biofilm bacteria

“…An attempt was made in the present study to determine whether bacterial species that were similar in inductive capacities are phylogenetically related, given that bacteria can be grouped by their different metabolic functions (Unabia & Hadfield 1999) as well as DNA sequence similarities (Huang & Hadfield 2003). The present study found no correlation between inductive capacities and phylogenetic relationships.…”

“…Previous studies have shown that specific bacterial species affect settlement in Hydroides elegans differently, and that a positive correlation exists between bacterial density and inductive capacity (Huang & Hadfield 2003). In the present study, there was only a positive correlation when the density was increased for the strongly inductive bacterium Pseudoalteromonas luteoviolacea, but not for the 3 other tested species (Alteromonas alvinellae, Vibrio harveyi, and Bacillus firmus) that were moderately or weakly inductive.…”

“…Species belonging to this genus have been shown to induce settlement of the larvae of the hydrozoan Hydractinia echinata (Müller 1973, Seipp et al 2007) and the corals Acropora willisae and A. millepora (Negri et al 2001). The species Pseudoalteromonas luteoviolacea also induces metamorphosis in the larvae of the polychaete Hydroides elegans (Huang & Hadfield 2003) and the sea urchin Heliocidaris erythrogramma (Huggett et al 2006). Hence, the specificity of larval settlement in response to P. luteoviolacea may be due to unknown properties that are uniquely associated with this bacterial species, making it very inductive to a range of different invertebrate taxa.…”

Spatio-temporal variability in Mediterranean rocky shore microphytobenthos

“…The EMPB provides food for many grazing invertebrates (such as gastropods and amphipods; e.g. Underwood 1978, Christofoletti et al 2011, Sanz-Lázaro et al 2015 and facilitates the settlement of algal propagules and invertebrate larvae (O'Connor & Richardson 1998, Huang & Hadfield 2003. In addition, relatively recent studies have shown that some invertebrates (namely littorinids and barnacles) can in turn positively affect EMPB biomass through facilitation mechanisms (Skov et al 2010, suggesting that interaction webs involving EMPB are complex.…”

Progress of marine biofouling and antifouling technologies

“…However, subsequent experiments have shown that biofilms do not facilitate settlement of all macroorganisms. This has been demonstrated in a variety of marine organisms such as barnacles, oysters, and Ulva [25] fed by bacteria [56] and diatoms [57]. Because of competition for nutrients and light, it is believed that microorganisms produce metabolites to repel specific macroorganisms [58].…”