bluuebunny/crossref_metadata_2025 huggingface dataset:
Factores de riesgo para trastornos hipertensivos del embarazo en la Unidad de Cuidados Intensivos del Hospital Regional Docente Materno Infantil El Carmen
Authors: García Inga Belinda Olga , Poma Salinas Jenny Giovana , Suasnabar Cueva Edith , Tello Carhuanca Rebeca
Published: July 2020

Objetivos: Determinar los factores de riesgo para los Trastornos Hipertensivos del Embarazo atendidos en la Unidad de Cuidados Intensivos del Hospital Regional- Docente Materno Infantil El Carmen Huancayo 2017. Material y Métodos: Estudio de tipo básico, nivel descriptivo y de corte transversal. El presente estudio comprendió un total de 60 historias clínicas (de pacientes ingresadas a la UCI) de la unidad de cuidados intensivos del Hospital Regional Docente Materno Infantil el Carmen en el periodo de enero a octubre del año 2017. Resultados: Se identificó factores socio demográficos que provienen de la zona rural y de un puesto de salud. Donde la mayoría de las madres tenían entre 15 y 35 años (73,3%) la ocupación de un alto porcentaje es de ama de casa (63,3%), tienen estudios de educación secundaria (48,3%), son convivientes el 43,3%, provienen de la zona rural el 51,7%, de un puesto de salud el 61,7%, el 100% es de raza mestiza, la persona con la que conviven es su primera pareja para el 55%, la mayoría no consumen alcohol (88,3%) y no consumen tabaco el 93,3%. Se identificó como factores de riesgo gíneco obstétricos el ser primigestas y el parto con cesárea. Se pudo notar que la edad gestacional fue de 32 a 34 semanas (50%), son primigestas el 35%, la mayoría recibió control prenatal (80%), el parto fue con cesárea en el 95% no tuvieron antecedentes de aborto el 80%, no tienen antecedentes hipertensivos el 91,7% el 95% tuvieron un solo niño. Se identificó como factores de riesgo patológicos; el tener hipertensión arterial 71,7%, también podemos ver que el 58,3% no tienen obesidad, no tuvieron enfermedades renales el 80%, ninguna tuvo diabetes mellitus ni enfermedad cardiaca. Conclusiones: Se ha determinado que el factor de riesgo para los trastornos hipertensivos del embarazo es el sociodemográfico; provienen de la zona rural y de un puesto de salud. Gíneco obstétricos el ser primigestas y el parto con cesárea y entre los factores patológicos es ser hipertenso.
Supervivencia de vieira patagónica de talla no comercial descartada por la pesquería
Authors: Schwartz Matías , Escolar Mariana , Marecos Ángel , Herrera Susana , Díaz Ronaldo , Villalba Javier , Campodónico Silvana
Published: July 2020

La pesquería bentónica más importante en extensión y producción del Atlántico Sudoccidental es la de vieira patagónica (Zygochlamys patagonica). La desarrollan cuatro buques factoría con redes de arrastre de fondo no selectivas y planta procesadora a bordo. Durante el proceso de selección se retienen las vieiras de talla comercial (≥ 55 mm de alto total) y las que no la alcanzan (< 55 mm AT) se descartan al mar. El objetivo del presente trabajo fue determinar el nivel de supervivencia de los ejemplares descartados al mar y el efecto del proceso de selección a bordo. Se seleccionaron vieiras de talla no comercial procedentes de cubierta (control) y descarte (tratamiento). Se las clasificó de acuerdo con el nivel de daño y se las colocó en bolsas de polipropileno para fondearlas (~ 100 m de profundidad). Cuando se recuperaron los fondeos, a los 10 y 54 d, se contabilizó la cantidad de individuos vivos en cada bolsa. Los mayores niveles de supervivencia se registraron en ejemplares sin daño o con daño solo en los bordes; en aquellos con roturas o perforaciones en la valva el porcentaje fue cercano al 50%. Se observó que la supervivencia disminuía a medida que aumentaba el tiempo de la experiencia.
Análise Comparativa dos Retornos Efetuados e Estimados de Ações de Empresas Brasileiras
Authors: Machado Kascilene Gonçalves
Published: July 2020

Este trabalho tem por objetivo verificar se valores estimados com os modelos propostos pelos autores Sharpe (1964) e Fama e French (1993) e 2015a) são eficientes para orientar os investidores. Para alcançar o objetivo proposto, realizou-se uma analise comparativa dos retornos efetuados e estimados das ações de 60 empresas brasileiras, no período de 2000 a 2018, através do cálculo das variações entre os retornos reais e estimados, identificando-se se os retornos realizados são próximos dos calculados. O trabalho mostra-se relevante, pois o estudo realizado testou e verificou se os modelos de precificação de ativos, clássicos da literatura de finanças, realmente são eficientes e devem ser utilizados pelos investidores como ferramenta de apoio a tomada de decisão em renda variável. A partir dos resultados da pesquisa, é possível responder quais modelos tendem a ser mais confiáveis e quais os cuidados que os investidores devem ter ao fazer uso desses modelos. Além disso, o artigo visa a preencher a lacuna de pesquisa sobre a eficiência dos modelos de precificação de ativos no mercado acionário brasileiro, abrangendo tanto uma quantidade maior de ações a serem analisadas quanto um período de pesquisa mais amplo, o que agrega diversos cenários econômicos (expansão, estagnação, crises econômicas e recessão). Os resultados obtidos a partir de análise comparativa dos retornos reais e estimados empregando o modelo de precificação de ativo de Sharpe (1964) e o modelo de três e cinco fatores proposto por Fama e French (1993) e (2015a) indicam que apenas um pequeno percentual dos retornos calculados ocorreu conforme os retornos efetuados no período de análise, o que evidencia que tais modelos devem ser empregados com outras ferramentas para apoio de decisão em investimentos em renda variáveis.
Trends and spatial shifts in lightning fires and smoke concentrations in response to 21st century climate over the national forests and parks of the western United States
Authors: Li Yang , Mickley Loretta J. , Liu Pengfei , Kaplan Jed O.
Published: July 2020

Abstract. Almost USD 3 billion per year is appropriated for wildfire management on public land in the United
States. Recent studies have suggested that ongoing climate change will lead to warmer and drier
conditions in the western United States, with a consequent increase in the number and size of
wildfires, yet large uncertainty exists in these projections. To assess the influence of future
changes in climate and land cover on lightning-caused wildfires in the national forests and parks
of the western United States and the consequences of these fires on air quality, we link a dynamic
vegetation model that includes a process-based representation of fire (LPJ-LMfire) to a global
chemical transport model (GEOS-Chem). Under a scenario of moderate future climate change (RCP4.5),
increasing lightning-caused wildfire enhances the burden of smoke fine particulate matter (PM),
with mass concentration increases of ∼53 % by the late 21st century during the fire
season in the national forests and parks of the western United States. In a high-emissions
scenario (RCP8.5), smoke PM concentrations double by 2100. RCP8.5 also shows enhanced
lightning-caused fire activity, especially over forests in the northern states.
Smartphone Pressure Data: Quality Control and Impact on Atmospheric Analysis
Authors: Li Rumeng , Zhang Qinghong , Sun Juanzhen , Chen Yun , Ding Lili , Wang Tian
Published: July 2020

Abstract. Smartphones are increasingly being equipped with atmospheric measurement sensors, providing huge auxiliary resources for global observations. Although China has the highest number of cellphone users, there is little research on whether these measurements provide useful information for atmospheric research. Here, for the first time, we present the global spatial and temporal variation of smartphone pressure measurements collected in 2016 from the Moji Weather app. The data have an irregular spatiotemporal distribution, with a high density in urban areas, a maximum in summer and two daily peaks corresponding to rush hours. With the dense dataset, we have developed a new bias correction method based on a machine learning approach without requiring users' personal information, which is shown to reduce the bias of pressure observation substantially. The potential application of the high-density smartphone data in cities is illustrated by a case study of a hailstorm occurred in Beijing in which high-resolution gridded pressure analysis is produced. It is shown that the dense smartphone pressure analysis during the storm can provide detailed information about fine-scale convective structure and decrease errors from an analysis based on surface meteorological-station measurements. This study demonstrates the potential value of smartphone data and suggests some future research need for its use in atmospheric science.
On the calibration of FIGAERO-ToF-CIMS: importance and impact of calibrant delivery for the particle phase calibration
Authors: Ylisirniö Arttu , Barreira Luis , Pullinen Iida , Buchholz Angela , Jayne John , Krechmer Jordan E. , Worsnop Douglas R. , Virtanen Annele , Schobesberger Siegfried
Published: July 2020

Abstract. The Filter Inlet for Gases and AEROsols (FIGAERO) coupled with a Time-of-Flight Chemical Ionization Mass Spectrometer (ToF-CIMS) enables online measurements of both gas-phase and particle phase chemical constituents of ambient aerosols. When properly calibrated, the incorporated particle filter collection and subsequent thermal desorption enable the direct measurement of volatility of said constituents. Previously published volatility calibration results however differ from each other significantly. In this study we investigate the reason for this discrepancy. We found a major source of error in the widely used syringe deposition calibration method that can lead to an overestimation of saturation vapour pressures by several orders of magnitude. We propose a new method for volatility calibration by using atomized calibration compounds that more accurately captures the evaporation of chemical constituents from ambient aerosol particles. We justify our claim with evaporation modelling and direct Scanning Electron Microscopy imaging, while also presenting possible error sources of the atomizer method. We finally present how typical calibration parameters derived with both methods impact the Volatility Basis Set (VBS) derived from measurements of Secondary Organic Aerosols (SOA).
Patterns in recent and Holocene pollen influxes across Europe; the Pollen Monitoring Programme Database as a tool for vegetation reconstruction
Authors: Abraham Vojtěch , Hicks Sheila , Svobodová-Svitavská Helena , Bozilova Elissaveta , Panajiotidis Sampson , Filipova-Marinova Mariana , Jensen Christin  Eldegard , Tonkov Spassimir , Pidek Irena Agnieszka , Święta-Musznicka Joanna , Zimny Marcelina , Kvavadze Eliso , Filbrandt-Czaja Anna , Hättestrand Martina , Karlıoğlu Kılıç Nurgül , Kosenko Jana , Nosova Maria , Severova Elena , Volkova Olga , Hallsdóttir Margrét , Kalniņa Laimdota , Noryśkiewicz Agnieszka , Noryśkiewicz Bożena , Pardoe Heather , Christodoulou Areti , Koff Tiiu , Fontana Sonia L. , Alenius Teija , Isaksson Elisabeth , Seppä Heikki , Veski Siim , Pędziszewska Anna , Weiser Martin , Giesecke Thomas
Published: July 2020

Abstract. The collection of modern spatially extensive pollen data are important for the interpretation of fossil pollen diagrams. Such datasets are readily available for percentage data but lacking for pollen accumulation rates (PAR). Filling this gap has been the motivation of the pollen monitoring network, whose contributors monitored pollen deposition in modified Tauber-traps for several years or decades across European latitudes. Here we present this monitoring dataset consisting of 351 trap locations with a total of 2742 annual samples covering the period from 1981 to 2017. This dataset shows that climate parameters correlating with latitude determine pollen productivity. A signal of regional forest cover can be detected in the data, while local tree cover seems more important. Pollen traps situated beyond 200 km of the distribution of the parent tree are still collecting occasional pollen grains of the tree in question. PAR’s of up to 30 grains cm−2yr−1 in fossil diagram should therefore be interpreted as long distance transport. Comparisons to fossil data from the same areas show comparable values. Comparisons often demonstrate that similar high values for temperate taxa in fossils sites are found further south or downhill. While modern situations comparable to high PAR values of some taxa (e.g. Corylus) may be hard to find, CO2 fertilization and land use may case high modern PAR’s that are not documented in the fossil record. The modern data is now publically available in the Neotoma Paleoecology Database and hopefully serves improving interpretations of fossil PAR data.
Using satellite data to identify the methane emission controls of South Sudan's wetlands
Authors: Pandey Sudhanshu , Houweling Sander , Lorente Alba , Borsdorff Tobias , Tsivlidou Maria , Bloom A. Anthony , Poulter Benjamin , Zhang Zhen , Aben Ilse
Published: July 2020

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) provides observations of atmospheric methane (CH4) at an unprecedented combination of high spatial resolution and daily global coverage. Hu et al. (2018) reported unexpectedly large methane enhancements over South Sudan in these observations. Here we assess methane emissions from the wetlands of South Sudan using two years (December 2017–November 2019) of TROPOMI total column methane observations. We estimate annual wetland emissions of 7.2 ± 3.2 Tg yr−1, which agrees with the multiyear GOSAT inversions of Lunt et al. (2019) but is an order of magnitude larger than estimates from wetland process models. This disagreement may be explained by the up to 4 times underestimation of inundation extent by the hydrological schemes used in those models. We investigate the seasonal cycle of the emissions and find the lowest emissions during the June–August season when the process models show the largest emissions. Using satellite altimetry-based river water height measurements, we infer that this seasonal mismatch is likely due to a seasonal mismatch in inundation extent. In models, inundation extent is controlled by regional precipitation, scaled to static wetland extent maps, whereas the actual inundation extent is driven by water inflow from rivers like the White Nile and the Sobat. TROPOMI emission estimates show better agreement, in terms of both seasonal cycle and annual mean, with model estimates that use a stronger temperature dependence. This suggests that temperature might be the best explanatory control for the emissions from wetlands in South Sudan. Our findings demonstrate the use of satellite instruments for quantifying emissions from inaccessible and uncertain tropical wetlands, providing clues for improvement of process models, and thereby improving our understanding of the currently uncertain contribution of wetlands to the global methane budget.
CRISPR interference knockdown screen identifies novel proteins involved in formation of structured macrocolonies in Staphylococcus aureus.
Authors: Kjos Morten , Morales Angeles Danae , Mårli Marita Torrissen , Heggenhougen Maria Victoria , de Bakker Vincent , Liu Xue , Veening Jan-Willem
Published: July 2020

Staphylococcus aureus biofilms play important roles during infection. The main components of these biofilms are well studied; however, we lack the full understanding of factors and genes involved in regulation of biofilm formation. To screen for essential and non-essential biofilm regulatory genes in S. aureus, we have created a pooled inducible CRISPR interference library. The pooled library is designed to allow knockdown of every transcriptional unit in the S. aureus genome, thus targeting both essential and non-essential genes. We used our library in S. aureus Newman, a strain which forms structured macrocolonies on agar plates. We performed an unbiased screen of 1500 macrocolonies and found 10 macrocolonies with stably altered structures. The genotypes of these macrocolonies were determined by sequencing the single guide RNAs of the CRISPR interference system. As a proof of the validity of the approach, we identified several genes previously reported to be implicated in biofilm and macrocolony formation, including ica-genes, and metabolic genes of the TCA-cycle and gluconeogenesis. In addition, three new genes (two encoding putative enzymes and one hypothetical genes) whose depletion resulted in completely altered macrocolonies were also identified. The molecular mechanisms explaining the roles of these proteins in biofilm formation are currently under investigation.
Interplay of microbial interaction and biofilm mechanics govern biofilm dynamics
Authors: Steinbach Gabi , Crisan Cristian , Ng Siu Lung , Hammer Brian , Yunker Peter
Published: July 2020

Biofilms are highly structured, densely packed bacterial consortia where many different species can coexist. During biofilm development and growth, the different species often form spatial distribution patterns that govern biofilm composition and function. In some cases, emerging structures have been explained as the result of social interactions between bacteria, e.g. cooperation and competition. Others emphasize the role of local mechanics, where spatial structuring arises from forces exerted between cells or between cells and their environment. Typically, these two lines of argumentation are treated separately. Here, we show that mechanics and social interactions can be strongly interrelated and their combination can crucially impact biofilm formation and dynamics. Using confocal microscopy and bacterial co-culture assays, we examine how bacterial antagonism impacts biofilm mechanics, and vice versa. We study competing Vibrio cholerae strains that kill on contact using the Type 6 secretion system. In case of mutual killers, i.e. two V. cholerae strains that can kill each other on contact, this social interaction leads to the formation of clonal domains of the competing strains (Mc Nally et al., Nat Commun, 2017). Intuitively, an unequal fight may enable a superior killer to invade and quickly eliminate a much weaker competitor. However, we observe that killer cells can coexist with killing-deficient target cells for very long times, and find that this results from the mechanical consequences of the deadly competition. Killing produces dead cells, which accumulates between domains of competing cells and prevents subsequent killing. Counterintuitively, our results suggest that antagonistic interactions stabilize coexistence in diverse communities. The findings demonstrate that the impact of social interactions in bacterial consortia is complex, requiring the understanding of the structural and the statistical-mechanical processes in biofilms.
The role of extracellular polymeric substances in biofilm community assembly and metabolic functions
Authors: Wu Yichao
Published: July 2020

Compared with the chemically defined synthetic wastewater (SynWW), real wastewater has been reported to exhibit distinct effects on microbial community development. Whether and how soluble microbial products in real wastewater contribute to different effects of synthetic and real wastewater on the fate of exogenous bacteria remains elusive. In this study, using a model wastewater bacterium Comamonas testosteroni, we first examined the influences of microfiltration filter-sterilized real wastewater (MF-WW) and SynWW on the retention of C. testosteroni in established wastewater flocs during bioaugmentation. In bioreactors fed with MF-WW, augmentation of C. testosteroni to wastewater flocs resulted in a substantially higher abundance of the augmented bacterial cells than those fed with SynWW. To identify the soluble microbial products in MF-WW contributing to the observed differences between bioaugmentation reactors fed with MF-WW and SynWW, we examined the effect of MF-WW and SynWW on the growth, floc formation, and biofilm development of C. testosteroni. When C. testosteroni grew in MF-WW, visible flocs formed within 2 h, which is in contrast to cell growth in SynWW where floc formation was not observed. We further demonstrated that the observed differences were mainly attributed to the high molecular weight fraction of the soluble extracellular polymeric substances (EPS) in MF-WW, in particular, proteins and extracellular DNA. The DLVO analysis suggested that, in the presence of soluble EPS, the bacterial cell surface exhibits an increased hydrophobicity and a diminished energy barrier, leading to irreversible attachment of planktonic cells and floc formation. The RNA-seq based transcriptional analysis revealed that, in the presence of soluble EPS, genes involved in nonessential metabolisms were downregulated while genes coding for Cco (cbb3- type) and Cox (aa3-type) oxidases with different oxygen affinities were upregulated, facilitating bacterial survival in flocs. Taken together, this study reveals the mechanisms underlying the contribution of soluble EPS to the recruitment of exogenous bacteria by microbial aggregates and provides implications to bioaugmentation.

 

References:

Wu, Y., Zaiden, N., Liu, X., Mukherjee, M. and Cao, B., 2020. Responses of Exogenous Bacteria to Soluble Extracellular Polymeric Substances in Wastewater: A Mechanistic Study and Implications on Bioaugmentation. Environmental Science & Technology. In press

Wu, Y., Cai, P., Jing, X., Niu, X., Ji, D., Ashry, N.M., Gao, C. and Huang, Q., 2019. Soil biofilm formation enhances microbial community diversity and metabolic activity. Environment international, 132, p.105116.
Blocking Vibrio cholerae-mediated hemagglutination with short peptide antagonists
Authors: Guo Shuaiqi , Lloyd Cameron , Kinrade Brett , Sherik Mustafa , Voets Ilja , Klose Karl , Davies Peter
Published: July 2020

Many bacteria use repeats-in-toxin (RTX) adhesins to mediate binding to host cells and facilitate subsequent colonisation and infection by forming biofilms. Vibrio cholerae, the causative agent of cholera, uses a 230-kDa RTX adhesin, FrhA, to facilitate intestinal colonization. FrhA also mediates hemagglutination of red-blood cells (erythrocytes). Here we have demonstrated that the hemagglutination capability of FrhA is localized to a ~ 20-kDa domain near its C terminus. Bioinformatic analyses indicated this erythrocyte-binding domain (VcEBD) is 65% identical to a peptide-binding module found in the 1.5-MDa ice-binding RTX adhesin that helps its Antarctic bacterium, Marinomonas primoryensis, form symbiotic biofilms with diatoms on the underside of sea ice. This suggested that the FrhA binds V. cholerae to proteins present on the cell surface of erythrocytes. X-ray crystallography revealed that VcEBD has an oblong β-sandwich fold with a shallow, Ca2+-dependent ligand-binding cavity that can anchor a peptidyl ligand with a free terminal carboxyl group. Using a structure-guided approach, we screened a small library of ~ 60 short peptides and optimized the affinity of VcEBD’s peptidyl ligands by roughly 1,000-fold. Importantly, the high-affinity ligands are effective at blocking V. cholerae from binding to erythrocytes at nano-molar concentrations. Structures of VcEBD in complex with three different peptides further elucidated the molecular basis for their interactions, which sets the stage for the development of ligand-based antagonists that may help disrupt V. cholerae interaction with intestinal cells to prevent or treat cholera. With the spread of antibiotic-resistant pathogenic bacteria, this work sheds light on an anti-adhesion approach for combating bacterial infections without the excessive use of antibiotics.
The SagS sensory protein modulates biofilm formation and c-di-GMP levels by Pseudomonas aeruginosa in response to glucose-6-phosphate.
Authors: Park Soyoung , Dingemans Jozef , Gowett Madison , Sauer Karin
Published: July 2020

In Pseudomonas aeruginosa, the orphan two-component sensor SagS contributes to both, the transition to biofilm formation and to biofilm cells gaining their heightened tolerance to antimicrobials. However, little is known about the identity of the signals or conditions sensed by SagS to induce the switch to the sessile, drug tolerant mode of growth. Using a modified Biolog phenotype assay to screen for compounds that modulate attachment in a SagS-dependent manner, we identified glucose-6-phosphate to enhance attachment in a manner dependent on the glucose-6-phosphate concentration and SagS. The stimulatory effect was not limited to the attachment as glucose-6-phosphate likewise enhanced biofilm formation. We show that exposure to glucose-6-phosphate results in decreased swarming motility but increased cellular c-di-GMP levels in biofilms. Genetic analysis indicated that the diguanylate cyclase NicD is an activator of biofilm formation and is not only required for enhanced biofilm formation in response to glucose-6-phosphate but also interacts with SagS. Our findings indicate glucose-6-phosphate to likely mimic a signal or conditions sensed by SagS to activate its motile-sessile switch function. Additionally, our findings provide new insight into the interfaces between the ligand-mediated TCS signaling pathway and c-di-GMP levels.
Biofilm Engineering Approaches for Improving the Performance of Bioelectrochemical Systems
Authors: Sani Rajesh
Published: July 2020

Biofilm Engineering Approaches for Improving the Performance of Bioelectrochemical Systems

 

ABSTRACT:

Bio-electrochemical devices are realized as promising technologies for a wide range of applications such bioenergy, and in biocommodity engineering.  Bioelectrochemical systems make use of electroactive biofilms as electrocatalysts for converting chemical energy to electrical energy and vice versa. In this presentation, surface engineering of electrodes (using biopolymers such as chitosan/alginate, nanomaterials such as reduced graphene oxide), extremophilic bioprocessing, and biofilm engineering strategies for enhancing the biofilm formation and performance of bio-electrochemical systems will be discussed. This talk will also cover the applications of biofilm for energy and environment.

 

Keywords: Electrochemical devices, Electrode materials, Bioelectricity, Biofilm Engineering, Biopolymers
Synthetic gene circuits for programmable Pseudomonas catalytic biofilms
Authors: Volke Daniel Christoph , Heuschkel Ingeborg , Bühler Katja , Nikel Pablo Iván
Published: July 2020

Nowadays, industrial fermentations rely almost entirely on the use of planktonic cells. However, biofilms (the most common form of bacterial growth in nature), offer several advantages to be exploited in modern fermentation processes. Bacteria in biofilms are more tolerant to several stresses than free cells, including toxic chemicals and shear stress. Furthermore, the adhesion of cells to surfaces can be exploited to operate a continuous fermentation process without excessive loss of biomass, thereby facilitating downstream processing. A programmable switch between planktonic and biofilm lifestyle is desirable to harness the advantages of both lifestyles. On this premise, we constructed a genetic gene circuit for biofilm formation in the platform strains Pseudomonas putida and Pseudomonas taiwanensis. Both P. putida and P. taiwanensis are robust, non-pathogenic soil bacteria and promising chassis for biotechnology as they can thrive under harsh operating conditions, displaying high tolerance towards several chemicals and can metabolize a broad range of substrates. These characteristics make them ideal for the production of a wide spectrum of chemicals. The synthetic circuit initiates biofilm formation upon detection of substrate or intermediate metabolites of the desired biotransformation, thus no additional inducer is needed. The circuit also allows for the propagation of cells in planktonic state prior employment in the bioreactor, which facilitates handling and speed up expansion of the culture. The design proposed herein employs a feedback-resistant diguanylate cyclase (DGC) from Caulobacter crescentus, which increases the concentration of DGC and therefore triggers biofilm formation. The resulting engineered strains were utilized for the biotransformation and degradation of chemicals (cyclohexanol) in continuous cultivation systems. This approach led to a ~300-fold increase in biofilm formation in microtiter plates, and was successfully used in diverse fermentation systems displaying increased catalytic efficiency.
Cellular L-arginine pools modulate c-di-GMP turnover and biofilm formation in Pseudomonas putida
Authors: Barrientos-Moreno Laura , Molina-Henares María Antonia , Ramos-González María Isabel , Espinosa-Urgel Manuel
Published: July 2020

The intracellular second messenger cyclic diguanylate (c-di-GMP) is broadly conserved in bacteria, where it influences processes such as virulence, stress resistance and biofilm development. In the plant-beneficial bacterium Pseudomonas putida KT2440, the response regulator with diguanylate cyclase activity CfcR is the main contributor to c-di-GMP levels in the stationary phase of growth. When overexpressed, CfcR increases c-di-GMP levels and gives rise to a pleiotropic phenotype that includes enhanced biofilm formation and crinkly colony morphology. Our group has previously reported that insertion mutants in argG and argH, the genes that encode the last two enzymes in the arginine biosynthesis pathway, do not display the crinkly colony morphology phenotype and show decreased c-di-GMP levels even in the presence of cfcR in multicopy (Ramos-González, M.I. et al. 2016. Front. Microbiol. 7, 1093). Here we present results indicating that L-arginine acts both as an environmental and as a metabolic signal that influences the lifestyles of P. putida through the modulation of c-di-GMP levels and changes in the expression of structural elements of biofilms. Exogenous L-arginine partially restores c-di-GMP levels in arginine biosynthesis mutants, a response that is transduced through CfcR and possibly (an)other diguanylate cyclase(s). At least three periplasmic binding proteins, each forming part of an amino acid transport system, contribute in different ways to the response to external L-arginine. We propose that the turnover of the second messenger c-di-GMP is modulated by the state of global arginine pools in the cell resulting both from anabolism and from uptake.
Use of enzymatic detergents to remove biofilms in food industries
Authors: Berga Mercè , Ylla Irene , Latorre Martirià
Published: July 2020

In the last decade concern about the presence of biofilms in food processing plants has increased. Biofilms in the environment of food processing plants represent a threat to food quality, safety and shelf-life. These biofilms can host pathogenic bacteria such as Listeria, Salmonella and Campylobacter, as well as spoilage microorganisms. Additionally, biofilms show some degree of resistance to conventional detergents and disinfectants that hinders their removal and favors re-growth. Therefore, there is a need for sanitizing products and protocols that are highly efficient at removing biofilms and suitable for food processing plants. Enzymatic detergents have recently been introduced as an alternative to conventional products against biofilms in food processing plants. These detergents contain one or more enzymes that disrupt the EPS of the biofilms, making the microorganisms present in the biofilm more vulnerable to disinfectants. Enzymatic detergents have been proofed to be more efficient in degrading biofilms than conventional detergents reducing both, EPS content and bacterial counts. Finally, higher efficiency on biofilm removal was observed after completing the entire sanitizing procedure (cleaning + disinfection) using an enzymatic detergent than a conventional detergent. These tests confirm the great potential of enzymatic detergents to remove biofilms.
Antibiofilm activity of Human Milk Oligosaccharides against pathogens isolated from cystic fibrosis patients
Authors: Jarzynka Sylwia , Strom Kamila , Makarewicz Oliwia , Minkiewicz-Zochniak Anna , Koryszewska-Baginska Anna , Oledzka Gabriela
Published: July 2020

Background: Human milk oligosaccharides (HMOs) are the third most abundant component of breast milk, after fat and lactose, that promote infant health. Recent studies have shown that HMOs demonstrated antimicrobial and antibiofilm activity against different strains. Cystic fibrosis (CF), it is one of the major respiratory diseases, the clinical management and definitive treatment of CF biofilm-mediated chronic bacterial lung infection remains a challenge.

Objective: In this study, we examine HMOs antibiofilm activity against pathogens isolated from CF patients.

Methods and results: In current work, we investigated the antibiofilm activity of the saccharide fraction obtained from pooled human milk of 9 donors against strains of: Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacteriaceae, Staphylococcus aureus and Burkholderia cenocepacia, an intrinsically multi-resistant pathogen associated with high mortality in CF patients. We tested the ability of HMOs to inhibit biofilm formation and to eradicate matured biofilms. Live/dead staining of the biofilms and CLSM image acquisition were used.

The pooled HMOs showed a biofilm eradicating effect on most tested pathogens. The HMOs effectively killed the bacteria at high concentration (20 mg/ml, corresponds to the concentration in human milk), but visible reduction of viable bacteria and biofilm mass was observed already at lower concentrations that varied between the species. The biofilm mass was also reduced in almost all pathogenic biofilms.

The data presented in this paper supporting the importance and potential inhibitory effect of HMOs in biofilm formation. HMOs could potentially be used as novel therapeutics to treat or prevent infectious disease in patient with CF.
Millimetric particles functionalized with biocide to improve biofouling control in RO system
Authors: Barros Ana C. , Pereira Ana , Melo Luís F.
Published: July 2020

Biofouling is responsible for more than 45% of all membrane fouling associated problems and is highly relevant for the performance of Reverse Osmosis systems (RO). Biofouling has a tremendous negative impact on the quality and quantity of permeate water and is responsible for high operational and maintenance costs associated with such systems. Current strategies targeting biofilm control on membrane systems often include the overuse of disinfectants which most of the time fail to effectively prevent biofouling build-up, can lead to the formation of dangerous disinfection by-products and represents high amounts of discharged biocides.

 

The present work aims to study how millimetric (1-3 mm length) alumina particles, functionalized with a well-known quaternary ammonium compound biocide (benzalkonium chloride) and immobilized into a Particle Biocide Bed Reactor can effectively contribute to mitigate biofilm formation in membrane systems. For that, the functionalized particles were chemically characterized, and their antimicrobial activity was assessed in batch and recirculation assays and quantified in terms of Culturability and Propidium Iodide (PI) uptake. Special attention has been given to biocides’s (free and immobilized) mechanism of action and potential biocide release was evaluated by High Performance Liquid Chromatography (HPLC) measurements.

 

The preliminary experiments indicate that the immobilized biocide (equivalent biocide concentration of 3 g/L) has an antimicrobial activity against Pseudomonas fluorescens (initial concentration 108 CFU/mL) by reducing 4 logs after 30 min and 8 logs after 1 h. On the other hand, the control assays (functionalized particles in water with no bacteria), also shows a biocide release between 0.8 and 1% to the bulk water after 30 min, both in batch and in the Particle Bed Reactor with recirculation experiments. No significant biocide increase is observed in the bulk liquid studies for two weeks. Nonetheless, some changes in the functionalization approach are being made to improve the biocidal anchoring to the particle.
Residual-chlorine concentration impacts the ecology of biofilms in drinking water pipes and their water quality response
Authors: Fish Katherine , Gaskin Paul , Boxall Joby
Published: July 2020

Drinking water distribution systems (DWDS) are an engineered system designed to protect water quality during delivery from treatment works to consumers’ taps. Biofilms form on the vast internal surfaces of DWDS, impacting water quality by their activity and/or mobilisation into the bulk-water. Disinfection-residuals are often maintained in drinking water to mitigate planktonic microbial contamination (and associated water quality/health risks). However, the impact of residual-disinfection upon biofilms, and the subsequent unintended risk they may present to water quality, is unclear.

To address this, an internationally-unique, temperature-controlled, full-scale DWDS test facility, fed with water from the local DWDS, was used to grow biofilms (for 28 days). The facility enables three simultaneous conditions to be run in replicate pipe loops (each ~200m long, 79mm internal diameter, PE100 pipe). Conditions studied were Low-, Medium- and High-chlorine regimes. Various water quality parameters were monitored throughout, biofilms were sampled every two weeks (n=5). Physical, chemical and molecular analyses were applied to characterise the matrix (structure and composition) and microbial communities (via analysis of bacterial 16S rRNA and fungal ITS genes) of biofilms developed under the different chlorine regimes. After growth, a “mobilisation” test was conducted simulating hydraulic changes that occur in DWDS. Biofilms from each chlorine regime were exposed to increasing shear stresses to determine any water quality degradation as a consequence of biofilm mobilisation.

High-chlorine residual concentration during development reduced biofilm bacterial concentrations but increased inorganics and selected for unique bacterial and fungal communities. Ultimately the biofilms developed under a High-chlorine residual resulted in the greatest decrease in water quality, in response to mobilisation, and the Low-chlorine regime resulted in biofilms which had the lowest impact on water quality. These unanticipated findings suggest chlorine-boosting should be considered carefully and may actually exacerbate water quality issues. The derived understanding could impact the long-term management of DWDS water quality and biofilm, whilst challenging the current mind-set of continuous residual-disinfection control strategies.
Increased biofilm in Shewanella oneidensis MR-1 leads to higher current generation in METs
Authors: V. Silva Ana , Edel Miriam , Gescher Johannes , M. Paquete Catarina
Published: July 2020

Biofilm formation is a central process in the function of Microbial Electrochemical Technologies (METs). These technologies have emerged in recent years as a promising alternative green source of energy, in which microbes consume organic matter to produce energy or valuable by-products. It is the ability of performing extracellular electron transfer that allows these microbes, called electroactive organisms, to exchange electrons with an electrode in these systems. The low levels of current achieved have been the set-back for the large-scale application of METs. Shewanella oneidensis MR-1 is one of the most studied electroactive organisms, and it has been demonstrated that its increased biofilm formation can lead to higher current generation. The bolA gene has been identified as a central player in biofilm formation in different organisms, with its overexpression leading to increased biofilm production. In this work, we explored the effect of this gene in biofilm formation and current production by S. oneidensis MR-1. Our results demonstrate that this gene is involved in the biofilm formation by this organism, with its over expression leading to an increased biofilm formation. We could also show that this increase in biofilm formation lead to a consequent higher current generation. This information is a relevant step for the optimization of electroactive organisms towards their practical application in METs.
Melt electro written three-dimensional scaffolds engineered as oral microcosm models-an in vitro study.
Authors: Ramachandra Srinivas , Abdal-hay Abdulla , Han Pingping , Lee Ryan , Ivanovski Saso
Published: July 2020

Introduction: Biofilms are 3-dimensional (3D) aggregates of microorganisms that are associated with a wide range of diseases. Although there have been several studies investigating biofilm formation on two-dimensional substrates, the use of 3D substrates may result in more representative and clinically relevant models. Accordingly, the aim of this study was to compare the growth of biofilms in the 3D substrates against biofilms grown in 2D substrates.
Material and Methods: Two grams of medical grade polycaprolactone (PCL) were loaded into a plastic Luer-lock 3 ml syringe and a 23G needle was used as a spinneret. The syringe was placed in a melt electro-writing (MEW) device to obtain fine fibers under controlled parameters. The 3-dimensional MEW PCL scaffolds were manufactured and characterised with an overall thickness of ~ 0.8 mm, with ~ 15 μm diameter fibers and ordered pore sizes of either 100 or 250 µm. PCL films employed as 2D substrates were manufactured by dissolving 10 gms of PCL in 100 ml chloroform and stirred for 3 h to obtain a transparent solution. Then, the solution was cast in glass petri dishes and dried to remove all organic solvents. In addition, commercial hydroxyapatite discs were also used as 2D controls. Unstimulated saliva from six healthy donors (gingival health) were used to grow biofilms. The formed biofilms were assessed at day 4, day 7 and day 10 using crystal violet assay, confocal microscopy, scanning electron microscopy and next-generation 16s sequencing.
Results: The results demonstrates that 3D PCL scaffolds dramatically enhanced biofilm biomass and thickness growth compared to that of the 2D controls. Confocal microscopy of biofilms at day 4 stained with SYTO 9 and propidium iodide showed thickness of biofilms in 2D substrates were 39 µm and 81µm for hydroxyapatite discs and PCL films, respectively. Biofilms in 3D substrates were 250 µm and 338 µm for MEW PCL 100µm pore size and MEW PCL 250 µm pore size, respectively. Similar results were noticed at day 7 and day 10. Scanning electron microscopy showed biofilm bridges formed over the fibers of the MEW scaffolds. Pilot trials of next generation sequencing detected similar taxa in biofilms formed in 3D scaffolds compared to that of 2D substrates.
Discussion: We have successfully investigated a 3D biofilm growth model using 3D medical grade PCL scaffolds. Thicker biofilms can be conveniently grown using this inexpensive static model. This will facilitate 3D microbial community studies that are more clinically relevant and improve our understanding of biofilm-associated disease processes.

 
Antibiofilm and antivirulence effect of stilbenes on clinically relevant staphylococci
Authors: Kašparová Petra , Maťátková Olga
Published: July 2020

Genus Staphylococcus comprises many greatly pathogenic species like S. aureus, S. epidermidis or S. saprophyticus. The great pathogenicity of stated species is often facilitated by their capability to form thick complex biofilms on various biotic or abiotic surfaces. Biofilm formation together with extracellular hydrolases or toxins represents important virulence factor, which increases persistence of staphylococci in host via enhancing their ability to evade host immune system and further promote the infection development. With an increased emergence of antibiotic resistance among pathogenic bacteria including staphylococci the search for novel antibiotic compounds with antivirulence effect is sought. Such substances might be stilbenes, phenolic compounds isolated from various plants (Vitis spp., Vaccinium spp., Pterocarpus spp., Pinus spp.). They possess strong antioxidant activity and a wide spectrum of beneficial pharmacological effects (antitumor, hypolipidemic, hypoglycemic). Apart from that, they also have great antimicrobial activity with a potent ability to enhance antibiotics action in combination.

Presented work focused on resveratrol, pterostilbene (PTE) and pinosylvine and their effect on S. aureus and S. epidermidis biofilm formation. The effect of stilbene representatives on production of other virulence factors (proteases, phospholipases, haemolysins), cell surface hydrophobicity and morphology was also observed.

PTE was found to be the most effective among studied stilbenes against S. aureus and S. epidermidis biofilm with minimum biofilm inhibitory concentrations (MBIC80) ranging from 40 to 130 mg/l. Its effect on mature staphylococcal biofilm eradication was even greater with 80% eradication rate achieved by 40-75 mg/l. PTE (49 mg/l) was found to have a potent combinatory antibiofilm activity with erythromycin or tetracycline (5 mg/l both) causing more than 80% inhibition in metabolic activity of biofilm cells. It was able to permeabilize cytoplasmic membrane, thus probably enabling antibiotic uptake by the cell. PTE also altered cell surface hydrophobicity and production of haemolysin.

PTE might be the solution to increasing biofilm-related resistance problem and a promising candidate with antibiofilm and antivirulence potential for future antibiotic treatment of staphylococcal infections.

 

This work was supported by the grant of Specific university research – grant No. A2_FPBT_2020_004.
The Impact of Shear Forces and Surface Hydrophobicity on Coccoid Cyanobacterial Biofilm Development
Authors: Faria Sara I. , Teixeira-Santos Rita , Romeu Maria J. , Morais João , Vasconcelos Vítor , Mergulhão Filipe J.
Published: July 2020

Biofouling is a natural process in marine environments with associated economic and ecological problems. Thus, understanding the conditions that affect cyanobacterial biofilm development is crucial to develop new antibiofouling strategies and decrease the impact of biofilms in the marine environment. In this study, we investigated the relative importance of shear forces and surface hydrophobicity on biofilm development by two coccoid cyanobacteria with different biofilm formation capacities. The strong biofilm-forming Synechocystis salina was used along with the weaker biofilm-forming Cyanobium sp. Biofilms were developed in defined hydrodynamic conditions using glass (a model hydrophilic surface) and a polymeric epoxy coating (a hydrophobic surface) as substrates. Biofilms developed in both surfaces at lower shear conditions contained a higher number of cells and presented higher values for wet weight, thickness, and chlorophyll a content. The impact of hydrodynamics on biofilm development was generally stronger than the impact of surface hydrophobicity, but a combined effect of these two parameters strongly affected biofilm formation for the weaker biofilm-producing organism. The antibiofilm performance of the polymeric coating was confirmed at the hydrodynamic conditions prevailing in ports. Shear forces were shown to have a profound impact on biofilm development in marine settings regardless of the fouling capacity of the existing flora and the hydrophobicity of the surface.