Response of bacterioplankton community structures to hydrological conditions and anthropogenic pollution in contrasting subtropical environments

Bacterioplankton community structures under contrasting subtropical marine environments (Hong Kong waters) were analyzed using 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) and subsequent sequencing of predominant bands for samples collected bimonthly from 2004 to 2006 at five stations. Generally, bacterial abundance was significantly higher in the summer than in the winter. The general seasonal variations of the bacterial community structure, as indicated by cluster analysis of the DGGE pattern, were best correlated with temperature at most stations, except for the station close to a sewage discharge outfall, which was best explained by pollution-indicating parameters (e.g. biochemical oxygen demand). Anthropogenic pollutions appear to have affected the presence and the intensity of DGGE bands at the stations receiving discharge of primarily treated sewage. The relative abundance of major bacterial species, calculated by the relative intensity of DGGE bands after PCR amplification, also indicated the effects of hydrological or seasonal variations and sewage discharges. For the first time, a systematic molecular fingerprinting analysis of the bacterioplankton community composition was carried out along the environmental and pollution gradient in a subtropical marine environment, and it suggests that hydrological conditions and anthropogenic pollutions altered the total bacterial community as well as the dominant bacterial groups. © 2009 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.published_or_final_versio

Prenatal Diagnosis of Agenesis of the Corpus Callosum and Cerebellar Vermian Hypoplasia Associated with a Microdeletion on Chromosome 1p32

We present the prenatal detection of a 1p32.1p31.3 microdeletion (3.46 Mb) by array comparative genomic hybridization (CGH) associated with fetal agenesis of the corpus callosum (ACC) and cerebellar vermian hypoplasia. Analysis of cultured amniocytes showed a normal karyotype. Our observations strengthen the association between this locus and central nervous system development. In addition, the fetus reported herein underscores the importance of array CGH analysis when ACC is detected prenatally, especially when there are additional central nervous system anomalies, to search for submicroscopic imbalances which can facilitate further management and parental counselling. Moreover, the presence of urinary tract anomalies should alert the clinician to the possibility of a 1p interstitial deletion, although the absence of such does not exclude it. Further reports will help to provide more information on the long-term outcomes of individuals with such microdeletion as there are only limited data.published_or_final_versio

Whole-Genome Array CGH Evaluation for Replacing Prenatal Karyotyping in Hong Kong

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Secondary Metabolites of Marine Microbes: From Natural Products Chemistry to Chemical Ecology

Marine natural products (MNPs) exhibit a wide range of pharmaceutically relevant bioactivities, including antibiotic, antiviral, anticancer, or anti-inflammatory properties. Besides marine macroorganisms such as sponges, algae, or corals, specifically marine bacteria and fungi have shown to produce novel secondary metabolites (SMs) with unique and diverse chemical structures that may hold the key for the development of novel drugs or drug leads. Apart from highlighting their potential benefit to humankind, this review is focusing on the manifold functions of SMs in the marine ecosystem. For example, potent MNPs have the ability to exile predators and competing organisms, act as attractants for mating purposes, or serve as dye for the expulsion or attraction of other organisms. A large compilation of literature on the role of MNPs in marine ecology is available, and several reviews evaluated the function of MNPs for the aforementioned topics. Therefore, we focused the second part of this review on the importance of bioactive compounds from crustose coralline algae (CCA) and their role during coral settlement, a topic that has received less attention. It has been shown that certain SMs derived from CCA and their associated bacteria are able to induce attachment and/or metamorphosis of many benthic invertebrate larvae, including globally threatened reef-building scleractinian corals. This review provides an overview on bioactivities of MNPs from marine microbes and their potential use in medicine as well as on the latest findings of the chemical ecology and settlement process of scleractinian corals and other invertebrate larvae

A Glycoprotein in Shells of Conspecifics Induces Larval Settlement of the Pacific Oyster Crassostrea gigas

Settlement of larvae of Crassostrea gigas on shell chips (SC) prepared from shells of 11 different species of mollusks was investigated. Furthermore, the settlement inducing compound in the shell of C. gigas was extracted and subjected to various treatments to characterize the chemical cue. C. gigas larvae settled on SC of all species tested except on Patinopecten yessoensis and Atrina pinnata. In SC of species that induced C. gigas larvae to settle, settlement was proportionate to the amount of SC supplied to the larvae. When compared to C. gigas SC, all species except Crassostrea nippona showed lower settlement inducing activities, suggesting that the cue may be more abundant or in a more available form to the larvae in shells of conspecific and C. nippona than in other species. The settlement inducing activity of C. gigas SC remained intact after antibiotic treatment. Extraction of C. gigas SC with diethyl ether (Et2O-ex), ethanol (EtOH-ex), and water (Aq-ex) did not induce larval settlement of C. gigas larvae. However, extraction of C. gigas SC with 2N of hydrochloric acid (HCl-ex) induced larval settlement that was at the same level as the SC. The settlement inducing compound in the HCl-ex was stable at 100°C but was destroyed or degraded after pepsin, trypsin, PNGase F and trifluoromethanesulfonic acid treatments. This chemical cue eluted between the molecular mass range of 45 and 150 kDa after gel filtration and revealed a major band at 55 kDa on the SDS-PAGE gel after staining with Stains-all. Thus, a 55 kDa glycoprotein component in the organic matrix of C. gigas shells is hypothesized to be the chemical basis of larval settlement on conspecifics

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 bioactivity of bacterial isolates in Hong Kong waters for the inhibition of barnacle (Balanus amphitrite Darwin) settlement

Three bacterial isolates (Micrococcus sp., Rhodovulum sp., and Vibrio sp.) from natural biofilms were investigated for their effects on cyprid settlement of Balanus amphitrite in laboratory bioassays. The inhibitive effect of these bacteria was clearly demonstrated by using a choice assay, in which cyprids settled preferentially on surfaces without bacterial pretreatment over those possessing a monospecies bacterial film. This result suggested that the inhibitive effect was mediated by direct larval contact with bacterial film surface rather than the perception of diffusible bacterial products. In a no-choice assay, monospecies bacterial films of different cell densities reduced cyprid settlement in a density-dependent manner. Vibrio sp. was the most potent inhibitor among the three isolates as it effectively inhibited cyprid settlement by relatively low-density films. The cells of Vibrio sp. were the smallest among the three isolates, suggesting that the correlation between bacterial cell density and cyprid settlement might not be merely due to the reduction of free-space availability. For all three isolates, films that were killed by formaldehyde or UV treatment were as potent as untreated, live films. These films remained inhibitive even in the presence of a strong promoter for cyprid settlement, namely conspecific settlement factor (SF), obtained from adult B. amphitrite. However, SF reverted the inhibitive effect of natural biofilms developed in the intertidal region. © 2003 Elsevier Science B.V. All rights reserved.link_to_subscribed_fulltex