Planktonic State Research Articles

Accumulated Copper Tailing Solid Wastes with Specific Compositions Encourage Advances in Microbial Leaching

Against the backdrop of the increasing copper demand in a low-carbon economy, this work statistically forecasted the distribution of China’s copper tailings for the first time, and then characterized them as finely crushed and low-grade mining solid wastes containing copper mainly in the form of chalcopyrite, bornite, covelline, enargite and chalcocite based on available research data. China is the globally leading refined copper producer and consumer, where the typical commercial-scale bioleaching of copper tailings is conducted in the Dexing, Zijinshan and Jinchuan mining regions. And these leaching processes were compared in this study. Widely used chemolithoautotrophic and mesophilic bacteria are Acidithiobacillus, Leptospirillum, Acidiphilium, Alicyclobacillus and Thiobacillus with varied metal resistance. They can be used to treat copper sulfide tailings such as pyrite, chalcopyrite, enargite, chalcocite, bornite and covellite under sufficient dissolved oxygen from 1.5 to 4.1 mg/L and pH values ranging from 0.5 to 7.2. Moderate thermophiles (Acidithiobacillus caldus, Acidimicrobium, Acidiplasma, Ferroplasma and Sulfobacillus) and extreme thermophilic archaea (Acidianus, Metallosphaera, Sulfurococcus and Sulfolobus) are dominant in leaching systems with operating temperatures higher than 40 °C. However, these species are vulnerable to high pulp density and heavy metals. Heterotrophic Acidiphilium multivorum, Ferrimicrobium, Thermoplasma and fungi use organic carbon as energy to treat copper oxides (malachite, chrysocolla and azurite) and weathered sulfides (bornite, chalcocite, digenite and covellite) under a wide pH range and high pulp density. We also compared autotrophs in a planktonic state or biofilm to treat different metal sulfides using various sulfur-cycling enzymes involved in the polysulfide or thiosulfate pathways against fungi that produce various organic acids to chelate copper from oxides. Finally, we recommended a bioinformatic analysis of functional genes involved in Fe/S oxidization and C/N metabolism, as well as advanced representation that can create new possibilities for the development of high-efficiency leaching microorganisms and insight into the mechanisms of bioleaching desired metals from complex and low-grade copper tailings.

Molecular Mechanisms of Biofilm Formation in Helicobacter pylori.

Biofilm formation in Helicobacter pylori (H. pylori) helps bacteria survive antibiotic exposure and supports bacterial colonization and persistence in the stomach. Most of the published articles have focused on one aspect of the biofilm. Therefore, we conducted the current study to better understand the mechanism of biofilm formation, how the biofilm contributes to antibiotic resistance, and how the biofilm modifies the medication delivery mechanism. We conducted a literature review analysis of the published articles on the Helicobacter pylori biofilm between 1998 and 2024 from the PubMed database to retrieve eligible articles. After applying the inclusion and exclusion criteria, two hundred and seventy-three articles were eligible for our study. The results showed that biofilm formation starts as adhesion and progresses through micro-colonies, maturation, and dispersion in a planktonic form. Moreover, specific genes modulate each phase of biofilm formation. Few studies have shown that mechanisms, such as quorum sensing and diffusible signal factors, enhance coordination among bacteria when switching from biofilm to planktonic states. Different protein expressions were also observed between planktonic and biofilm strains, and the biofilm architecture was supported by exopolysaccharides, extracellular DNA, and outer membrane vesicles. This infrastructure is responsible for the increased survival of bacteria, especially in harsh environments or in the presence of antibiotics. Therefore, understanding the biofilm formation for H. pylori is crucial. This study illustrates biofilm formation in H. pylori to help improve the treatment of H. pylori infection.

Hypervirulent Carbapenem-Susceptible Klebsiella pneumoniae ST412/K57 with Strong Biofilm Formation: association with gas gangrene and sepsis.

Hypervirulent Klebsiella pneumoniae (hvKp) poses a serious public health threat. Gas gangrene caused by hvKp was rarely reported, potentially resulting in a poor prognosis. In this study, we described the case of a hospitalized patient with gas gangrene and sepsis by hvKP. The carbapenem-susceptible hypervirulent Klebsiella pneumoniae (CS-hvKp) strains KPLSN and KPLSX were isolated from the knee joint pus and blood specimens of the patient for further investigations. Whole genome sequencing revealed that KPLSN and KPLSX were highly homologous (SNPs<10) and belonging to ST412/K57. The minimum inhibitory concentration and minimum bactericidal concentration under biofilm values of meropenem in KPLSN and KPLSX were significantly higher than planktonic state (>128 mg/L versus 0.25 mg/L, P<0.0001). These two strains had high biofilm formation ability, and fluorescence staining experiments results showed that they were not easily killed by meropenem in the biofilm state. KPLSN and KPLSX showed high capsular production and were confirmed with high virulence through experiments with the Galleria mellonella and BALB/c mice abdominal infection model. The persistent symptoms may be due to enhanced biofilm and capsule formation. Global ST412 strains phylogenetic analysis showed their evolution towards higher virulence and resistance. It emphasizes the critical need for judicious antibiotic use and novel therapeutic approaches to combat special infections caused by these pathogens.

L-Rhamnose Globally Changes the Transcriptome of Planktonic and Biofilm Escherichia coli Cells and Modulates Biofilm Growth.

L-rhamnose, a naturally abundant sugar, plays diverse biological roles in bacteria, influencing biofilm formation and pathogenesis. This study investigates the global impact of L-rhamnose on the transcriptome and biofilm formation of PHL628 E. coli under various experimental conditions. We compared growth in planktonic and biofilm states in rich (LB) and minimal (M9) media at 28 °C and 37 °C, with varying concentrations of L-rhamnose or D-glucose as a control. Our results reveal that L-rhamnose significantly affects growth kinetics and biofilm formation, particularly reducing biofilm growth in rich media at 37 °C. Transcriptomic analysis through RNA-seq showed that L-rhamnose modulates gene expression differently depending on the temperature and media conditions, promoting a planktonic state by upregulating genes involved in rhamnose transport and metabolism and downregulating genes related to adhesion and biofilm formation. These findings highlight the nuanced role of L-rhamnose in bacterial adaptation and survival, providing insight into potential applications in controlling biofilm-associated infections and industrial biofilm management.

Development, evaluation and application of propidium monoazide (PMA) based methodologies on viable cell quantification of Pediococcus acidilactici in rice noodles products

Pediococcus acidilactici provides a special taste during dough fermentation, but its improper presence will accelerate the spoilage of rice noodles products. In this study, propidium monoazide (PMA) based methodologies on viable cells quantification of P. acidilactici were developed, evaluated and applied in rice noodles products. Prior to qPCR and RT-qPCR detection, PMA treatment was included to effectively remove the residual DNA from membrane-compromised (dead) cells. Firstly, considering the influence of food component and PMA on qPCR result determination, 4 standard curves corresponding Ct value to P. acidilactici cell number were established in 4 different rice noodle products, respectively. The 4 standard curves were subsequently applied for viable cell quantification of P. acidilactici. Secondly, mimicking the storage conditions of rice noodles products and growth states of P. acidilactici, planktonic and biofilm (early, mediate, mature) cells in 4 types of rice noodles products stored at −20 °C and 4 °C were taken into consideration to evaluate the efficiency of PMA-qPCR for viable cell quantification. Thirdly, stress response gene expression in P. acidilactici was monitored by PMA-RT-qPCR and compared with culturable and viable cell number quantification. The PMA-qPCR method with specific standard curves for 4 types of rice noodle products was applicable for viable cell quantification of P. acidilactici in planktonic and biofilm (early, mediate, and mature) states. The planktonic and biofilm cells of P. acidilactici maintained high and stable in both culturable and viable cell number in different growth states, rice noodles products, and low temperature conditions, but acquired significantly different gene expression levels. The findings provided viable cells quantification methods and an alarm for P. acidilactici contamination risk in instant rice noodles products.

Effect of Zinc Oxide Nanorods on biofilms of different pathovars of Pseudomonas syringae

The P. syringae bacteria is one of the most relevant pathogens for agriculture due to the large number of agricultural species it infects. At this point, the formation of biofilms contributes to determining its virulence and fitness. In agriculture, the ZnO nanoparticles are recognized for their potential use as nanofertilizers and antimicrobial compounds. In this sense, this work aimed to study the effect of ZnO nanorods (ZnONRs) on biofilms and in the planktonic state of different pathovars of the plant pathogen P. syringae. In contrast with the literature, our results showed that the tested pathovars are highly resistant to shaped-rod ZnO with tiny sizes because they showed no inhibitory effect in mature biofilms exposed to high concentrations of up to 500 µg/mL of nanoparticles.

Dental Caries: Unveiling the State-of-the-art Insights and Crafting Hypotheses for Oral Health.

The pathophysiological understanding of dental caries explains that the primary factor responsible is linked to an imbalance in microbial composition within the oral cavity, stemming from both artificial and natural sources. Streptococcus mutans (S. mutans) is the most accountable and prevalent pathogen for caries development among the diverse pool. S. mutans, an acidogenic bacterium, lowers oral pH through the metabolic conversion of dietary sugar into organic acids, leading to enamel demineralization and dental caries. Numerous antibacterial interventions have been employed in the past to address this issue. However, adopting such an approach poses the risk of exacerbating concerns related to Antimicrobial Resistance (AMR) and long-term oral cytotoxicity. In response to this, a sustainable strategy is suggested, involving the utilization of L-Arginine (L-Arg) as a probiotic nutrient supplement for non-pathogenic microbes. It will help in creating a natural competitive environment against the pathogenic microbes responsible for initiating dental caries. The hypothesis involves utilizing a combination of a nutrient supplement and the repurposed drug Piceatannol, specifically for its anti-biofilm properties. This combination synergistically improves the effectiveness of the therapy by converting the complex microbial biofilm into a planktonic state.

Influence of Copper on Oleidesulfovibrio alaskensis G20 Biofilm Formation.

Copper is known to have toxic effects on bacterial growth. This study aimed to determine the influence of copper ions on Oleidesulfovibrio alaskensis G20 biofilm formation in a lactate-C medium supplemented with variable copper ion concentrations. OA G20, when grown in media supplemented with high copper ion concentrations of 5, 15, and 30 µM, exhibited inhibited growth in its planktonic state. Conversely, under similar copper concentrations, OA G20 demonstrated enhanced biofilm formation on glass coupons. Microscopic studies revealed that biofilms exposed to copper stress demonstrated a change in cellular morphology and more accumulation of carbohydrates and proteins than controls. Consistent with these findings, sulfur (dsrA, dsrB, sat, aprA) and electron transport (NiFeSe, NiFe, ldh, cyt3) genes, polysaccharide synthesis (poI), and genes involved in stress response (sodB) were significantly upregulated in copper-induced biofilms, while genes (ftsZ, ftsA, ftsQ) related to cellular division were negatively regulated compared to controls. These results indicate that the presence of copper ions triggers alterations in cellular morphology and gene expression levels in OA G20, impacting cell attachment and EPS production. This adaptation, characterized by increased biofilm formation, represents a crucial strategy employed by OA G20 to resist metal ion stress.

Cocktail Approach with Polyserotonin Nanoparticles and Peptides for Treatment of Streptococcus mutans.

Dental plaque, formed by a Streptococcus mutans biofilm, is a major contributor to cavity formation. While antimicrobial strategies exist, the growing risk of antibiotic resistance necessitates alternative therapeutic solutions. Polyserotonin nanoparticles (PSeNPs), recently recognized for their photothermal property and promising biomedical applications, open up a new avenue for antimicrobial use. Here, we introduced a UV-initiated synthetic route for PSeNPs with improved yield. Using these PSeNPs, a cocktail treatment to reduce the viability of this cavity-causing bacteria was developed. This cocktail comprises an S. mutans-targeting antimicrobial peptide (GH12), an intraspecies competence-stimulating peptide that triggers altruistic cell death in S. mutans, and laser-activated heating of PSeNPs. The "peptide + PSeNP + laser" combination effectively inhibits S. mutans growth in both planktonic and biofilm states. Moreover, the cocktail approach remains effective in reducing the viability of S. mutans in a more virulent dual-species biofilm with Candida albicans. Overall, our results reinforce the utility of a multipronged therapeutic strategy to reduce cariogenic bacteria in the complex model oral biofilm.

Lactate promotes the biofilm-to-invasive-planktonic transition in Salmonella enterica serovar Typhimurium via the de novo purine pathway.

Salmonella enterica serovar Typhimurium (S. Typhimurium) infection triggers an inflammatory response that changes the concentration of metabolites in the gut impacting the luminal environment. Some of these environmental adjustments are conducive to S. Typhimurium growth, such as the increased concentrations of nitrate and tetrathionate or the reduced levels of Clostridia-produced butyrate. We recently demonstrated that S. Typhimurium can form biofilms within the host environment and respond to nitrate as a signaling molecule, enabling it to transition between sessile and planktonic states. To investigate whether S. Typhimurium utilizes additional metabolites to regulate its behavior, our study delved into the impact of inflammatory metabolites on biofilm formation. The results revealed that lactate, the most prevalent metabolite in the inflammatory environment, impedes biofilm development by reducing intracellular c-di-GMP levels, suppressing the expression of curli and cellulose, and increasing the expression of flagellar genes. A transcriptomic analysis determined that the expression of the de novo purine pathway increases during high lactate conditions, and a transposon mutagenesis genetic screen identified that PurA and PurG, in particular, play a significant role in the inhibition of curli expression and biofilm formation. Lactate also increases the transcription of the type III secretion system genes involved in tissue invasion. Finally, we show that the pyruvate-modulated two-component system BtsSR is activated in the presence of high lactate, which suggests that lactate-derived pyruvate activates BtsSR system after being exported from the cytosol. All these findings propose that lactate is an important inflammatory metabolite used by S. Typhimurium to transition from a biofilm to a motile state and fine-tune its virulence.IMPORTANCEWhen colonizing the gut, Salmonella enterica serovar Typhimurium (S. Typhimurium) adopts a dynamic lifestyle that alternates between a virulent planktonic state and a multicellular biofilm state. The coexistence of biofilm formers and planktonic S. Typhimurium in the gut suggests the presence of regulatory mechanisms that control planktonic-to-sessile transition. The signals triggering the transition of S. Typhimurium between these two lifestyles are not fully explored. In this work, we demonstrated that in the presence of lactate, the most dominant host-derived metabolite in the inflamed gut, there is a reduction of c-di-GMP in S. Typhimurium, which subsequently inhibits biofilm formation and induces the expression of its invasion machinery, motility genes, and de novo purine metabolic pathway genes. Furthermore, high levels of lactate activate the BtsSR two-component system. Collectively, this work presents new insights toward the comprehension of host metabolism and gut microenvironment roles in the regulation of S. Typhimurium biology during infection.

Multi-omics analysis reveals genes and metabolites involved in Streptococcus suis biofilm formation

BackgroundStreptococcus suis is an important zoonotic pathogen. Biofilm formation largely explains the difficulty in preventing and controlling S. suis. However, little is known about the molecular mechanism of S. suis biofilm formation.ResultsIn this study, transcriptomic and metabolomic analyses of S. suis in biofilm and planktonic states were performed to identify key genes and metabolites involved in biofilm formation. A total of 789 differential genes and 365 differential metabolites were identified. By integrating transcriptomics and metabolomics, five main metabolic pathways were identified, including amino acid pathway, nucleotide metabolism pathway, carbon metabolism pathway, vitamin and cofactor metabolism pathway, and aminoacyl-tRNA biosynthesis metabolic pathway.ConclusionsThese results provide new insights for exploring the molecular mechanism of S. suis biofilm formation.

Green synthesis and antibacterial-antibiofilm properties of biogenic silver nanoparticles

The biosynthesis of metallic nanoparticles is gaining prominence as an alternative to traditional physicochemical methods, offering several advantages such as simplicity, non-toxicity, lower energy requirements and short reaction times leading to environmentally sustainable processes. The aims of this work were: to study the extracellular biosynthesis of silver nanoparticles (AgNPs) by Pseudomonas extremaustralis 2E-UNGS, to characterise the shape, monodispersity and size of AgNPs, to explore their antimicrobial and antibiofilm activities, and to evaluate the role of nitrate reductase activity in the biosynthesis process. The novelty of this work relies on the development of a green and sustainable method for the synthesis of stable AgNPs with optimal properties for potential applications in antimicrobial materials, especially when incorporated into polymeric matrices or used as agrochemical substitutes. Optimal conditions for the biosynthesis of spherical AgNPs were determined to be pH 7, 38 °C, 4 h of darkness and 120 rpm using stationary phase culture supernatants of P. extremaustralis 2E-UNGS. The involvement of extracellular nitrate reductase in AgNP biosynthesis was confirmed by enzymatic assays and supported by bioinformatics analysis, which identified the presence of the napA2 gene linked to the nirBD cluster. Antimicrobial assays demonstrated the inhibitory effect of AgNPs against both Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa PA01 in both planktonic and biofilm states. In addition, the potential application of AgNPs in innovative antibacterial polymers was explored by incorporating them into polyurethane matrices either alone (PU-AgNP) or in combination with crystal violet as a photosensitizer (PU-AgNP-CV). Subsequent inoculation with a clinical isolate of Pseudomonas aeruginosa resulted in significant reductions in viable bacterial counts on both PU-AgNP-CV and PU-AgNP. Biogenic AgNPs showed antibacterial and antibiofilm properties for new antimicrobial material development.

Antibacterial activity evaluation of a novel K3-specific phage against Acinetobacter baumannii and evidence for receptor-binding domain transfer across morphologies

Acinetobacter baumannii (A. baumannii) poses a serious public health challenge due to its notorious antimicrobial resistance, particularly carbapenem-resistant A. baumannii (CRAB). In this study, we isolated a virulent phage, named P1068, from medical wastewater capable of lysing CRAB, primarily targeting the K3 capsule type. Basic characterization showed that P1068 infected the A. baumannii ZWAb014 with an optimal MOI of 1, experienced a latent period of 10 ​min and maintained stability over a temperature range of 4–37 ​°C and pH range of 3–10. Phylogenetic and average nucleotide identity analyses indicate that P1068 can be classified as a novel species within the genus Obolenskvirus of the Caudoviricetes class as per the most recent virus classification released by the International Committee on Taxonomy of Viruses (ICTV). Additionally, according to classical morphological classification, P1068 is identified as a T4-like phage (Myoviridae). Interestingly, we found that the tail fiber protein (TFP) of P1068 shares 74% coverage and 88.99% identity with the TFP of a T7-like phage (Podoviridae), AbKT21phiIII (NC_048142.1). This finding suggests that the TFP gene of phages may undergo horizontal transfer across different genera and morphologies. In vitro antimicrobial assays showed that P1068 exhibited antimicrobial activity against A. baumannii in both biofilm and planktonic states. In mouse models of intraperitoneal infection, P1068 phage protected mice from A. baumannii infection and significantly reduced bacterial loads in various tissues such as the brain, blood, lung, spleen, and liver compared to controls. In conclusion, this study demonstrates that phage P1068 might be a potential candidate for the treatment of carbapenem-resistant and biofilm-forming A. baumannii infections, and expands the understanding of horizontal transfer of phage TFP genes.

Biofilm mitigation in hybrid chemical-biological upcycling of waste polymers.

Introduction: Accumulation of plastic waste in the environment is a serious global issue. To deal with this, there is a need for improved and more efficient methods for plastic waste recycling. One approach is to depolymerize plastic using pyrolysis or chemical deconstruction followed by microbial-upcycling of the monomers into more valuable products. Microbial consortia may be able to increase stability in response to process perturbations and adapt to diverse carbon sources, but may be more likely to form biofilms that foul process equipment, increasing the challenge of harvesting the cell biomass. Methods: To better understand the relationship between bioprocess conditions, biofilm formation, and ecology within the bioreactor, in this study a previously-enriched microbial consortium (LS1_Calumet) was grown on (1) ammonium hydroxide-depolymerized polyethylene terephthalate (PET) monomers and (2) the pyrolysis products of polyethylene (PE) and polypropylene (PP). Bioreactor temperature, pH, agitation speed, and aeration were varied to determine the conditions that led to the highest production of planktonic biomass and minimal formation of biofilm. The community makeup and diversity in the planktonic and biofilm states were evaluated using 16S rRNA gene amplicon sequencing. Results: Results showed that there was very little microbial growth on the liquid product from pyrolysis under all fermentation conditions. When grown on the chemically-deconstructed PET the highest cell density (0.69g/L) with minimal biofilm formation was produced at 30°C, pH 7, 100rpm agitation, and 10sL/hr airflow. Results from 16S rRNAsequencing showed that the planktonic phase had higher observed diversity than the biofilm, and that Rhodococcus, Paracoccus, and Chelatococcus were the most abundant genera for all process conditions. Biofilm formation by Rhodococcus sp. And Paracoccus sp. Isolates was typically lower than the full microbial community and varied based on the carbon source. Discussion: Ultimately, the results indicate that biofilm formation within the bioreactor can be significantly reduced by optimizing process conditions and using pure cultures or a less diverse community, while maintaining high biomass productivity. The results of this study provide insight into methods for upcycling plastic waste and how process conditions can be used to control the formation of biofilm in bioreactors.

Poly Lactic-co-Glycolic Acid (PLGA) Loaded with a Squaraine Dye as Photosensitizer for Antimicrobial Photodynamic Therapy.

Antimicrobial Photodynamic Therapy (aPDT) is an innovative and promising method for combating infections, reducing the risk of antimicrobial resistance compared to traditional antibiotics. Squaraine (SQ) dyes can be considered promising photosensitizers (PSs) but are generally hydrophobic molecules that can self-aggregate under physiological conditions. To overcome these drawbacks, a possible solution is to incorporate SQs inside nanoparticles (NPs). The present work deals with the design and development of innovative nanophotosensitizers based on poly lactic-co-glycolic acid (PLGA) NPs incorporating a brominated squaraine (BrSQ) with potential application in aPDT. Two designs of experiments (DoEs) based on the single emulsion and nanoprecipitation methods were set up to investigate how different variables (type of solvent, solvent ratio, concentration of PLGA, stabilizer and dye, sonication power and time) can affect the size, zeta (ζ)-potential, yield, entrapment efficiency, and drug loading capacity of the SQ-PLGA NPs. SQ-PLGA NPs were characterized by NTA, FE-SEM, and UV-Vis spectroscopy and the ability to produce reactive oxygen species (ROS) was evaluated, proving that ROS generation ability is preserved in SQ-PLGA. In vitro antimicrobial activity against Gram-positive bacteria in planktonic state using Staphylococcus aureus was conducted in different conditions and pH to evaluate the potential of these nanophotosensitizers for aPDT in the local treatment of infections.

Dynamic Adhesive Behavior and Biofilm Formation of Staphylococcus aureus on Polylactic Acid Surfaces in Diabetic Environments.

Interest in biodegradable implants has focused attention on the resorbable polymer polylactic acid. However, the risk of these materials promoting infection, especially in patients with existing pathologies, needs to be monitored. The enrichment of a bacterial adhesion medium with compounds that are associated with human pathologies can help in understanding how these components affect the development of infectious processes. Specifically, this work evaluates the influence of glucose and ketone bodies (in a diabetic context) on the adhesion dynamics of S. aureus to the biomaterial polylactic acid, employing different approaches and discussing the results based on the physical properties of the bacterial surface and its metabolic activity. The combination of ketoacidosis and hyperglycemia (GK2) appears to be the worst scenario: this system promotes a state of continuous bacterial colonization over time, suppressing the stationary phase of adhesion and strengthening the attachment of bacteria to the surface. In addition, these supplements cause a significant increase in the metabolic activity of the bacteria. Compared to non-enriched media, biofilm formation doubles under ketoacidosis conditions, while in the planktonic state, it is glucose that triggers metabolic activity, which is practically suppressed when only ketone components are present. Both information must be complementary to understand what can happen in a real system, where planktonic bacteria are the ones that initially colonize a surface, and, subsequently, these attached bacteria end up forming a biofilm. This information highlights the need for good monitoring of diabetic patients, especially if they use an implanted device made of PLA.

A closer look at plastic colonisation: Prokaryotic dynamics in established versus newly synthesised marine plastispheres and their planktonic state

The taxonomy of marine plastisphere communities has been extensively studied, demonstrating the ubiquity of hydrocarbonoclastic bacteria of potential biotechnological significance. However, prokaryotic functioning on plastic surfaces has received limited attention, and the question of whether these microorganisms are active and expressing specific molecular mechanisms underpinning plastisphere colonisation remains to be addressed. The aim of this study was to investigate the plastic colonisation process, to identify the active taxa involved in biofilm formation and the mechanisms used to initiate colonisation. To achieve this, a marine plastisphere characterised by active hydrocarbonoclastic genera was used as the inoculum for a short-term microcosm experiment using virgin low-density polyethylene as the sole carbon source. Following incubation for 1 and 2 weeks (representing early and late colonisation, respectively), a taxonomic and comparative metaproteomic approach revealed a significant shift in plastisphere diversity and composition, yet highlighted stability in the predominance of active Proteobacteria spanning 16 genera, including Marinomonas, Pseudomonas, and Pseudoalteromonas. Relative quantification of 1762 proteins shared between the initial plastisphere inoculum, the microcosm plastisphere and the planktonic cells in the surrounding artificial seawater, provided insights into the differential regulation of proteins associated with plastisphere formation. This included the upregulation of proteins mediating cellular attachment in the plastisphere, for example flagellin expressed by Marinomonas, Cobetia, Pseudoalteromonas, and Pseudomonas, and curli expressed by Cobetia. In addition to the differential regulation of energy metabolism in Marinomonas, Psychrobacter, Pseudomonas and Cobetia within the plastisphere relative to the surrounding seawater. Further, we identified the upregulation of amino acid metabolism and transport, including glutamine hydrolysis to glutamate in Marinomonas and unclassified Halomonadaceae, potentially coupled to ammonia availability and oxidative stress experienced within the plastisphere. Our study provides novel insights into the dynamics of plastisphere formation and function, highlighting potential targets for regulating plastisphere growth to enhance plastic bioremediation processes.

Evaluation of phenotypic and genotypic methods for the identification and characterization of bacterial isolates recovered from catheter-associated urinary tract infections.

Urinary tract infections are the most common hospital-acquired infection, 80% of which are associated with catheterization. Diagnostic methods may influence the reported identities of these pathogens, and phenotypic testing under laboratory conditions may not reflect infection phenotypes. This study aimed to evaluate the efficacy of diagnostic methods and whether medium composition alters phenotypes by characterizing catheter-associated urinary tract infection isolates from a UK hospital. We compared five bacterial identification methods, including biochemical testing, matrix-assisted laser desorption/ionization biotyping, and genome sequencing, finding differences in genus- or species-level identifications. Antibiotic susceptibility comparisons between phenotypic assays and genomic predictions showed high agreement only in multidrug-resistant strains. To determine whether growth rate and biofilm formation were affected by medium composition, strains were grown in both planktonic and biofilm states. Low planktonic growth and significant biofilm formation were observed in artificial urine compared to rich laboratory media, underscoring the importance of assay design. This study highlights the risks of relying on a single diagnostic method for species identification, advocating for whole-genome sequencing for accuracy. It emphasizes the continued importance of phenotypic methods in understanding antibiotic resistance in clinical settings and the need for characterization conditions that mirror those encountered by pathogens in the body.

PLGA nanoparticle-encapsulated lysostaphin for the treatment of Staphylococcus aureus infections

Staphylococcus aureus possesses the ability to become pathogenic, leading to severe and life-threatening infections. Its methicillin-resistant variant MRSA has garnered high-priority status due to its increased morbidity and associated mortality. This emphasizes the urgency for novel anti-staphylococcal agents. The bacteriocin lysostaphin stands out for its remarkable bactericidal activity against S. aureus, including MRSA, outperforming conventional antibiotics. However, the clinical application of lysostaphin faces challenges, including enzymatic activity loss under physiological conditions and potential immunogenicity. This study introduces a novel approach by encapsulating lysostaphin within polylactic-co-glycolic acid (PLGA) nanoparticles, a biodegradable copolymer known for its biocompatibility and sustained drug release ability. The study assesses the antimicrobial activity of lysostaphin-loaded PLGA nanoparticles against different S. aureus strains, and we also used GFP-expressing S. aureus for facilitating its traceability in planktonic, biofilm, and intracellular infection models. The results showed the significant reduction in bacteria viability both in planktonic and biofilm states. The in vitro intracellular infection model demonstrated the significantly enhanced efficiency of the developed nanoparticles compared to the treatment with the free bacteriocin. This research presents lysostaphin encapsulation within PLGA nanoparticles and offers promising avenues for enhancing lysostaphin's therapeutic efficacy against S. aureus infections.

High efficacy treatment of murine Pseudomonas aeruginosa catheter-associated urinary tract infections using the c-di-GMP modulating anti-biofilm compound Disperazol in combination with ciprofloxacin.

Persistent urinary tract infections (UTIs) in hospitalized patients constitute an important medical problem. It is estimated that 75% of nosocomial UTIs are associated with urinary tract catheters with P. aeruginosa being a species that forms biofilms on these catheters. These infections are highly resistant to standard-of-care antibiotics, and the effects of the host immune defenses, which allows for development of persistent infections. With antibiotics losing their efficacy, new treatment options against resilient infections, such as catheter-associated urinary tract infections (CAUTIs), are critically needed. Central to our anti-biofilm approach is the manipulation of the c-di-GMP signaling pathway in P. aeruginosa to switch bacteria from the protective biofilm to the unprotected planktonic mode of life. We recently identified a compound (H6-335-P1), that stimulates the c-di-GMP degrading activity of the P. aeruginosa BifA protein which plummets the intracellular c-di-GMP content and induces dispersal of P. aeruginosa biofilm bacteria into the planktonic state. In the present study, we formulated H6-335-P1 as a hydrochloride salt (Disperazol), which is water-soluble and facilitates delivery via injection or oral administration. Disperazol can work as a monotherapy, but we observed a 100-fold improvement in efficacy when treating murine P. aeruginosa CAUTIs with a Disperazol/ciprofloxacin combination. Biologically active Disperazol reached the bladder 30 min after oral administration. Our study provides proof of concept that Disperazol can be used in combination with a relevant antibiotic for effective treatment of CAUTIs.