Planktonic Microorganisms Research Articles

Investigating Community Dynamics and Performance During Microbial Electrochemical Degradation of Whey

AbstractWhey is a main by‐product of the dairy industry and is difficult to valorise for small and medium enterprises. Microbial electrochemical technologies could be the key for these enterprises to exploit this current waste product. Whey removal and conversion to electrical current was investigated at microbial anodes using potentiostatically controlled half‐cell experiments. The anodes were fed with a whey solution containing ca. 1 g L−1 COD. This can be reliably cleaned with average removal efficiencies of 65.8±10.9 %. The removal coincided with maximum current densities of 0.31±0.06 mA cm−2 and Coulomb efficiencies of 37.1±10.8 %. The anodes are based on a robust complex microbial community. This was established in bioelectrochemical reactors by end of four batch cycles showing an efficient niche differentiation from the following successive enrichments. The microbial analysis revealed a division of labour with mainly planktonic microorganisms degrading the complex whey components by fermentation to organic acids, part of which are subsequently used by the electroactive bacteria at the anode. The results show the need for deciphering microbial structure‐function relationships for future process steering as well as engineering approaches.

Therapeutic Potential of Bauhinia forficata Link in Dental Biofilm Treatment.

The oral cytotoxicity, antimicrobial and anti-demineralizing effects of a tincture from Bauhinia forficata Link tincture (BFLT) were evaluated in vitro and ex vivo. Susceptibility tests (minimum inhibitory and microbicidal concentrations-MIC and time-kill assay-MMC) were performed against planktonic oral microorganisms. The contents of phenolic compounds were investigated. Cytotoxic potential was evaluated on oral fibroblasts after 1-5 min exposure to BFLT. Blocks of sound bovine enamel (N = 60) were inoculated with a saliva pool and sustained in a multiple plaque growth system for 48 h to form a biofilm. Biofilm blocks were randomly divided into groups-G (n = 10): G1-Baseline (48 h maturation biofilm), G2-BFLT 23.2 mg/mL, G3-Ethanol 81.20 g/mL, G4-Chlorhexidine 0.12%, G5-Growth control, and G6-Blank control. Treatments (50 μL/1 min) were performed once a day for a week. Streptococcus spp. (S) and total microorganism (TM) counts were expressed as Log10 CFU/mL. Biofilm height was evaluated by confocal microscopy analyses (CMA). Final surface hardness was assessed and percentage of microhardness loss (% MHL) was calculated. Results were significant when P < .05. BFLT inhibited all tested microorganisms (MIC = 1.3-23.2 mg/mL) and promoted optical reduction (0.05-0.22 nm) of all microorganisms after 48-h treatment compared with controls. After 5-min treatment, BFLT showed low values of cell death (3.20%). G2-BFLT reduced S (6.61 ± 0.20) and TM (7.14 ± 0.38) compared with G1-Baseline (S = 7.82 ± 0.28; TM = 8.81 ± 0.67) and G5-Growth control (S = 7.48 ± 0.39; TM = 7.89 ± 0.68); but G4-chlororexidine (S = 6.11 ± 0.48; TM = 6.45 ± 0.16) showed the highest antibiofilm activity. CMA was not different among treatment groups. G2 showed lower % MHL compared with G5, although G4 presented the lowest. Results suggest BFLT is beneficial against dental caries, showing antimicrobial effects against a mature dental biofilm and no cytotoxicity.

A novel process for the biological detoxification of non-metal residue from waste copper clad laminate treatment: From lab to pilot scale

A new process of biological detoxification and comprehensive utilization of non-metal residue from waste copper clad laminates treatment was proposed. The process mainly includes microbial cultivation, bioleaching, metal recovery, and wastewater treatment. The leaching rate of metal by bioleaching in acidic environment with pH1.0–2.0 was close to 100% and was 8.7% higher than that by dilute sulfuric acid leaching, and about 11.4% higher than that by circulating tailings leaching. Through a series of continuous batch operation, it was found that Eh (Oxidation/Reduction Potential), pH, c (Cu2+), c (TFe, total iron) of solutions in each section fluctuated within the expected range. Although the concentration of accumulated iron ions in the solution exceeds 20 g/L, the concentration of planktonic microorganisms was still above 6 × 107 cells/mL, and the activated microbial solution still had a good leaching effect on metals in the waste. The residue directly obtained through a filter press had a water content of less than 30%, while that dried residue has a copper content of less than 524 mg/kg. In addition, the grade of sponge copper prepared in the replacement section could reach 86.63%, and the direct yield of copper can reach more than 90%. Furthermore, an economic analysis mainly based on material balance had further confirmed the feasibility of the green treatment process.

Urbanization and Waterborne Pathogen Emergence in Low-Income Countries: Where and How to Conduct Surveys?

A major forthcoming sanitary issue concerns the apparition and spreading of drug-resistant microorganisms, potentially threatening millions of humans. In low-income countries, polluted urban runoff and open sewage channels are major sources of microbes. These microbes join natural microbial communities in aquatic ecosystems already impacted by various chemicals, including antibiotics. These composite microbial communities must adapt to survive in such hostile conditions, sometimes promoting the selection of antibiotic-resistant microbial strains by gene transfer. The low probability of exchanges between planktonic microorganisms within the water column may be significantly improved if their contact was facilitated by particular meeting places. This could be specifically the case within biofilms that develop on the surface of the myriads of floating macroplastics increasingly polluting urban tropical surface waters. Moreover, as uncultivable bacterial strains could be involved, analyses of the microbial communities in their whole have to be performed. This means that new-omic technologies must be routinely implemented in low- and middle-income countries to detect the appearance of resistance genes in microbial ecosystems, especially when considering the new ‘plastic context.’ We summarize the related current knowledge in this short review paper to anticipate new strategies for monitoring and surveying microbial communities.

Utilization of 1-butylpyrrolidinium Chloride Ionic Liquid as an Eco-friendly Corrosion Inhibitor and Biocide for Oilfield Equipment: Combined Weight Loss, Electrochemical and SEM Studies

Abstract With the help of the weight loss, and electrochemical techniques the suppressing action of the commercially available ionic liquid, 1-butylpyrrolidinium chloride [BPm1,1] Cl for carbon steel corrosion in 3.5% NaCl medium was scrutinized. It found that this compound acts as an excellent inhibitor with protection performance raised by an increase of its concentration and temperature. The adsorption behavior of the investigated ionic liquid was a mixed-type inhibitor subordinating Langmuir adsorption isotherm. To expounding adsorption and corrosion inhibition mechanisms, various thermodynamics and activation parameters such as adsorption constant (Kads), Gibb’s standard free energy ( Δ G ∗ $\Delta{{\text{G}}^{\ast}}$ ), activation energy (Ea), activation enthalpy ( Δ H ∗ $\Delta{{\text{H}}^{\ast}}$ ), and activation entropy ( Δ S ∗ $\Delta{{\text{S}}^{\ast}}$ ) were determined and debated. It has appeared that there is a strong interaction between the inhibitor molecules and the carbon steel surface in a predominantly chemisorptions manner. The presence of a protective inhibitor film on the metal surface was confirmed using a corroborative SEM tool. Moreover, the IL has screened for antibacterial activity against planktonic and sessile microorganisms. The obtained results emphasized that the utilized ionic liquid can be regarded as an efficacious biocide for both bacterial strains with a dissimilar efficiency.

Structural design and development of a water transfer sample

Understanding rare suspended particulate matter (including planktonic microorganisms) in the deep ocean is important but difficult to sample, for which we deigned a large-sized in-situ water sampler (200-1000L), i.e., a large volume water transfer system sampler. The system comprises of a deep-ocean pump, a filtering device, data acquisition and control devices, a supporting frame, a power supply component, a connecting mechanism, and a flow meter, etc. The filtering device integrates membranes for three-graded filtration at 0.22, 1, and 5μm, and an additional membrane aperture upon the need. The control device adopts two working modes: depth trigger and time trigger. The system can be added with a CTD and a fluorescence meter, etc. In addition, for a stationed site survey, several sets (such as 3 sets) of the system can be fixed at an interval on the suspension cable to work at different depths simultaneously. The system can be applied for high-level multi-layer filtration to obtain suspended particles. The system has been applied in several marine expeditions. The development of this system provides an ideal tool for deep-ocean in-situ sampling technology in China. The applications of the large volume water transfer system sampler for in-situ sampling in deep-ocean have been launched for a few times. Some interesting phenomena have been discovered and the advantages of in situ sampling are proved.

Are there Invasive Planktonic Microbes?

The translocation of species by human activities is a problem that increases with the globalization. However, the examples of non-indigenous or exotic planktonic microbes can be questioned as they predominantly have cosmopolitan distributions and natural mechanisms for wide dispersion. In reality, the categorization of any species as non-indigenous requires solving two difficult issues: knowledge of where the ‘natural’ population is, and demonstration of a substantial geographic discontinuity between the supposed source and the introduced populations. With regard to planktonic microorganisms, a non-indigenous taxon could have been previously unnoticed during routine microscopical analyses due to: A) difficult identification at the species level in routine observations such as for the diatoms (Pseudo-nitzschia, Skeletonema, Thalassiosira, Pleurosigma), unarmoured dinoflagellates (Karenia, Karlodinium) and Raphidophytes, and B) species with strong interannual fluctuations of abundance, only detected during bloom periods when they are misinterpreted as newcomers (i.e., Coscinodiscus wailesii or Trieres chinensis, junior synonyms of C. cylindricus and T. regia, respectively, or Gymnodinium catenatum). Rather than attempting to add to the lists of non-indigenous species with planktonic microbes, the monitoring surveys should also pay attention in the less common species with important fluctuations of abundance, independent of tentative labels as exotic or indigenous, because they are potentially useful as bio-indicators of environmental changes.

Trophic networks improve the performance of microbial anodes treating wastewater

Microbial anodes represent a distinct ecological niche that is characterized mainly by the terminal electron acceptor, i.e., the anode potential, and the substrate, i.e., the electron source. Here, we determine the performance and the biofilm community of anode microbiomes while using substrates of increasing complexity (organic acids or organic acids and sugar or real domestic wastewater) to mimic different, practically relevant, trophic levels. α-Diversity values increased with substrate complexity. In addition, the higher abundance value of Deltaproteobacteria in the biofilms corresponds to higher reactor performance (i.e., COD removal, current density, and Coulombic efficiency). In reactors exploiting real wastewater, the diversity of the planktonic microorganisms was only little affected. Microbiome network analysis revealed two important clusters for reactor performance as well as performance-independent pathogen-containing clusters. Interestingly, Geobacter was not found to be integrated in the network underlining its outstanding individual ecological role in line with its importance for the efficiency of the electron harvest for all reactors. The microbiome analysis of different trophic levels and their temporal development from initial colonization to stable treatment demonstrate important principles for the implementation of microbial anodes for wastewater treatment.

The role of sedimentation in the structuring of microbial communities in biofloc-dominated aquaculture tanks

In no water exchange aquaculture operations, sedimentation has been employed to control the level of microbial flocs to decrease oxygen consumption and to prevent clogging of gills in cultured organisms. Nevertheless, the impact of this practice on the culture microbial community was not documented. The current study evaluated the impact of adding different concentrations of sedimentation from an intensive shrimp culture tank on the microbial communities in an experimental tank system operated with no water exchange. The trial evaluated three concentrations (mg L−1) of total suspended solids levels: <200, 680, and 1030. The analysis showed that settleable microbial community has a different set of species compared with the unsettled biomass, which was also less diverse. We argue that the difference in species composition is probably related to the biological flocculation, i.e., the ability exhibited by microorganisms to spontaneously form large, dense and quick settling aggregates. The results suggest that settling tanks act as a selective force by reducing the abundance of microorganisms strongly associated with the settled flocs, whilst favoring planktonic lifestyle bacteria or microorganisms associated with small and open flocs. These effects, especially loss of diversity, need to be considered in aquaculture management practices since it can increase the risk for invasion of opportunistic pathogenic species.

Pulsed and continuous light UV LED: microbial inactivation, electrical, and time efficiency

Ultraviolet light emitting diodes (UV LEDs) have increasing applications in the inactivation of microorganisms in water, air, food, and on surfaces. System designers currently have metrics for comparison of the microbial and energy efficiency of UV LEDs, but these have not included a time component. Without including the time efficiency of a UV LED, neither the fluence-basis nor the electrical-basis of comparison clarifies which UV LED wavelength and operating condition is optimal for a design space. This research explores microbial inactivation of UV LEDs at various wavelengths under continuous and pulsing operating conditions. Planktonic microorganisms of relevance to public water supplies and UV system design are included: E. coli and MS-2 for benchmarking against previous studies and P. aeruginosa which has not been studied in pulsed systems or for continuous and combined UV LED wavelengths.Pulsing UV LEDs at various duty rates (percent of cycle spent on) and frequencies (number of cycles per second) does not result in a statistically significant disinfection performance difference over the continuous light operation at that respective wavelength. UV LEDs emitting at peak wavelengths corresponding to the peak action spectrum of a microorganism are optimal on a fluence-basis, but these are typically less electrically efficient UV LEDs. System designers can compare the normalized microbial inactivation, electrical, and time efficiencies (ENETO) of various UV LEDs; ENETO ≥1 for a pulsing condition ensures equal or improved efficiency compared to the continuous light condition while expanding the lifetime of the UV LED and decreasing the size or cost of associated power supplies.

The catalytic role of planktonic aerobic heterotrophic bacteria in protodolomite formation: Results from Lake Jibuhulangtu Nuur, Inner Mongolia, China

Abstract Dolomite nucleation and subsequent crystallization are kinetically-controlled processes. Modern dolomite-forming environments provide clues to the trigger factors that facilitate dolomite formation under Earth surface conditions. It has been documented that certain types of benthic microorganisms promoted the precipitation of protodolomite from sediment pore waters. As protodolomite is thought to be a possible precursor of sedimentary ordered dolomite, microbial mediation has thus been suggested as one interpretation of the occurrence of dolomite in modern sediments. To date, however, it is still unclear whether planktonic microorganisms could directly initiate protodolomite crystallization in the upper water column of present dolomite depositing environments. In this study, we report on the occurrence of authigenic protodolomite in the upmost sediments of a high-sulfate, Chinese inland saline lake (Lake Jibuhulangtu Nuur). This lake was therefore considered to be a natural laboratory to test the catalytic effect of planktonic aerobic heterotrophic bacteria on protodolomite formation. Laboratory mineralization experiments were conducted in a liquid medium that mimicked the ion concentrations and pH condition of lake surface water. The incubation experiments showed that aragonite formed in the abiotic systems, while protodolomite predominantly occurred in the bioreactors using either an enrichment culture or pure isolates of aerobic heterotrophic and halophilic bacteria from lake water. The resulting microbially-induced protodolomite crystals displayed spherical morphology and had MgCO3 composition ranging from 42.7 mol% to 47.1 mol%. These protodolomite spherulites were formed by aggregation of randomly-distributed nano-crystals. Compared to synthetic abiotic protodolomite, microbially-induced protodolomite contained considerable amounts of organic matter, which might occur as intracrystalline inclusion or was located between nano-crystals of protodolomite spherulite. Our results support the emerging view that dissolved sulfate is not an inhibitor for the formation of low-temperature (proto-)dolomite. The presence of organic matter intimately associated with dolomite crystals may serve as a hallmark indicative of a biotically induced origin for some types of dolomite.

Synthesis, physico-chemical characterization, antimicrobial activity and toxicological features of Ag[sbnd]ZnO nanoparticles

Silver-zinc oxide nanoparticles (AgZnO NPs) were chemically synthesized by the deposition of Ag NPs on the surface of ZnO NPs using silver nitrate, three types of anionic polyelectrolytes and citric acid as reagents. The Wavelength Dispersive X-ray Fluorescence (WDXRF) spectrometry of AgZnO NPs revealed 0.41–0.69 wt% Ag, and balance ZnO. The existence of Ag NPs on the surface of ZnO NPs with hexagonal wurtzite structure was highlighted by X-ray Diffraction (XRD) analysis, scanning electron microscopy (SEM), and Ultraviolet–Visible (UV–Vis) spectroscopy. The diffuse reflectance absorption of AgZnO NPs in the visible light region increased with the increase of Ag NPs content. The Fourier Transform Infrared (FTIR) spectrometry revealed no chemical bonding between Ag NPs and ZnO NPs and confirmed the presence of functional groups characteristic to ZnO and carboxylic acid salts. The newly synthesized AgZnO NPs displayed antimicrobial activity against all the tested medically relevant pathogens, with minimal (biofilm) inhibitory concentrations ranging from 1.875 mg/mL to 7.5 mg/mL. Although the in vitro genotoxicity assay revealed a relatively high micronuclei index, the in vivo micronucleus (MN) test revealed a low MN frequency in animals treated with AgZnO NPs. The histopathological analysis revealed non-significant structural changes of the hepatic parenchyma, renal cortex and intestinal mucosa and minimal inflammatory reactions. The AgZnO NPs administration induced TUNEL positive nuclei of Kupffer cells in the liver parenchyma. The present study shows that the newly synthesized AgZnO NPs are active against planktonic and adherent microorganisms and could be exploited to develop novel antimicrobial strategies for the biotechnology and biomedical fields. Easy scalability of the developed chemical synthesis is a major advantage in producing large batches of AgZnO NPs with reproducible properties.

Inactivation of oral biofilms using visible light and water-filtered infrared A radiation and indocyanine green.

Aim: To investigate the antimicrobial photodynamic therapy (aPDT) of visible light and water-filtered infrared A radiation in combination with indocyanine green (ICG) on planktonic oral microorganisms as well as on oral biofilm. Methods: The irradiation was conducted for 5 min in combination with ICG. Treatment with chlorhexidine served as a positive control. The number of colony forming units and bacterial vitality were quantified. Results: All tested bacterial strains and salivary bacteria were killed at a level of 3log10. The colony forming units of the initial mature oral biofilms were strongly reduced. The high bactericidal effect of aPDT was confirmed by live/dead staining. Conclusion: The aPDT using visible light and water-filtered infrared A radiation and ICG has the potential to treat periodontitis and peri-implantitis.

Warming and CO2 Enhance Arctic Heterotrophic Microbial Activity.

Ocean acidification and warming are two main consequences of climate change that can directly affect biological and ecosystem processes in marine habitats. The Arctic Ocean is the region of the world experiencing climate change at the steepest rate compared with other latitudes. Since marine planktonic microorganisms play a key role in the biogeochemical cycles in the ocean it is crucial to simultaneously evaluate the effect of warming and increasing CO2 on marine microbial communities. In 20 L experimental microcosms filled with water from a high-Arctic fjord (Svalbard), we examined changes in phototrophic and heterotrophic microbial abundances and processes [bacterial production (BP) and mortality], and viral activity (lytic and lysogenic) in relation to warming and elevated CO2. The summer microbial plankton community living at 1.4°C in situ temperature, was exposed to increased CO2 concentrations (135–2,318 μatm) in three controlled temperature treatments (1, 6, and 10°C) at the UNIS installations in Longyearbyen (Svalbard), in summer 2010. Results showed that chlorophyll a concentration decreased at increasing temperatures, while BP significantly increased with pCO2 at 6 and 10°C. Lytic viral production was not affected by changes in pCO2 and temperature, while lysogeny increased significantly at increasing levels of pCO2, especially at 10°C (R2 = 0.858, p = 0.02). Moreover, protistan grazing rates showed a positive interaction between pCO2 and temperature. The averaged percentage of bacteria grazed per day was higher (19.56 ± 2.77% d-1) than the averaged percentage of lysed bacteria by virus (7.18 ± 1.50% d-1) for all treatments. Furthermore, the relationship among microbial abundances and processes showed that BP was significantly related to phototrophic pico/nanoflagellate abundance in the 1°C and the 6°C treatments, and BP triggered viral activity, mainly lysogeny at 6 and 10°C, while bacterial mortality rates was significantly related to bacterial abundances at 6°C. Consequently, our experimental results suggested that future increases in water temperature and pCO2 in Arctic waters will produce a decrease of phytoplankton biomass, enhancement of BP and changes in the carbon fluxes within the microbial food web. All these heterotrophic processes will contribute to weakening the CO2 sink capacity of the Arctic plankton community.

Marine fungal dark matter in the global ocean

Marine fungi are a major part of ‘microbial dark matter’, with most organisms known from sequence data and currently not in culture. Interest in marine fungi has substantially increased over the past decade, and studies using culture independent methods have indicated that fungal diversity in the oceans may be greater than previously estimates based on cultivation alone. There remains much to learn about the true diversity of marine fungi in the global oceans and the ecological roles that they could play. The Tara Oceans expedition has allowed for significant advancements in our understanding of the global diversity of planktonic microorganisms. Interrogation of the Tara Oceans 18S rRNA gene dataset for fungal sequences shows that fungi are found throughout the global oceans, appearing in all marine regions covered by the Tara Oceans expedition. In the survey, Ascomycota and Basidiomycota were common, while some locations had increased abundances of Chytridiomycota. Differences in community composition were observed between oceanic regions and, although clear signals were not apparent due to the nature of the sampling, there was some indication of community variation between upwelling, coastal, shelf and gyral provinces. Different size sampling fractions appeared to capture different portions of the pelagic fungal community. These findings highlight a number of ecological questions: How important are oceanic currents in determining fungal biogeography? What is the relationship between marine fungi and biogeochemical processes? What is actually there? By targeting these questions directly, we will be able to bring the dark matter of marine fungi into the light.

Inhibition of microbial growth by cold atmospheric plasma compared with the antiseptics chlorhexidine digluconate, octenidine dihydrochloride, and polyhexanide

The inhibition of microbial growth is the first step toward avoiding the formation of biofilms. Therefore, this study aimed to compare the microbiostatic activity of cold atmospheric pressure plasma (CAP) with three commonly used antiseptic agents to find an alternative to or supplementary concept for antiseptic treatment. The efficacy of two CAP generating devices − the plasma jet kINPen09® and a hollow dielectric barrier electrode (HDBD) − both working with argon with or without admixture of 1% oxygen, was compared with chlorhexidine digluconate (CHG 0.0001 and 0.00000625%), polyhexanide (PHMB 0.0001 and 0.000025%) and octenidine dihydrochloride (OCT 0.0002 and 0.00005%). The antiseptics were added to the planktonic stage of the biofilm‐forming strains Pseudomonas aeruginosa SG 81, Staphylococcus epidermidis RP 62A, Streptococcus mutans DSM 20523 and Candida albicans ATCC 10231 resp. SC 5314. The antiseptics were present during the subsequent cultivation period (32.5 h), whereas CAP was applied for only 60 s with the same cultivation period after the exposition. During the cultivation period, growth was measured every hour by optical density and analyzed with the calculated area under the curve (AUC) to determine the delay of exponential growth. Except for the higher resistance of C. albicans against PHMB and S. mutans against CHG, P. aeruginosa was the most resistant test organism against the other antiseptic treatments. OCT 0.0002% was the most effective among the tested antiseptic agents. The plasma jet did not differ from OCT in its efficacy against C. albicans and S. mutans. Against P. aeruginosa and both Candida strains, the plasma jet was more effective than against both Gram‐positive test strains. In terms of efficacy against Candida spp., the HDBD (dielectric barrier discharge plasma) did not differ significantly from the plasma jet with argon plasma; in contrast, the bacteriostatic efficacy was significantly higher. While the addition of 1% O2 did not change the efficacy of the plasma jet, the efficacy of the HDBD against S. epidermidis increased significantly. The antimicrobial efficacy of CAP as demonstrated in earlier studies was confirmed with planktonic microorganisms showing delayed growth during cultivation for 32.5 h after a single application of CAP for 60 s. Short treatment with CAP could be an effective alternative or supplement to conventional antiseptics, for example, to inhibit the growth of microorganisms in an infected wound. OCT in the concentration used here showed the best microbial growth inhibitory results among the antiseptics.

Marine biofilms constitute a bank of hidden microbial diversity and functional potential

Recent big data analyses have illuminated marine microbial diversity from a global perspective, focusing on planktonic microorganisms. Here, we analyze 2.5 terabases of newly sequenced datasets and the Tara Oceans metagenomes to study the diversity of biofilm-forming marine microorganisms. We identify more than 7,300 biofilm-forming ‘species’ that are undetected in seawater analyses, increasing the known microbial diversity in the oceans by more than 20%, and provide evidence for differentiation across oceanic niches. Generation of a gene distribution profile reveals a functional core across the biofilms, comprised of genes from a variety of microbial phyla that may play roles in stress responses and microbe-microbe interactions. Analysis of 479 genomes reconstructed from the biofilm metagenomes reveals novel biosynthetic gene clusters and CRISPR-Cas systems. Our data highlight the previously underestimated ocean microbial diversity, and allow mining novel microbial lineages and gene resources.

Synthetic lipids as a biocide candidate for disinfection of ballast water

The objective of this study is to propose the use of specific synthetic lipid as an active substance (biocide) in the control of harmful aquatic microorganisms, such as pathogens and non-indigenous species, transported in ships' ballast water. The biocide candidate, without metal or halogen components, was produced from a sub-product of the edible oil industry, the lecithin. Laboratory assays were conducted with phytoplankton, zooplankton, and marine bacteria to evaluate the efficiency of the biocide. The study also considers specific biocide's characteristics related to environmental risks, such as chemical composition, persistence, bioaccumulation, and toxicity. Results showed that, in the first 24 h of treatment, the biocide effectively reduced the concentration of the planktonic micro-organisms to very low levels. Additionally, a preliminary risk evaluation pointed that biocide candidate has a low residual toxicity, also a low potential for persistence and bioaccumulation in the environment.

Efficacy of a Surfactant-Based Wound Dressing in the Prevention of Biofilms.

To assess the biofilm prevention action of two wound dressings, a concentrated surfactant gel preserved with antimicrobials and a concentrated surfactant gel with 1% silver sulfadiazine. The microorganisms Staphylococcus aureus, methicillin-resistant S aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Enterococcus faecalis were used. Several biofilm models were used whereby the surfaces of each model were coated with either the concentrated surfactant gel preserved with antimicrobials or the concentrated surfactant gel with SSD before biofilm growth. Results showed the concentrated surfactant gel with SSD prevented biofilm growth in the modified minimum biofilm eradication concentration and Centers for Disease Control and Prevention biofilm models. The concentrated surfactant gel preserved with antimicrobials prevented microbial penetration for up to 48 hours, whereas the concentrated surfactant with SSD prevented microbial penetration for at least 72 hours. Using confocal laser scanning microscopy, researchers showed that a surface coated with the concentrated surfactant gel preserved with antimicrobials enhanced microbial sequestration of planktonic microorganisms. These results demonstrated that a concentrated surfactant gel preserved with antimicrobials can sequester and cause the immobilization of planktonic bacteria. Further, the concentrated surfactant gel with SSD can effectively kill planktonic and sessile microorganisms.

Monitoring biofouling based on aerobic respiration in reverse osmosis system

A monitoring method of biofouling in reverse osmosis (RO) system was proposed based on the fluorescent signal of resorufin, which is reduced by nicotinamide adenine dinucleotide released from viable cells during aerobic respiration. The fluorescent signal of resorufin reduced by planktonic cells and microorganisms of biofilm showed linearity, indicating its feasibility to monitor biofouling in a RO system. For the application of the method to the lab-scale RO system, the injection concentration of resazurin and the injection flow rate were optimized. Biofilm on RO membranes continuously operated in a lab-scale RO system was estimated by resorufin fluorescence under optimized detection condition. As a result, resorufin fluorescence on RO membrane showed a significant increase in which the permeability of RO system decreased by 30.48%. Moreover, it represented the development of biofilm as much as conventional biofilm parameters such as adenosine triphosphate, extracellular polymeric substances, and biofilm thickness. The proposed method could be used as a sensitive and low-cost technology to monitor biofouling without autopsy of membranes.