Biofilm Density Research Articles

Antibiofilm effect of Theobroma cacao (cacao pod) extract on Aggregatibacter actinomycetemcomitans biofilm in vitro

Successful of periodontal treatment is to eradicate biofilm of bacteria. Aggregatibacter actinomycetemcomitans is a Gram-negative bacterium that have been suggested to be the main causes of periodontal disease. Theobroma cacao (cacao pod) is a medicinal plant that has a broad range of pharmacological effects. The aim of this study was to assess the antibiofilm effect of cacao pod extract against A. actinomycetemcomitans biofilm in vitro. A. actinomycetemcomitans were cultured in Brain Heart Infusion broth. Crystal-violet staining in biofilm assays were used to evaluate the cacao pod extract effect on A. actinomycetemcomitans ATCC 33384 biofilms and 0.2% chlorhexidine-gluconate was used as a positive control. After 24 hours of incubation, the optical density of each well in microtiter plates was measured. The results showed that the biofilm density after incubation with the cacao pod extract was significantly decreased in all concentrations and all incubation times (p<0.05). The most effective concentration for inhibiting biofilm A. actinomycetemcomitans was 100% cacao pod extract and 3 hrs of incubation time (p<0.05) with a 98.9% reduction of biofilm compared to negative control. Cacao pod extract is effective in inhibiting the growth of A. actinomycetemcomitans biofilm.

Ability of Microorganisms, Causing Respiratory Infections in Children, to Form Biofilms in vitro

The purpose of the study was to detect ability to form biofilms by microorganisms that cause respiratory tract infections. Materials and methods. The study involved 97 strains of microorganisms. Microorganisms were isolated from children with respiratory tract infections. All strains, isolated from patients, were able to form biofilms. There were 44 strains of S. aureus (from patients with pneumonia – 13 strains, from patients with other respiratory diseases – 31), 34 strains of S. pneumoniae (pneumonia – 27 strains, other respiratory diseases – 7), 13 strains of K. pneumoniae (pneumonia – 6 strains, other respiratory diseases – 7), 6 strains of P. aeruginosa (pneumonia – 5 strains, other respiratory diseases – 1). Children were treated at the pulmonary department and intensive care unit in Kharkiv Regional Children's Clinical Hospital. Results and discussion. The optical density of primary biofilms formed by Gram-positive microorganisms was 1.33±0.24 Units of OD, and their secondary biofilms was 0.32±0.10 Units of OD. In patients with pneumonia optical density of primary biofilms of Gram-positive microorganisms was 1.48±0.21 Units of OD and of secondary biofilms was 0.30±0.08 Units of OD. Optical density of primary biofilms of Gram-positive microorganisms in patients with other respiratory infections was 1.18±0.15 Units of OD, of secondary biofilms was 0.35±0.12 Units of OD. The optical density of primary biofilms formed by Gram-negative microorganisms was 2.01±1.03 Units of OD, optical density of secondary biofilms was 1.06±0.42 Units of OD. In patients with pneumonia optical density of primary biofilms of Gram-negative microorganisms was 2.57±0.87 Units of OD, of secondary biofilms was 1.21±0.50 Units of OD. Optical density of primary biofilms of Gram-negative microorganisms in patients with other respiratory infections was 1.24±0.66 Units of OD, of secondary biofilms was 0.84±0.11 Units of OD. Conclusion. Gram-negative microorganisms in general formed more massive biofilms compared with Gram-positive microorganisms. Among all microorganisms P. aeruginosa formed the thickest primary and secondary biofilms. Strains of P. aeruginosa isolated from patients with pneumonia formed the thickest primary and secondary biofilms. Strains of S. aureus isolated from patients with other respiratory infections formed most massive primary biofilms, strains of K. pneumoniae formed the hardest secondary biofilms in this group

Simultaneous enhancement of nitrate removal flux and methane utilization efficiency in MBfR for aerobic methane oxidation coupled to denitrification by using an innovative scalable double-layer membrane

Endevours on the enhancement of nitrate removal efficiency during methane oxidation coupled with denitrification (AME-D) has always overlooked the role of membrane employed. It would be highly beneficial to enrich the biomass content and to manage biofilm on the membrane, in the utilization of methane and denitrification. In this study, an innovative and scalable double-layer membrane (DLM) was designed and prepared for a membrane biofilm reactor (MBfR), to simultaneously enhance nitrate removal flux and methane utilization efficiency during aerobic methane oxidation coupled with the denitrification (AME-D) process. The DLM allowed quick bacterial attachment and biomass accumulation for biofilm growth, which would be then self-regulated for well distribution of functional microbes on/within the DLM. Upon a high biofilm density of over 70 g-VSS m−2 achieved on the DLM, the methane utilization efficiency of the MBfR was enhanced significantly to over 1.3 times than the control MBfR with conventional polypropylene membrane. The MBfR employed DLM also demonstrated the maximum nitrate removal flux of 740 mg-NO3−-N m−2 d−1 that was approximately 1.64 times of that in control MBfR at continuous-mode operation. This DLM indeed favored the enrichment of Type II aerobic methanotrophs of Methylocystaceae, and methanol-utilization denitrifiers of Rhodocyclaceae that preferentially utilize methanol as the cross-feeding intermediates to promote the methane utilization efficiency, and thus to enhance the nitrate removal flux. These results raised from new designed DLM confirmed the importance of membrane surface properties on the effectiveness of MBfR, and offered great potential to address challenging problems of MBfRs during engineering application.

Autoinducer-2 Could Affect Biofilm Formation by Food-Derived Bacillus cereus.

Bacillus cereus is a foodborne pathogen and cause a frequent problem due to the biofilms forming in equipment of food production plants. Autoinducer-2 (AI-2) involved in interspecies communication, plays a role in the biofilm formation of B. cereus. In this study, biofilm formation by thirty-nine B. cereus strains isolated from foods produced in Korea was determined. To investigate the effect of AI-2 on biofilm formation by B. cereus SBC27, which had the highest biofilm-forming ability, biofilm densities formed after addition of the AI-2 from Staphylococcus aureus and Escherichia coli were analysed. As a result, it was found that the quorum sensing molecule AI-2 could induce biofilm formation by B. cereus within 24h, but it may also inhibit biofilm formation when more AI-2 is added after 24h. Thus, these results improve our understanding of biofilm formation by food-derived B. cereus and provide clues that could help to reduce the impact of biofilms, the biggest problem in food processing environments, which has an impact on public health as well as the economy.

Translocation of Epipelic Biofilms and Their Short-Term Responses to Urbanization Impacts in Nutrient Rich Streams.

Stream biofilms are among the first to react to environmental degradation, since their structural and functional characteristics are tightly linked to the physicochemical variables in the water and sediment. The objectives of this research were to study the differences in chlorophyll-a, bacterial density and metabolism endpoints of epipelic biofilms in nutrient-rich streams under different physical-chemical conditions in the stream water in relation to changes in urbanization, and to measure the short-term responses (up to 72 h) in the biofilm when translocated to more urbanized sites. For these purposes, chlorophyll-a, bacterial density, biofilm respiration (electron transfer activity) and O2 consumption were measured in epipelic biofilms in nutrient-rich streams exposed to different levels of urbanization after a 30 day colonization. Afterward, biofilms were translocated downstream to more polluted sites, and sampled to identify any fast occurring changes to be considered as potential indicators of environmental degradation. Results show that in the nutrient-rich streams studied, the structural characteristics of the biofilm were linked to urbanization, and even after a short time following the translocation, chlorophyll-a and bacterial density varied, reflecting the environmental degradation. On the other hand, metabolic variables were highly variable and produced inconsistent results when representing an increase in urbanization.

In-vitro Antibacterial and Antibiofilm Activity of Cinnamomum verum Leaf Oil against Pseudomonas aeruginosa, Staphylococcus aureus and Klebsiella pneumoniae.

Phytomedicines are becoming more popular in treatment of infectious diseases worldwide. Cinnamomum verum essential oil (EO) has been used as a therapeutic alternative for various diseases. This study aimed to evaluate the antibacterial and antibiofilm activity of the C. verum leaf EO against Pseudomonas aeruginosa, Staphylococcus aureus and Klebsiella pneumoniae. Effect of EO vapor on planktonic cells was determined using microatmosphere technique. CLSI M7-A10 method was employed in Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) experiments. Effect of EO on established biofilms was quantified and visualized using XTT and Scanning Electron Microscope (SEM). In-vitro toxicity was evaluated using Human Keratinocytes (HaCaT). Chemical analysis of EO was done using Gas Chromatography- Mass Spectrometry (GC-MS). All tested strains were sensitive to cinnamon oil vapor. EO exhibited 0.5 and 1.0 mg/mL MIC and MBC against all test strains. Minimum Biofilm Inhibitory and Biofilm Eradication Concentrations (MBIC50 and MBEC) were 1.0 and 4.0 mg/mL. SEM indicated cellular shrinkages, cell wall damages, and decreased biofilm densities. Cinnamon oil didn't show any toxicity on HaCaT cell at any concentration tested. Eugenol was the most abundant compound in C. verum oil. C. verum EO shows an antibacterial and antibiofilm activity with minimal toxicity on host.

El rol de los bañados de desborde fluvial en la retención de nutrientes y su actividad metabólica

El objetivo de este trabajo fue analizar los efectos de los bañados de desborde fluvial sobre la calidad del agua y el metabolismo del curso de agua. Para ello se estudiaron cuatro cauces, dos que recorren la periferia de un casco urbano y que tienen zonas de bañados de desborde fluvial conservados, y que mantienen su conexión con el agua subterránea, y otros dos periurbanos y que sus bañados de desborde fluvial han sido degradados por el avance de la urbanización, desconectándolos de las capas freáticas. En cada uno, se muestrearon tres tramos de 50 metros de longitud. El primero, localizado aguas arriba de la zona de bañados (llamado “Arriba”), el segundo en el tramo medio del curso de agua que recorre el bañado (llamado “Medio”), y el último aguas abajo del bañado (llamado “Abajo”). Las variables estudiadas incluyeron, en cuatro períodos del año y en cada tramo, parámetros físico-químicos (temperatura, conductividad, pH, oxígeno disuelto, turbidez, sólidos disueltos y suspendidos, concentraciones de formas del nitrógeno y fósforo disuelto y total) y biológicos, vinculados a la actividad metabólica del biofilm y a la densidad de bacterias. Además, en dos momentos del año, se realizaron ensayos de retención de nutrientes y metabolismo fluvial en los tramos medios de los cursos fluviales. Los resultados muestran que los bañados de desborde fluvial mejor conservados a) disminuyen significativamente el oxígeno disuelto y aumentan la concentración de sólidos suspendidos en el cauce; b) incrementan significativamente los procesos metabólicos fluviales, tales como la respiración o la producción primaria; c) poseen tasas elevadas de asimilación de nutrientes por la biota; d) actúan como depuradores de bacterias coliformes en el cauce principal. Estos patrones generales pueden ser detectados aunque se observa mucha variabilidad en los cauces, y su intensidad varía a lo largo del año y en función de las condiciones físico-químicas del flujo.

Combined Addition of Ethanol and Ethylenediaminetetraacetic Acid Enhances Antibacterial and Antibiofilm Effects in Methylene Blue-Mediated Photodynamic Treatment against Pseudomonas aeruginosa In Vitro.

Antimicrobial photodynamic treatment (aPDT) for infection with drug-resistant bacteria has received much attention. For P.aeruginosa, however, efficient formation of biofilms and the nature of Gram-negative bacteria often limit the efficacy of aPDT. In this study, we investigated the effects of ethanol and ethylenediaminetetraacetic acid (EDTA) as additives on bacterial viability, biofilm biomass, and structures of bacteria and biofilms in methylene blue (MB)-mediated aPDT in vitro. Matured P.aeruginosa biofilms were incubated with 32-µm MB solutions with different concentrations of additives and then illuminated with 665-nm light from an LED array. The combined addition of 10% ethanol and 10mm EDTA to MB resulted in significantly greater bactericidal effects than those of MB alone and of MB with 10% ethanol or 10mm EDTA. Crystal violet assays showed significant reductions in biofilm biomass by aPDT with addition of both ethanol and EDTA compared to that in the case of aPDT with MB alone. Scanning electron microscopy showed broken bacterial cells and reduction in the cell density and amount of biofilm under those conditions. Ethanol addition alone did not improve aPDT efficacy. Reduced amount of biofilm by EDTA addition would have improved the transportation of MB and ethanol to bacteria.

Enhancing CO2 photo-biochemical conversion in a newly-designed attached photobioreactor characterized by stacked horizontal planar waveguide modules

Aiming at alleviating the adverse effects on attached microalgae biofilm growth caused by heterogeneous spatial light distributions within the attached cultivation photobioreactors (PBRs), an innovative PBR integrated with stacked horizontal planar waveguide modules (SHPW-PBR) was proposed in this work. Different from the conventional PBR, the emergent light from the external LED light bars were guided and evenly redistributed within the SHPW-PBR by the planar waveguides and hence provided light energy for microalgae cells photoautotrophic growth. In comparison with the control PBR, the average light intensity illuminating the attached Chlorella vulgaris biofilm in the SHPW-PBR was elevated by 204.11% and contributed to a 145.20% improvement on areal C. vulgaris biofilm production. Thereafter, responses of attached C. vulgaris biofilm growth in the SHPW-PBR to various light intensities were evaluated and the maximum areal C. vulgaris biofilm density reached 90.43 g m−2 under the light intensity of 136 μmol m−2 s−1 after 9 days cultivation. Furthermore, the SHPW-PBR can be easily scaled-up by increasing the quantity of the stacked planar waveguide modules and thus shows great potential in biofilm-based biomass production.

Antimicrobial Substance Produced by Pseudomonas aeruginosa Isolated from Slaughterhouse Sediment: Physicochemical Characterization, Purification, and Identification

This study aimed to produce the novel bacteriocin from Pseudomonas aeruginosa 43. The bacteriocin was purified through 80% ammonium sulfate precipitation, cation exchange chromatography, and gel filtration, and the specific antimicrobial activity was 400 AU/ml of protein. The molecular weight of purified bacteriocin was 10 kDa determined by SDS-PAGE. It was shown to be heat stable at 121 °C for 30 min and functioned well at low pH in a range of 3–7. Reduction of activity was shown after treatment with proteinase K, trypsin, papain, and α-amylase that confirmed its proteinaceous nature. Bacteriocin also showed its stability against various organic solvents and chemical reagents. Scanning electron microscope analysis indicated that bacteriocin from P. aeruginosa 43 damaged the morphology of methicillin-resistant Staphylococcus aureus (MRSA). Also, the novel bacteriocin exhibited an enhanced ability to impair biofilm formation and to reduce the density of established biofilms. LC–MS analysis study showed elastase is a novel peptide produced by P. aeruginosa 43 which has broad spectrum of inhibition against MRSA. The study suggested that bacteriocin from P. aeruginosa 43 could be developed as a antimicrobial agent for skin infection.

Inhibitory Potential of Mangiferin on Glucansucrase Producing Streptococcus mutans Biofilm in Dental Plaque

Glucansucrase secreted by Streptococcus mutans and composed of virulence genes alters oral microbiota, creating adherent environment for structural bacteria colony forming dental biofilm. The present investigation studied the inhibitory and binding potentials of mangiferin against S. mutans and its enzyme glucansucrase implicated in biofilm formation. Antibacterial activity against planktonic S. mutans was carried out. Using reverse transcription PCR, the expression of crucial virulence genes, gtfB, gtfC, gtfD, gbpB, and comDE were determined. The effect of mangiferin on teeth surfaces biofilm was ascertained by scanning electron microscopy (SEM). Docking analysis of S. mutans glucansucrase and mangiferin revealed the binding energy of −7.35 and ten hydrogen interactions. Antibacterial study revealed that mangiferin was not lethal to planktonic S. mutans, but a concentration-dependent inhibition of glucansucrase activity was observed. The inhibitory effect of water-insoluble glucan synthesis was apparently more marked relative to water-soluble glucan synthesis attenuation. Mangiferin significantly downregulated the expression of the virulence genes, indicating a mechanism involving glucanotranferases, specifically inhibiting colony formation by attenuating bacterial adherence. SEM images revealed that S. mutans biofilm density was scanty in mangiferin treated teeth compared to non-treated control teeth. Our data therefore suggest that mangiferin inhibited S. mutans biofilms formation by attenuating glucansucrase activities without affecting bacteria growth.

Diffusion profiles in L. lactis biofilms under different conditions.

Despite being an important topic in biofilm research, we still know little about diffusion in biofilms. Emerging biofilms of Lactococcus lactis growing in custom‐made flow‐cells were monitored and diffusion constants across the height of the biofilms recorded. The biofilms showed different diffusional behavior with regard to flow rate and pH variations, despite growing to similar thickness. At a higher flow rate, the biofilm exhibits slower diffusion compared to the reference cultivation at lower flow rate. By increasing pH, the biofilm exhibited fast growth and little difference in diffusion compared to the reference cultivation. Furthermore, the diffusion inside of the biofilms differed depending on the position in the flow‐cell. The present study reveals new insights in how external factors can affect structure and density of biofilms. The method can be reliably used for L. lactis biofilms with a thickness up to 120 μm.

The effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms in river ecosystems.

Biofilms were cultivated for a 68-day period under different hydrodynamic conditions, and the effect of hydrodynamics on the succession of autotrophic and heterotrophic organisms of biofilms was investigated. Five obvious stages were observed during biofilm formation. At Stage I, the attachment of algae was delayed, especially under turbulent conditions. After Stage II, algal density and heterotrophic biomass of biofilms increased, which were obvious under turbulent flow. Therefore, the algal density and heterotrophic biomass of biofilms were largest under turbulent condition, followed by laminar condition, and then transitional condition. Diatoms were dominant in all flumes and were most abundant under turbulent conditions. The proportion of cyanobacteria was highest under laminar conditions. The ratio of aerobic to anaerobic bacteria decreased and their co-existence could facilitate the nitrification and denitrification in the biofilm. The ratio of monounsaturated fatty acids to saturated fatty acids was highest under turbulent conditions on the 15th day. While the ratio was highest under laminar condition on the 48th day, the high ratio indicates the high ability of biofilm to obtain nutrients, which affect the growth of algae. The regulation of hydrodynamics is a useful technology which can affect the growth of the microorganisms of biofilm, and further improve water quality.

Vibrio cholerae adapts to sessile and motile lifestyles by cyclic di-GMP regulation of cell shape

The cell morphology of rod-shaped bacteria is determined by the rigid net of peptidoglycan forming the cell wall. Alterations to the rod shape, such as the curved rod, occur through manipulating the process of cell wall synthesis. The human pathogen Vibrio cholerae typically exists as a curved rod, but straight rods have been observed under certain conditions. While this appears to be a regulated process, the regulatory pathways controlling cell shape transitions in V. cholerae and the benefits of switching between rod and curved shape have not been determined. We demonstrate that cell shape in V. cholerae is regulated by the bacterial second messenger cyclic dimeric guanosine monophosphate (c-di-GMP) by posttranscriptionally repressing expression of crvA, a gene encoding an intermediate filament-like protein necessary for curvature formation in V. cholerae. This regulation is mediated by the transcriptional cascade that also induces production of biofilm matrix components, indicating that cell shape is coregulated with V. cholerae's induction of sessility. During microcolony formation, wild-type V. cholerae cells tended to exist as straight rods, while genetically engineering cells to maintain high curvature reduced microcolony formation and biofilm density. Conversely, straight V. cholerae mutants have reduced swimming speed when using flagellar motility in liquid. Our results demonstrate regulation of cell shape in bacteria is a mechanism to increase fitness in planktonic and biofilm lifestyles.

Biofilm and microbiome response of attached growth nitrification systems across incremental decreases to low temperatures

The study investigates low temperature attached growth rates and nitrifying biofilm, biomass, and microbiome responses down to 1 °C. Two moving bed biofilm reactors (MBBR) were acclimatized from 10 °C to 1 °C by incremental decreases in temperatures. A non-linear decline in nitrification with decreasing temperatures was recorded with a kinetic threshold temperature delineated between 4 °C and 2 °C, at which a significant decline in efficiency of 22.47% occurred. An increase in biofilm thickness of 25.47% occurs between 10 °C and 4 °C, followed by lesser increases of 6.55% and 9.60% at 2 °C and 1 °C. Biofilm density decreases between 10 °C and 1 °C. An increase in embedded viable cells of 24.01% occurs between 10 °C and 4 °C, followed by lesser non-statistically relevant increases at 2 °C and 1 °C. No statistically significant change in the number of estimated species is observed; however, β-diversity analysis indicates greater microbial community shifts above the kinetic threshold followed by lesser shifts between 2 °C and 1 °C. Nitrosomanadacea and Nitrosopira are the ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) families in the biofilm with relative abundances of 3.43 ± 0.51% and 0.94 ± 0.44% respectively at 10 °C. A change in NOB relative abundance occurred between the temperatures of 10 °C and 1 °C, decreasing to 0.19 ± 0.10% above the kinetic threshold. The estimation of nitrifiers per carrier in the bioreactors, based on biofilm thickness, biomass viability and relative abundances shows an increase of 30.2% in AOB/carrier above the kinetic threshold temperature (> 4 °C) followed by lesser increases down to 1 °C.

Parameters influencing the development of highly conductive and efficient biofilm during microbial electrosynthesis: the importance of applied potential and inorganic carbon source

Cathode-driven applications of bio-electrochemical systems (BESs) have the potential to transform CO2 into value-added chemicals using microorganisms. However, their commercialisation is limited as biocathodes in BESs are characterised by slow start-up and low efficiency. Understanding biosynthesis pathways, electron transfer mechanisms and the effect of operational variables on microbial electrosynthesis (MES) is of fundamental importance to advance these applications of a system that has the capacity to convert CO2 to organics and is potentially sustainable. In this work, we demonstrate that cathodic potential and inorganic carbon source are keys for the development of a dense and conductive biofilm that ensures high efficiency in the overall system. Applying the cathodic potential of −1.0 V vs. Ag/AgCl and providing only gaseous CO2 in our system, a dense biofilm dominated by Acetobacterium (ca. 50% of biofilm) was formed. The superior biofilm density was significantly correlated with a higher production yield of organic chemicals, particularly acetate. Together, a significant decrease in the H2 evolution overpotential (by 200 mV) and abundant nifH genes within the biofilm were observed. This can only be mechanistically explained if intracellular hydrogen production with direct electron uptake from the cathode via nitrogenase within bacterial cells is occurring in addition to the commonly observed extracellular H2 production. Indeed, the enzymatic activity within the biofilm accelerated the electron transfer. This was evidenced by an increase in the coulombic efficiency (ca. 69%) and a 10-fold decrease in the charge transfer resistance. This is the first report of such a significant decrease in the charge resistance via the development of a highly conductive biofilm during MES. The results highlight the fundamental importance of maintaining a highly active autotrophic Acetobacterium population through feeding CO2 in gaseous form, which its dominance in the biocathode leads to a higher efficiency of the system.

Exopolysaccharide related gene bcsG affects biofilm formation of Cronobacter spp.

Cronobacter spp. is a conditioned pathogen found mainly in milk powder; it can seriously harm infant health. We investigated biofilm formation in eight strains of Cronobacter spp. and found that DSM 18707 had the strongest capacity to form biofilm. Biofilm-related genes bcsA, bcsG, flgJ, and flhE were selected for qRT-PCR detection. Expression of bcsG in Cronobacter spp. was associated with the ability to form biofilm. Knockout of bcsG in DSM 18707 was associated with markedly reduced biofilm formation and exopolysaccharide content relative to the wild type. Moreover, fluorescence microscopy revealed that the knockout mutants had comparatively lower biofilm density. In the knockout mutants, bcsA, flgJ, and flhE were up-regulated in the first three days but down-regulated by days 4 and 5. Hence, the expression levels of bacterial biofilm-related genes may change with biofilm production; moreover, bcsG positively regulates the formation of exopolysaccharides and biofilm in Cronobacter spp.

Effect of Glucose Induction on Biofilm Density in Clinical Isolate Acinetobacter baumannii Patients in Intensive Care Unit of Dr. Soetomo Hospital, Surabaya

This study aimed to analyze the effect of glucose induction on the clinical isolate biofilm density of Acinetobacter baumannii. Thirteen clinical isolates of A. baumannii non biofilm forming were collected from non-DM patients who were treated at the ICU of Dr. Soetomo Hospital, Surabaya, was treated with the addition of 0.08% glucose, 0.15% glucose, 0.2% glucose, and 0.4% glucose in TSB growth media, followed by biofilm density examination with Tissue Culture Plate Method (TCPM) using 96 wells flatbottomed polyesterene tissue culture plate and read by autoreader ELISA with a wavelength of 630 nm (OD630). Biofilm density obtained was analyzed using ANOVA statistical analysis. The results of OD630 showed that the biofilm density increased significantly at the addition of 0.2% and 0.4% glucose. There was a significant increase in biofilm density at the addition of 0.2% and 0.4% glucose so that the management of blood sugar levels in ICU patients was needed before and when medical devices were installed.

Impact of solid surface hydrophobicity and micrococcal nuclease production on Staphylococcus aureus Newman biofilms

Staphylococcus aureus is commonly associated with biofilm-related infections and contributes to the large financial loss that accompany nosocomial infections. The micrococcal nuclease Nuc1 enzyme limits biofilm formation via cleavage of eDNA, a structural component of the biofilm matrix. Solid surface hydrophobicity influences bacterial adhesion forces and may as well influence eDNA production. Therefore, it is hypothesized that the impact of Nuc1 activity is dependent on surface characteristics of solid surfaces. For this reason, this study investigated the influence of solid surface hydrophobicity on S. aureus Newman biofilms where Nuc1 is constitutively produced. To this end, biofilms of both a wild-type and a nuc1 knockout mutant strain, grown on glass, salinized glass and Pluronic F-127-coated silanized glass were analysed. Results indicated that biofilms can grow in the presence of Nuc1 activity. Also, Nuc1 and solid surface hydrophobicity significantly affected the biofilm 3D-architecture. In particular, biofilm densities of the wild-type strain on hydrophilic surfaces appeared higher than of the mutant nuc1 knockout strain. Since virulence is related to bacterial cell densities, this suggests that the virulence of S. aureus Newman biofilms is increased by its nuclease production in particular on a hydrophilic surface.

Promoting electricity generation of shewanella putrefaciens in a microbial fuel cell by modification of porous poly(3-aminophenylboronic acid) film on carbon anode

We report here that the electricity generation of Shewanella putrefaciens in a microbial fuel cell (MFC) can be greatly boosted by modification of a porous poly(3-aminophenylboronic acid) (p-PAPBA) film on carbon cloth (CC) anode. The p-PAPBA/CC electrode was prepared by electropolymerization of 3-aminophenylboronic acid on SiO2 nanoparticles modified CC electrode, followed by HF leaching. The boronic acid-saccharide interactions between p-PAPBA film and bacterial cell surfaces enabled rapid biofilm growth and increased biofilm density, and the porous structure of p-PAPBA film facilitated the mediated extracellular electron transfer of Shewanella putrefaciens via self-secreted flavins, all of which resulted in promoted electricity generation of Shewanella putrefaciens in the MFC. A maximal power density of 928 ± 20 mW m−2 was generated by the MFC using the p-PAPBA/CC anode, which was 4.4-fold that of the MFC using the CC anode. This study provides a promising way to promote the electricity generation of Shewanella putrefaciens in MFCs by making full use of the boronic acid-saccharide interactions.