An ɑ2-adrenergic receptor is involved in larval metamorphosis in the mussel, Mytilus coruscus.

Metamorphosis is crucial in the life-cycle transition between the larval and juvenile stages of marine invertebrates. Although a number of agonists and antagonists of the adrenergic receptor (AR) are known to regulate larval metamorphosis in Mytilus coruscus (Mc), the molecular basis of the modulation of larval metamorphosis by the AR gene in this species remains elusive. Herein, the role of the AR gene in M. coruscus larval metamorphosis using the RNA interference technique was examined. The Mcα2AR transcript was observed to be present during the entire process of larval development and its level in the post-larvae was significantly increased compared to that in the pediveligers. Mcα2AR-knockdown resulted in a substantial reduction in the abundance of the Mcα2AR transcript and significantly inhibited the metamorphosis of M. coruscus larvae. These findings provide new insights into the molecular basis of modulation of larval metamorphosis in M. coruscus by the AR gene.

Silver Nanoparticles Impact Biofilm Communities and Mussel Settlement.

Silver nanoparticles (AgNPs) demonstrating good antimicrobial activity are widely used in many fields. However, the impact of AgNPs on the community structures of marine biofilms that drive biogeochemical cycling processes and the recruitment of marine invertebrate larvae remains unknown. Here, we employed MiSeq sequencing technology to evaluate the bacterial communities of 28-day-old marine biofilms formed on glass, polydimethylsiloxane (PDMS), and PDMS filled with AgNPs and subsequently tested the influence of these marine biofilms on plantigrade settlement by the mussel Mytilus coruscus. AgNP-filled PDMS significantly reduced the dry weight and bacterial density of biofilms compared with the glass and PDMS controls. AgNP incorporation impacted bacterial communities by reducing the relative abundance of Flavobacteriaceae (phylum: Bacteroidetes) and increasing the relative abundance of Vibrionaceae (phylum: Proteobacteria) in 28-day-old biofilms compared to PDMS. The settlement rate of M. coruscus on 28-day-old biofilms developed on AgNPs was lower by >30% compared to settlement on control biofilms. Thus, the incorporation of AgNPs influences biofilm bacterial communities in the marine environment and subsequently inhibits mussel settlement.

The effect of carbon nanotubes and titanium dioxide incorporated in PDMS on biofilm community composition and subsequent mussel plantigrade settlement.

This study investigated the effect of carbon nanotubes (CNTs) and titanium dioxide (TiO2) incorporated in PDMS on biofilm formation and plantigrade settlement of Mytilus coruscus. TiO2 increased bacterial density, and CNTs also increased bacterial density but reduced diatom density in biofilms after 28 days. Further analysis was conducted between bacterial communities on glass, PDMS, CNTs (0.5 wt%) and TiO2 (7.5 wt%). ANOSIM analysis revealed significant differences (R > 0.9) between seven, 14, 21 and 28 day-old bacterial communities. MiSeq sequencing showed that CNTs and TiO2 impacted the composition of 28 day-old bacterial communities by increasing the abundance of Proteobacteria and decreasing the abundance of Bacteroidetes. The maximum decreased settlement rate in 28 day-old biofilms on CNTs and TiO2 was > 50% in comparison to those on glass and PDMS. Thus, CNTs and TiO2 incorporated in PDMS altered the biomass and community composition of biofilms, and subsequently decreased mussel settlement.

Draft Genome Sequence of Pseudoalteromonas sp. Strain ECSMB14103, Isolated from the East China Sea.

Pseudoalteromonas sp. strain ECSMB14103 was isolated from marine biofilms formed on the East China Sea. The draft genome sequence comprises 4.11 Mp with a G+C content of 39.7%. The information from the draft genome will contribute to an understanding of bacteria-animal interaction.

Larval settlement and metamorphosis of the mussel Mytilus coruscus in response to monospecific bacterial biofilms.

The effects of bacterial biofilms (BFs) on larval settlement and metamorphosis of the mussel, Mytilus coruscus, were investigated in the laboratory. Of nine different isolates, Shewanella sp.1 BF induced the highest percentage of larval settlement and metamorphosis, whereas seven other isolates had a moderate inducing activity and one isolate, Pseudoalteromonas sp. 4, had a no inducing activity. The inducing activity of individual bacterial isolates was not correlated either with their phylogenetic relationship or with the surfaces from which they were isolated. Among the eight bacterial species that demonstrated inducing activity, bacterial density was significantly correlated with the inducing activity for each strain, with the exception of Vibrio sp. 1. The Shewanella sp. 1 BF cue that was responsible for inducing larval settlement and metamorphosis was further investigated. Treatment of the BFs with formalin, antibiotics, ultraviolet irradiation, heat, and ethanol resulted in a significant decrease in their inducing activities and cell survival. BF-conditioned water (CW) did not induce larval metamorphosis, but it triggered larval settlement behavior. A synergistic effect of CW with formalin-fixed Shewanella sp. 1 BF significantly promoted larval metamorphosis. Thus, a cocktail of chemical cues derived from bacteria may be necessary to stimulate larval settlement and metamorphosis in this species.

HMGB1/SREBP-1 mediated IFN-gamma-induced lipid deposition in mouse mesangial cells / 中国应用生理学杂志

<p><b>OBJECTIVE</b>To explore the possible mechanism of lipid deposition induced by interferon-gamma (IFN-gamma).</p><p><b>METHODS</b>The mouse mesangial cells (MMC) were randomly divided into control group, stimulation group, stimulation + control vector group (sh-HMGB1) and stimulation+ specific sh-vector group (sh-SREBP-1). RT-PCR was used to detect the expression of HMGB1, SREBP-1 and fatty acid synthetase (FAS) mRNA; the protein expression was determined by Western blot.</p><p><b>RESULTS</b>The Oil Red O staining revealed that the mouse mesangial cells showed significant lipid droplet in IFN-gamma group. IFN-gamma up-regulated the expression of HMGB1, SREBP-1, FAS mRNA and protein time-dependently; Transfection of MMC with HMGB1 siRNA resulted in the suppression of SREBP-1, FAS protein levels induced by IFN-gamma, following with decrease of lipid deposition. Stimulation with HMGB1 markedly induced expression of SREBP-1, FAS expression and peaked at 8 h, decreased at 12 h compared with that at 8 h. Sh-SREBP-1 decreased the lipid deposition induced by HMGB1 in MMC.</p><p><b>CONCLUSION</b>IFN-gamma might induce lipid deposition in mouse mesangial cells partly by up-regulating the expression of HMGB1/SREBP-1/FAS.</p>

Larval settlement and metamorphosis of the mussel Mytilus coruscus in response to natural biofilms.

Settlement and metamorphosis of pediveliger larvae of Mytilus coruscus in response to natural biofilms was investigated in the laboratory. Pediveliger larvae settled and metamorphosed in response to biofilms and post-larval settlement and metamorphosis increased with biofilm age. The activity of the biofilm was positively correlated with biofilm age, dry weight, bacterial density and diatom density, but had no apparent relationship with chlorophyll a concentration. The change in bacterial community composition corresponding to biofilm age may explain differences in the age-dependent inducing activities of biofilms, which in turn may play an important role in larval settlement in this species.

Larval metamorphosis of the mussel Mytilus galloprovincialis Lamarck, 1819 in response to neurotransmitter blockers and tetraethylammonium.

The metamorphic response of pediveliger larvae of Mytilus galloprovincialis to the neurotransmitter blockers chlorpromazine, amitriptyline, rauwolscine, idazoxan, atenolol and butoxamine, and to tetraethylammonium chloride (TEA) was investigated through a series of bioassays. Chlorpromazine, amitriptyline and idazoxin inhibited larval metamorphosis induced by 10⁻4 M epinephrine. The concentration that inhibited metamorphosis by 50% (IC50) for chlorpromazine and amitriptyline was 1.6 x 10⁻6 M and 6.6 x 10⁻5 M, respectively. Idazoxan was less effective with an IC50 of 4.4 x 10¹³ M. Moreover, these three inhibitors showed no toxicity at any of the concentrations tested. The larval metamorphic response to K+ was not inhibited by 10⁻³ M tetraethylammonium chloride after 96 h. Thus, the neurotransmitter blockers chlorpromazine and amitriptyline are inhibitors of larval metamorphosis, and will be useful tools for antifouling studies.

Copper affects biofilm inductiveness to larval settlement of the serpulid polychaete Hydroides elegans (Haswell).

Copper (Cu) contamination is a potential threat to the marine environment due to the use of Cu-based antifouling paints. Cu stress on larval settlement of the polychaete Hydroides elegans was investigated, and this was linked to Cu stress on biofilms and on the biofilm development process. The inductiveness of young biofilms was more easily altered by Cu stress than that of old biofilms, indicating the relative vulnerability of young biofilms. This might result from changes in bacterial survival, the bacterial community composition and the chemical profiles of young biofilms. Cu also affected biofilm development and the chemical high performance liquid chromatograph fingerprint profile. The results indicate that Cu affected larval settlement mainly through its effect on the process of biofilm development in the marine environment, and the chemical profile was crucial to biofilm inductiveness. It is strongly recommended that the effects of environmentally toxic substances on biofilms are evaluated in ecotoxicity bioassays using larval settlement of invertebrates as the end point.

Induction of metamorphosis of pediveliger larvae of the mussel Mytilus galloprovincialis Lamarck, 1819 using neuroactive compounds, KCl, NH4Cl and organic solvents.

Pediveliger larvae of Mytilus galloprovincialis were subjected to a series of bioassays to investigate the induction of metamorphosis using neuroactive compounds, K(+), NH(4)(+) and organic solvents. Growth and survival of post-larvae obtained using ethanol and methanol were also observed. Epinephrine, phenylephrine, clonidine and metanephrine induced larval metamorphosis at 10(-6) to 10(-4) M in both 24-h and continuous exposure assays. In 24-h exposure assays, alpha-methyldopa at 5 x 10(-5) M and methoxyphenamine at 5 x 10(-5)-10(-4) M induced 55-94% metamorphosis. Similarly, excess K(+) at 3 x 10(-2) M induced 39% metamorphosis and NH(4)(+) at 1-5 x 10(-2) M induced 63-78% metamorphosis. The EC50s of seven organic solvents ranged from 0.04 to 0.82 M. Post-larvae that metamorphosed using ethanol and methanol survived as juveniles and grew at the same rate as those from microbial biofilm. Thus, the above compounds can be useful inducers of metamorphosis for antifouling studies using larvae and juveniles of M. galloprovincialis.

Detection and analysis of antibiotic resistance of Salmonella from retail meats in some districts of Shaanxi province / 中华预防医学杂志

<p><b>OBJECTIVE</b>Salmonella isolates recovered from retail meats that were collected in supermarkets and free markets in Xi'an and Yangling areas of Shaanxi province were studied to determine antibiotic susceptibility.</p><p><b>METHOD</b>Antimicrobial susceptibility to 14 antibiotics of 193 salmonella isolates were determined by using agar dilution method, which was recommended by National Committee of Clinical Laboratory Standard (NCCLS), and E.coli ATCC25922 and E.faecalis ATCC29212 as standard control strains.</p><p><b>RESULTS</b>The 44.6% of the salmonella isolates were resistant to sulfamethoxazole, followed by resistance to kanamycin (40.9%), tetracycline (37.8%), amoxicillin (26.9%), ampicillin (25.4%), gentamicin (23.3%) and chloramphenicol (21.8%). Some isolates also showed resistance to fluoroquinolones, the rates for ciprofloxacin, enrofloxacin, levofloxacin and gatifloxacin were 22.3%, 21.8%, 20.8% and 21.2%, respectively. 55 isolates (28.5%) were multidrug resistant (MDR) strains, 28 of 193 isolates (14.5%) could resist at least 13 antibiotics, 24 isolates (12.4%) were resistant to from 4 to 12 antibiotics.</p><p><b>CONCLUSION</b>Salmonella isolates recovered from retail meats in Xi'an district of Shaanxi province were seriously resistant to antimicrobials commonly used as human and veterinary medicine.</p>