Promoted water transport across graphene oxide-poly(amide) thin film composite membranes and their antibacterial activity

Hybrid composite membranes have great potential for desalination applications since water transport can be favorably promoted by selective diffusion at the interface between matrix and reinforcement materials. In this paper, graphene oxide nano-sheets were successfully incorporated across 200nm thick poly(amide) films by interfacial polymerization to form novel thin-film composite membranes. The impact of the graphene oxide on the morphology, chemistry, and surface charge of the ultra-thin poly(amide) layer, and the ability to desalinate seawater was investigated. The graphene oxide nano-sheets were found to be well dispersed across the composite membranes, leading to a lower membrane surface energy and an enhanced hydrophilicity. The iso-electric point of the samples, key to surface charge repulsion during desalination, was found to be consistently shifted to higher pH values with an increasing graphene oxide content. Compared to a pristine poly(amide) membrane, the pure water flux across the composite membranes with 0.12wt.% of graphene oxide was also found to increase by up to 80% from 0.122 to 0.219L·μm·m-2·h-1·bar-1 without significantly affecting salt selectivity. Furthermore, the inhibitory effects of the composite membrane on microbial growth were evaluated and the novel composite membranes exhibited superior anti-microbial activity and may act as a potential anti-fouling membrane material.

Soil microbial biomass in organic farming system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Soil microbial biomass and organic matter fractions during transition from conventional to organic farming systems

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

In vivo antimicrobial activity of 2% chlorhexidine used as a root canal irrigating solution

The aim of the present study was to evaluate the in vivo antimicrobial activity of 2% chlorhexidine gluconate (FCFRP-USP) used as a root canal irrigating solution in teeth with pulp necrosis and radiographically visible chronic periapical reactions. Culture techniques and measurement of the inhibition zone were used. Twenty-two root canals of incisors and molars of 12 patients were used. After accessing the canal, the first root canal sample was collected with two sterile paper points that were transferred to a tube containing reduced transport fluid. The root canal was instrumented using chlorhexidine solution. A small sterile cotton pellet was placed at the root canal entrance, and the cavity was sealed with zinc oxide-eugenol cement. The canals were maintained empty for 48 h. Three sterile paper points were then introduced to absorb the root canal fluid (second sample). One paper point was placed on an agar plate inoculated with Micrococcus luteus ATCC 9341 and incubated for 24 h at 37°C, and the other two were submitted to microbiological evaluation. Present in 10 cases at baseline, mutans streptococci was reduced by 100% at the second assessment. Treatment showed an efficiency of 77.78% for anaerobic microorganisms at the second assessment. These data suggest that chlorhexidine prevents microbial activity in vivo with residual effects in the root canal system up to 48 h. Copyright © 1999 by The American Association of Endodontists.

Cellulolytic activity of wild type and mutant Trichoderma pseudokoningii

Strains of Trichoderma pseudokoningii are promising objects for genetic studies and cellulase production. Auxotrophic mutants with deficiencies in the biosynthesis of aminoacids, nucleotides and vitamins (up to five markers) in addition to morphological aspects like conidial colour were obtained from two strains of double auxotrophic mutants using UV radiation. In order to compare the cellulolytic capabilities of the T. pseudokoningii (wild type strain), some of its mutants and T. reesei QM9414 we performed semiquantitative cellulase assays and quantitative determination of the enzymes exoglucanase and endoglucanase. The semiquantitative test showed that the strains with minimal mycelial growth rate were better producers. Both tests revealed that two of the studied mutants, TG3 and TG4 presented a yield higher than the wild type, reaching 30% more exoglucanase and 70% more endoglucanase. These results indicate that the wild type was improved for cellulase production. Highly significant values of correlation were found for exoglucanase and endoglucanase activities, suggesting that these enzymes may be co-regulated in T. pseudokoningii.

Antioxidant effects of quercetin and naringenin are associated with impaired neutrophil microbicidal activity

Naringenin and quercetin are considered antioxidant compounds with promising activity against oxidative damage in human cells. However, no reports have described their effects on reactive oxygen species (ROS) production by phagocytes during microbicidal activity. Thus, the present study evaluated the effects of naringenin and quercetin on ROS production, specifically hypochlorous acid (HOCl), and their involvement in the microbicidal activity of neutrophils. Naringenin and quercetin inhibited HOCl production through different systems, but this inhibition was more pronounced for quercetin, even in the cell-free systems. With regard to the microbicidal activity of neutrophils, both naringenin and quercetin completely inhibited the killing of Staphylococcus aureus. Altogether, these data indicate that the decrease in the oxidant activity of neutrophils induced by these compounds directly impaired the microbicidal activity of neutrophils. Naringenin and quercetin exerted their effects by controlling the effector mechanisms of ROS production, with both positive and negative effects of these antioxidant agents in oxidative stress conditions and on ROS in the microbicidal activity of phagocytes. The present results challenge the traditional view of antioxidants as improvers of pathological conditions. © 2013 Francielli de Cássia Yukari Nishimura et al.

Soil microbial properties after 5 years of consecutive amendment with composted tannery sludge

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Limitations of microbial hydrocarbon degradation at the Amon Mud Volcano (Nile Deep Sea Fan)

The Amon mud volcano (MV), located at 1250 m water depth on the Nile Deep Sea Fan, is known for its active emission of methane and non-methane hydrocarbons into the hydrosphere. Previous investigations showed a low efficiency of hydrocarbon-degrading anaerobic microbial communities inhabiting the Amon MV center in the presence of sulphate and hydrocarbons in the seeping subsurface fluids. By comparing spatial and temporal patterns of in situ biogeochemical fluxes, temperature gradients, pore water composition and microbial activities over three years, we investigated why the activity of anaerobic hydrocarbon degraders can be low despite high energy supplies. We found that the central dome of the Amon MV, as well as a lateral mud flow at its base, showed signs of recent exposure of hot subsurface muds lacking active hydrocarbon degrading communities. In these highly disturbed areas, anaerobic degradation of methane was less than 2% of the methane flux. Rather high oxygen consumption rates compared to low sulphide production suggest a faster development of more rapidly growing aerobic hydrocarbon degraders in highly disturbed areas. In contrast, the more stabilized muds surrounding the central gas and fluid conduits hosted active anaerobic hydrocarbon-degrading microbial communities. Furthermore, within three years, cell numbers and hydrocarbon degrading activity increased at the gas-seeping sites. The low microbial activity in the hydrocarbon-vented areas of Amon mud volcano is thus a consequence of kinetic limitations by heat and mud expulsion, whereas most of the outer mud volcano area is limited by hydrocarbon transport.

An in vitro study of the anti-microbial efficacy of a 1% silver sulphadiazine and 0.2% chlorhexidine digluconate cream Silvazine (TM), 1% silver sulphadiazine cream Flamazine (TM) and a silver coated dressing Acticoat (TM)

Burn sepsis is a leading cause of mortality and morbidity in patients with major burns. The use of topical anti-microbial agents has helped improve the survival in these patients. There are a number of anti-microbials available, one of which, Silvazine(TM) (1% silver sulphadiazine (SSD) and 0.2% chlorhexidine digluconate), is used only in Australasia. No study, in vitro or clinical, had compared Silvazine(TM) with the new dressing Acticoat(TM). This study compared the anti-microbial activity of Silvazine(TM), Acticoa(TM) and 1% silver sulphadiazine (Flamazine(TM)) against eight common burn wound pathogens. Methods: Each organism was prepared as a suspension. A 10 mul inoculum of the chosen bacterial isolate (representing approximately between 104 and 105 total bacteria) was added to each of four vials, followed by samples of each dressing and a control. The broths were then incubated and 10 mul loops removed at specified intervals and transferred onto Horse Blood Agar. These plates were then incubated for 18 hours and a colony count was performed. Results: The data demonstrates that the combination of 1% SSD and 0.2% chlorhexidine digluconate (Silvazine(TM)) results in the most effective killing of all bacteria. SSD and Acticoat(TM) had similar efficacies against a number of isolates, but Acticoat(TM) seemed only bacteriostatic against E. faecalis and methicillin-resistant Staphylococcus aureus. Viable quantities of Enterobacter cloacae and Proteus mirabilis rei named at 24 h. Conclusion: The combination of 1% SSD and 0.2% chlorhexidine digluconate (Silvazine(TM)) is a more effective anti-microbial against a number of burn wound pathogens in this in vitro study. A clinical study of its in vivo anti-microbial efficacy is required. (C) 2003 Elsevier Ltd and ISBI. All rights reserved.

Spatial and temporal variation of microbial properties in the water column of Florida Bay

Physical and biological properties of the water column of Florida Bay were examined at seven study sites over an eighteen month period. The results indicated seasonality in some parameters, but was not evident in others. The data displayed statistically significant (P < 0.05) differences between study sites indicating spatial variation. The presence of seagrass affected the overlying water column, especially with respect to the biological parameters: those areas overlying seagrass beds displayed statistically significantly higher values than those over sparsely covered or barren areas. During the period of the study, Florida Bay experienced a seagrass die-off event: microbial activity and numbers were statistically significantly higher over areas of dying seagrass than over healthy or dead areas. The results of this study pointed to phosphorus being the controlling, or limiting factor, for microbial activity in the water column of Florida Bay.

Microbial metabolism mediates interactions between dissolved organic matter and clay minerals in streamwater

Sorption of organic molecules to mineral surfaces is an important control upon the aquatic carbon (C) cycle. Organo-mineral interactions are known to regulate the transport and burial of C within inland waters, yet the mechanisms that underlie these processes are poorly constrained. Streamwater contains a complex and dynamic mix of dissolved organic compounds that coexists with a range of organic and inorganic particles and microorganisms. To test how microbial metabolism and organo-mineral complexation alter amino acid and organic carbon fluxes we experimented with 13C-labelled amino acids and two common clay minerals (kaolinite and montmorillonite). The addition of 13C-labelled amino acids stimulated increased microbial activity. Amino acids were preferentially mineralized by the microbial community, concomitant with the leaching of other (non-labelled) dissolved organic molecules that were removed from solution by clay-mediated processes. We propose that microbial processes mediate the formation of organo-mineral particles in streamwater, with potential implications for the biochemical composition of organic matter transported through and buried within fluvial environments.

Effects of wetting frequency and afforestation on carbon, nitrogen and the microbial community in soil

Afforestation of agricultural land is increasing, partly because it is an important biological method for reducing the concentration of atmospheric CO2 and potentially mitigating climate change. Rainfall patterns are changing and prolonged dry periods are predicted for many regions of the world, including southern Australia. To accurately predict land-use change potential for mitigating climate change, we need to have a better understanding of how changes in land-use (i.e. afforestation of pastures) may change the soils response to prolonged dry periods. We present results of an incubation study characterising C and N dynamics and the microbial community composition in soil collected from two tree plantings and their adjacent pastures under a baseline and reduced frequency. While the concentration of soil C was similar in pasture and tree planting soils, heterotrophic respiration was significantly lower in soil from pastures than tree plantings. Although there was little difference in the composition of the soil microbial community among any of the soils or treatments, differences in N cycling could indicate a difference in microbial activity, which may explain the differences in heterotrophic respiration between pastures and tree plantings. Soils from pastures and tree plantings responded similarly to a reduction in wetting frequency, with a decrease in microbial biomass (measured as total PLFA), and a similar reduction in heterotrophic respiration from the soil. This suggests that the responses to changes in future wetting cycles may be less dependent on land-use type than expected.

Enzymatic activity on sediments and nematode assemblage responses during seagrass beds habitat recovery following the disturbance of the traditional digging activity of bivalves harvesting.

Sediment digging is an anthropogenic activity connected to the exploitation of living resources in estuarine and marine environments. The knowledge on the functional responses of the benthic assemblages to the physical disturbance is an important baseline to understand the ecological processes of the habitat recovery and restoration and to develop tools for the management of the harvesting activities. To investigate the effects of the digging activity of the bivalves on Zostera noltii seagrass beds a manipulative field experiment was conducted that included the enzymatic activity of sediments and the associated nematode assemblages. Four plots (two undisturbed serving as control and two dug to collect bivalves - treatment) with 18 subplots were randomly located at seagrass beds in the Mira estuary at the SW coast of Portugal. Samples were randomly and unrepeatably collected from three subplots of each plot in five different occasions, before sediment digging (T0) up to six months after disturbance (T5). Microbial activity in sediments was assess by determining the extracelular enzymatic activity of six hydrolytic enzymes (sulfatase, phosphatase, b -N-acetilglucosaminidase, b-glucosidase, urease, protease) and two oxidoreductases (phenol oxidase and peroxidase). The microbial community status was also assessed through the measurement of dehydrogenase, which reflects microbial respiration. The nematode assemblages composition, biodiversity and trophic composition at different sampling occasions were also analyzed. The fluorometric and biochemical parameters analysed of the Z. noltii plants during the experimental period showed a recovery of the seagrass beds, and it was detected an increase of the enzymatic activity of the sediments after disturbance. The nematodes assemblages were similar in all sampling occasions. The seagrass beds and the nematodes assemblages associated showed a high resilience to the stress caused by the traditional bivalves digging activity. The obtained results allow the development of a management programme for the commercial fishing activity to maintain the good environmental status and minimized the secondary environmental effects on marine and estuarine habitats through the establishment of a baseline for the regulation of the harvesting frequency.

In vivo performance of melimine as an antimicrobial coating for contact lenses in models of CLARE and CLPU

Purpose: One strategy to minimize bacteria-associated adverse responses such as microbial keratitis, contact lens–induced acute red eye (CLARE), and contact lens induced peripheral ulcers (CLPUs) that occur with contact lens wear is the development of an antimicrobial or antiadhesive contact lens. Cationic peptides represent a novel approach for the development of antimicrobial lenses.---------- Methods: A novel cationic peptide, melimine, was covalently incorporated into silicone hydrogel lenses. Confirmation tests to determine the presence of peptide and anti-microbial activity were performed. Cationic lenses were then tested for their ability to prevent CLPU in the Staphylococcus aureus rabbit model and CLARE in the Pseudomonas aeruginosa guinea pig model. ---------- Results: In the rabbit model of CLPU, melimine-coated lenses resulted in significant reductions in ocular symptom scores and in the extent of corneal infiltration (P < 0.05). Evaluation of the performance of melimine lenses in the CLARE model showed significant improvement in all ocular response parameters measured, including the percentage of eyes with corneal infiltrates, compared with those observed in the eyes fitted with the control lens (P ≤ 0.05). ---------- Conclusions: Cationic coating of contact lenses with the peptide melimine may represent a novel method of prevention of bacterial growth on contact lenses and consequently result in reduction of the incidence and severity of adverse responses due to Gram-positive and -negative bacteria during lens wear.

Oxygen transport in soil and the vertical distribution of roots

An analytical solution for steady-state oxygen transport in soils including 2 sink terms, viz roots and microbes with the corresponding vertical distribution scaling lengths forming a ratio p, showed p governed the critical air-filled porosity, θ_c, needed by most plants. For low temperature and p, θ_c was <0.1 but at higher temperatures and p = 1, θ_c was >0.15 m³/m³. When root length density at the surface was 10⁴ m/m³ and p > 3, θ_c was 0.25 m³/m³, more than half the pore space. Few combinations of soil and climate regularly meet this condition. However, for sandy soils and seasonally warm, arid regions, the theory is consistent with observation, in that plants may have some deep roots. Critical θ_c values are used to formulate theoretical solutions in a forward mode, so different levels of oxygen uptake by roots may be compared to microbial activity. The proportion of respiration by plant roots increases rapidly with p up to p ≈2.