Relationship between bacterial community profile in biofilm and attachment of the acorn barnacle Balanus amphitrite

The relationship between bacterial community profile in biofilm and attachment of the acorn barnacle Balanus amphitrite was investigated using a double-dish choice larval attachment bioassay and the DNA fingerprinting technique T-RFLP (terminal-restriction fragment length polymorphism). Biofilms for bioassays were either developed at 3 intertidal heights (i.e. high, mid and low) for 6 d or at the mid-intertidal height for 3 to 12 d. A clear distinction among biofilm communities at the 3 intertidal heights was revealed in the bacterial community profiles (determined by T-RFLP), biomass (determined by total organic carbon analysis), and abundance of bacteria and diatoms. Overall, cyprids of B. amphitrite preferred intertidal biofilms (i.e. 6 d old) over unfilmed surfaces for attachment. Moreover, cyprids also preferred to attach on biofilms of mid-intertidal height over high-intertidal or subtidal heights. There was no correlation between cypris attachment and any of the 3 biofilm attributes (i.e. biomass, abundance of bacteria and diatoms). Therefore, it was concluded that changes in the bacterial community profile in the biofilm affect the attractiveness of the biofilm to barnacle larvae and, thus, may determine the behavior (accepting or rejecting a surface) of settling larvae. We hypothesize that the temporal and spatial changes in the microbial community profile lead to the temporal and spatial recruitment pattern of marine invertebrates at a microscopic scale.link_to_subscribed_fulltex

Cypris habitat selection facilitated by microbial films influences the vertical distribution of subtidal barnacle Balanus trigonus

The potential driving force(s) of the vertical distribution of subtidal barnacle Balanus trigonus Darwin were investigated using both field and laboratory experiments. Early juveniles (∼24 h old) placed in intertidal [∼0.5 m above mean low water level (MLWL)] and subtidal (∼3 m below MLWL) habitats survived equally well, indicating that the intertidal absence of B. trigonus in Hong Kong waters was not determined by differential mortality. However, enhanced attachment of cyprids in subtidal habitats indicated the importance of differential larval choice in determining their vertical distribution. In the laboratory, cyprids preferred to attach in response to subtidal microbial films, which may implicate microbial films as a primary cue in driving the adult vertical distribution. Microbial films developed in these two habitats differed in their biomass (=total organic carbon), abundance of bacteria and diatoms (determined by fluorescence microscopy), and bacterial diversity (determined by DNA fingerprinting analysis). For example, 6-day films in subtidal habitat had a significantly higher biomass than in films from intertidal habitat (P0.05); however, bacterial abundance was greater in subtidal films than in intertidal films, irrespective of the age of the film, although there was no difference in diatom abundance in films from these two habitats. Neither the abundance of bacteria and diatoms nor the biomass correlated with the attachment preferences of cyprids. This study has not provided any data to prove the existence of inductive and inhibitive (to cyprid attachment) bacterial species in subtidal and intertidal films, respectively; however, results indicate that bacterial community provided qualitative information that might explain the preferential attachment of B. trigonus cyprids in subtidal habitat. © Springer Science+Business Media, Inc. 2006.link_to_subscribed_fulltex

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

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 x 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.link_to_subscribed_fulltex

The demographic window and economic dependency ratio in the Hong Kong SAR

Hong Kong, like other countries with developed economies, is experiencing significant population ageing. The shift in the population age structure results from a combination of decreasing mortality rates and prolonged low fertility rates. This paper investigates the economic impact of changes in a population's age structure. We forecast on sex-specific labour force participation rates (LFPRs) and the economic dependency ratio (EDR) using different scenarios. Our results show that the below-unity level for the EDR-prevalent since 1996-will exceed unity in 2015 and rise steeply thereafter. By 2036, the projected EDR will reach an unprecedented high of 1.4, where every three economically-inactive persons will be supported by two economically-active persons in Hong Kong. This projection not only reflects a significant age shift towards the older end of the age spectrum, but is also driven by declining LFPRs among men. © 2010 Taylor & Francis.link_to_subscribed_fulltex

Surgical navigation for implant-supported ear prosthesis manufactured by CAD/CAM technology

Concurrent Session - SESSION VIII: Digital Impact on Facial Prosthetic and RehabilitationThe 4th International Conference on Advanced Digital Technology in Head and Neck Reconstruction, Freiburg, Germany, 5-8 May 2011