Bacterial Aggregation Research Articles

Suppressive effects of gecko cathelicidin on biofilm formation and cariogenic virulence factors of Streptococcus mutans

ObjectiveThe aims of this study were to investigate the effectivity of gecko cathelicidin Gj-CATH2 on biofilm formation and cariogenic virulence factors of S. mutans, and preliminary explore its function mechanisms. DesignMinimum inhibitory concentration and bacterial killing kinetics assays were performed to assess the antimicrobial effect of Gj-CATH2.The influence of Gj-CATH2 on S. mutans biofilm formation was determined by crystal violet staining method and observed by SEM. The effects of Gj-CATH2 on exopolysaccharides (EPS) synthesis, bacterial aggregation, acidogenicity and aciduricity of S. mutans were also investigated. Quantitative real-time PCR was conducted to acquire the expression profile of related genes. ResultsGj-CATH2 showed strong bactericidal and anti-biofilm effects on S. mutans. SEM confirmed the reduction of the dense structure in S. mutans biofilm in Gj-CATH2-treated groups. Gj-CATH2 significantly inhibited EPS synthesis, cell aggregation, acid production of S. mutans, but showed no influence on its acid proof. Furthermore, the expression of genes related to biofilm formation (gtfB/C/D, gbpB/D), quorum sensing system (luxS and comD/E) and acidogenicity (ldh) was significantly suppressed by Gj-CATH2. Gj-CATH2 also displayed advantageous resistance in human saliva and exhibited negligible toxicity against mammalian cells. ConclusionsGj-CATH2 inhibited S. mutans biofilm formation by targeting the bacterial adhesion and the biofilm maturation stages. Gj-CATH2 significantly suppressed virulence factors production of S. mutans, resulting in decreased EPS synthesis and reduced acidogenicity of bacteria. These findings suggest Gj-CATH2 might be a promising agent for clinical application in prevention of dental caries.

Thermonucleases Contribute to Staphylococcus aureus Biofilm Formation in Implant-Associated Infections-A Redundant and Complementary Story.

Biofilms formed by Staphylococcus aureus are one of the predominant causes of implant-associated infections (IAIs). Previous studies have found that S. aureus nucleases nuc1 and nuc2 modulate biofilm formation. In this study, we found low nuc1/nuc2 expression and high biofilm-forming ability among IAI isolates. Furthermore, in a mouse model of exogenous IAIs, Δnuc1/2 exhibited higher bacterial load on the surface of the implant than that exhibited by the other groups (WT, Δnuc1, and Δnuc2). Survival analysis of the hematogenous IAI mouse model indicated that nuc1 is a virulence factor related to mortality. We then detected the influence of nuc1 and nuc2 on biofilm formation and immune evasion in vitro. Observation of in vitro biofilm structures with scanning electron microscopy and evaluation of bacterial aggregation with flow cytometry revealed that both nuc1 and nuc2 are involved in biofilm structuring and bacterial aggregation. Unlike nuc1, which is reported to participate in immune evasion, nuc2 cannot degrade neutrophil extracellular traps. Moreover, we found that nuc1/nuc2 transcription is negatively correlated during S. aureus growth, and a possible complementary relationship has been proposed. In conclusion, nuc1/nuc2 are complementary genes involved in biofilm formation in exogenous IAIs. However, nuc2 contributes less to virulence and is not involved in immune evasion.

UV-C LED Irradiation Reduces Salmonella on Chicken and Food Contact Surfaces.

Ultraviolet (UV-C) light-emitting diode (LED) light at a wavelength of 250–280 nm was used to disinfect skinless chicken breast (CB), stainless steel (SS) and high-density polyethylene (HD) inoculated with Salmonella enterica. Irradiances of 2 mW/cm2 (50%) or 4 mW/cm2 (100%) were used to treat samples at different exposure times. Chicken samples had the lowest Salmonella reduction with 1.02 and 1.78 Log CFU/cm2 (p ≤ 0.05) after 60 and 900 s, respectively at 50% irradiance. Higher reductions on CB were obtained with 100% illumination after 900 s (>3.0 Log CFU/cm2). Salmonella on SS was reduced by 1.97 and 3.48 Log CFU/cm2 after 60 s of treatment with 50% and 100% irradiance, respectively. HD showed a lower decrease of Salmonella, but still statistically significant (p ≤ 0.05), with 1.25 and 1.77 Log CFU/cm2 destruction for 50 and 100% irradiance after 60 s, respectively. Longer exposure times of HD to UV-C yielded up to 99.999% (5.0 Log CFU/cm2) reduction of Salmonella with both irradiance levels. While UV-C LED treatment was found effective to control Salmonella on chicken and food contact surfaces, we propose three mechanisms contributing to reduced efficacy of disinfection: bacterial aggregation, harboring in food and work surface pores and light absorption by fluids associated with CB.

SdiA, a Quorum-Sensing Regulator, Suppresses Fimbriae Expression, Biofilm Formation, and Quorum-Sensing Signaling Molecules Production in Klebsiella pneumoniae

Klebsiella pneumoniae is a Gram-negative pathogen that has become a worldwide concern due to the emergence of multidrug-resistant isolates responsible for various invasive infectious diseases. Biofilm formation constitutes a major virulence factor for K. pneumoniae and relies on the expression of fimbrial adhesins and aggregation of bacterial cells on biotic or abiotic surfaces in a coordinated manner. During biofilm aggregation, bacterial cells communicate with each other through inter- or intra-species interactions mediated by signallng molecules, called autoinducers, in a mechanism known as quorum sensing (QS). In most Gram-negative bacteria, intra-species communication typically involves the LuxI/LuxR system: LuxI synthase produces N-acyl homoserine lactones (AHLs) as autoinducers and the LuxR transcription factor is their cognate receptor. However, K. pneumoniae does not produce AHL but encodes SdiA, an orphan LuxR-type receptor that responds to exogenous AHL molecules produced by other bacterial species. While SdiA regulates several cellular processes and the expression of virulence factors in many pathogens, the role of this regulator in K. pneumoniae remains unknown. In this study, we describe the characterization of sdiA mutant strain of K. pneumoniae. The sdiA mutant strain has increased biofilm formation, which correlates with the increased expression of type 1 fimbriae, thus revealing a repressive role of SdiA in fimbriae expression and bacterial cell adherence and aggregation. On the other hand, SdiA acts as a transcriptional activator of cell division machinery assembly in the septum, since cells lacking SdiA regulator exhibited a filamentary shape rather than the typical rod shape. We also show that K. pneumoniae cells lacking SdiA regulator present constant production of QS autoinducers at maximum levels, suggesting a putative role for SdiA in the regulation of AI-2 production. Taken together, our results demonstrate that SdiA regulates cell division and the expression of virulence factors such as fimbriae expression, biofilm formation, and production of QS autoinducers in K. pneumoniae.

КОРОТКОТРИВАЛА АКУСТИЧНА ОБРОБКА ВОДИ

Purpose. To investigate the process of treatment of different waters with short-term action of acoustic cavitation and to establish the expediency of simultaneous bubbling of different gases into the reaction medium and cavitation. Methodology. The duration of the disaggregation process during the processing of the model medium is 2–3 minutes, while for natural water – 30 minutes. The number of microorganisms (NM) before and after the experiments was determined by counting the colonies that grew on the Petri dishes. For the research we used a model medium based on distilled water with the addition of bacillary cells and natural water. The model environment was exposed to gases of different nature and acoustic cavitation, and natural water was treated only by cavitation. Results. It was found that the process of water purification consists of two processes: the accumulation of microbial counts caused by the destruction of microbial aggregates and the reduction of microbial counts caused by the destruction of microbial cells. Such stages are revealed both at acoustic processing of the microbic water formed on the basis of disaerated distilled water, and natural. It has been experimentally shown that the use of bubbling gases accelerates the disaggregation process by almost 10 times. The proposed method of treatment of different waters with short-term exposure allowed to detect the process of disaggregation of microbial cells with their subsequent destruction in the aqueous medium and to achieve a high degree of water disinfection. Originality. The article proposes the supply of gases of different nature in the reaction medium for disinfection of water from bacteria under cavitation. It has been proven that gas supply during the first three minutes of the process accelerates the breakdown of aggregate aggregates in the aquatic environment under acoustic conditions, which is associated with the formation of additional cavitation nuclei, compared to the process in the absence of gas supply. It was found that at the initial moment of the reaction, the energy of cavitation was spent on breaking up clusters of bacterial aggregates into single cells, and death occurs more slowly than disaggregation. Practical value. It has been experimentally proved that the accumulation of microbial counts in the first stage of the water purification process with short-term action of acoustic cavitation is due to the processes of disaggregation of microorganisms. References 27, figures 2.

A rat model of polymicrobial infection in full-thickness excision wounds

AimA reproducible animal model is required to study the pathophysiology of wound infections and for development of effective therapeutic interventions. The objective of this study was to produce an infected skin wound model utilizing the cecal microbiota in non-immunocompromised rats. Materials and methodsAn excision wound was created on the dorsal surface of rats and inoculated with different concentration of cecal slurry (CS). Wound progression was investigated macroscopically by wound scoring and imaging. The rats were sacrificed on day 6 and microbial load, myeloperoxidase activity, histopathology, and scanning electron microscopy (SEM) were performed in wound tissue. ResultsInoculation of CS into excision wounds caused significantly (p < 0.05) delayed wound healing in comparison to non-infected wounds as revealed by slow wound closure (9.1 to 12.83%). A significant (p < 0.05) difference in wound score was observed between the infected and non-infected wounds. A significantly (p < 0.05) high microbial load (~10 9 CFU/gm) was observed in infected wound which was supported by the presence of intensive bacterial colonization with sparse development of amorphous material on wound tissue during SEM analysis. A maximum increase of 1.76-fold in myeloperoxidase activity was observed in the infected wounds in comparison to non-infected wounds. Histopathology revealed increased amount of cellular infiltration, hematoma formation, and presence of bacterial aggregates in deep tissues. ConclusionThe study reports a reproducible and relevant clinical model of wound infection where cecal microbiota was used as a source of infection. This model can provide a suitable platform for evaluation of new therapeutic interventions.

Virulence of Lactobacillus spp. misidentified as Enterococcus faecalis from children’s carious dentine

Objective: This study aimed to search for Enterococcus faecalis in children’s deep carious dentine and characterize their virulence traits. Material and Methods: Eight isolates from 15 carious molars identified by 16S rDNA species-specific PCR as E. faecalis were included. These eight isolates were subject to identification by MALDI‐TOF and characterized regarding: (i) bacterial aggregation and biofilm formation on polystyrene and glass, with/without saliva, as single or dual-species (associated to Streptococcus mutans); (ii) environmental pH measurement before and after 24 h incubation; (iii) acidogenicity; (iv) gelatinase production; (v) macrophage adherence; and (vi) toxicity towards Caenorhabditis elegans. Statistical analyses were performed using two-way ANOVA/Tukey or Fisher’s exact tests. Results: All isolates initially identified as E. faecalis by PCR were correctly identified as Lactobacillus by MALDI-TOF, being designated as Lactobacillus misidentified as Enterococcus (LME). These isolates produced biofilm in the presence of saliva and in the dual-species assays. Bacterial aggregation was only observed in the dual-species model. After 24 h, environmental pH dropped from 7.5 to 4.5 for seven of eight isolates, and to 4.0 in all dual-species models. LME isolates were acidogenic, none of them produced gelatinase or adhered to macrophages, but all presented toxicity towards C. elegans. Conclusions: No E. faecalis were identified in the children’s caries lesions. All LME isolates presented important virulence traits, including biofilm formation and high acidogenicity, which cause enamel demineralization, that might increase the risk of dental caries in children carrying LME. Thus, the correct identification and in-depth virulence characterization of microorganisms isolated from dental caries are important to understand the dynamics of this disease.

Enhanced dechlorination of 1,2-dichloropropane to propene in a bioelectrochemical system mediated by Dehalogenimonas

Bioelectrochemical systems (BES) are promising technologies to enhance the growth of organohalide-respiring bacteria and to treat chlorinated aliphatic hydrocarbons. In this study, two carbon-based cathodic electrode materials, a graphite brush and a carbon cloth, were used as hydrogen suppliers to couple growth of Dehalogenimonas and dechlorination of 1,2-DCP to nontoxic propene in the cathode vessel. The BES with graphite brush electrode consumed ~4000 µM 1,2-DCP during 110 days and exhibited a degradation rate 5.6-fold higher than the maximum value obtained with the carbon cloth electrode, with a cathode potential set at −0.7 V. Quantitative PCR confirmed that Dehalogenimonas gene copies increased by two orders of magnitude in the graphite brush BES, with an average yield of 1.2·108±5·107 cells per µmol of 1,2-DCP degraded. The use of a pulsed voltage operation (cathode potential set at −0.6 V for 16 h and −1.1 V for 8 h) increased the coulombic efficiency and degradation of 1,2-DCP when compared with a continuous voltage operation of −1.1 V. Bacterial cell aggregates were observed in the surface of the graphite brush electrodes by electron scanning microscopy, suggesting biofilm formation. This study expands the range of chlorinated compounds degradable and organohalide-respiring bacteria capable of growing in BES.

Hybrid Histidine Kinase BinK Represses Vibrio fischeri Biofilm Signaling at Multiple Developmental Stages.

The symbiosis between the Hawaiian bobtail squid, Euprymna scolopes, and its exclusive light organ symbiont, Vibrio fischeri, provides a natural system in which to study host-microbe specificity and gene regulation during the establishment of a mutually beneficial symbiosis. Colonization of the host relies on bacterial biofilm-like aggregation in the squid mucus field. Symbiotic biofilm formation is controlled by a two-component signaling (TCS) system consisting of regulators RscS-SypF-SypG, which together direct transcription of the symbiosis polysaccharide Syp. TCS systems are broadly important for bacteria to sense environmental cues and then direct changes in behavior. Previously, we identified the hybrid histidine kinase BinK as a strong negative regulator of V. fischeri biofilm regulation, and here we further explore the function of BinK. To inhibit biofilm formation, BinK requires the predicted phosphorylation sites in both the histidine kinase (H362) and receiver (D794) domains. Furthermore, we show that RscS is not essential for host colonization when binK is deleted from strain ES114, and imaging of aggregate size revealed no benefit to the presence of RscS in a background lacking BinK. Strains lacking RscS still suffered in competition. Finally, we show that BinK functions to inhibit biofilm gene expression in the light organ crypts, providing evidence for biofilm gene regulation at later stages of host colonization. Overall, this study provides direct evidence for opposing activities of RscS and BinK and yields novel insights into biofilm regulation during the maturation of a beneficial symbiosis. IMPORTANCE Bacteria are often in a biofilm state, and transitions between planktonic and biofilm lifestyles are important for pathogenic, beneficial, and environmental microbes. The critical nature of biofilm formation during Vibrio fischeri colonization of the Hawaiian bobtail squid light organ provides an opportunity to study development of this process in vivo using a combination of genetic and imaging approaches. The current work refines the signaling circuitry of the biofilm pathway in V. fischeri, provides evidence that biofilm regulatory changes occur in the host, and identifies BinK as one of the regulators of that process. This study provides information about how bacteria regulate biofilm gene expression in an intact animal host.

Green Tea-Derived Epigallocatechin Gallate Inhibits Acid Production and Promotes the Aggregation of Streptococcus mutans and Non-Mutans Streptococci

It has been suggested that green tea-derived epigallocatechin gallate (EGCG), which has antimicrobial properties, might help prevent dental caries. However, the detailed properties of EGCG remain unclear. In this study, the antimicrobial properties of EGCG were evaluated by examining its bactericidal activity, its inhibitory effects against bacterial growth, acid production, acidic end-product formation, and sugar uptake (phosphoenolpyruvate-dependent phosphotransferase system, PEP-PTS activity), and its effects on bacterial aggregation, using monocultured planktonic cells of Streptococcus mutans and non-mutans streptococci. Coincubating S. mutans with EGCG (1 mg/mL) for 4 h had no bactericidal effects, while it decreased the growth and acid production of S. mutans by inhibiting the activity of the PEP-PTS. EGCG (2 mg/mL) caused rapid bacterial cell aggregation and had reduced the optical density of S. mutans cell suspension by 86.7% at pH 7.0 and 90.7% at pH 5.5 after 2 h. EGCG also reduced the acid production of non-mutans streptococci, including S. sanguinis, S. gordonii, and S. salivarius, and promoted the aggregation of these non-mutans streptococci. Furthermore, these antimicrobial effects of short-term EGCG treatment persisted in the presence of saliva. These results suggest that EGCG might have short-term antibacterial effects on caries-associated streptococci in the oral cavity.

Genetically Programmable Microbial Assembly.

Engineered microbial communities show promise in a wide range of applications, including environmental remediation, microbiome engineering, and synthesis of fine chemicals. Here we present methods by which bacterial aggregates can be directed into several distinct architectures by inducible surface expression of heteroassociative protein domains (SpyTag/SpyCatcher and SynZip17/18). Programmed aggregation can be used to activate a quorum-sensing circuit, and aggregate size can be tuned via control of the amount of the associative protein displayed on the cell surface. We further demonstrate reversibility of SynZip-mediated assembly by addition of soluble competitor peptide. Genetically programmable bacterial assembly provides a starting point for the development of new applications of engineered microbial communities in environmental technology, agriculture, human health, and bioreactor design.

Mycobacterium avium subsp. hominissuis (MAH) Microaggregate induction of host innate immunity is linked to biofilm formation

Bacterial aggregation is a strategy employed by many pathogens to establish infection. Mycobacterium avium subsp. hominissuis (MAH) undergoes a phenotypic change, microaggregation, when exposed to the respiratory epithelium. We therefore compared how non-aggregated bacteria, or planktonic, and microaggregated MAH can establish lung infections by evaluating mucosal epithelial cell and phagocytic cell responses. It was determined that human mucosal lung epithelial cells recognition of MAH occurs through toll-like receptors 1 and 2. MAPK 1/3 is phosphorylated at 30 min post infection, and active at the transcriptional level 2 h post infection for both phenotypes. Microaggregate infected BEAS-2B cells up-regulated CCL5, IL-1β, and TNF-α cDNA, while planktonic infected cells only up-regulated IL-1β cDNA at 2 h post infection. Microaggregates are associated with increased uptake by macrophages after 1 h compared to planktonic bacteria (8.83% vs. 5.00%, P < 0.05). In addition, the microaggregate phenotype, when internalized by macrophages, had reduced growth compared to planktonic bacteria, which increased when the host cells were exposed to microaggregate supernatant, obtained from the incubation of MAH with HEp-2 cells. Moreover, microaggregate supernatant stimulated biofilm formation by planktonic and microaggregated bacteria. Microaggregate supernatant also induces the production of both pro- and anti-inflammatory cytokines, which was suppressed following MAH infection. The results suggest that epithelial recognition occurs during MAH infection, and the microaggregate phenotype stimulates an inflammatory response. The initial bacterial interaction with the mucosal epithelium and development of the microaggregate phenotype has a role in pathogenesis, allowing for more robust biofilm formation and infection establishment.

Staphylococcus aureus Floating Biofilm Formation and Phenotype in Synovial Fluid Depends on Albumin, Fibrinogen, and Hyaluronic Acid.

Biofilms are typically studied in bacterial media that allow the study of important properties such as bacterial growth. However, the results obtained in such media cannot take into account the bacterial localization/clustering caused by bacteria–protein interactions in vivo and the accompanying alterations in phenotype, virulence factor production, and ultimately antibiotic tolerance. We and others have reported that methicillin-resistant or methicillin-susceptible Staphylococcus aureus (MRSA or MSSA, respectively) and other pathogens assemble a proteinaceous matrix in synovial fluid. This proteinaceous bacterial aggregate is coated by a polysaccharide matrix as is characteristic of biofilms. In this study, we identify proteins important for this aggregation and determine the concentration ranges of these proteins that can reproduce bacterial aggregation. We then test this protein combination for its ability to cause marked aggregation, antibacterial tolerance, preservation of morphology, and expression of the phenol-soluble modulin (PSM) virulence factors. In the process, we create a viscous fluid that models bacterial behavior in synovial fluid. We suggest that our findings and, by extension, use of this fluid can help to better model bacterial behavior of new antimicrobial therapies, as well as serve as a starting point to study host protein–bacteria interactions characteristic of physiological fluids.

Novel Strategies to Combat Bacterial Biofilms.

Biofilms are considered as a severe problem in the treatment of bacterial infections; their development causes some noticeable resistance to antibacterial agents. Biofilms are responsible for at least two-thirds of all infections, displaying promoted resistance to classical antibiotic treatments. Therefore, finding new alternative therapeutic approaches is essential for the treatment and inhibition of biofilm-related infections. Therefore, this review aims to describe the potential therapeutic strategies that can inhibit bacterial biofilm development; these include the usage of antiadhesion agents, AMPs, bacteriophages, QSIs, aptamers, NPs and PNAs, which can prevent or eradicate the formation of biofilms. These antibiofilm agents represent a promising therapeutic target in the treatment of biofilm infections and development of a strong capability to interfere with different phases of the biofilm development, including adherence, polysaccharide intercellular adhesion (PIA), quorum sensing molecules and cell-to-cell connection, bacterial aggregation, planktonic bacteria killing and host-immune response modulation. In addition, these components, in combination with antibiotics, can lead to the development of some kind of powerful combined therapy against bacterial biofilm-related infections.

Biofilm Formation on Dental Implant Biomaterials by Staphylococcus aureus Strains Isolated from Patients with Cystic Fibrosis.

Implants made of ceramic and metallic elements, which are used in dentistry, may either promote or hinder the colonization and adhesion of bacteria to the surface of the biomaterial to varying degrees. The increased interest in the use of dental implants, especially in patients with chronic systemic diseases such as cystic fibrosis (CF), is caused by an increase in disease complications. In this study, we evaluated the differences in the in vitro biofilm formation on the surface of biomaterials commonly used in dentistry (Ti-6Al-4V, cobalt-chromium alloy (CoCr), and zirconia) by Staphylococcus aureus isolated from patients with CF. We demonstrated that S. aureus adherence and growth depends on the type of material used and its surface topography. Weaker bacterial biofilm formation was observed on zirconia surfaces compared to titanium and cobalt-chromium alloy surfaces. Moreover, scanning electron microscopy showed clear differences in bacterial aggregation, depending on the type of biomaterial used. Over the past several decades, S. aureus strains have developed several mechanisms of resistance, especially in patients on chronic antibiotic treatment such as CF. Therefore, the selection of an appropriate implant biomaterial with limited microorganism adhesion characteristics can affect the occurrence and progression of oral cavity infections, particularly in patients with chronic systemic diseases.

Isolation and genetic characterization of Flavobacterium columnare from grass carp, Ctenopharyngodon idellus, in China

Flavobacterium columnare is the causal agent of columnaris disease and has severe impacts on the grass carp, Ctenopharyngodon idellus, aquaculture industry. The genetic characteristics of F. columnare strains isolated from grass carp in China are not clear. Therefore, in this study, we obtained 45 bacterial isolates from grass carp with columnaris disease from 11 provinces of China. The 45 bacterial isolates were identified as F. columnare according to phenotypic traits, biochemical characteristics, and molecular identification with 16S rDNA gene sequencing. Furthermore, based on the analysis of restriction fragment length polymorphism of the 16S rDNA gene (16S-RFLP), 37 isolates belonged to genomovar I, 5 isolates were ascribed to genomovar II, and 3 isolates were identified as genomovar III. Phylogenetic analysis further confirmed the genetic differences between the three genomovar isolates and revealed a closer relationship between genomovar I and II isolates. The colony pseudo-root morphology and the degree of bacterial aggregation of the three genomovar isolates were significantly different when they were cultured under the same conditions. We concluded that there are three genotypes of F. columnare currently identified in grass carp, and genomovar I was the main type. These findings provide a basis for the genetic diversity of F. columnare in grass carp in China.

In Vitro and In Silico Screening and Characterization of Antimicrobial Napin Bioactive Protein in Brassica juncea and Moringa oleifera.

The study aimed to investigate the antibacterial activity of Mustard (Brassica juncea) and Moringa (Moringa oleifera) leaf extracts and coagulant protein for their potential application in water treatment. Bacterial cell aggregation and growth kinetics studies were employed for thirteen bacterial strains with different concentrations of leaf extracts and coagulant protein. Moringa oleifera leaf extract (MOS) and coagulant protein showed cell aggregation against ten bacterial strains, whereas leaf extract alone showed growth inhibition of five bacterial strains for up to 6 h and five bacterial strains for up to 3 h. Brassica juncea leaf extract (BJS) showed growth inhibition for up to 6 h, and three bacterial strains showed inhibition for up to 3 h. The highest inhibition concentration with 2.5 mg/mL was 19 mm, and furthermore, the minimum inhibitory concentration (MIC) (0.5 mg/mL) and MBC (1.5 mg/mL) were determined to have a higher antibacterial effect for <3 KDa peptides. Based on LCMS analysis, napin was identified in both MOS and BJS; furthermore, the mode of action of napin peptide was determined on lipoprotein X complex (LpxC) and four-chained structured binding protein of bacterial type II topoisomerase (4PLB). The docking analysis has exhibited moderate to potent inhibition with a range of dock score −912.9 Kcal/mol. Thus, it possesses antibacterial-coagulant potential bioactive peptides present in the Moringa oleifera purified protein (MOP) and Brassica juncea purified protein (BJP) that could act as an effective antimicrobial agent to replace currently available antibiotics. The result implies that MOP and Brassica juncea purified coagulant (BJP) proteins may perform a wide degree of antibacterial functions against different pathogens.

Delayed neutrophil recruitment allows nascent Staphylococcus aureus biofilm formation and immune evasion

Biofilms that form on implanted medical devices cause recalcitrant infections. The early events enabling contaminating bacteria to evade immune clearance, before a mature biofilm is established, are poorly understood. Live imaging in vitro demonstrated that Staphylococcus aureus sparsely inoculated on an abiotic surface can go undiscovered by human neutrophils, grow, and form aggregates. Small (~50 μm2) aggregates of attached bacteria resisted killing by human neutrophils, resulting in neutrophil lysis and bacterial persistence. In vivo, neutrophil recruitment to a peritoneal implant was spatially heterogenous, with some bacterial aggregates remaining undiscovered by neutrophils after 24 h. Intravital imaging in mouse skin revealed that attached S. aureus aggregates grew and remained undiscovered by neutrophils for up to 3 h. These results suggest a model in which delayed recruitment of neutrophils to an abiotic implant presents a critical window in which bacteria establish a nascent biofilm and acquire tolerance to neutrophil killing.

Implant-associated osteomyelitis: Development, characterisation, and application of a porcine model.

Implant-associated osteomyelitis: Development, characterisation, and application of a porcine model.

Particle Collection in Imhoff Sedimentation Cones Enriches Both Motile Chemotactic and Particle-Attached Bacteria.

Marine heterotrophic microorganisms remineralize about half of the annual primary production, with the microbiomes on and around algae and particles having a major contribution. These microbiomes specifically include free-living chemotactic and particle-attached bacteria, which are often difficult to analyze individually, as the standard method of size-selective filtration only gives access to particle-attached bacteria. In this study, we demonstrated that particle collection in Imhoff sedimentation cones enriches microbiomes that included free-living chemotactic bacteria and were distinct from particle microbiomes obtained by filtration or centrifugation. Coastal seawater was collected during North Sea phytoplankton spring blooms, and the microbiomes were investigated using 16S rRNA amplicon sequencing and fluorescence microscopy. Enrichment factors of individual operational taxonomic units (OTUs) were calculated for comparison of fractionated communities after separation with unfractionated seawater communities. Filtration resulted in a loss of cells and yielded particle fractions including bacterial aggregates, filaments, and large cells. Centrifugation had the lowest separation capacity. Particles with a sinking rate of >2.4 m day–1 were collected in sedimentation cones as a bottom fraction and enriched in free-living chemotactic bacteria, i.e., Sulfitobacter, Pseudoalteromonas, and Vibrio. Subfractions of these bottom fractions, obtained by centrifugation, showed enrichment of either free-living or particle-attached bacteria. We identified five distinct enrichment patterns across all separation techniques: mechano-sensitive and mechano-stable free-living bacteria and three groups of particle-attached bacteria. Simultaneous enrichment of particle-attached and chemotactic free-living bacteria in Imhoff sedimentation cones is a novel experimental access to these groups providing more insights into the diversity, structure, and function of particle-associated microbiomes, including members of the phycosphere.