Evolution of Biofilm and Its Effect on Microstructure of Mortar Surfaces in Simulated Seawater

To explore the role of biofilm formation on the corrosion of marine concrete structures, we investigated the attachment of biofilm on mortar surfaces in simulated seawater and the influence of biofilm on the microstructure of mortar surfaces. The results show that the evolution of biofilm on mortar surfaces in simulated seawater is closely related to the corrosion suffered by the mortar, and the process of biofilm attachment and shedding is continuous and cyclical. It is found that the specimens in the absence of biofilm attachment are more severely eroded internally by the corrosive medium in simulated seawater than those in the presence of biofilm attachment. For the specimens without biofilm attachment, after 60 days, gypsum forms,and after 120 days, the number of pores in the mortar is reduced. In contrast, for the specimens in the presence of biofilm attachment, gypsum could only be detected after 90 days, and fewer pores are filled. Therefore, the formation of biofilm could delay the invasion of the corrosive medium into the interior of mortar during the evolution of biofilm on mortar surfaces, mitigating the corrosion of mortars in seawater.

Anti-biofilm and anti-virulence potential of cell free supernatant of Akkermansia muciniphila against Salmonella

Akkermansia muciniphila is one of the commensals residing within the mammalian gut and co-evolving with the host.Numerous studies have demonstrated the benefits of A.muciniphila in ameliorating metabolic disorders,while little is known about the antimicrobial potential of A.muciniphila against pathogens.Here,we examined the antimicrobial and anti-virulence properties of cell free supernatant(CFS)of A.muciniphila against Salmonella Typhimurium.CFS retarded bacterial growth and inhibited the motility of S.Typhimurium SL1344 and S.Typhimurium 14028.CFS dose-dependently reduced cell hydrophobicity and auto-aggregation of both strains.Also,CFS from A.muciniphila significantly attenuated biofilm formation.Compared with untreated bacteria,CFS-treated bacteria significantly decreased adhesion and invasion to Caco-2 cells,and reduced intracellular survival in macrophages.CFS maintained antimicrobial properties after treatment with high temperatures and various proteases,while it lost its antimicrobial activity after pH neutralization.Gas chromatography-mass spectrometry(GC-MS)confirmed that A.muciniphila produced a certain amount of acetate and propionate,and ultra-high-performance liquid chromatography-mass spectrometry(UHPLCMS)identified other organic acids and metabolites in CFS.In summary,CFS from A.muciniphila exhibited anti-biofilm and anti-virulence properties against Salmonella and could be potentially utilized in the food industry for controlling Salmonella contamination and reducing infection.

Staphylococcus aureus and biofilms:transmission, threats, and promising strategies in animal husbandry

Staphylococcus aureus(S. aureus) is a common pathogenic bacterium in animal husbandry that can cause diseases such as mastitis, skin infections, arthritis, and other ailments. The formation of biofilms threatens and exacerbates S. aureus infection by allowing the bacteria to adhere to pathological areas and livestock product surfaces, thus triggering animal health crises and safety issues with livestock products. To solve this problem, in this review, we provide a brief overview of the harm caused by S. aureus and its biofilms on livestock and animal byproducts(meat and dairy products). We also describe the ways in which S. aureus spreads in animals and the threats it poses to the livestock industry. The processes and molecular mechanisms involved in biofilm formation are then explained. Finally, we discuss strategies for the removal and eradication of S. aureus and biofilms in animal husbandry, including the use of antimicrobial peptides, plant extracts, nanoparticles, phages, and antibodies. These strategies to reduce the spread of S. aureus in animal husbandry help maintain livestock health and improve productivity to ensure the ecologically sustainable development of animal husbandry and the safety of livestock products.

Charge adaptive phytochemical-based nanoparticles for eradication of methicillin-resistant staphylococcus aureus biofilms

The intrinsic resistance of MRSA coupled with biofilm antibiotic tolerance challenges the antibiotic treatment of MRSA biofilm infections.Phytochemical-based nanoplatform is a promising emerging approach for treatment of biofilm infection.However,their therapeutic efficacy was restricted by the low drug loading capacity and lack of selectivity.Herein,we constructed a surface charge adaptive phytochemical-based nanoparticle with high isoliquiritigenin(ISL)loading content for effective treatment of MRSA biofilm.A dimeric ISL prodrug(ISL-G2)bearing a lipase responsive ester bond was synthesized,and then encapsulated into the amphiphilic quaternized oligochitosan.The obtained ISL-G2loaded NPs possessed positively charged surface,which allowed cis-aconityl-D-tyrosine(CA-Tyr)binding via electrostatic interaction to obtain ISL-G2@TMDCOS-Tyr NPs.The NPs maintained their negatively charged surface,thus prolonging the blood circulation time.In response to low pH in the biofilms,the fast removal of CA-Tyr led to a shift in their surface charge from negative to positive,which enhanced the accumulation and penetration of NPs in the biofilms.Sequentially,the pH-triggered release of D-tyrosine dispersed the biofilm and lipase-triggered released of ISL effectively kill biofilm MRSA.An in vivo study was performed on a MRSA biofilm infected wound model.This phytochemical-based system led to~2log CFU(>99%)reduction of biofilm MRSA as compared to untreated wound(P<0.001)with negligible biotoxicity in mice.This phytochemical dimer nanoplatform shows great potential for long-term treatment of resistant bacterial infections.

Structural insights on anti-biofilm mechanism of heated slightly acidic electrolyzed water technology against multi-resistant Staphylococcus aureus biofilm on food contact surface

Slightly acidic electrolyzed water(SAEW)has proven to be an efficient and novel sanitizer in food and agriculture field.This study assessed the efficacy of SAEW(30 mg/L)at 40℃on the inactivation of foodbome pathogens and detachment of multi-resistant Staphylococcus aureus(MRSA)biofilm.Furthermore.the underlying mechanism of MRS A biofilm under heated SAEW at 40℃treatment on metabolic profiles was investigated.The results showed that the heated SAEW at 40℃significantly effectively against foodbome pathogens of 1.96-7.56(lg(CFU/g))reduction in pork,chicken,spinach,and lettuce.The heated SAEW at 40℃treatment significantly reduced MRS A biofilm cells by 2.41(lg(CFU/cm^(2))).The synergistic effect of SAEW treatment showed intense anti-biofilm activity in decreasing cell density and impairing biofilm cell membranes.Global metabolic response of MRSA biofilms,treated by SAEW at 40℃,revealed the alterations of intracellular metabolites,including amino acids,organic acid,fatty acid,and lipid.Moreover,signaling pathways involved in amino acid metabolism,energy metabolism,nucleotide synthesis,carbohydrate metabolites,and lipid biosynthesis were functionally disrupted by the SAEW at 40℃treatment.As per our knowledge,this is the first research to uncover the potential mechanism of heated SAEW treatment against MRSA biofilm on food contact surface.

The biofilm characteristics and enhanced performance of a marine microbial-electrolysis-cell-based biosensor under positive anodic potential

Microbial fuel cells have already been used as biosensors to monitor assimilable organic carbon(AOC).However,their signal production from AOC is known to be completely suppressed by dissoved oxygen(DO).In this study,two identical microbial electrolysis cell(MEC)based biosensors were inoculated with marine sediment and operated at two different anodic potentials,namely-300 mV and+250 mV relative to Ag/AgCl.The MEC biosensor operated under positive anodic potential conditions had electrochemically active microbial communities on the anode,including members of the Shewanellaceae,Pseudoalteromonadaceae,and Clostridiaceae families.However,the strictly anaerobic members of the Desulfuromonadaceae,Desulfobulbaceae and Desulfobacteraceae families were found only in the negative anodic potential MEC biosensor.The positive anodic potential MEC biosensor showed several other advantages as well,such as faster start-up,significantly higher maximum current production,fivefold improvement in the AOC detection limit,and tolerance of low dissolved oxygen,compared to those obtained from the negative anodic potential MEC biosensor.The developed positive anodic potential MEC biosensor can thus be used as a real-time and inexpensive detector of AOC concentrations in high saline and low DO seawater.

Contemporary strategies and approaches for characterizing composition and enhancing biofilm penetration targeting bacterial extracellular polymeric substances

Extracellular polymeric substances(EPS)constitutes crucial elements within bacterial biofilms,facili-tating accelerated antimicrobial resistance and conferring defense against the host's immune cells.Developing precise and effective antibiofilm approaches and strategies,tailored to the specific charac-teristics of EPS composition,can offer valuable insights for the creation of novel antimicrobial drugs.This,in turn,holds the potential to mitigate the alarming issue of bacterial drug resistance.Current analysis of EPS compositions relies heavily on colorimetric approaches with a significant bias,which is likely due to the selection of a standard compound and the cross-interference of various EPS compounds.Considering the pivotal role of EPS in biofilm functionality,it is imperative for EPS research to delve deeper into the analysis of intricate compositions,moving beyond the current focus on polymeric materials.This ne-cessitates a shift from heavy reliance on colorimetric analytic methods to more comprehensive and nuanced analytical approaches.In this study,we have provided a comprehensive summary of existing analytical methods utilized in the characterization of EPS compositions.Additionally,novel strategies aimed at targeting EPS to enhance biofilm penetration were explored,with a specific focus on high-lighting the limitations associated with colorimetric methods.Furthermore,we have outlined the challenges faced in identifying additional components of EPS and propose a prospective research plan to address these challenges.This review has the potential to guide future researchers in the search for novel compounds capable of suppressing EPS,thereby inhibiting biofilm formation.This insight opens up a new avenue for exploration within this research domain.

Antimicrobial Activities of Extracts of Macrosphyra longistyla against Gram-Positive Oral Biofilm-Formers from School Children in Southwestern Nigeria and Toxicity Studies Using Brine Shrimps

The world will benefit from more effective antimicrobial agents against oral conditions arising from the actions of biofilm forming bacteria. Also, information is lacking on the oral biofilm-forming bacterial diversity in Southwestern Nigeria. In this study, we isolate and characterize oral biofilm producing bacteria in the oral cavities of schoolchildren in Southwestern Nigeria. We also investigate the antimicrobial properties of Macrosphyra longistyla extracts against the biofilm-formers and the toxicity of potent extracts. Samples were obtained from 109 schoolchildren aged 4 - 14 years from Lagos, Oyo and Osun States. Agar well diffusion technique was used in the antimicrobial susceptibility testing. Toxicity testing was done using brine shrimps (Artemia salina). Biofilm-formers in this study are Klebsiella sp., Streptococcus sp., Staphylococcus sp., and Micrococcus sp. Ethanol leaf extracts had the highest activity against all biofilm-producing bacteria. Ethanol stem bark extract, which elicited activity against Klebsiella only, was found to be less toxic than the ethanol leaf extract. Staphylococcus showed >10 mm susceptibility to the ethanol and aqueous extracts of Macrosphyra longistyla. Streptococcus and Micrococcus were susceptible to the antimicrobial actions of the ethanolic leaf extracts. Although the ethanol extracts of the leaves had lower minimum inhibitory concentrations than the ethanol extracts of the stem bark, toxicity studies showed ethanol extracts of the stem-bark to be more toxic than the ethanol extracts of the leaves. In conclusion, ethanolic extracts of Macrosphyra longistyla show potential as sources of antimicrobials against gram-positive, oral biofilm-forming bacteria.

Bacterial Exofactors Modulate Biofilm Growth and Resistivity to Antimicrobial Drugs

Some bacteria have the ability to co-exist, proliferate and survive in a multicellular community, biofilm. Each participating bacteria can form its colonies and encases itself by a self-produced insoluble extracellular matrix substance (EPS). Microcolonies within biofilm are held together by interactions and bonding of the substances present in the EPS with their separation from the water channels. Similar to insoluble EPS, bacterial microcolonies release soluble exofactors that have direct impacts on the survivability, growth and antibacterial resistivity of other microcolonies made of single- or multi-species bacteria in the same biofilm. How the exofactors of microcolonies of one-type bacteria impact on microcolonies of other-type bacteria is still unclear. We studied about the role of exofactors released from Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa, which are common biofilm-forming pathogenic bacteria. Exofactors facilitate to transform the microenvironment where bacteria can acquire alternative lifestyle with a long survival period and resistivity to certain antimicrobial drugs.

Evaluation of Azadirachta indica cultivated in Egypt against biofilm formation by Pseudomonas aeruginosa: Insights from molecular docking studies targeting LasR

Background:Azadirachta indica(A.indica),commonly known as neem,is a widely distributed medicinal plant in Asia and Africa and is well known to have a wide spectrum of biological activity.A.indica is considered a skin food that was traditionally used in different cultures to treat a wide range of skin disorders.A.indica was reported to possess antibacterial activity against Pseudomonas aeruginosa(P.aeruginosa)which is considered the most common biofilm model organism.This study aims to investigate the ability of A.indica cultivated in Egypt to inhibit/reduce the biofilm formation by P.aeruginosa.Methods:The microtiter plate assay was used to evaluate the anti-biofilm activity of neem,cultivated in Egypt,leaves against P.aeruginosa as well as the ability to reduce the activity of P.aeruginosa.To investigate the phytocompounds responsible for their bioactivity and to explore potential interactions between their bioactive components and one of the quorum-sensing regulatory proteins of P.aeruginosa involved in biofilm formation,liquid chromatography-mass spectrometric and molecular docking studies were done.Results:Results showed that methanol extract of leaves can reduce the formation of P.aeruginosa biofilm at lower concentrations than those reported in other regions with 1.25 mg/mL as the optimum concentration.The two-way analysis of variance revealed the significance of the extract effect and its concentration on the reduction of biofilm formation(P<0.05).Liquid chromatography-mass spectrometric study revealed the presence of fourteen compounds that belong to limonoids and flavonoids.Molecular docking analysis against LasR,the quorum-sensing regulatory protein,of P.aeruginosa supported these findings.Nimbolinin,a limonoid,has achieved the highest Libdock score of 138.769.Conclusion:It was concluded that A.indica,cultivated in Egypt,leaves can target LasR as a new mechanism of action for biofilm control by A.indica and therefore could be a good source of leads for anti-biofilm medicine.

Numerical Modeling of Mass Transfer in the Interaction between River Biofilm and a Turbulent Boundary Layer

In this article dedicated to the modeling of vertical mass transfers between the biofilm and the bulk flow, we have, in the first instance, presented the methodology used, followed by the presentation of various results obtained through analyses conducted on velocity fields, different fluxes, and overall transfer coefficients. Due to numerical constraints (resolution of relevant spatial scales), we have restricted the analysis to low Schmidt numbers (Sc=0.1, Sc=1, and Sc=10) and a single roughness Reynolds number (Re*=150). The analysis of instantaneous concentration fields from various simulations revealed logarithmic concentration profiles above the canopy. In this zone, the concentration is relatively homogeneous for longer times. The analysis of results also showed that the contribution of molecular diffusion to the total flux depends on the Schmidt number. This contribution is negligible for Schmidt numbers Sc≥0.1, but nearly balances the turbulent flux for Sc=0.1. In the canopy, the local Sherwood number, given by the ratio of the total flux (within or above the canopy) to the molecular diffusion flux at the wall, also depends on the Schmidt number and varies significantly between the canopy and the region above. The exchange velocity, a purely hydrodynamic parameter, is independent of the Schmidt number and is on the order of 10% of in the present case. This study also reveals that nutrient absorption by organisms near the wall depends on the Schmidt number. Such absorption is facilitated by lower Schmidt numbers.

The clinical impact of bacterial biofilms

Bacteria survive in nature by forming biofilms on surfaces and probably most, if not all, bacteria （and fungi） are capable of forming biofilms. A biofilm is a structured consortium of bacteria embedded in a self-produced polymer matrix consisting of polysaccharide, protein and extracellular DNA. Bacterial biofilms are resistant to antibiotics, disinfectant chemicals and to phagocytosis and other components of the innate and adaptive inflammatory defense system of the body. It is known, for example, that persistence of staphylococcal infections related to foreign bodies is due to biofilm formation. Likewise, chronic Pseudomonas aeruginosa lung infections in cystic fibrosis patients are caused by biofilm growing mucoid strains. Gradients of nutrients and oxygen exist from the top to the bottom of biofilms and the bacterial cells located in nutrient poor areas have decreased metabolic activity and increased doubling times. These more or less dormant cells are therefore responsible for some of the tolerance to antibiotics. Biofilm growth is associated with an increased level of mutations. Bacteria in biofilms communicate by means of molecules, which activates certain genes responsible for production of virulence factors and, to some extent, biofilm structure. This phenomenon is called quorum sensing and depends upon the concentration of the quorum sensing molecules in a certain niche, which depends on the number of the bacteria. Biofilms can be prevented by antibiotic prophylaxis or early aggressive antibiotic therapy and they can be treated by chronic suppressive antibiotic therapy. Promising strategies may include the use of compounds which can dissolve the biofilm matrix and quorum sensing inhibitors, which increases biofilm susceptibility to antibiotics and phagocytosis.

Bacterial Biofilm Degradation Using Extracellular Enzymes Produced by <i>Penicillium janthinellum</i>EU2D-21 under Submerged Fermentation

Bacterial biofilms are the bacterial aggregates that are embedded in the self-produced matrix of extracellular polymeric substances (EPS) that cause persistent bacterial infections posing significant medical challenges. They are recalcitrant to antibiotics and host defenses which make the treatments difficult and costly. Penicillium janthinellum mutant EU2D-21 was found to produce extracellular enzyme complex (amylase, cellulase, protease) under submerged fermentation. Maximum specific enzyme activities were found to be 3.04 IU/mg, 2.61 IU/mg and 3.39 IU/mg for alpha-amylase, cellulase and protease respectively, after 8 days of incubation at 30?C. We evaluated the enzyme complex for its ability to target and degrade the biofilms of different bacteria. We found that it degraded biofilms of Escherichia coli (85.5%), Salmonella enterica (79.72%), Pseudomonas aeruginosa (88.76%) and Staphyloccus aureus (87.42%) within 1 h of incubation at 50?C. The scanning electron microscopy (SEM), quantitation of biofilm removal assay and Crystal violet assay demonstrated that the enzyme complex detached the biofilm exo-polysaccharide matrix and bacteria from the cell surface. These results illustrate the feasibility and benefits of using this enzyme complex as anti-biofilm therapeutics to eradicate biofilms. This can also be used as a promising strategy to improve treatment of multidrug resistant bacterial infections.

温度对改良后Atmosphere-exposed Biofilm系统处理特性的影响

研究利用改良后Atmosphere-exposed Biofilm系统处理了模拟废水,调查分析了温度对改良后系统处理性能的影响。同时,通过菲尔普斯公式探求了改良后系统的温度系数。结果,在10~35℃温度范围内,改良后Atmosphere-exposed Biofilm系统的COD、TN及TP出水浓度呈下降趋势,去除率及去除速率呈上升趋势,与改良前相比系统在低温及高温阶段TN、TP的处理具有一定耐温性。改良后系统的COD、TN及TP温度系数分别为1.007 3、1.029 7及1.030 6,温度对TP的影响最大。

Research Development and Application of Nitrogen and Phosphorus Removal in Sequencing Batch Biofilm Reactor

Frequent variations of the wastewater quality and quantity and other uncertain factors are the challenges faced by many wastewater treatment plants during the operation. Sequencing batch biofilm reactor（ SBBR） process provides a new idea for an effective solution to this problem. This paper introduces the basic processes and characteristics of the sequencing batch biofilm reactor（ SBBR） process,and summarizes the research status of this process in wastewater treatment. Factors affecting the nitrogen and phosphorus removal effect of the SBBR process are also analyzed.

Inhibition of Biofilms by Non-Thermal Plasma Treated Novel Solutions

Biofilms act as a reservoir of infection, and periodically release cells in vicinity that are capable of developing new biofilm colonies and disseminate infection. Many chronic bacterial infections are serious that are associated with biofilms and have high morbidity and mortality, partly due to their higher resistance to antimicrobial agents, and partly due to lack of strong biocides which can efficiently treat and inhibit biofilm formation. We recently demonstrated that nonequilibrium non-thermal dielectric-barrier discharge plasma (Plasma) can also be applied to control pathogens via applying treated-liquids, and these liquids acquire broad-spectrum antimicrobial properties. In present studies we demonstrated a range of plasma-activated simple chemical solutions which significantly inhibited biofilm formation by multidrug-resistant bacterial pathogens. Plasma-activated methionine solution exhibited strong inhibitory activity against the biofilms of car-bapenem-resistant Acinetobacter baumannii, methicillin-resistant Staphylococcus aureus, metal-lo-β-lactamase (NDM1)-positive Klebsiella pneumoniae, and Enterococcus faecalis, and prevented the formation of biofilms by about 70% as compared to untreated controls in single exposure. In addition to inhibition of biofilm formation, a complete inactivation of biofilm-embedded bacterial cells was observed in less than 30 minute’s exposure to candidate plasma-activated methionine solution. These findings suggest that plasma-activated solutions have a potential to prevent biofilm formation, and as biofilm inhibitor.

水力负荷对Atmosphere-Exposed Biofilm(AEB)净化效果的影响

本文采用Atmosphere-Exposed Biofilm（AEB）处理模拟废水，调查分析了水力负荷（4．3、8．5、12．7、17．0、21．3rn／d）对系统处理特性的影响。结果表明，水力负荷对COD、TN、TP具有不同程度的影响，COD、TN、TP最佳去除率分别出现17．0、17．0、21．3m／d。在17．0～21．3m／d负荷范围内，COD、TN出水浓度满足了《城镇污水处理厂污染物排放标准》一级A标准，TP满足一级B标准。在所有运行范围内，系统COD、TN、TP去除速率相对恒定。系统水力负荷与进出水浓度比（C／C0）拟合结果，水力负荷与系统处理特性具有一定相关性。综合水力负荷对系统处理特性的影响，水力负荷为17．0m／d时，Atmosphere．Exposed Biofilm（AEB）系统处理效果较优。

Determination of the Anti-Adhesive and Anti-Biofilm Capacity of a Wheat Extract on <i>Staphylococcus aureus</i>in Farms

The formation of biofilm by pathogenic microorganisms has become a problem in the livestock industry since it is considered a potential source of infection for farm animals while increasing microbial resistance to physical and chemical agents. Some plant extracts, such as soluble wheat extract, have been shown to be effective in inhibiting or destroying the biofilm of certain micro-organisms under specific conditions. The objective of this study is to evaluate the capacity of the pathogen to form biofilm on different surfaces used in livestock, as well as to evaluate the anti-biofilm capacity of the soluble wheat extract against S. aureus on these surfaces. The inhibition potential of inhibition or destruction of biofilm was tested in vitro. Wheat extract at a concentration of 0.29 mg/100mL showed anti-biofilm activity on S. aureus, inhibiting its formation, as well as destroying it greatly after a contact time of 24 hours, on those surfaces where the microorganism presents more adhesion capacity.

Atmosphere-Exposed Biofilm(AEB)滤料填充率优化研究

采用Atmosphere-Exposed Biofilm（AEB）处理模拟废水,考察了400、500、600和700 m/m3等不同滤料填充率运行条件下系统的处理特性,并确定了最佳滤料填充率。结果表明,在滤料填充率为400~700 m/m3时,COD（化学需氧量）、TN（总氮）及TP（总磷）出水浓度均满足《城镇污水处理厂污染物排放标准》中的一级B标准;填充率为600 m/m3时,COD、TN出水浓度最低,去除率最高。在400~700 m/m3运行范围内,滤料填充率与单位长度滤料上污染物去除速率具有很好的相关性。结合AEB系统处理特性及单位容积、单位长度滤料上污染物去除速率,确定系统最佳滤料填充率为600 m/m3。

Clogging processes caused by biofilm growth and organic particle accumulation in lab-scale vertical flow constructed wetlands

The accumulation of organic matter in substratum pores is regarded as an important factor causing clogging separately in the subsurface flow constructed wetlands.In this study,the developing process of clogging caused by biofilm growth or organic particle accumulation instead of total organic matter accumulation was investigated in two groups of lab-scale vertical flow constructed wetlands（VFCWs）,which were fed with glucose（dissolved organic matter） and starch（particulate organic matter） influent.Results showed that the growth of biofilms within the substratum pores certainly caused remarkable reduction of effective porosity,especially for the strong organic wastewater,whereas its influence on infiltration rate was negligible.It was implied that the most important contribution of biofilm growth to clogging was accelerating the occurrence of clogging.In comparison with biofilm growth,particles accumulation within pores could rapidly reduce infiltration rate besides effective porosity and the clogging occurred in the upper 0-15 cm layer.With approximately equal amount of accumulated organic matter,the effective porosity of the clogged layer in starch-fed systems was far less than that of glucose-fed systems,which indicated that composition and accumulation mode in addition to the amount of the accumulated organic matter played an important role in causing clogging.