Mechanisms Of Biofilm Formation Research Articles

Mycobacterial Biofilm: Mechanisms, Clinical Problems, and Treatments

Tuberculosis (TB) remains a threat to human health worldwide. Mycobacterium tuberculosis (Mtb) and other nontuberculous mycobacteria (NTM) can form biofilms, and in vitro and animal experiments have shown that biofilms cause serious drug resistance and mycobacterial persistence. Deeper investigations into the mechanisms of mycobacterial biofilm formation and, consequently, the exploration of appropriate antibiofilm treatments to improve the efficiency of current anti-TB drugs will be useful for curing TB. In this review, the genes and molecules that have been recently reported to be involved in mycobacterial biofilm development, such as ABC transporter, Pks1, PpiB, GroEL1, MprB, (p)ppGpp, poly(P), and c-di-GMP, are summarized. Biofilm-induced clinical problems, including biofilm-related infections and enhanced virulence, as well as their possible mechanisms, are also discussed in detail. Moreover, we also illustrate newly synthesized anti-TB agents that target mycobacterial biofilm, as well as some assistant methods with high efficiency in reducing biofilms in hosts, such as the use of nanoparticles.

Tyrosol blocks E. coli anaerobic biofilm formation via YbfA and FNR to increase antibiotic susceptibility

Bacteria within mature biofilms are highly resistant to antibiotics than planktonic cells. Oxygen limitation contributes to antibiotic resistance in mature biofilms. Nitric oxide (NO) induces biofilm dispersal; however, low NO levels stimulate biofilm formation, an underexplored process. Here, we introduce a mechanism of anaerobic biofilm formation by investigating the antibiofilm activity of tyrosol, a component in wine. Tyrosol inhibits E. coli and Pseudomonas aeruginosa biofilm formation by enhancing NO production. YbfA is identified as a target of tyrosol and its downstream targets are sequentially determined. YbfA activates YfeR, which then suppresses the anaerobic regulator FNR. This suppression leads to decreased NO production, elevated bis-(3’−5’)-cyclic dimeric GMP levels, and finally stimulates anaerobic biofilm formation in the mature stage. Blocking YbfA with tyrosol treatment renders biofilm cells as susceptible to antibiotics as planktonic cells. Thus, this study presents YbfA as a promising antibiofilm target to address antibiotic resistance posed by biofilm-forming bacteria, with tyrosol acting as an inhibitor.

Bacterial biofilm formation in seafood: Mechanisms and inhibition through novel non‐thermal techniques

AbstractSeafoods are susceptible to microbial contamination due to their high moisture, nutrient contents and neutral pH. Among various microorganisms, biofilm‐forming bacteria pose a severe threat to the seafood supply chain as well as consumer health. Bacterial biofilm formation in seafood is primarily caused by Aeromonas hydrophila, Vibrio cholerae, V. vulnificus, V. parahaemolyticus, Salmonella spp., and Listeria monocytogenes. Biofilm formation is an important protective mechanism of microorganisms causing spoilage of seafood and disease threats to consumers. The attachment of microbes on the surface of seafood followed by the growth and proliferation of bacterial cells leads to the production of exopolymer compounds and the formation of biofilm. This biofilm is difficult to destroy or inhibit through conventional prevention/destruction techniques. The occurrence of bacterial strains/biofilms with more resistance to different preventive strategies is a big challenge for the seafood processing industry. This review covers the mechanisms of biofilm formation by bacteria and various non‐thermal processing approaches to prevent microbial contamination and biofilm formation in seafood products. The aforementioned non‐thermal processing techniques for the destruction of biofilm and quality control of seafood products include cold plasma treatment, irradiation, pulsed electric field technology, hydrostatic pressure processing, photosensitisation, natural bioactive compounds and so on. All these techniques effectively inhibit the bacterial biofilm and microbial growth without altering sensorial properties. However, further research validation and applications at the industry level are still required.

Genome-Wide Computational Prediction and Analysis of Noncoding RNAs in Oleidesulfovibrio alaskensis G20.

Noncoding RNAs (ncRNAs) play key roles in the regulation of important pathways, including cellular growth, stress management, signaling, and biofilm formation. Sulfate-reducing bacteria (SRB) contribute to huge economic losses causing microbial-induced corrosion through biofilms on metal surfaces. To effectively combat the challenges posed by SRB, it is essential to understand their molecular mechanisms of biofilm formation. This study aimed to identify ncRNAs in the genome of a model SRB, Oleidesulfovibrio alaskensis G20 (OA G20). Three in silico approaches revealed genome-wide distribution of 37 ncRNAs excluding tRNAs in the OA G20. These ncRNAs belonged to 18 different Rfam families. This study identified riboswitches, sRNAs, RNP, and SRP. The analysis revealed that these ncRNAs could play key roles in the regulation of several pathways of biosynthesis and transport involved in biofilm formation by OA G20. Three sRNAs, Pseudomonas P10, Hammerhead type II, and sX4, which were found in OA G20, are rare and their roles have not been determined in SRB. These results suggest that applying various computational methods could enrich the results and lead to the discovery of additional novel ncRNAs, which could lead to understanding the "rules of life of OA G20" during biofilm formation.

Multifunctional application of seagrass-derived rosmarinic acid in mitigating biofilm and quorum-sensing virulence transcripts of methicillin-resistant Staphylococcus aureus

Anti-microbial drug resistance is a primary public health concern, and the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) infections is gradually increasing. Considering the folk medicinal value of the seagrass Cymodocea rotundata and its antioxidant potential, the aim of this study was to assess C. rotundata for bioactive constituents that mitigate biofilm formation and quorum-sensing (QS) mechanism of MRSA. Different solvent extracts (chloroform, ethyl acetate, methanol, and distilled water) of C. rotundata were used, of which the methanolic extract exhibited maximum biofilm inhibition with complete cell lysis in 2 h. Column fractionation of the methanolic extract was performed, and 22 fractions were obtained. Fraction 7 exhibited maximum anti-biofilm potential, and the lead molecule was separated using thin-layer chromatography and characterized with high-performance liquid chromatography and nuclear magnetic resonance spectroscopy. The active constituent was identified as rosmarinic acid (RA), and the minimum inhibitory concentration was found to be 61.5 µg/mL; RA inhibited MRSA virulence factors such as protease by 89.37 %, lipase by 87.69 %, α-hemolysin by 91.52 %, and exopolysaccharides by 81.79 %, with an effective anti-adherence potential. Moreover, the lead molecule RA exhibited significant downregulation of QS-mediated virulence genes such as agrA, sarA, RNAIII, fnbA, fnbB, icaA, and icaD. Thus, seagrass C. rotundata has bioactive compounds with anti-microbial potential, and RA was found to control MRSA infection.

Phosphate recovery from urban sewage by the biofilm sequencing batch reactor process: Key factors in biofilm formation and related mechanisms

The biofilm sequencing batch reactor (BSBR) technique has been deployed in the laboratory to enrich phosphorus from simulated wastewater, but it is still not clear what its performance will be when real world sewage is used. In this work, the effluent from the multi-stage anoxic-oxic (AO) activated sludge process at a sewage plant was used as the feed water for a BSBR pilot system, which had three reactors operating at different levels of dissolved oxygen (DO). The phosphorus adsorption and release, the biofilm growth, and the extracellular polymeric substances (EPS) components and contents were examined. The microbial communities and the signaling molecules N-acyl-l-homoserine lactones (AHLs) were also analyzed. Gratifyingly, the BSBR process successfully processed the treated sewage, and the biofilm developed phosphorus accumulation capability within 40 days. After entering stable operation, the system concentrated phosphate from 2.59 ± 0.77 mg/L in the influent to as much as 81.64 mg/L in the recovery liquid. Sludge discharge had profound impacts on all aspects of BSBR, and it was carried out successfully when the phosphorus absorption capacity of the biofilm alone was comparable to that of the reactor containing the activated sludge. Shortly after the sludge discharge, the phosphate concentration of the recovery liquid surged from 50 to 140 mg/L, the biofilm thickness grew from 20.56 to 67.32 μm, and the diversity of the microbial population plunged. Sludge discharge stimulated Candidatus competibacter to produce a large amount of AHLs, which was key in culturing the biofilm. Among the AHLs, both C10-HSL and 3OC12-HSL were significantly positively correlated with EPS and the abundance of Candidatus competibacter. The current results demonstrated BSBR as a viable option to enrich phosphorus from real world sewage with low phosphorus content and fluctuating chemistry. The mechanistic explorations also provided theoretical guidance for cultivating phosphorus-accumulating biofilms.

Biofilm Inhibition on Medical Devices and Implants Using Carbon Dots: An Updated Review.

Biofilms are an intricate community of microbes that colonize solid surfaces, communicating via a quorum-sensing mechanism. These microbial aggregates secrete exopolysaccharides facilitating adhesion and conferring resistance to drugs and antimicrobial agents. The escalating global concern over biofilm-related infections on medical devices underscores the severe threat to human health. Carbon dots (CDs) have emerged as a promising substrate to combat microbes and disrupt biofilm matrices. Their numerous advantages such as facile surface functionalization and specific antimicrobial properties, position them as innovative anti-biofilm agents. Due to their minuscule size, CDs can penetrate microbial cells, inhibiting growth via cytoplasmic leakage, reactive oxygen species (ROS) generation, and genetic material fragmentation. Research has demonstrated the efficacy of CDs in inhibiting biofilms formed by key pathogenic bacteria such as Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. Consequently, the development of CD-based coatings and hydrogels holds promise for eradicating biofilm formation, thereby enhancing treatment efficacy, reducing clinical expenses, and minimizing the need for implant revision surgeries. This review provides insights into the mechanisms of biofilm formation on implants, surveys major biofilm-forming pathogens and associated infections, and specifically highlights the anti-biofilm properties of CDs emphasizing their potential as coatings on medical implants.

Anti-biofilm activity of marine algae-derived bioactive compounds.

A large number of microbial species tend to communicate and produce biofilm which causes numerous microbial infections, antibiotic resistance, and economic problems across different industries. Therefore, advanced anti-biofilms are required with novel attributes and targets, such as quorum sensing communication system. Meanwhile, quorum sensing inhibitors as promising anti-biofilm molecules result in the inhibition of particular phenotype expression blocking of cell-to-cell communication, which would be more acceptable than conventional strategies. Many natural products are identified as anti-biofilm agents from different plants, microorganisms, and marine extracts. Marine algae are promising sources of broadly novel compounds with anti-biofilm activity. Algae extracts and their metabolites such as sulfated polysaccharides (fucoidan), carotenoids (zeaxanthin and lutein), lipid and fatty acids (γ-linolenic acid and linoleic acid), and phlorotannins can inhibit the cell attachment, reduce the cell growth, interfere in quorum sensing pathway by blocking related enzymes, and disrupt extracellular polymeric substances. In this review, the mechanisms of biofilm formation, quorum sensing pathway, and recently identified marine algae natural products as anti-biofilm agents will be discussed.

Evolution of <I>Yersinia pestis</I> as the Causative Agent of a Vector-Borne Disease Transmitted by Arthropods

The review summarizes the data of modern domestic and foreign studies on the mechanisms of evolutionary adaptation of the plague pathogen to transmissive spread by arthropods. The data on the molecular basis of the rapid formation of a highly pathogenic bacterium due to the acquisition of new genetic information; structural and functional changes in the genome, causing the disruption of functionality of some genes that prevent survival in the vector are presented. The stage of the complex life cycle of the pathogen associated with the peculiarities of its stay in the vector’s organism and its tactics of evasion from the action of antibacterial substances formed by the flea is considered. The importance of biofilm formation for effective transmission of the pathogen is discussed. A complex cascade of transcriptional regulators of biofilm in Yersinia pestis is considered, which includes activators and repressors of biofilm formation, as well as regulators of synthesis or modification/transport of exopolysaccharide. The hms-dependent mechanism of biofilm formation in Y. pestis is described in detail, as well as the impact on biofilm formation through the regulation of LPS-related genes and its role in the modification and transport of biofilm exopolysaccharide. The data from our own studies on the variability of genes involved in biofilm formation in the main subspecies of the plague pathogen in comparison with non-main subspecies of the plague pathogen, as well as on the ability of strains of different subspecies to form biofilm not only in the proventriculus of the flea, but also on the cuticle of soil nematodes of the Tylenchida and Rhabditida orders and the genus Panagrolaimus are presented. The latter allows us to assume the possible participation of soil and entomoparasitic nematodes in the removal of Y. pestis biofilms from the soil to the above-ground biocoenosis of the natural plague focus.

Microbiological aspects and challenges of dairy powders – II: Biofilm/biofouling

Biofilms generated during production of dairy/whey powders can cause contamination, spoilage and equipment failures, posing a significant challenge in the agri‐food sector. Factors including temperature, protein composition, equipment structures and surface topography influence biofilm formation and resistance to cleaning and sanitation. Several species of bacteria are well adapted to these challenges, posing the most pressing concerns of dairy whey process. Despite efforts to improve cleaning‐in‐place strategies, bacteria persist in difficult‐to‐clean areas. This review provides insights into bacterial biofouling in dairy protein powders, highlighting the mechanism of biofilm formation, predominant bacterial genera, critical processing steps and strategies to manage biofilm formation during the manufacturing process.

Reconstitution of a biofilm adhesin system from a sulfate-reducing bacterium in Pseudomonas fluorescens

Biofilms of sulfate-reducing bacterium (SRB) like Desulfovibrio vulgaris Hildenborough (DvH) can facilitate metal corrosion in various industrial and environmental settings leading to substantial economic losses. Although the mechanisms of biofilm formation by DvH are not yet well understood, recent studies indicate the large adhesin, DvhA, is a key determinant of biofilm formation. The dvhA gene neighborhood resembles the biofilm-regulating Lap system of Pseudomonas fluorescens but is curiously missing the c-di-GMP-binding regulator LapD. Instead, DvH encodes an evolutionarily unrelated c-di-GMP-binding protein (DVU1020) that we hypothesized is functionally analogous to LapD. To study this unusual Lap system and overcome experimental limitations with the slow-growing anaerobe DvH, we reconstituted its predicted SRB Lap system in a P. fluorescens strain lacking its native Lap regulatory components (ΔlapGΔlapD). Our data support the model that DvhA is a cell surface-associated LapA-like adhesin with a N-terminal "retention module" and that DvhA is released from the cell surface upon cleavage by the LapG-like protease DvhG. Further, we demonstrate DVU1020 (named here DvhD) represents a distinct class of c-di-GMP-binding, biofilm-regulating proteins that regulates DvhG activity in response to intracellular levels of this second messenger. This study provides insight into the key players responsible for biofilm formation by DvH, thereby expanding our understanding of Lap-like systems.

Molecular Mechanisms of Biofilm Formation on Orthopaedic Implants: Review of the Literature

Molecular Mechanisms of Biofilm Formation on Orthopaedic Implants: Review of the Literature

Biofilm Formation in Mycobacterial Genus; Mechanism of Biofilm Formation and Anti-Mycobacterial Biofilm Agents.

Mycobacterium tuberculosis, Mycobacterium leprae, and non-tuberculous mycobacteria (NTM) are among the most significant human pathogens within the Mycobacterium genus. These pathogens can infect people who come into contact with biomaterials or have chronic illnesses. A characteristic pathogenic trait of mycobacteria is the development of biofilms, which involves several molecules, such as the GroEL1 chaperone, glycopeptidolipids, and shorter-chain mycolic acids. Bacterial behavior is influenced by nutrients, ions, and carbon sources, which also play a regulatory role in biofilm development. Compared to their planktonic phase, mycobacterial biofilms are more resilient to environmental stresses and disinfectants. Mycobacteria that produce biofilms have been found in several environmental studies, particularly in water systems. NTM can cause respiratory problems in individuals with underlying illnesses such as cystic fibrosis, bronchiectasis, and old tuberculosis scars. Mycobacteria that grow slowly, like those in the Mycobacterium avium complex (MAC), or rapidly, like Mycobacterium abscessus, can be pathogens. Infections related to biomaterials represent a significant category of biofilm-associated infections, with rapidly growing mycobacteria being the most frequently identified organisms. A biofilm produced by M. tuberculosis can contribute to caseous necrosis and cavity formation in lung tissue. Additionally, M. tuberculosis forms biofilms on clinical biomaterials. Biofilm formation is a major contributor to antimicrobial resistance, providing defense against drugs that would typically be effective against these bacteria in their planktonic state. The antibiotic resistance of biofilm-forming microbes may render therapy ineffective, necessitating the physical removal of biofilms to cure the infection. Recently, new approaches have been developed with potential anti-biofilm compounds to increase treatment effectiveness. Understanding biofilms is crucial for the appropriate treatment of various NTM diseases, and the recent discovery of M. tuberculosis biofilms has opened up a new field of study. This review focuses on the biofilm formation of the Mycobacterial genus, the mechanisms of biofilm formation, and anti-mycobacterial biofilm agents.

Relationship between biofilm formation and antibiotic resistance of Klebsiella pneumoniae and updates on antibiofilm therapeutic strategies.

Klebsiella pneumoniae is a Gram-negative bacterium within the Enterobacteriaceae family that can cause multiple systemic infections, such as respiratory, blood, liver abscesses and urinary systems. Antibiotic resistance is a global health threat and K. pneumoniae warrants special attention due to its resistance to most modern day antibiotics. Biofilm formation is a critical obstruction that enhances the antibiotic resistance of K. pneumoniae. However, knowledge on the molecular mechanisms of biofilm formation and its relation with antibiotic resistance in K. pneumoniae is limited. Understanding the molecular mechanisms of biofilm formation and its correlation with antibiotic resistance is crucial for providing insight for the design of new drugs to control and treat biofilm-related infections. In this review, we summarize recent advances in genes contributing to the biofilm formation of K. pneumoniae, new progress on the relationship between biofilm formation and antibiotic resistance, and new therapeutic strategies targeting biofilms. Finally, we discuss future research directions that target biofilm formation and antibiotic resistance of this priority pathogen.

Discovery of Melittin as Triple-Action Agent: Broad-Spectrum Antibacterial, Anti-Biofilm, and Potential Anti-Quorum Sensing Activities.

The development of antibiotic-resistant microorganisms is a major global health concern. Recently, there has been an increasing interest in antimicrobial peptides as a therapeutic option. This study aimed to evaluate the triple-action (broad-spectrum antibacterial, anti-biofilm, and anti-quorum sensing activities) of melittin, a membrane-active peptide present in bee venom. The minimum inhibitory concentration and minimum bactericidal concentration of the melittin were determined using the microdilution method and agar plate counting. Growth curve analysis revealed that melittin showed a concentration-dependent antibacterial activity. Scanning electron microscope analysis revealed that melittin treatment altered the morphology. Confocal laser scanning microscope revealed that melittin increased the membrane permeability and intracellular ROS generation in bacteria, all of which contribute to bacterial cell death. In addition, the crystal violet (CV) assay was used to test the anti-biofilm activity. The CV assay demonstrated that melittin inhibited biofilm formation and eradicated mature biofilms. Biofilm formation mediated by quorum sensing (QS) plays a major role in this regard, so molecular docking and molecular dynamics analysis confirmed that melittin interacts with LasR receptors through hydrogen bonds, and further evaluates the anti-QS activity of melittin through the production of virulence factors (pyocyanin, elastase, and rhamnolipid), exopolysaccharides secretion, and bacterial motility, that may be the key to inhibiting the biofilm formation mechanism. The present findings highlight the promising role of melittin as a broad-spectrum antibacterial, anti-biofilm agent, and potential QS inhibitor, providing a new perspective and theoretical basis for the development of alternative antibiotics.

SMR peptide antagonizes Staphylococcus aureus biofilm formation.

The emergence and international dissemination of multi-drug resistant Staphylococcus aureus (S. aureus) strains challenge current antibiotic-based therapies, representing an urgent threat to public health worldwide. In the U.S. alone, S. aureus infections are responsible for 11,000 deaths and 500,000 hospitalizations annually. Biofilm formation is a major contributor to antibiotic tolerance and resistance-induced delays in empirical therapy with increased infection severity, frequency, treatment failure, and mortality. Developing novel treatment strategies to prevent and disrupt biofilm formation is imperative. In this article, we test the Secretion Modification Region (SMR) peptides for inhibitory effects on resistant S. aureus biofilm-forming capacity by targeting the molecular chaperone DnaK. The dose effect of SMR peptides on biofilm formation was assessed using microtiter plate methods and confocal microscopy. Interaction between the antagonist and DnaK was determined by immune precipitation with anti-Flag M2 Affinity and Western blot analysis. Increasing SMR peptide concentrations exhibited increasing blockade of S. aureus biofilm formation with significant inhibition found at 18 µM, 36 µM, and 72 µM. This work supports the potential therapeutic benefit of SMR peptides in reducing biofilm viability and could improve the susceptibility to antimicrobial agents.IMPORTANCEThe development of anti-biofilm agents is critical to restoring bacterial sensitivity, directly combating the evolution of resistance, and overall reducing the clinical burden related to pervasive biofilm-mediated infections. Thus, in this study, the SMR peptide, a novel small molecule derived from the HIV Nef protein, was preliminarily explored for anti-biofilm properties. The SMR peptide was shown to effectively target the molecular chaperone DnaK and inhibit biofilm formation in a dose-dependent manner. These results support further investigation into the mechanism of SMR peptide-mediated biofilm formation and inhibition to benefit rational drug design and the identification of therapeutic targets.

Nanobiomaterials in the Management of Oral Biofilms

The oral cavity inhabits diverse microorganisms with members of all age groups including children being associated with oral infections. Bacteria being the principle component of this resident microflora along with the diverse group of other species reflect the wide range of viscerously derived nutrients, the heterogenous habitats for colonization contributing to the survival of the biofilm. Biofilms constitute surface- adherent communities of microorganisms like Streptococcus mutans along with other bacterial species embedded in an extracellular matrix material. The commensal relationship between the host and the microflora can be disrupted in numerous ways, resulting in compromised oral health causing conditions like dental caries and endodontic infections, gingival and periodontal conditions, oral candidiasis and peri-implantitis. Biofilm-related infections prove to be a major threat from both an economical and health perspective. Innovative treatment options remain limited despite of advancements in understanding the mechanisms of biofilm formation. The concept of nanotechnology is based on controlling atoms on an individual basis and creating structures less than 100 nm (10_7 m) in size thereby greatly influencing the properties. Incorporation of metals and other nanoparticles with polymers and coating of surfaces provide antimicrobial and anti-adhesive benefits within the oral cavity. Therefore, this paper seeks to throw light into the current advancements in nanoparticle mediated treatment approaches of oral biofilms and its future implications in pediatric dentistry. Keywords: Biofilm, Oral Cavity, Metal Oxides, Nanoparticles, Reactive Oxygen Species, Antibiofilm Efficacy

Multispecies Bacterial Biofilms and Their Evaluation Using Bioreactors.

Pathogenic biofilm formation within food processing industries raises a serious public health and safety concern, and places burdens on the economy. Biofilm formation on equipment surfaces is a rather complex phenomenon, wherein multiple steps are involved in bacterial biofilm formation. In this review we discuss the stages of biofilm formation, the existing literature on the impact of surface properties and shear stress on biofilms, types of bioreactors, and antimicrobial coatings. The review underscores the significance of prioritizing biofilm prevention strategies as a first line of defense, followed by control measures. Utilizing specific biofilm eradication strategies as opposed to a uniform approach is crucial because biofilms exhibit different behavioral outcomes even amongst the same species when the environmental conditions change. This review is geared towards biofilm researchers and food safety experts, and seeks to derive insights into the scope of biofilm formation, prevention, and control. The use of suitable bioreactors is paramount to understanding the mechanisms of biofilm formation. The findings provide useful information to researchers involved in bioreactor selection for biofilm investigation, and food processors in surfaces with novel antimicrobial coatings, which provide minimal bacterial attachment.

Enriched functional exoproteins and increased exopolysaccharides with altered molecular conformation mutually promoted indigenous microalgal-bacterial consortium biofilm growth under high light intensity

Indigenous microalgal-bacterial consortium (IMBC) biofilm technology holds great promise for wastewater treatment. However, the efficient start-up of IMBC biofilm system remains a technical challenge, partially impeding its large-scale application due to the unclear biofilm formation mechanism. In this study, high light intensity (HL) irradiation was firstly demonstrated as an effective strategy to promote IMBC biofilm development, as evidenced by the 498.3% higher biofilm formation ratio on average. Interaction energy between IMBC and carrier, exoproteins (PN) annotation and exopolysaccharides (PS) chain characteristics were investigated to reveal the potential mechanism. The decreased interfacial free energy (by 33.8%) and negative total interaction energies between IMBC and carriers in the HL group indicated enhanced microbial initial adhesion onto carriers. PN and PS were believed to mutually promote biofilm proliferation. Specifically, enriched PN with signal transduction potential and transmembrane transporter activity ensured efficient production of extracellular polymeric substances (EPS) for biofilm development. On one hand, PN annotated with binding capacities contributed to a tightly-interconnected EPS matrix. On the other hand, the increased PS with higher branding degree, height, and width (by 473%, 63.4%, and 28.9%, respectively) significantly enhanced the structural stability of biofilm landscape. These findings enrich our knowledge of the roles of EPS in IMBC biofilm growth, and are expected to promote the development of IMBC wastewater bioremediation technology.

Biofilm dynamic changes in drip irrigation emitter flow channels using reclaimed water

Reusing reclaimed water through drip irrigation offers an effective way to overcome freshwater scarcity. However, biofilm accumulation in the flow channel of drip emitters is the primary obstacle. So far, biofilm development in the emitters remains largely unknown. Here, industrial computed tomography was used to quantify the emitter biofilm developments. Results showed that biofilm typically accumulated in the inlet of the emitter flow channel and decreased toward the flow direction. Biofilm was also typically accumulated in dead areas having low flow velocities, such as edge, corner, and adjacent surface zones in flow channels. The dynamics of the emitter biofilm variation mechanisms were also elucidated. Specifically, particle and nutrient transport appeared to be dominant in shaping the initial biofilm formation (i.e., 5% emitter clogging degree), resulting in biofilm abundant in the inlet of the flow channel. However, it changed the hydraulic conditions in emitter flow channels, increased local water shear stress, which made the biofilm easier to be washed away in the inlet, and caused biofilm to grow faster in the middle and outlet regions of the flow channel at 20% emitter clogging degree. At 50% clogging degree, biofilm in inlet regions grew faster again. Finally, some biofilm control approaches such as water quality management and emitter flow channel structure optimization were proposed. This study provided a better understanding of biofilm formation mechanisms in the emitter flow channels, which is critical for designing appropriate biofilm control technologies and will facilitate the reuse of reclaimed water in agricultural irrigation.