Effects of Surface Charges on the Bactericide Activity of CdTe/ZnS Quantum Dots: A Cell Membrane Disruption Perspective.

The inhibitory effects of CdTe/ZnS quantum dots (QDs) modified with 3-mercaptopropionic acid (negatively charged) or cysteamine (positively charged) on the metabolic activity of Escherichia coli were investigated using biological microcalorimetry. Results show that the inhibitory ratio of positive QDs is higher than that of negative QDs. Transmission electron microscopy images indicate that QDs are prone to be adsorbed on the surface of E. coli. This condition disturbs the membrane structure and function of E. coli. Fluorescence anisotropy results demonstrate that positive QDs show a significant increase in the membrane fluidity of E. coli and dipalmitoylphosphatidylcholine (DPPC) model membrane. Furthermore, fluorescence anisotropy values of DPPC membrane in the gel phase decreased upon the addition of positive QDs. By contrast, anisotropy values in the liquid-crystalline phase are almost constant. The change in membrane fluidity is associated with the increased permeability of the membrane. Finally, the kinetics of dye leakage from liposomes demonstrate that the surface charge of QDs is crucial to the interaction between QDs and membrane.

Ecological roles of dominant and rare prokaryotes in acid mine drainage revealed by metagenomics and metatranscriptomics.

High-throughput sequencing is expanding our knowledge of microbial diversity in the environment. Still, understanding the metabolic potentials and ecological roles of rare and uncultured microbes in natural communities remains a major challenge. To this end, we applied a 'divide and conquer' strategy that partitioned a massive metagenomic data set (>100 Gbp) into subsets based on K-mer frequency in sequence assembly to a low-diversity acid mine drainage (AMD) microbial community and, by integrating with an additional metatranscriptomic assembly, successfully obtained 11 draft genomes most of which represent yet uncultured and/or rare taxa (relative abundance <1%). We report the first genome of a naturally occurring Ferrovum population (relative abundance >90%) and its metabolic potentials and gene expression profile, providing initial molecular insights into the ecological role of these lesser known, but potentially important, microorganisms in the AMD environment. Gene transcriptional analysis of the active taxa revealed major metabolic capabilities executed in situ, including carbon- and nitrogen-related metabolisms associated with syntrophic interactions, iron and sulfur oxidation, which are key in energy conservation and AMD generation, and the mechanisms of adaptation and response to the environmental stresses (heavy metals, low pH and oxidative stress). Remarkably, nitrogen fixation and sulfur oxidation were performed by the rare taxa, indicating their critical roles in the overall functioning and assembly of the AMD community. Our study demonstrates the potential of the 'divide and conquer' strategy in high-throughput sequencing data assembly for genome reconstruction and functional partitioning analysis of both dominant and rare species in natural microbial assemblages.

Comparative metagenomic and metatranscriptomic analyses of microbial communities in acid mine drainage.

The microbial communities in acid mine drainage have been extensively studied to reveal their roles in acid generation and adaption to this environment. Lacking, however, are integrated community- and organism-wide comparative gene transcriptional analyses that could reveal the response and adaptation mechanisms of these extraordinary microorganisms to different environmental conditions. In this study, comparative metagenomics and metatranscriptomics were performed on microbial assemblages collected from four geochemically distinct acid mine drainage (AMD) sites. Taxonomic analysis uncovered unexpectedly high microbial biodiversity of these extremely acidophilic communities, and the abundant taxa of Acidithiobacillus, Leptospirillum and Acidiphilium exhibited high transcriptional activities. Community-wide comparative analyses clearly showed that the AMD microorganisms adapted to the different environmental conditions via regulating the expression of genes involved in multiple in situ functional activities, including low-pH adaptation, carbon, nitrogen and phosphate assimilation, energy generation, environmental stress resistance, and other functions. Organism-wide comparative analyses of the active taxa revealed environment-dependent gene transcriptional profiles, especially the distinct strategies used by Acidithiobacillus ferrivorans and Leptospirillum ferrodiazotrophum in nutrients assimilation and energy generation for survival under different conditions. Overall, these findings demonstrate that the gene transcriptional profiles of AMD microorganisms are closely related to the site physiochemical characteristics, providing clues into the microbial response and adaptation mechanisms in the oligotrophic, extremely acidic environments.

Microbial communities evolve faster in extreme environments.

Evolutionary analysis of microbes at the community level represents a new research avenue linking ecological patterns to evolutionary processes, but remains insufficiently studied. Here we report a relative evolutionary rates (rERs) analysis of microbial communities from six diverse natural environments based on 40 metagenomic samples. We show that the rERs of microbial communities are mainly shaped by environmental conditions, and the microbes inhabiting extreme habitats (acid mine drainage, saline lake and hot spring) evolve faster than those populating benign environments (surface ocean, fresh water and soil). These findings were supported by the observation of more relaxed purifying selection and potentially frequent horizontal gene transfers in communities from extreme habitats. The mechanism of high rERs was proposed as high mutation rates imposed by stressful conditions during the evolutionary processes. This study brings us one stage closer to an understanding of the evolutionary mechanisms underlying the adaptation of microbes to extreme environments.

Correlating microbial diversity patterns with geochemistry in an extreme and heterogeneous environment of mine tailings.

Recent molecular surveys have advanced our understanding of the forces shaping the large-scale ecological distribution of microbes in Earth's extreme habitats, such as hot springs and acid mine drainage. However, few investigations have attempted dense spatial analyses of specific sites to resolve the local diversity of these extraordinary organisms and how communities are shaped by the harsh environmental conditions found there. We have applied a 16S rRNA gene-targeted 454 pyrosequencing approach to explore the phylogenetic differentiation among 90 microbial communities from a massive copper tailing impoundment generating acidic drainage and coupled these variations in community composition with geochemical parameters to reveal ecological interactions in this extreme environment. Our data showed that the overall microbial diversity estimates and relative abundances of most of the dominant lineages were significantly correlated with pH, with the simplest assemblages occurring under extremely acidic conditions and more diverse assemblages associated with neutral pHs. The consistent shifts in community composition along the pH gradient indicated that different taxa were involved in the different acidification stages of the mine tailings. Moreover, the effect of pH in shaping phylogenetic structure within specific lineages was also clearly evident, although the phylogenetic differentiations within the Alphaproteobacteria, Deltaproteobacteria, and Firmicutes were attributed to variations in ferric and ferrous iron concentrations. Application of the microbial assemblage prediction model further supported pH as the major factor driving community structure and demonstrated that several of the major lineages are readily predictable. Together, these results suggest that pH is primarily responsible for structuring whole communities in the extreme and heterogeneous mine tailings, although the diverse microbial taxa may respond differently to various environmental conditions.

Development of test strips for rapid buprenorphine detection in vitro.

OBJECTIVES: Buprenorphine (BUP) is the primary treatment for narcotic addiction, but it is often abused by opioid-dependent patients in many countries. For timely and effective detection and controlling the amount of BUP used in therapy, a rapid and sensitive test is needed. In the present study, we describe the development of test strips using monoclonal antibodies (MAbs) for the detection of BUP. DESIGN AND METHODS: The MAbs were generated from hybridomas, and purified MAbs were used to create colloidal gold-antibody conjugates that were placed in the test strips. RESULTS: The BUP test strips had a limit of detection (LOD) of 12.5 ng/mL and did not cross-react with other drugs tested at physiological levels. CONCLUSIONS: Therefore, this assay has sufficient sensitivity and specificity for BUP detection in urine specimens so that the dosage of BUP given to individuals being treated for opioid dependence can be monitored.

Contemporary environmental variation determines microbial diversity patterns in acid mine drainage.

A wide array of microorganisms survive and thrive in extreme environments. However, we know little about the patterns of, and controls over, their large-scale ecological distribution. To this end, we have applied a bar-coded 16S rRNA pyrosequencing technology to explore the phylogenetic differentiation among 59 microbial communities from physically and geochemically diverse acid mine drainage (AMD) sites across Southeast China, revealing for the first time environmental variation as the major factor explaining community differences in these harsh environments. Our data showed that overall microbial diversity estimates, including phylogenetic diversity, phylotype richness and pairwise UniFrac distance, were largely correlated with pH conditions. Furthermore, multivariate regression tree analysis also identified solution pH as a strong predictor of relative lineage abundance. Betaproteobacteria, mostly affiliated with the 'Ferrovum' genus, were explicitly predominant in assemblages under moderate pH conditions, whereas Alphaproteobacteria, Euryarchaeota, Gammaproteobacteria and Nitrospira exhibited a strong adaptation to more acidic environments. Strikingly, such pH-dependent patterns could also be observed in a subsequent comprehensive analysis of the environmental distribution of acidophilic microorganisms based on 16S rRNA gene sequences previously retrieved from globally distributed AMD and associated environments, regardless of the long-distance isolation and the distinct substrate types. Collectively, our results suggest that microbial diversity patterns are better predicted by contemporary environmental variation rather than geographical distance in extreme AMD systems.

Induction of synapse associated protein 102 expression in cyclosporin A-stimulated hair growth.

Cyclosporin A (CsA) has been used as a potent immunosuppressive agent for inhibiting the graft rejection after organ transplantation. However, CsA provokes lots of side effects including hirsutism, the phenomenon of abnormal hair growth in the body. In the present study, we investigated the hair growth stimulating effect of CsA using in vivo and in vitro test models. When topically applied on the back skin of mice, CsA induced fast telogen to anagen transition. In contrast, CsA had no effect on the growth of human hair follicle tissues cultured in vitro, indicating that it might not have the mitogenic effect on hair follicles. To identify the genes related with CsA-induced hair growth, we performed differential display RT-PCR. Among the genes obtained, the expression of synapse associated protein 102 (SAP102) was verified using competitive RT-PCR. The result showed that the expression of SAP102 was significantly induced by CsA treatment in the back skin of C57BL/6 mice. However, the increase of SAP102 mRNA was also seen in spontaneous anagen mice, suggesting that induction of SAP102 is one event of the anagen hair growth response regardless of how the growth state was induced. SAP102 was not expressed in cultured human hair outer root sheath and dermal papilla cells. Immunohistochemistry analysis showed that CsA induced the expression of SAP102 in perifollicular region of mouse anagen hair. Together, these results suggest that SAP102 is one of hair-cycle-dependent genes, whose expression is related with the anagen progression.