Mechanisms Of Biofilm Formation Research Articles

Xanthene Derivatives Targeting Bacterial Efflux Pumps, Quorum-Sensing, and Biofilm Formation

The rise of multidrug resistance (MDR) bacteria in nosocomial and health-care institutions is widespread and is currently recognized as a major medical challenge. Mechanisms of bacterial resistance, namely, quorum sensing (QS), biofilm formation, and efflux pumps, have been identified as critical biological processes in MDR bacteria. Following previous reports on the activity of phenothiazines against mechanisms of bacterial resistance, in this work we focus on the synthesis of xanthene derivatives aiming to discover phenothiazine bioisosteres with improved activity. Four compounds were obtained from the conjugation of xanthydrol with sulfonamides and aniline and were fully characterized. Their antibacterial activity was assessed considering their minimum inhibitory concentration (MIC) against Gram-positive and Gram-negative strains, efflux pump inhibition, influence on biofilm formation and quorum-sensing (QS) inhibition. It was observed that the MIC of all the tested compounds was above 64 µg/mL The four 9-xanthenyl derivatives obtained, particularly the xanthene sulfonamide derivatives 3b and 3c, showed promising results on QS inhibition with a reduction of pigment production of 48 and 41 mm, and on biofilm formation with a reduction of 78 and 79%, respectively.

Antibioflm effects of extracellular matrix degradative agents on the biofilm of different strains of multi-drug resistant Corynebacterium striatum

BackgroundCorynebacterium striatum is a microorganism with an excellent capacity for biofilm production and thus has been correlated with nosocomial transmission and invasive infections. However, little is known about the mechanism of biofilm formation of this commensal pathogen. In this study, we aimed to investigate the biofilm formation abilities of multidrug-resistant Corynebacterium striatum clinical isolates and the roles of extracellular proteins, exopolysaccharides and extracellular DNA in mediating more robust biofilm formation by the isolates of C. striatum.MethodsC. striatum isolates were identified using VITEK-2 ANC card, matrix-assisted laser desorption/ionization-time of flight mass spectrometry and 16S rRNA sequencing. The antibiotic susceptibility test was performed using the broth microdilution method. The distribution of spaDEF genes among C. striatum isolates was detected by polymerase chain reaction, and pulsed-field gel electrophoresis typing was employed to analyze the genotypes of the isolates. Crystal violet staining and scanning electron microscopy techniques were used to detect biofilm production by C. striatum isolates. Biofilm degradation assay was performed to observe the effects of extracellular matrix degradative agents (proteinase K, dispersin B, and DNase I) on C. striatum biofilms.ResultsTwenty-seven C. striatum isolates were enrolled in the study, and the resistance rates were the highest (100%, 27/27) against penicillin and ceftriaxone. Approximately 96.3% (26/27) C. striatum isolates were resistant to at least three different types of antimicrobial agents tested. All isolates were confirmed to be biofilm producers, and 74.07% (20/27) isolates presented moderate to strong biofilm production abilities. P7 genotype (44.4%, 12/27) was identified to as the predominant genotype, and all of isolates belonging to this genotype were multidrug-resistant and had stronger biofilm-forming abilities. Most C. striatum isolates (74.07%, 20/27) carry spaD, spaE, and spaF genes, which encode spa-type pili. However, the correlation between the expression of spa-type genes and the biofilm production abilities of the C. striatum isolates was not found. The biofilms of 80% (8/10), 90% (9/10), and 100% (10/10) C. striatum isolates with moderate to strong biofilm production abilities were significantly eliminated upon the treatment of dispersin B (20 μg/mL), DNase I (20 μg/mL), and proteinase K (20 μg/mL) (p < 0.05), respectively. For the combination groups with two kinds of biofilm-degradative agents, the combination of 20 μg/mL proteinase K/dispersin B showed the strongest biofilm-eliminating effects, when the biofilms of 90% (9/10) C. striatum isolates degraded more than 50%.ConclusionsThe C. striatum isolates that belonged to the predominant genotype showed a multidrug resistance (MDR) phenotype and strong biofilm formation abilities. Extracellular matrix seems to be an essential determinant in mediating biofilm formation of MDR C. striatum, since extracellular matrix degradative agents (proteinase K, dispersin B and DNase I) showed strong biofilm-eliminating effects toward multidrug-resistant C. striatum isolates. The findings of this study highlight new ideas/directions to explore the whole nature of biofilm formation of C. striatum and the function of extracellular matrix in this process.

Bacteriophage therapy in infection after fracture fixation (IAFF) in orthopaedic surgery

Infection after fracture fixation (IAFF) in orthopaedic surgery is a significant complication that can lead to disability due to chronic infection and/or relapsing disease, non-union necessitating revision surgery. Management of IAFF is a major challenge facing orthopaedic surgeons across the world due to two key pathogenic mechanisms of Biofilm formation and antimicrobial resistance (AMR) against traditional antibiotics. Advanced prophylactic and treatment strategies to help eradicate established infections and prevent the development of such infections are necessary. Bacteriophage therapy represents an innovative modality to treat IAFF due to multi-drug resistant organisms. We assess the current role and potential therapeutic applications of the novel bacteriophage therapy in the management of these recalcitrant infections to achieve a successful outcome.

The Effect Citrox BCL on Legionella pneumophila Mechanisms of Biofilm Formation, Oxidative Stress and Virulence.

Legionella pneumophila is responsible for causing Legionnaires' disease and Pontiac fever, also known as legionellosis. The aim of this study was to investigate the mechanistic effect of a mixture of natural antimicrobials (Citrox BCL) in preventing L. pneumophila biofilm formation and reducing its in vitro virulence. The minimum inhibitory concentrations were detected at 0.06%, and the MBC was established at 0.125%. Based on the growth curve profile, the sub-inhibitory concentration of 0.02% was further used to study the mechanistic implications in the absence of a cytotoxic effect on A549 cells. At 24 h post-infection, Citrox BCL reduced (p = 0.005) the intracellular growth of L. pneumophila when the A549 cells or the bacteria were pre-treated with 0.02% Citrox BCL. This result was replicated when Citrox BCL was added during the 24 h infection assay leading to a reduction in intracellular growth (p = 0.003). Herein we show that at the sub-inhibitory concentration of 0.02%, Citrox CBL lowers the ROS levels in infected A549 cells and causes a 45% reduction in L. pneumophila EPS production, a reduction associated with the decline in biofilm formation. Overall, our results corroborate the low c-di-GMP production with the decrease in biofilm formation and low EPS levels. The low EPS levels seemed to be caused by the downregulation of the tatB and tatC gene expressions. Moreover, inhibition of pvcA and pvcB gene expressions, leading to lower siderophore levels, suggests that Citrox BCL reduces the ability of L. pneumophila to sequester iron and reduce biofilm formation through iron starvation.

Recent Advance in Polymer Coatings Combating Bacterial Adhesion and Biofilm Formation†

Comprehensive SummaryImplantable medical device‐associated infections (DAIs) originating from bacterial adhesion and biofilm formation have threatened to the health and life of patients. Antibacterial polymer coatings with antifouling and/or bactericidal properties have showed great potentials to combat DAI issues. In this review, we report recent advances in antibacterial polymer coatings fighting bacterial adhesion and biofilm formation on implantable biomaterial surfaces. We summarize the mechanisms of bacterial adhesion and biofilm formation, which provides guidance for the design of antibacterial coatings. We describe the polymer and coating preparation methods and discuss the structure‐property relationships of antibacterial polymer coatings. Applications of these polymer coatings in medical catheters, orthopaedic implants, and other applications are elaborated. Future challenges and prospects associated with antibacterial polymer coatings for implantable medical devices are discussed.

Biofilm Signaling, Composition and Regulation in Burkholderia pseudomallei.

The incidence of melioidosis cases caused by the gram-negative pathogen Burkholderia pseudomallei (BP) is seeing an increasing trend that has spread beyond its previously known endemic regions. Biofilms produced by BP have been associated with antimicrobial therapy limitation and relapse melioidosis, thus making it urgently necessary to understand the mechanisms of biofilm formation and their role in BP biology. Microbial cells aggregate and enclose within a self-produced matrix of extracellular polymeric substances (EPSs) to form biofilm. The transition mechanism of bacterial cells from planktonic state to initiate biofilm formation, which involves the formation of surface attachment microcolonies and the maturation of the biofilm matrix, is a dynamic and complex process. Despite the emerging findings on the biofilm formation process, systemic knowledge on the molecular mechanisms of biofilm formation in BP remains fractured. This review provides insights into the signaling systems, matrix composition, and the biosynthesis regulation of EPSs (exopolysaccharide, eDNA and proteins) that facilitate the formation of biofilms in order to present an overview of our current knowledge and the questions that remain regarding BP biofilms.

Natural Strategies as Potential Weapons against Bacterial Biofilms.

Microbial biofilm is an aggregation of microbial species that are either attached to surfaces or organized into an extracellular matrix. Microbes in the form of biofilms are highly resistant to several antimicrobials compared to planktonic microbial cells. Their resistance developing ability is one of the major root causes of antibiotic resistance in health sectors. Therefore, effective antibiofilm compounds are required to treat biofilm-associated health issues. The awareness of biofilm properties, formation, and resistance mechanisms facilitate researchers to design and develop combating strategies. This review highlights biofilm formation, composition, major stability parameters, resistance mechanisms, pathogenicity, combating strategies, and effective biofilm-controlling compounds. The naturally derived products, particularly plants, have demonstrated significant medicinal properties, producing them a practical approach for controlling biofilm-producing microbes. Despite providing effective antibiofilm activities, the plant-derived antimicrobial compounds may face the limitations of less bioavailability and low concentration of bioactive molecules. The microbes-derived and the phytonanotechnology-based antibiofilm compounds are emerging as an effective approach to inhibit and eliminate the biofilm-producing microbes.

Bacterial Biofilm Probed by Scanning Electrochemical Microscopy: A Review

AbstractBacterial biofilm, a highly structured community with developmental processes from cell adherence to highly dense biofilms, is of critical concern in many industries. Investigations of parameters mediating biofilm formation, interactions between bacterial species, and parameters governing biofilm stability are quite important for understanding mechanism of biofilm formation. Scanning electrochemical microscopy (SECM), a local electrochemical technique using a microelectrode as its probe, can monitor microbe interactions in situ via detection of small molecules or biochemical cues with spatial and temporal resolution. In this review, we summarize the recent advances in biofilm research using SECM. First, we introduce the applications and potential biochemical cues of biofilms. Then, we classify the applications based on the bacterial species of interest, focusing on SECM to study key biochemical cues and highlighting underlying metabolic processes involved in biofilm formation. Finally, we discuss the challenges and limitations given the complexity and diversity of biofilms for future SECM studies.

Mechanism of biofilm formation by Salmonella typhimurium ST19 in a high-glucose environment revealed by transcriptomics

Salmonella is one of the most common foodborne pathogens in the world, and Salmonella typhimurium, the most frequently isolated serotype, can cause zoonosis. In this study, we evaluated the effect of glucose concentration on the biofilm formation of 11 strains of Salmonella typhimurium. We found that among the selected strains, low-sugar conditions were more conducive to the formation of biofilms, although strain ST19 followed another rule. As the glucose concentration increased, biofilm formation showed an increasing trend. When the concentration of glucose reached 1.5%, other strains no longer formed biofilms, while strain ST19 still had strong biofilm formation ability. Therefore, we selected a culture medium containing 1.5% glucose to collect biofilms and planktonic cells of strain ST19 and compared them with strain CDC3, which did not produce a biofilm under these conditions, for transcriptomics analysis. The results showed that the related genes in the phosphotransferase system (PTS) and the operon genes regulated by AI-2 signaling molecules were highly downregulated in the biofilm bacteria of strain ST19 with a glucose content of 1.5%. At the same time, the genes involved in the two-component system, carbon metabolism and transcription regulation were significantly upregulated, which indicated that strain ST19 could adapt to a high-glucose environment by regulating glucose transport and metabolism in bacteria under a high-glucose environment and regulate biofilm formation by upregulating the expression of related genes in the two-component system. These findings illustrated that the regulated mechanism of Salmonella typhimurium's biofilm formation, which are significant to control biofilm contamination.

Current Status of Preventive and Therapeutic Strategies Against Biofilm Formation in Arthroplasty

Total joint replacements have increased significantly, resulting in a corresponding increase in infections. Consequently, patients may undergo additional surgical procedures and be prescribed antibiotics for a prolonged period due to these infections. Periprosthetic joint infections are associated with the development of bacterial biofilms. The biofilm is a microbial community attached to a surface containing one or more bacterial species. In orthopedics, biofilm-forming bacteria are the most severe infection that can lead to multiple operations, prolonged antibiotic therapy, morbidity, and increased health-care expenditures. These biofilm communities pose several clinical challenges relating to infection prevention, detection, and treatment. Over the past few years, biofilm formation mechanisms have been extensively studied, as have the mechanisms by which bacteria communicate within biofilms to perform specialized functions, such as persister cells. Currently, the orthopedic literature is very scarce, and understanding the cause and eradicating the disease requires a deep understanding. Several studies have demonstrated that the delivery of antibiotics locally through absorbable carriers and novel coatings for prostheses can deliver high concentrations of antibiotics. This literature review aims to identify mechanisms and structures of biofilm, especially in the context of arthroplasty, and to provide strategic guidance on current diagnosis, prevention, and target-specific treatment. In addition, the review discusses future diagnostic and therapeutic advancements.

Biofilm formation and inhibition mediated by bacterial quorum sensing.

As a complex microbial aggregate, biofilm is a group behavior of bacterial ability to adapt to the environment. Bacteria produce biofilm substrates that enhance their tolerance to stress and cause microbial infections. Biofilm infection is usually closely related to virulence, pathogenicity, and even life-threatening to immunocompromised patients. Therefore, studying bacterial biofilm generation and regulatory mechanisms has become one of the most important fields. It is well known that biofilm formation involves group behavior and relies on complex regulation of quorum sensing (QS). A series of small molecule compounds such as indole, AI-2 (autoinducer-2), AHL (N-acyl-homoserine lactone), AIP (auto-inducing peptide), and DSF (diffusible signal factor) are widely available intraspecific or interspecific signaling molecules, with regulatory functions on a wide range of physiological activities of bacteria, including biofilm formation. Given that various bacteria employ QS mechanisms to regulate biofilm formation, inhibition of QS becomes a promising potential strategy for the treatment of bacterial infections. Here, we describe how bacterial intraspecific and interspecific signaling molecules regulate the mechanism of biofilm formation and dispersion. This may contribute to anti-biofilm active molecules and provide ideas or directions for studies on controlling bacterial infections by inhibiting biofilm formation through QS. KEY POINTS: • The formation and hazard of biofilm have been discussed. • The effects of quorum sensing on biofilm formation have been highlighted. • The inhibition of biofilm through quorum sensing has been discussed and highlighted.

Is biofilm formation intrinsic to the origin of life?

Biofilms are multicellular, often surface-associated, communities of autonomous cells. Their formation is the natural mode of growth of up to 80% of microorganisms living on this planet. Biofilms refractory towards antimicrobial agents and the actions of the immune system due to their tolerance against multiple environmental stresses. But how did biofilm formation arise? Here, I argue that the biofilm lifestyle has its foundation already in the fundamental, surface-triggered chemical reactions and energy preserving mechanisms that enabled the development of life on earth. Subsequently, prototypical biofilm formation has evolved and diversified concomitantly in composition, cell morphology and regulation with the expansion of prokaryotic organisms and their radiation by occupation of diverse ecological niches. This ancient origin of biofilm formation thus mirrors the harnessing environmental conditions that have been the rule rather than the exception in microbial life. The subsequent emergence of the association of microbes, including recent human pathogens, with higher organisms can be considered as the entry into a nutritional and largely stress-protecting heaven. Nevertheless, basic mechanisms of biofilm formation have surprisingly been conserved and refunctionalized to promote sustained survival in new environments.

Microbiologically Influenced Corrosion Mechanism of Ferrous Alloys in Marine Environment

In marine environments, microbial attacks on metallic materials result in microbiologically influenced corrosion (MIC), which could cause severe safety accidents and high economic losses. To date, MIC of a number of metallic materials ranging from common steels to corrosion-resistant ferrous alloys has been reported. The MIC process has been explained based on (1) bio-catalyzed oxygen reduction; (2) kinetics alternation of the corrosion process by increasing the mass transport of the reactants and products; (3) production of corrosive substances; and (4) generation of auxiliary cathodic reactants. However, it is difficult to have a clear understanding of the MIC mechanism of ferrous alloys due to the interdisciplinary nature of MIC and lack of deep knowledge about the interfacial reaction between the biofilm and ferrous alloys. In order to better understand the effect of the MIC process on ferrous alloys, here we comprehensively summarized the process of biofilm formation and MIC mechanisms of ferrous alloys.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment.

Due to the continuous rise in biofilm‐related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

Control of Salmonella in mung bean sprouts by antagonistic spore-forming Bacilli

Sprouting seeds are considered part of a healthy and nutritious diet, and accordingly, their consumption increases globally. However, edible sprouts are occasionally linked to outbreaks of foodborne diseases, with Salmonella enterica being a frequent contaminant. Biocontrol was recently proposed as a possible approach to combat sprout contamination during production. The purpose of this study was to identify sprout-derived Salmonella-antagonists as a basis for the development of new biocontrol agents. To this end, spore-forming bacteria were isolated from sprouted mung bean seeds, based on either in vitro anti-Salmonella activity or rough colony morphology and tested in planta for inhibition of mung bean sprout colonization. Artificially contaminated seeds (2 log CFU/g) treated with selected Bacillus strains (7 log CFU/ml) demonstrated extensive inhibition of Salmonella growth after 4-days of sprouting, resulting in 3.3–5.4 log CFU/g reduction compared to control (untreated). The potent antagonistic activity of the selected Bacillus isolates was confirmed for different S. enterica serovars. Interestingly, some of the antagonistic strains that demonstrated activity in vitro were not active in planta and vice versa, indicating that in vitro testing may not be the best strategy for screening potential biocontrol strains in sprouts. Confocal microscopy imaging demonstrated that in the absence of Bacillus, Salmonella readily proliferates and colonizes the entire sprouting seed. Treatment with an antagonistic Bacillus isolate markedly inhibited the colonization of Salmonella. Scanning electron microscopy of Bacillus-treated sprouts demonstrated the colonization of the sprout with biofilm-like structures, indicating the activation of the biofilm formation mechanism during sprout colonization. The identified Bacillus isolates provide a basis for the future development of novel biocontrol agents against Salmonella and perhaps other foodborne pathogens in edible sprouts.

Mechanism of Biofilm Formation on Installation Materials and Its Impact on the Quality of Tap Water

In the conducted study, an attempt was made to verify and evaluate the impact of the biofilm formed on the surfaces of the installation material on the quality and sanitary safety of tap water reaching the consumer. For biofilm studies, fractal analysis and quantitative bacteriological analysis were used. The quality of tap water flowing through the experimental installation (semi-technical scale) was determined using physicochemical and microbiological parameters. The quantitative analysis of the biofilm showed that an increase in the number of microorganisms was observed in the initial phase of biofilm formation (reached 1.4 × 104 CFU/mL/cm2 on day 14). During this period, there was a chaotic build-up of bacterial cells, as evidenced by an increase in the roughness of the profile lines. Unstable elevations of the biofilm formed in this way could be easily detached from the structure of the material, which resulted in deterioration of the bacteriological quality of the water leaving the installation. The obtained results indicate that the biofilm completely and permanently covered the surface of the tested material after 25 days of testing (the surface roughness described by the fractal dimension decreased). Moreover, the favorable temperature (22.6 °C) and the recorded decrease in the content of inorganic nitrogen (by 15%), phosphorus (by 14%), and dissolved oxygen (by 15%) confirm the activity of microorganisms. The favorable environmental conditions in the installation (the presence of nutrients, low chlorine concentration, and high temperature) contributed to the secondary development of microorganisms, including pathogenic organisms in the tested waters.

Deletion of luxS gene mediated by λRed gene recombination technology reduces biofilm formation and stress resistance of Lactobacillus fermentum

This study investigated the effects of the luxS gene on the biofilm formation of Lactobacillus fermentum and its stress resistance. Deletion of the luxS gene was related to the physiological characteristics of biofilm development, strain resistance, bacterial morphology, biofilm morphology, functional group types, the main components of the biofilm, and the expression of related genes. Therefore, a luxS gene-deficient strain was constructed using λRed gene recombination technology, and the biofilm production and stress resistance of the WT and ΔluxS strains were compared. Deletion of the gene reduced the biofilm formation of L. fermentum and its resistance to acid, bile salt, high temperatures, and a hypertonic environment. Further, this work found that its deletion affects the types of functional groups in biofilms, and at the same time downregulate the expressions of the fabI, cysE, argR, and purD genes, thus reducing the levels of fatty acids, exopolysaccharide, protein, and eDNA in biofilms. A correlation analysis found that protein in biofilms was the most important factor affecting biofilm formation. In conclusion, the luxS gene in L. fermentum is involved in the regulation of biofilm formation and stress resistance. These findings provide a theoretical basis for the study of the mechanism of biofilm formation in beneficial bacteria.

Growth and biofilm formation of Cupriavidus metallidurans CH34 on different metallic and polymeric materials used in spaceflight applications

Bacteria biofilm formation and its complications are of special concern in isolated structures, such as offshore stations, manned submarines and space habitats, as maintenance and technical support are poorly accessible due to costs and/or logistical challenges. In addition, considering that future exploration missions are planned to adventure farther and longer in space, unlocking biofilm formation mechanisms and developing new antifouling solutions are key goals in order to ensure spacecraft’s efficiency, crew’s safety and mission success. In this work, we explored the interactions between Cupriavidus metallidurans, a prevalently identified contaminant onboard the International Space Station, and aerospace grade materials such as the titanium alloy TiAl6V4, the stainless steel AISI 316 (SS316) and Polytetrafluoroethylene (PTFE) or Teflon. Borosilicate glass was used as a control and all surfaces were investigated at two different pH values (5.0 and 7.0). Biofilms were almost absent on stainless steel and the titanium alloy contrary to Teflon and glass that were covered by an extensive biofilm formed via monolayers of scattered matrix-free cells and complex multilayered clusters or communities. Filamentous extracellular DNA structures were observed specifically in the complex multilayered clusters adherent to Teflon, indicating that the employed attachment machinery might depend on the physicochemical characteristics of the surface.

Arginine inhibits Saccharomyces cerevisiae biofilm formation by inducing endocytosis of the arginine transporter Can1.

Biofilms are formed by the aggregation of microorganisms into multicellular structures that adhere to surfaces. Biofilm formation by yeast is a critical issue in clinical and industrial fields because of the strong adhesion of yeast biofilm to abiotic surfaces and tissues. Here, we clarified the arginine-mediated inhibition of biofilm formation by yeast. First, we showed that arginine inhibits biofilm formation in fungi such as Saccharomyces cerevisiae, Candida glabrata, and Cladosporium cladosporioides, but not in bacteria. In regard to the underlying mechanism, biochemical analysis indicated that arginine inhibits biofilm formation by suppressing Flo11-dependent flocculation. Intriguingly, a strain with deletion of the arginine transporter-encoding CAN1 was insensitive to arginine-mediated inhibition of biofilm formation. Finally, Can1 endocytosis appeared to be required for the inhibitory mechanism of biofilm formation by arginine. The present results could help to elucidate the molecular mechanism of yeast biofilm formation and its control.

A Flagella Hook Coding Gene flgE Positively Affects Biofilm Formation and Cereulide Production in Emetic Bacillus cereus.

Bacillus cereus, an important foodborne pathogen, poses a risk to food safety and quality. Robust biofilm formation ability is one of the key properties that is responsible for the food contamination and food poisoning caused by B. cereus, especially the emetic strains. To investigate the mechanism of biofilm formation in emetic B. cereus strains, we screened for the mutants that fail to form biofilms by using random mutagenesis toward B. cereus 892-1, an emetic strain with strong biofilm formation ability. When knocking out flgE, a flagellar hook encoding gene, the mutant showed disappearance of flagellar structure and swimming ability. Further analysis revealed that both pellicle and ring presented defects in the null mutant compared with the wild-type and complementary strains. Compared with the flagellar paralytic strains Δ motA and Δ motB, the inhibition of biofilm formation by Δ flgE is not only caused by the inhibition of motility. Interestingly, Δ flgE also decreased the synthesis of cereulide. To our knowledge, this is the first report showing that a flagellar component can both affect the biofilm formation and cereulide production in emetic B. cereus, which can be used as the target to control the biohazard of emetic B. cereus.