Bacterial Surface Research Articles

The Next-Generation Probiotic E. coli 1917-pSK18a-MT Ameliorates Cadmium-Induced Liver Injury by Surface Display of Metallothionein and Modulation of Gut Microbiota.

Cadmium (Cd) is recognized as being linked to several liver diseases. Currently, due to the limited spectrum of drugs available for the treatment of Cd intoxication, developing and designing antidotes with superior detoxification capacity and revealing their underlying mechanisms remains a major challenge. Therefore, we developed the first next-generation probiotic E. coli 1917-pSK18a-MT that delivers metallothionein (MT) to overcome Cd-induced liver injury in C57BL/6 mice by utilizing bacterial surface display technology. The results demonstrate that E. coli 1917-pSK18a-MT could efficiently express MT without altering the growth and probiotic properties of the strain. Moreover, we found that E. coli 1917-pSK18a-MT ameliorated Cd contamination-induced hepatic steatosis, inflammatory cell infiltration, and liver fibrosis by decreasing the expression of aminotransferases along with inflammatory factors. Activation of the Nrf2-Keap1 signaling pathway also further illustrated the hepatoprotective effects of the engineered bacteria. Finally, we showed that E. coli 1917-pSK18a-MT improved the colonic barrier function impaired by Cd induction and ameliorated intestinal flora dysbiosis in Cd-poisoned mice by increasing the relative abundance of the Verrucomicrobiota. These data revealed that the combination of E. coli 1917 and MT both alleviated Cd-induced liver injury to a greater extent and restored the integrity of colonic epithelial tissues and bacterial dysbiosis.

Speed-dependent bacterial surface swimming.

In the early phase of biofilm formation, bacteria identify surfaces and increase the intracellular level of the second messenger c-di-GMP, resulting in a decrease in swimming speed. Here, we utilized advanced microscopy techniques to investigate the impact of swimming speed on bacterial surface swimming, focusing on Escherichia coli and Pseudomonas aeruginosa. We found that an increase in swimming speed led to an increase in the radius of curvature and a decrease in surface detention time. These effects were explained through hydrodynamic modeling as a result of an increase in the cell-surface distance with increasing swimming speed. We also observed distinct surface-escaping mechanisms between the two bacterial species. Our study suggests that a decrease in swimming speed could enhance the likelihood of cells adhering to the surface, promoting biofilm formation. This sheds light on the role of reduced swimming speed in the transition from motile to sedentary bacterial lifestyles.

Fighting bacteria with bacteria: A biocompatible living hydrogel patch for combating bacterial infections and promoting wound healing

Bacterial infections are among the most critical global health challenges that seriously threaten the security of human. To address this issue, a biocompatible engineered living hydrogel patch was developed by co-embedding engineered photothermal bacteria (EM), photosensitizer (porphyrin) and reactive oxygen species amplifier (laccase) in a protein hydrogel. Remarkably, the genetice engineered bacteria can express melanin granules in vivo and this allows them to exhibit photothermal response upon being exposed to NIR-II laser (1064 nm) irradiation. Besides, electrostatically adhered tetramethylpyridinium porphyrin (TMPyP) on the bacterial surface and encapsulated laccase (Lac) in protein gel can generate highly toxic singlet oxygen (1O2) and hydroxyl radical (·OH) in the presence of visible light and lignin, respectively. Interestingly, the engineered bacteria hydrogel patch (EMTL@Gel) was successfully applied in synergistic photothermal, photodynamic and chemodynamic therapy, in which it was able to efficiently treat bacterial infection in mouse wounds and enhance wound healing. This work demonstrates the concept of “fighting bacteria with bacteria” combining bacterial engineering and material engineering into an engineered living hydrogel path that can synergistically boost the therapeutic outcome. Statement of significanceGenetically engineered bacteria produce melanin granules in vivo, exhibiting remarkable photothermal properties. These bacteria, along with a photosensitizer (TMPyP) and a reactive oxygen species amplifier (laccase), are incorporated into a biocompatible protein hydrogel patch. Under visible light, the patch generates toxic singlet oxygen (1O2) and hydroxyl radical (·OH), demonstrates outstanding synergistic effects in photothermal, photodynamic, and chemodynamic therapy, effectively treating bacterial infections and promoting wound healing in mice.

Bacterial metallothionein, PmtA, a novel stress protein found on the bacterial surface of Pseudomonas aeruginosa and involved in management of oxidative stress and phagocytosis.

The pathogen Pseudomonas aeruginosa is a highly problematic multidrug-resistant (MDR) pathogen with complex virulence networks. MDR P. aeruginosa infections have been associated with increased clinical visits, very poor healthcare outcomes, and these infections are ranked as critical on priority lists of both the Centers for Disease Control and Prevention and the World Health Organization. Known P. aeruginosa virulence factors have been extensively studied and are implicated in counteracting host defenses, causing direct damage to the host tissues, and increased microbial competitiveness. Targeting virulence factors has emerged as a new line of defense in the battle against MDR P. aeruginosa strains. Bacterial metallothionein is a newly recognized virulence factor that enables evasion of the host immune response. The studies described here identify mechanisms in which bacterial metallothionein (PmtA) plays a part in P. aeruginosa pathogenicity and identifies PmtA as a potential therapeutic target.

Bacterial surface lipoproteins mediate epithelial microinvasion by Streptococcus pneumoniae.

Streptococcus pneumoniae, a common colonizer of the upper respiratory tract, invades nasopharyngeal epithelial cells without causing disease in healthy participants of controlled human infection studies. We hypothesized that surface expression of pneumococcal lipoproteins, recognized by the innate immune receptor TLR2, mediates epithelial microinvasion. Mutation of lgt in serotype 4 (TIGR4) and serotype 6B (BHN418) pneumococcal strains abolishes the ability of the mutants to activate TLR2 signaling. Loss of lgt also led to the concomitant decrease in interferon signaling triggered by the bacterium. However, only BHN418 lgt::cm but not TIGR4 lgt::cm was significantly attenuated in epithelial adherence and microinvasion compared to their respective wild-type strains. To test the hypothesis that differential lipoprotein repertoires in TIGR4 and BHN418 lead to the intraspecies variation in epithelial microinvasion, we employed a motif-based genome analysis and identified an additional 525 a.a. lipoprotein (pneumococcal accessory lipoprotein A; palA) encoded by BHN418 that is absent in TIGR4. The gene encoding palA sits within a putative genetic island present in ~10% of global pneumococcal isolates. While palA was enriched in the carriage and otitis media pneumococcal strains, neither mutation nor overexpression of the gene encoding this lipoprotein significantly changed microinvasion patterns. In conclusion, mutation of lgt attenuates epithelial inflammatory responses during pneumococcal-epithelial interactions, with intraspecies variation in the effect on microinvasion. Differential lipoprotein repertoires encoded by the different strains do not explain these differences in microinvasion. Rather, we postulate that post-translational modifications of lipoproteins may account for the differences in microinvasion.IMPORTANCEStreptococcus pneumoniae (pneumococcus) is an important mucosal pathogen, estimated to cause over 500,000 deaths annually. Nasopharyngeal colonization is considered a necessary prerequisite for disease, yet many people are transiently and asymptomatically colonized by pneumococci without becoming unwell. It is therefore important to better understand how the colonization process is controlled at the epithelial surface. Controlled human infection studies revealed the presence of pneumococci within the epithelium of healthy volunteers (microinvasion). In this study, we focused on the regulation of epithelial microinvasion by pneumococcal lipoproteins. We found that pneumococcal lipoproteins induce epithelial inflammation but that differing lipoprotein repertoires do not significantly impact the magnitude of microinvasion. Targeting mucosal innate immunity and epithelial microinvasion alongside the induction of an adaptive immune response may be effective in preventing pneumococcal colonization and disease.

Evaluating Bacterial Spore Preparation Methods for Scanning Electron Microscopy.

Scanning electron microscopy (SEM) can reveal the ultrastructure of bacterial spores, including morphology, surface features, texture, spore damage, germination, and appendages. Understanding these features can provide a basis for adherence, how physical and environmental stressors affect spore viability, integrity, and functionality, as well as the distribution and function of surface appendages. However, the spore sample preparation method can significantly impact the SEM images' appearance, resolution, and overall quality. In this study, we compare different spore preparation methods to identify optimal approaches for preparation time, spore appearance and resolved features, including the exosporium and spore pili, for SEM imaging. We use Bacillus paranthracis as model species and evaluate the efficacy of preparation protocols using different fixation and drying methods, as well as imaging under room- and cryogenic temperatures. We compare and assess method complexity to the visibility of the spore exosporium and spore appendages across different methods. Additionally, we use Haralick texture features to quantify the differences in spore surface appearance and determine the most suitable method for preserving spore structures and surface features during SEM evaluation. The findings from this study will help establish protocols for preparing bacterial spores for SEM and facilitating accurate and reliable analysis of spores' characteristics.

Unveiling the role of novel carbohydrate-binding modules in laminarin interaction of multimodular proteins from marine Bacteroidota during phytoplankton blooms.

Laminarin, a β(1,3)-glucan, serves as a storage polysaccharide in marine microalgae such as diatoms. Its abundance, water solubility and simple structure make it an appealing substrate for marine bacteria. Consequently, many marine bacteria have evolved strategies to scavenge and decompose laminarin, employing carbohydrate-binding modules (CBMs) as crucial components. In this study, we characterized two previously unassigned domains as laminarin-binding CBMs in multimodular proteins from the marine bacterium Christiangramia forsetii KT0803T, thereby introducing the new laminarin-binding CBM families CBM102 and CBM103. We identified four CBM102s in a surface glycan-binding protein (SGBP) and a single CBM103 linked to a glycoside hydrolase module from family 16 (GH16_3). Our analysis revealed that both modular proteins have an elongated shape, with GH16_3 exhibiting greater flexibility than SGBP. This flexibility may aid in the recognition and/or degradation of laminarin, while the constraints in SGBP could facilitate the docking of laminarin onto the bacterial surface. Exploration of bacterial metagenome-assembled genomes (MAGs) from phytoplankton blooms in the North Sea showed that both laminarin-binding CBM families are widespread among marine Bacteroidota. The high protein abundance of CBM102- and CBM103-containing proteins during phytoplankton blooms further emphasizes their significance in marine laminarin utilization.

Monitoring of enteropathogenic Gram-negative bacteria in wastewater treatment plants: a multimethod approach

The wastewater treatment processes are associated with the emission of microbial aerosols, including enteropathogenic bacteria. Their presence in this work environment poses a real threat to the health of employees, both through the possibility of direct inhalation of the contaminated air and indirectly through the pollution of all types of surfaces with such bioaerosol particles. This study aimed to investigate the prevalence of enteropathogenic bacteria in the air, on surfaces, and in wastewater samples collected in four wastewater treatment plants (WWTPs). The effectiveness of conventional culture-biochemical, as well as spectrometric and molecular methods for the rapid detection of enteropathogenic bacteria at workstations related to particular stages of wastewater processing, was also evaluated. Bioaerosol, surface swab, and influent and effluent samples were collected from wastewater plants employing mechanical–biological treatment technologies. The air samples were collected using MAS-100 NT impactor placed at a height of 1.5 m above the floor or ground, simulating aspiration from the human breathing zone. Surface samples were collected with sterile swabs from different surfaces (valves, handles, handrails, and coveyor belts) at workplaces. The raw influent and treated effluent wastewater samples were aseptically collected using sterile bottles. The identification of bacterial entheropathogens was simultaneously conducted using a culture-based method supplemented with biochemical (API) tests, mass-spectrometry (MALDI TOF MS), and molecular (multiplex real-time PCR) methods. This study confirmed the common presence of bacterial pathogens (including enteropathogenic and enterotoxigenic Escherichia coli, Salmonella spp., Campylobacter spp., and Yersinia enterocolitica) in all air, surface, and wastewater samples at studied workplaces. Higher concentrations of enteropathogenic bacteria were observed in the air and on surfaces at workplaces where treatment processes were not hermetized. The results of this study underline that identification of enteropathogenic bacteria in WWTPs is of great importance for the correct risk assessment at workplaces. From the analytical point of view, the control of enteropathogenic bacterial air and surface pollution using rapid multiplex-PCR method should be routinely performed as a part of hygienic quality assessment in WWTPs.

Lysine aggregates‐based nanostructured antimicrobial peptides for cariogenic biofilm microenvironment‐activated caries treatment

AbstractDental caries is one of the most prevalent and costly biofilm‐induced oral diseases that causes the deterioration of the mineralized tooth tissue. Traditional antimicrobial agents like antibiotics and antimicrobial peptides (AMPs) struggle to effectively eradicate bacteria in biofilms without eliciting resistance. Herein, we demonstrate the construction of FeOOH@Fe‐Lysine@Au nanostructured AMPs (nAMPs) distinguished by their AMP‐like antibacterial activity and self‐producing reactive oxygen species (ROS) capacity for caries treatment. On the one hand, FeOOH@Fe‐Lysine@Au nAMPs can catalyze glucose oxidation to generate ROS within the cariogenic biofilm microenvironment, resulting in the disintegration of the extracellular polymeric substance matrix and the exposure of bacteria. On the other hand, FeOOH@Fe‐Lysine@Au nAMPs can attach to bacterial surfaces via electrostatic attractions, proceeding to damage membranes, disrupt metabolic pathways, and inhibit protein synthesis through the aggregated lysine and the generated ROS. Based on this antibacterial mechanism, FeOOH@Fe‐Lysine@Au nAMPs can effectively eradicate Streptococcus mutans and its associated biofilm, significantly impeding the progression of dental caries. Given the straightforward and cost‐efficient preparation of FeOOH@Fe‐Lysine@Au nAMPs compared to AMPs that require specific sequences, and their minimal adverse impacts on gingival/palatal tissues, major organs, and oral/gut microbiomes, our research may promote the development of novel therapeutic agents in dental health maintenance.

Fraxetin Targeting to Sortase A Decreases the Pathogenicity of Streptococcus agalactiae to Nile Tilapia.

Sortase A (SrtA) is responsible for anchoring surface proteins to the cell wall, and has been identified as a promising target developing anti-infective drugs of Gram-positive bacteria. The aim of the study was to identify inhibitors of Streptococcus agalactiae (S. agalactiae) SrtA from natural compounds to overcome the spread of antibiotic resistance in aquaculture. Here, we found that the MIC of fraxetin against S. agalactiae was higher than 256 μg/mL, indicating that fraxetin had no anti- S. agalactiae activity. But fraxetin could dose-dependently decrease the activity of SrtA in vitro at concentrations ranging between 4-32 μg/mL by a fluorescence resonance energy transfer (FRET) assay. Moreover, the inhibition of SrtA by fraxetin decreased the anchoring of surface proteins with the LPXTG motif to the cell wall by detecting the immunofluorescence change of serine-rich repeat protein 1 (Srr1) on the bacterial cell surface. The results of fibronectin binding and cell adhesion assays indicated that fraxetin could significantly decrease the adhesion ability of S. agalactiae in a dose-dependent manner. The results were further proven by immunofluorescence staining. Animal challenge results showed that treatment with fraxetin could reduce the mortality of tilapia infected with S. agalactiae to 46.67%, indicating that fraxetin could provide a significant amount of protection to tilapia by inactivating SrtA. Taken together, these findings provided a novel inhibitor of S. agalactiae SrtA and a promising candidate for treating S. agalactiae infections in aquaculture.

Probable Role of Type IV Pili of Aeromonas hydrophila in Human Pathogenicity.

Aeromonas hydrophila is a widely recognized broad-spectrum pathogen that primarily targets the gastrointestinal tract. Type IV pili (T4P) are proteinaceous nano-machines located on the bacterial cell surface, playing a crucial role in host colonization and infection. Regrettably, the T4P systems of A. hydrophila remain largely underexplored. A. hydrophila genomes with complete genome assembly and annotation reports up to 31 March 2023, were obtained from the NCBI Genome database or KEGG genome database, followed by a global search for T4P secretion system genes. Protein sequences of these manually curetted genes were used as secondary quarry for Synteny analysis. Protein-protein interaction analysis was performed by string analysis and in silico study of genomic islands. We identified 27 orthologs of type IV pili (T4P) nano-machine components in A. hydrophila. These orthologs are primarily distributed across three operons: pilABCD, pilMNOPQ, and pilVWXY. While the first two operons are commonly found in all experimental genomes, the presence of the pilVWXY operon, coding for 11 orthologs, is reported here for the first time in A. hydrophila. Notably, the complete pilVWXY operon is absent in nonvirulent strains. A genomic islands study between a nonvirulent and hypervirulent strain also confirms absence of most of the genes coded by pilVWXY in nonvirulent strain. Interestingly, among the 51 experimental genomes analyzed, the pilVWXY operon was completely absent in 10 strains, most of which are categorized as nonvirulent; Conclusions: The distribution of two major type IV pili (T4P) nano-machines, PilABCDMNOPQ and PilVWXY, is reported here for the first time in A. hydrophila. Additionally, this study suggests a potential role for the PilVWXY nano-machine in establishing human disease.

Fenton reaction enhanced enzyme free electrochemical biosensor for rapid and highly sensitive detection of Salmonella

To fulfill the stringent demands of clinical Salmonella detection, this study employed the benefits of Ni-TCPP(Fe2+) and ConA to establish a novel approach that is culture-free, enzyme-free, secondary antibody-free, and ultra-sensitive. Our investigations revealed two key mechanisms that significantly bolster the signal-to-noise ratio (SNR) and enhance detection stability: firstly, the Fenton reaction and the mimic enzyme catalysis of Ni-TCPP(Fe2+) improved the sensitivity of the biosensor; secondly, the substitution of the secondary antibody with ConA led to increased binding of Ni-TCPP(Fe2+) due to the abundance of ConA receptors on the bacterial surface. With proper assembly, the developed biosensor exhibited high sensitivity in the range of 101–107 CFU/mL, along with a detection limit as low as 4 CFU/mL, and achieved rapid detection within a mere 2 h. Moreover, this biosensor has proven its efficacy in detecting Salmonella in clinical biological samples. Its advantages of being culture-free, secondary antibody-free, and ultra-sensitive establish a solid research foundation for the expedited detection of Salmonella in clinical settings and point-of-care testing (POCT).

New Insights into the Biological Functions of Essential TsaB/YeaZ Protein in Staphylococcus aureus.

TsaB/YeaZ represents a promising target for novel antibacterial agents due to its indispensable role in bacterial survival, high conservation within bacterial species, and absence of eukaryotic homologs. Previous studies have elucidated the role of the essential staphylococcal protein, TsaB/YeaZ, in binding DNA to mediate the transcription of the ilv-leu operon, responsible for encoding key enzymes involved in the biosynthesis of branched-chain amino acids-namely isoleucine, leucine, and valine (ILV). However, the regulation of ILV biosynthesis does not account for the essentiality of TsaB/YeaZ for bacterial growth. In this study, we investigated the impact of TsaB/YeaZ depletion on bacterial morphology and gene expression profiles using electron microscopy and deep transcriptomic analysis, respectively. Our results revealed significant alterations in bacterial size and surface smoothness upon TsaB/YeaZ depletion. Furthermore, we pinpointed specific genes and enriched biological pathways significantly affected by TsaB/YeaZ during the early and middle exponential phases and early stationary phases of growth. Crucially, our research uncovered a regulatory role for TsaB/YeaZ in bacterial autolysis. These discoveries offer fresh insights into the multifaceted biological functions of TsaB/YeaZ within S. aureus.

In situ captured antibacterial action of membrane-incising peptide lamellae

Developing unique mechanisms of action are essential to combat the growing issue of antimicrobial resistance. Supramolecular assemblies combining the improved biostability of non-natural compounds with the complex membrane-attacking mechanisms of natural peptides are promising alternatives to conventional antibiotics. However, for such compounds the direct visual insight on antibacterial action is still lacking. Here we employ a design strategy focusing on an inducible assembly mechanism and utilized electron microscopy (EM) to follow the formation of supramolecular structures of lysine-rich heterochiral β3-peptides, termed lamellin-2K and lamellin-3K, triggered by bacterial cell surface lipopolysaccharides. Combined molecular dynamics simulations, EM and bacterial assays confirmed that the phosphate-induced conformational change on these lamellins led to the formation of striped lamellae capable of incising the cell envelope of Gram-negative bacteria thereby exerting antibacterial activity. Our findings also provide a mechanistic link for membrane-targeting agents depicting the antibiotic mechanism derived from the in-situ formation of active supramolecules.

Synthesis of New Multifunctional Linolenic Acid Vanillyl Ester and Investigation of Antioxidant and Antibacterial Activities.

Vanillyl alcohol (VA) possesses potent antioxidant activity, yet its applicability is hindered by its limited solubility in emulsions or non-polar organic solvents. Conversely, long-chain polyunsaturated fatty acids exhibit antibacterial properties. The combination of these compounds offers the prospect of developing novel phenolic lipid compounds with dual antioxidant and antibacterial activities, alongside enhanced solubility capabilities. In this investigation, linolenic acid vanillyl ester (LAVE) was synthesized from VA and linseed oil (LO) through a transesterification reaction employing immobilized lipase. Optimization of LAVE production was achieved by varying reaction temperature, substrate concentration, and reaction time. LAVE demonstrated efficacy in scavenging both 2,2-diphenyl-1-picryhydrazyl and 2,2'-azino-bis (3-ethylbenthiazoline-6-sulphonic acid) radicals in organic solvents. Antioxidant testing via lipid oxidation analysis revealed that LAVE, when distributed within emulsions, effectively impeded the formation of conjugated dienes and conjugated trienes. Furthermore, LAVE exhibited antibacterial activity against four strains of spoilage bacteria: Bacillus subtilis, Bacillus coagulans, Pseudomonas fluorescens, and Alcaligenes faecalis. Zeta potential analysis substantiated the binding of LAVE to the bacterial cell surface. Propidium iodide uptake assay and fluorescence microscopy further elucidated that LAVE induces cell lysis by augmenting membrane permeability.

Effects of p-coumaric acid on probiotic properties of Lactobacillus acidophilus LA-5 and lacticaseibacillus rhamnosus GG.

Probiotics are defined as "live microorganisms that provide health benefits to the host when administered in adequate amounts." Probiotics have beneficial effects on human health, including antibacterial activity against intestinal pathogens, regulation of blood cholesterol levels, reduction of colitis and inflammation incidence, regulation of the immune system, and prevention of colon cancer. In addition to probiotic bacteria, some phenolic compounds found in foods we consume (both food and beverages) have positive effects on human health. p-coumaric acid (p-CA) is one of the most abundant phenolic compounds in nature and human diet. The interactions between these two different food components (phenolics and probiotics), resulting in more beneficial combinations called synbiotics, are not well understood in terms of how they will affect the gut microbiota by promoting the probiotic properties and growth of probiotic bacteria. Thus, this study aimed to investigate synbiotic relationship between p-CA and Lactobacillus acidophilus LA-5 (LA-5), Lacticaseibacillus rhamnosus GG (LGG). Probiotic bacteria were grown in the presence of p-CA at different concentrations, and the effects of p-CA on probiotic properties, as well as its in vitro effects on AChE and BChE activities, were investigated. Additionally, Surface analysis was conducted using FTIR. The results showed that treatment with p-CA at different concentrations did not exhibit any inhibitory effect on the growth kinetics of LA-5 and LGG probiotic bacteria. Additionally, both probiotic bacteria demonstrated high levels of antibacterial properties. It showed that it increased the auto-aggregation of both probiotics. While p-CA increased co-aggregation of LA-5 and LGG against Escherichia coli, it decreased co-aggregation against Staphylococcus aureus. Probiotics grown with p-CA were more resistant to pepsin. While p-CA increased the resistance of LA-5 to bile salt, it decreased the resistance of LGG. The combinations of bacteria and p-CA efficiently suppressed AChE and BChE with inhibition (%) 11.04-68.43 and 13.20-65.72, respectively. Furthermore, surface analysis was conducted using FTIR to investigate the interaction of p-coumaric acid with LA-5 and LGG, and changes in cell components on the bacterial surface were analyzed. The results, recorded in range of 4000 -600cm-1 with resolution of 4cm-1, demonstrated that p-CA significantly affected only the phosphate/CH ratio for both bacteria. These results indicate the addition of p-CA to the probiotic growth may enhance the probiotic properties of bacteria.

The Pseudomonas aeruginosa 1244 pilin glycan increases susceptibility to human beta defensin 2 but enhances twitching motility.

SHANIA DAVIS & JOSEPH HORZEMPA, Department of Biomedical Sciences, West LibertyUniversity, West Liberty, WV USA. The Pseudomonas aeruginosa 1244 pilin glycan increasessusceptibility to human beta defensin 2 but enhances twitching motility. Pseudomonas aeruginosa is an ESKAPE (highly drug resistant) pathogen that is commonlyacquired during hospital stays. This bacterium produces type IV pili which are adhesins andmotor appendages that mediate a surface motility referred to as “twitching.” These pili arepolymers of protein subunits referred to as pilin. The pilin subunit of P. aeruginosa 1244 isglycosylated. Previous studies have shown that the pilin glycan affects the efficiency oftwitching motility under certain conditions and the surface polarity of these fibers. Becausemodulation of the bacterial surface charge has been shown to mediate defensin resistance inother organisms, we tested whether pilin glycosylation affected sensitivity to human betadefensin 2 (HBD-2). Interestingly, the isogenic mutant strain lacking the pilin glycan (1244G7)showed increased resistance to HBD-2 compared to wild type bacteria and those completelylacking a type IV pilus (1244.47). This increased resistance to HBD-2 could explain data from arecent study in which various P. aeruginosa clinical strains were isolated that had pilinglycosylation defects. We also confirmed and extended previous findings that indicated that the1244 pilin glycan enhances twitching motility and we showed that this is especially true onpositively charged surfaces (poly L-lysine coated plastic). However, the positively chargedsurface was also capable of enhancing twitching of strains producing non-glycosylated pili or piliwith an incomplete glycan (1244.2.1).

Paper-based fluorescence sensor array with functionalized carbon quantum dots for bacterial discrimination using a machine learning algorithm

The rapid discrimination of bacteria is currently an emerging trend in the fields of food safety, medical detection, and environmental observation. Traditional methods often require lengthy culturing processes, specialized analytical equipment, and bacterial recognition receptors. In response to this need, we have developed a paper-based fluorescence sensor array platform for identifying different bacteria. The sensor array is based on three unique carbon quantum dots (CQDs) as sensing units, each modified with a different antibiotic (polymyxin B, ampicillin, and gentamicin). These antibiotic-modified CQDs can aggregate on the bacterial surface, triggering aggregation-induced fluorescence quenching. The sensor array exhibits varying fluorescent responses to different bacterial species. To achieve low-cost and portable detection, CQDs were formulated into fluorescent ink and used with an inkjet printer to manufacture paper-based sensor arrays. A smartphone was used to collect the responses generated by the bacteria and platform. Diverse machine learning algorithms were utilized to discriminate bacterial types. Our findings showcase the platform's remarkable capability to differentiate among five bacterial strains, within a detection range spanning from 1.0 × 103 CFU/mL to 1.0 × 107 CFU/mL. Its practicality is further validated through the accurate identification of blind bacterial samples. With its cost-effectiveness, ease of fabrication, and high degree of integration, this platform holds significant promise for on-site detection of diverse bacteria.Graphical abstract

Evaluation and activity of new porphyrin-peptide cage-type conjugates for the photoinactivation of Mycobacterium abscessus.

Mycobacterium abscessus is increasingly recognized as an emerging opportunistic pathogen causing severe lung diseases and cutaneous infections. However, treatment of M. abscessus infections remains particularly challenging, largely due to intrinsic resistance to a wide panel of antimicrobial agents. New therapeutic alternatives are urgently needed. Herein, we show that, upon limited irradiation with a blue-light source, newly developed porphyrin-peptide cage-type photosensitizers exert a strong bactericidal activity against smooth and rough variants of M. abscessus in planktonic cultures and in biofilms, at low concentrations. Atomic force microscopy unraveled important morphological alterations that include a wrinkled and irregular bacterial surface. The potential of these compounds for a photo-therapeutic use to treat M. abscessus skin infections requires further evaluations.IMPORTANCEMycobacterium abscessus causes persistent infections and is extremely difficult to eradicate. Despite intensive chemotherapy, treatment success rates remain very low. Thus, given the unsatisfactory performances of the current regimens, more effective therapeutic alternatives are needed. In this study, we evaluated the activity of newly described porphyrin-peptide cage-type conjugates in the context of photodynamic therapy. We show that upon light irradiation, these compounds were highly bactericidal against M. abscessus in vitro, thus qualifying these compounds for future studies dedicated to photo-therapeutic applications against M. abscessus skin infections.

Transcriptome analysis reveals vanadium reduction mechanisms in a bacterium of Pseudomonas balearica

The continuously elevated concentration of vanadium (V) in the environment is of great concern due to its potential risks to organisms. Microbial reduction is considered a green way to remediate the V-contaminated sites. This study presents the first demonstration of Pseudomonas balearica, a bacterium flourishing in vanadium-titanium magnetite tailings, exhibiting the capacity to reduce pentavalent V [V(V)]. We found that P. balearica exhibited strong tolerance to high V(V) levels, despite lacking known V(V)-reducing genes. After 48 h of incubation, the reduction rates of V(V) by P. balearica under 0.5 mM and 10 mM V(V) stress reached 81.1% and 60.6%, respectively. The phosphorus group and carboxyl group on the bacterial cell surface contributed to V(V) binding and reduction. Both extracellular and intracellular V(V) reduction was significantly facilitated by many critical V-induced differentially expressed genes (DEGs) encoding nitrate/nitrite reductases, ABC transporters, NADH, and c-type cytochromes. In addition, up-regulation of DEGs associated with reactive oxygen species (ROS)-scavenging enzymes, such as glutathione peroxidase, superoxide dismutase, and catalase, was observed as a protective response to oxidative stress triggered by V(V). Moreover, some up-regulated DEGs (ureC, ureE, ureA, and ureG) encoding urease subunit or urease accessory proteins significantly enriched in the nickel cation binding pathway, indicating that P. balearica may be resistant to Ni stress by regulating urease activity. This study will help to more thoroughly elucidate the characteristics and mechanisms of V(V) reduction by microbes and provide a native bacterium flourishing in tailings for potential bioremediation of V pollution and bioleaching of V-sources.