Roles of bacterial community composition in biofilms as a mediator for larval settlement of three marine invertebrates

Abstract

This study investigated (1) the effects of salinity and temperature on the bacterial community composition of developing biofilms, and (2) the responses of marine invertebrate larvae (the polychaete Hydroides elegans and the barnacles Balanus amphitrite and B. trigonus) to these biofilms during settlement (i.e. attachment to a surface and metamorphosis into juveniles). Biofilms developed in a 3 × 3 array of salinity and temperature treatments resulted in different bacterial community compositions (revealed by DGGE and T-RFLP), bacterial densities and total biomasses. Larval settlement of B. amphitrite and B. trigonus was induced by biofilms developed at high temperatures (23 and 30°C), but was unaffected (B. amphitrite) or inhibited (B. trigonus) by those developed at a low temperature (16°C). The settlement response of these barnacles did not correlate with the biomass or the bacterial density of the biofilms, but did coincide with the marked differences in bacterial community composition between the biofilms developed at different temperatures. In contrast, larval settlement of H. elegans differed slightly among biofilms developed in different salinities, but not among those developed at different temperatures. This settlement response was moderately correlated with bacterial density but had no apparent relationship with bacterial community composition of the biofilms. Our results implied that the community composition and cell density of bacteria in biofilms, which can vary with local environmental conditions, may allow larvae of the 2 barnacles and H. elegans, respectively, to distinguish between habitats with different environmental conditions. KEY WORDS: Bacterial community · Barnacle · Biofilm · DGGE · Larval settlement · Polychaete · T-RFLP Resale or republication not permitted without written consent of the publisherAquat Microb Ecol 38: [41][42][43][44][45][46][47][48][49][50][51] 2005 Bourget 1988, Pearce & Scheibling 1991, Keough & Raimondi 1996. This subtle response is believed to be mediated by the structural and/or physiological attributes of biofilms, which may vary spatially and temporally according to the biotic (e.g. availability and physiology of colonizing species, competition and cooperation among species, and grazing pressure) and abiotic factors (e.g. latitude, depth, illumination, exposure time, season, water chemistry, nutrient supply, flow shear and substratum characteristics) of the local environment (Wieczorek & Todd 1998).Despite decades of study, the bioactive components of biofilms that mediate larval settlement are still largely unknown. Many investigations have nevertheless highlighted the bacterial component of biofilms as a major mediator for larval settlement of many invertebrates (Holmström et al. 1992, Harder et al. 2002. In laboratory assays, monospecies films of bacteria can influence larval settlement in a variety of ways (from inhibition to neutral to induction), depending on the species of bacteria and larvae of concern. The specificity of larval response ...

Bacterial community succession and chemical profiles of subtidal biofilms in relation to larval settlement of the polychaete Hydroides elegans

“…However, Qian (1999) demonstrated that after the bacterial density in a biofilm had reached a certain level, reducing the bacterial density by adding antibiotics did not significantly reduce the larval settlement of H. elegans, leading to the hypothesis that the larval settlement of H. elegans is controlled by the presence of specific cues present in the biofilm, regardless of the density of the bacteria. In our study, we observed increases in the bacterial densities of biofilms over time (Figure 1), which is similar to the findings of many earlier studies (Harder et al, 2002a;Huang and Hadfield, 2003;Lau et al, 2005).…”

“…Similarly, bacterial community structure has been suggested as an indicator of habitat suitability for settling H. elegans larvae (Unabia and Hadfield, 1999;Qian et al, 2003;Lau et al, 2005). Our results show that the bacterial community changed more with age than with substratum type (Figure 2).…”

“…The bacterial genomic DNA was extracted with a standard sodium dodecyl sulfate-based extraction protocol (Zhou et al, 1996). Bacterial communities in the biofilm samples were analyzed by denaturing gradient gel electrophoresis (DGGE) according to the procedures described by Lau et al (2005). The 16S rRNA genes (16S rDNA) in the crude DNA extracts were amplified by PCR using the universal primers 341F-GC (Muyzer et al, 1996) and 907R (Ishii et al, 2000) under the following PCR conditions: 95 1C for 2 min; 10 touchdown cycles of 95 1C for 1 min, 65 1C (reduced to 55 1C in increments of 1 1C per cycle) for 1 min, and 72 1C for 1 min; 15 cycles at a constant annealing temperature of 55 1C for 1 min and 72 1C for 5 min.…”

“…Studies have increasingly focused on explaining how the bacterial community structure of natural (multispecies) biofilms mediates larval settlement in the field. The bacterial communities of natural biofilms vary in their responses to environmental factors such as salinity, temperature (Lau et al, 2005), tidal level Dobretsov and Qian, 2006), dissolved oxygen (Nocker et al, 2007), and habitat (Chiu et al, 2007;Hung et al, 2007). Natural biofilms formed under different environmental conditions vary in their attractiveness to settling larvae (Lau et al, 2005;Dobretsov and Qian, 2006;Chiu et al, 2007;Hung et al, 2007).…”

Indole derivatives inhibited the formation of bacterial biofilm and modulated Ca2+ efflux in diatom

“…The formation of biofilm is very important for the adhesion of subsequent fouling organisms. The studies had proved that bacterial biofilm of Pseudoalteromonas spongiae was associated with its induction of larval settlement of the polychaete Hydroides elegans and the settlement was correlated with bacterial density (Lau et al, 2005;Huang et al, 2007), and the reports suggested that the extracellular polymers of benthic diatoms induced larval settlement in the polychaete Hydroides elegans (Lam et al, 2003(Lam et al, , 2005. Similarly, bacterial biofilm promoted the settlement of Ulva spores and Balanus improvisus cyprid (Joint et al, 2002;Tait and Havenhand, 2013).…”