Bacterial Cell Surface Research Articles

An ultrasensitive electrochemical aptasensor using Tyramide-assisted enzyme multiplication for the detection of Staphylococcus aureus

In this study, we aimed to introduce a new electrochemical aptasensor based on the tyramide signal amplification (TSA) technology for a highly-sensitive detection of the pathogenic bacterium, Staphylococcus aureus, as a model of foodborne pathogens. In this aptasensor, the primary aptamer, SA37, was used to specifically capture bacterial cells; the secondary aptamer, SA81@HRP, was used as the catalytic probe; and a TSA-based signal enhancement system comprising of biotinyl-tyramide and streptavidin-HRP as electrocatalytic signal tags was adopted to fabricate the sensor and improve the detection sensitivity. S. aureus cells were selected as the pathogenic bacteria to verify the analytical performance of this TSA-based signal-enhancement electrochemical aptasensor platform. After the simultaneous binding of SA37-S. aureus-SA81@HRP formed on the gold electrode, thousands of @HRP molecules could be bound onto the biotynyl tyramide (TB) displayed on the bacterial cell surface through a catalytic reaction between HRP and H2O2, resulting in the generation of the highly amplified signals mediated by HRP reactions. This developed aptasensor could detect S. aureus bacterial cells at an ultra-low concentration, with a limit of detection (LOD) of 3 CFU/mL in buffer. Furthermore, this chronoamperometry aptasensor successfully detected target cells in both tap water and beef broth with LOD to be 8 CFU/mL, which are very high sensitivity and specificity. Overall, this electrochemical aptasensor using TSA-based signal-enhancement could be a very useful tool for the ultrasensitive detection of foodborne pathogens in food and water safety and environmental monitoring.

Utilization of Enterobacter cloacae WW1 Biomass for Biosorption of Lead(II) from Aqueous Solution

The present study evaluated lead biosorption by Enterobacter cloacae WW1 isolated from tannery wastewaters under different initial Pb2+ concentrations, biomass concentrations, and contact times. The results showed that at an initial Pb2+ concentration of 80 mg.L-1, the optimal conditions for living cells were a biomass concentration of 7 g.L-1 and a contact time of 120 min. For non-living cells, biomass was a biomass concentration of 4 g.L-1 and contact time of 45 min, which provided removal efficiencies of 92.03 ± 0.10% and 99.51 ± 0.01%, respectively. The maximum biosorption capacity obtained for non-living cells using an initial Pb2+ concentration of 640 mg.L-1 was 76.65 ± 0.05 mg.g-1. The equilibrium data followed the Langmuir and Freundlich models for living cells, and the data for non-living cell biosorbents fit the Langmuir model. The biosorption kinetics for living and non-living cells fit well with a pseudo-second-order kinetic equation. SEM-EDX analysis clearly showed the morphology and presence of Pb2+ particles on non-living cell surfaces after biosorption. In addition, the results revealed that functional groups such as hydroxyl, amino, carboxyl, amide, and phosphate groups on the bacterial cell surface detected by FTIR were associated with the binding of Pb2+ ions. The results indicated that E. cloacae WW1, a lead-resistant bacterium, can be used as an alternative biosorbent for lead removal from wastewater.

Characterization of a highly conserved MUC5B-degrading protease, MdpL, from Limosilactobacillus fermentum.

MUC5B is the predominant glycoprotein in saliva and is instrumental in the establishment and maintenance of multi-species eubiotic biofilms in the oral cavity. Investigations of the aciduric Lactobacillaceae family, and its role in biofilms emphasizes the diversity across different genera of the proteolytic systems involved in the nutritional utilization of mucins. We have characterized a protease from Limosilactobacillus fermentum, MdpL (Mucin degrading protease from Limosilactobacillus) with a high protein backbone similarity with commensals that exploit mucins for attachment and nutrition. MdpL was shown to be associated with the bacterial cell surface, in close proximity to MUC5B, which was sequentially degraded into low molecular weight fragments. Mapping the substrate preference revealed multiple hydrolytic sites of proteins with a high O-glycan occurrence, although hydrolysis was not dependent on the presence of O-glycans. However, since proteolysis of immunoglobulins was absent, and general protease activity was low, a preference for glycoproteins similar to MUC5B in terms of glycosylation and structure is suggested. MdpL preferentially hydrolyzed C-terminally located hydrophobic residues in peptides larger than 20 amino acids, which hinted at a limited sequence preference. To secure proper enzyme folding and optimal conditions for activity, L. fermentum incorporates a complex system that establishes a reducing environment. The importance of overall reducing conditions was confirmed by the activity boosting effect of the added reducing agents L-cysteine and DTT. High activity was retained in low to neutral pH 5.5-7.0, but the enzyme was completely inhibited in the presence of Zn2+. Here we have characterized a highly conserved mucin degrading protease from L. fermentum. MdpL, that together with the recently discovered O-glycanase and O-glycoprotease enzyme groups, increases our understanding of mucin degradation and complex biofilm dynamics.

Fish Probiotics: Cell Surface Properties of Fish Intestinal Lactobacilli and Escherichia coli

The properties of intestinal bacteria/probiotics, such as cell surface hydrophobicity (CSH), auto-aggregation, and biofilm formation ability, play an important role in shaping the relationship between the bacteria and the host. The current study aimed to investigate the cell surface properties of fish intestinal bacteria and probiotics. Microbial adhesion to hydrocarbons was tested according to Kos and coauthors. The aggregation abilities of the investigated strains were studied as described by Collado and coauthors. The ability of bacterial isolates to form a biofilm was determined by performing a qualitative analysis using crystal violet staining based on the attachment of bacteria to polystyrene. These studies prove that bacterial cell surface hydrophobicity (CSH) is associated with the growth medium, and the effect of the growth medium on CSH is species-specific and likely also strain-specific. Isolates of intestinal lactobacilli from fish (Salmo ischchan) differed from isolates of non-fish/shrimp origin in the relationship between auto-aggregation and biofilm formation. Average CSH levels for fish lactobacilli and E. coli might were lower compared to those of non-fish origin, which may affect the efficiency of non-fish probiotics use in fisheries due to the peculiarities of the hosts' aquatic lifestyles.

Defining the Surface Oxygen Threshold That Switches the Interaction Mode of Graphene Oxide with Bacteria.

As antimicrobials, graphene materials (GMs) may have advantages over traditional antibiotics due to their physical mechanisms of action which ensure less chance of development of microbial resistance. However, the fundamental question as to whether the antibacterial mechanism of GMs originates from parallel interaction or perpendicular interaction, or from a combination of these, remains poorly understood. Here, we show both experimentally and theoretically that GMs with high surface oxygen content (SOC) predominantly attach in parallel to the bacterial cell surface when in the suspension phase. The interaction mode shifts to perpendicular interaction when the SOC reaches a threshold of ∼0.3 (the atomic percent of O in the total atoms). Such distinct interaction modes are highly related to the rigidity of GMs. Graphene oxide (GO) with high SOC is very flexible and thus can wrap bacteria while reduced GO (rGO) with lower SOC has higher rigidity and tends to contact bacteria with their edges. Neither mode necessarily kills bacteria. Rather, bactericidal activity depends on the interaction of GMs with surrounding biomolecules. These findings suggest that variation of SOC of GMs is a key factor driving the interaction mode with bacteria, thus helping to understand the different possible physical mechanisms leading to their antibacterial activity.

Identification of Potential Proteinaceous Ligands of GI.1 Norovirus in Pacific Oyster Tissues.

Human norovirus (HuNoV) is the leading foodborne pathogen causing nonbacterial gastroenteritis worldwide. The oyster is an important vehicle for HuNoV transmission, especially the GI.1 HuNoV. In our previous study, oyster heat shock protein 70 (oHSP 70) was identified as the first proteinaceous ligand of GII.4 HuNoV in Pacific oysters besides the commonly accepted carbohydrate ligands, a histo-blood group antigens (HBGAs)-like substance. However the mismatch of the distribution pattern between discovered ligands and GI.1 HuNoV suggests that other ligands may exist. In our study, proteinaceous ligands for the specific binding of GI.1 HuNoV were mined from oyster tissues using a bacterial cell surface display system. Fifty-five candidate ligands were identified and selected through mass spectrometry identification and bioinformatics analysis. Among them, the oyster tumor necrosis factor (oTNF) and oyster intraflagellar transport protein (oIFT) showed strong binding abilities with the P protein of GI.1 HuNoV. In addition, the highest mRNA level of these two proteins was found in the digestive glands, which is consistent with GI.1 HuNoV distribution. Overall the findings suggested that oTNF and oIFT may play important roles in the bioaccumulation of GI.1 HuNoV.

Surveying membrane landscapes: a new look at the bacterial cell surface.

Recent studies applying advanced imaging techniques are changing the way we understand bacterial cell surfaces, bringing new knowledge on everything from single-cell heterogeneity in bacterial populations to their drug sensitivity and mechanisms of antimicrobial resistance. In both Gram-positive and Gram-negative bacteria, the outermost surface of the bacterial cell is being imaged at nanoscale; as a result, topographical maps of bacterial cell surfaces can be constructed, revealing distinct zones and specific features that might uniquely identify each cell in a population. Functionally defined assembly precincts for protein insertion into the membrane have been mapped at nanoscale, and equivalent lipid-assembly precincts are suggested from discrete lipopolysaccharide patches. As we review here, particularly for Gram-negative bacteria, the applications of various modalities of nanoscale imaging are reawakening our curiosity about what is conceptually a 3D cell surface landscape: what it looks like, how it is made and how it provides resilience to respond to environmental impacts.

Antibacterial Components and Modes of the Methanol-Phase Extract from Commelina communis Linn.

Infectious diseases caused by pathogenic bacteria severely threaten human health. Traditional Chinese herbs are potential sources of new or alternative medicine. In this study, we analyzed for the first time antibacterial substances in the methanol-phase extract from a traditional Chinese herb-Commelina communis Linn-which showed an inhibition rate of 58.33% against 24 species of common pathogenic bacteria. The extract was further purified using preparative high-performance liquid chromatography (Prep-HPLC), which generated four single fragments (Fragments 1 to 4). The results revealed that Fragment 1 significantly increased bacterial cell surface hydrophobicity and membrane permeability and decreased membrane fluidity, showing disruptive effects on cell integrity of Gram-positive and Gram-negative bacteria, such as Bacillus cereus, Enterococcus faecalis, Staphylococcus aureus, and Salmonella enterica subsp., compared to the control groups (p < 0.05). In sum, 65 compounds with known functions in Fragment 1 were identified using liquid chromatography and mass spectrometry (LC-MS), of which quercetin-3-o-glucuronide was predominant (19.35%). Comparative transcriptomic analysis revealed multiple altered metabolic pathways mediated by Fragment 1, such as inhibited ABC transporters, ribosome, citrate cycle and oxidative phosphorylation, and upregulated nitrogen metabolism and purine metabolism, thereby resulting in the repressed bacterial growth and even death (p < 0.05). Overall, the results of this study demonstrate that Fragment 1 from C. communis Linn is a promising candidate against common pathogenic bacteria.

Dynamics of Antibody Response to &lt;i&gt;Yersinia pestis&lt;/i&gt; Proteins in Plague Affected Guinea Pigs

Designing of new means for the specific prevention of plague, especially protein subunit vaccines, is impossible without studying the role of individual antigens in the manifestation of the pathogenic and immunogenic properties of Yersinia pestis. The aim of the present study was to determine the antibody levels to Y. pestis antigens in guinea pigs that survived infection with sub-lethal doses of virulent plague agent strains using enzyme immunoassay (ELISA). Materials and methods. Guinea pigs were inoculated subcutaneously with 30 CFU of the wild type Y. pestis subsp. Pestis strain 231 or non-capsular Y. pestis subsp. pestis Caf1-negative strain 358/12. Blood samples from sick or recovered guinea pigs were collected on day 15, 30, 60, and 90 after infection. The antibody response was assessed by 18 recombinant Y. pestis proteins in ELISA. Results and discussion. Heterogeneity of the antibody responses to the majority of the antigens with variation of IgG titers from animal to animal has been revealed. We observed increase in antibody titers by day 90 for the most analyzed antigens in the sera of the guinea pigs injected with wild type Y. pestis 231. On the contrary we found reduction in antibody titers by day 90 in case of inoculation with Y. pestis 358/12. The preservation of antibodies to Y. pestis proteins of different localization in the organism of the guinea pigs, as well functional activity, and the degree of representation on the surface of bacterial cell for a prolonged period of time indicates the multiplex nature of the plague immunity formation. Our findings are significant for the future design and development of effective vaccines against plague and the search for new targets for diagnostics of this disease.

Host Immune Responses to Surface S-Layer Proteins (SLPs) of Clostridioides difficile.

Clostridioides difficile, a nosocomial pathogen, is an emerging gut pathobiont causing antibiotic-associated diarrhea. C. difficile infection involves gut colonization and disruption of the gut epithelial barrier, leading to the induction of inflammatory/immune responses. The expression of two major exotoxins, TcdA and TcdB is the major cause of C. difficile pathogenicity. Attachment of bacterial abundant cell wall proteins or surface S-layer proteins (SLPs) such as SlpA with host epithelial cells is critical for virulence. In addition to being toxins, these surface components have been shown to be highly immunogenic. Recent studies indicate that C. difficile SLPs play important roles in the adhesion of the bacteria to the intestinal epithelial cells, disruption of tight junctions, and modulation of the immune response of the host cells. These proteins might serve as new targets for vaccines and new therapeutic agents. This review summarizes our current understanding of the immunological role of SLPs in inducing host immunity and their use in the development of vaccines and novel therapeutics to combat C. difficile infection.

Investigating the sequence properties that govern disorder and secretion of bacterial virulence proteins.

Many proteins contain disordered segments that play important roles in vivo. Autotransporter (AT) proteins are key virulence proteins from pathogenic Gram-negative bacteria. AT proteins have disordered properties that have been shown to be crucial for their efficient secretion to the bacterial cell surface. We have extensively studied pertactin, a virulence protein secreted by Bordetella pertussis, the bacterium that causes whooping cough. Like several other ATs, the mature pertactin virulence protein contains two segments with distinctly different folding properties. In isolation, the more stable C-terminal segment (PCt) is stably folded whereas the N-terminal segment (PNt) is disordered. Our previous studies indicate that folding of PCt is important for the efficient secretion of pertactin. Moreover, we recently showed that local clustering of hydrophobic residues leads to a significant collapse of PNt in vitro. Interestingly, we found that the extent to which PNt adopts a disordered, highly expanded conformational ensemble regulates the efficient secretion of pertactin through the bacterial outer membrane. Taken together, these observations suggest that PNt contains sequence properties important for secretion. Because disordered properties are important for AT secretion, understanding the connections between amino acid sequence features, disordered conformations, and AT secretion will improve our understanding of virulence protein secretion. The present research project aims to build upon our recent findings to develop a predictive understanding of the sequence factors that regulate disorder in pertactin and other proteins. We are using a combination of biophysical and biochemical approaches to characterize the sequence determinants of disorder and test their impact on AT secretion. We expect that insight into the regulation of disorder in pertactin will likely also apply to other members of the AT protein family, the largest family of secreted virulence proteins in Gram-negative bacterial pathogens.

Plasticity and Stereotypic Rewiring of the Transcriptome Upon Bacterial Evolution of Antibiotic Resistance.

Bacterial evolution of antibiotic resistance frequently has deleterious side effects on microbial growth, virulence, and susceptibility to other antimicrobial agents. However, it is unclear how these trade-offs could be utilized for manipulating antibiotic resistance in the clinic, not least because the underlying molecular mechanisms are poorly understood. Using laboratory evolution, we demonstrate that clinically relevant resistance mutations in Escherichia coli constitutively rewire a large fraction of the transcriptome in a repeatable and stereotypic manner. Strikingly, lineages adapted to functionally distinct antibiotics and having no resistance mutations in common show a wide range of parallel gene expression changes that alter oxidative stress response, iron homeostasis, and the composition of the bacterial outer membrane and cell surface. These common physiological alterations are associated with changes in cell morphology and enhanced sensitivity to antimicrobial peptides. Finally, the constitutive transcriptomic changes induced by resistance mutations are largely distinct from those induced by antibiotic stresses in the wild type. This indicates a limited role for genetic assimilation of the induced antibiotic stress response during resistance evolution. Our work suggests that diverse resistance mutations converge on similar global transcriptomic states that shape genetic susceptibility to antimicrobial compounds.

Isolates multi resistant to antibiotics and observed by Scanning electron microscopy

One hundred fifty six samples collected included: inflammation of the urinary tract, swabs wounds and pus from patients coming to Rizgary Teaching Hospital and Rozhawa Hospital in Erbil city from March to September 2013, scrubbed and confirmed the diagnosis (42) strain which belongs to staphylococcus aureus and by (26.9%) based on cultural characteristics, microscopically features and biochemical tests in addition to the API Staph. These strains sensitivity to 12 types of antibiotics. It gave the species a high resistance against the Ampicillin (AM / 10μg) by 88% and resistant to Amoxicillin (AX / 25μg)by (81%) were less resistant to Nitrofurantoin (NF / 300μg), Ciprofloxacin (CIP / 5μg), Gentamicin (GM / 10μg ) by (31,26,21.4%) respectively Ten isolates were selected according to their pattern of the highest resistance as these showing multi-drug resistances and tested to specify their minimum inhibitory concentration (MIC) for the antibiotics and two types of Nanoparticles include Silver in different sizes (20, 90)nm and Zinc Oxide in different sizes (20, 30, 50~150)nm. The results showed that the MIC for Ag 20 nm was between (650-2600) μg/ml while Ag90nm was between (325 -2600) μg/ml and the MIC for ZnO20nm between (325-2600) μg/ml and MIC of ZnO 30, 50 ~ 150nm between (162.5-2600) μg/ml. Synergism effect between the antibiotics and the Nanoparticles when they integrate increased their effect of Staphylococcus aureus. Morphological changes of bacteria found using light and scanning electron microscope (SEM) when treating with Nanoparticles. While there a pressure on the bacterial cell surface with losing of bacterial compound.

Development in the Concept of Bacterial Polysaccharide Repeating Unit-Based Antibacterial Conjugate Vaccines.

The surface of cells is coated with a dense layer of glycans, known as the cell glycocalyx. The complex glycans in the glycocalyx are involved in various biological events, such as bacterial pathogenesis, protection of bacteria from environmental stresses, etc. Polysaccharides on the bacterial cell surface are highly conserved and accessible molecules, and thus they are excellent immunological targets. Consequently, bacterial polysaccharides and their repeating units have been extensively studied as antigens for the development of antibacterial vaccines. This Review surveys the recent developments in the synthetic and immunological investigations of bacterial polysaccharide repeating unit-based conjugate vaccines against several human pathogenic bacteria. The major challenges associated with the development of functional carbohydrate-based antibacterial conjugate vaccines are also considered.

Bacterial surface roughness regulates nanoparticle scavenging in seawater

AbstractOrganic nanoparticles are abundant in marine environments and constitute important nutrient sources for bacteria. Bacteria have evolved cell surfaces over 3.8 billion years to efficiently utilize food particles, and they contribute to material cycling in the world's oceans. Nanoscale roughness of bacterial cell surfaces reflects outer membrane structures and extracellular polymers that potentially affect cell–particle interactions. However, the variability of surface roughness of marine bacteria has been little studied and its involvement in nanoparticle attachment to bacteria is essentially unknown. Here, for the first time, we show the surface roughness of marine bacteria, evaluated as the root mean square deviation of height (Rq), determined by atomic force microscopy of over 1000 cells of coastal and offshore bacteria in the upper ocean. The Rq varied about 10‐fold among cells (range: 1.0–13.7 nm) and decreased with increasing seawater temperature, implying that bacteria–nanoparticle interactions differ among oceanographic areas. Microcosm experiments using two Gammaproteobacteria (isolated from coastal waters) and modeled with nanoparticle (polystyrene beads and viruses) show that the Rq is a strong predictor of nanoparticle attachment to marine bacteria, that is, bacterial nanoparticle scavenging increases with Rq. This relationship can be explained by steeper peaks/valleys and larger surface area of rougher cells. Measurement of nanoscale surface topography of marine bacteria provides novel insights into bacterial strategies for resource utilization and their contribution to marine biogeochemical cycles.

PROBIOTIC BIFIDOBACTERIUM AND A NEW GENERATION POSTBIOTIC: ALGINIC ACID

Abstract AIMS OF THE STUDY According to International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus (2019),Postbiotics are defined as a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host. Postbiotic Alginic acid, also called algin, is a naturally occurring, edible exopolysaccharide found in brown algae. Alginic acid and its Na/Ca salt form of Alginate show the capability in water-binding, water-retention water, and immense swelling and gelation, which could act as a protective barrier via promoting biofilm formation on the bacterial cell surfaces. Alginic acid is a potent inducer of Th1 pathway.We aimed to analyze the Postbiotic alginate formed by the human intestinal beneficial bacteria, bifidobacteria,by degrading sodium alginate. METHODS In these study, which were designed in Yildiz Technical University / Istanbul, Biohybrid films were produced by using both Bifidobacterium animalis subsp.lactis BB-12 probiotic strain and Bifidobacterium infantis in combination with sodium alginate (SA), which demonstrates biocompatibility and facilitated gelation properties in aeorobic atmospheric condition were considered as bifidobacterial surfactan source. RESULTS In biohybrid biofilm study(1), based on the spectroscopic and mechanical analysis, it was found that mechanical strength increased in films produced by adding Bifidobacterium infantis in SA while this increase was relatively lower as compared to those containing Bifidobacterium animalis subsp. lactis BB-12 as crosslinking ratio increases. Besides, bacteria contained in bio-hybrid films increased the percentage of amorphous zone of SA in SA/bacteria films, which reduced the crystallinity ratio. This indicated that crystalline chains contained in the structure of SA are degraded by probiotic bifidobacteria(Fig.1) CONCLUSIONS This is the first study that Biohybrid biosurfactan that contains Bifidobacterium infantis, Bifidobacterium animalis subsp. lactis BB-12 and SA structures coated medical/nonmedical devices and sets can be a pioneering approach to reduce carbon emissions, as well as to prevent secondary infections and increase device protection. Also, It paved the way for the postbiotic use of alginic acid/Alginate by probiotic Bifidobacteria.

Comparison of Small Biomolecule Ionization and Fragmentation in Pseudomonas aeruginosa Using Common MALDI Matrices.

Different bacterial cell surface associated biomolecules can be analyzed by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and coupled with collision induced dissociation (CID) for identification. Pseudomonas aeruginosa is an opportunistic, Gram-negative bacterium that causes acute or chronic biofilm infections. Cells of P. aeruginosa communicate through a system of signaling biomolecules known as quorum sensing (QS). The QS system can result in the production of biosurfactant rhamnolipids known to associate and alter the cellular membrane. MALDI-TOF utilizes a variety of matrices that can interact differently with biomolecules for selective ionization. We examined six common matrices to determine the optimal matrix specific to different molecule classes in P. aeruginosa associated with cell surfaces. Three major molecule classes (quinolones, rhamnolipids, and phospholipids) were observed to ionize selectively with the different matrices tested. Sodiated and protonated adducts differed between matrices utilized in our study. Isobaric ions were identified as different molecule classes depending on the matrix used. We highlight the role of matrix selection in MALDI-TOF identification of molecules within a complex biological mixture.

Staphylococcal Periscope proteins Aap, SasG, and Pls project noncanonical legume-like lectin adhesin domains from the bacterial surface

Staphylococcus aureus and Staphylococcus epidermidis are frequently associated with medical device infections that involve establishment of a bacterial biofilm on the device surface. Staphylococcal surface proteins Aap, SasG, and Pls are members of the Periscope Protein class and have been implicated in biofilm formation and host colonization; they comprise a repetitive region ("B region") and an N-terminal host colonization domain within the "A region," predicted to be a lectin domain. Repetitive E-G5 domains (as found in Aap, SasG, and Pls) form elongated "stalks" that would vary in length with repeat number, resulting in projection of the N-terminal A domain variable distances from the bacterial cell surface. Here, we present the structures of the lectin domains within A regions of SasG, Aap, and Pls and a structure of the Aap lectin domain attached to contiguous E-G5 repeats, suggesting the lectin domains will sit at the tip of the variable length rod. We demonstrate that these isolated domains (Aap, SasG) are sufficient to bind to human host desquamated nasal epithelial cells. Previously, proteolytic cleavage or a deletion within the A domain had been reported to induce biofilm formation; the structures suggest a potential link between these observations. Intriguingly, while the Aap, SasG, and Pls lectin domains bind a metal ion, they lack the nonproline cis peptide bond thought to be key for carbohydrate binding by the lectin fold. This suggestion of noncanonical ligand binding should be a key consideration when investigating the host cell interactions of these bacterial surface proteins.

Single-Probe-Based Colorimetric and Photothermal Dual-Mode Identification of Multiple Bacteria.

Effective identification of multiple pathogenic bacteria in unknown samples is important for disease prevention and control but remains a challenge yet. A single-mode array-based sensing approach is simple and sensitive, but it usually relies on the use of multiple cross-reactive receptors to construct sensor arrays, which is cumbersome and insufficiently accurate. Here, we developed a sensor array with colorimetric and photothermal dual mode of differentiating multiple pathogenic bacteria. The sensor array was based on boronic acid-functionalized Au-Fe3O4 nanoparticles (BA-GMNPs), which not only possess localized surface plasmon resonance properties, showing a burgundy color similar to that of AuNPs, but also exhibit mild superparamagnetism, allowing for the differentiation of bacteria before and after binding to the nanoparticles. Immobilization of BA-GMNPs on the bacterial cell surface by covalent bonding would diminish NaCl-induced assembly of BA-GMNPs. Different BA-GMNPs@bacterial complexes differed in their ability to resist assembly and produced different colorimetric and photothermal response signals. A unique molecular fingerprint of each bacterium was obtained by linear discriminant analysis of the response patterns, demonstrating an effective differentiation among the six species studied. Compared with single-mode sensing arrays based on multiple receptors, this method only requires the preparation of a single nanomaterial, which produces two signal outputs for the identification of multiple bacteria with better differentiation. It can distinguish not only multiple pathogenic bacteria but also Gram-negative and Gram-positive bacteria, and, more importantly, it can perform preliminary discrimination of unknown samples.

Metal Microwires Functionalized with Cell-Imprinted Polymer for Capturing Bacteria in Water

Molecularly imprinted polymers (MIPs) and cell-imprinter polymers (CIPs) have emerged as synthetic recognition elements in biomimetic sensors. In this paper, we have conducted a parametric study to optimize a bulk polymerization methodology for uniform functionalization of stainless steel microwires (MWs) with CIPs comprising single to fourplex combinations of functional monomers (FMs). MWs are widely used in biosensors, and their functionalization with single-FM MIPs has been demonstrated. Complex MIPs comprising multiple FMs have shown enhanced selectivity toward microorganisms, but their coating on MWs has yet to be shown. Moreover, imprinting microorganisms into these coatings has not been reported. In our studies, solvent, FM, cross-linker-to-FM ratio, polymerization temperature, and time were found to significantly influence the thickness and uniformity of CIP coatings on MWs. Reproducible CIP coatings with a thickness of 2.2 ± 0.4 μm, imprinted with E. coli OP50 as the template, were achieved. E. coli rebinding assays demonstrated a 76 ± 10% capture efficiency in a suspension with an initial bacteria count of 104 CFU/mL, using a 3 cm long CIP-MW with an optimized fourplex CIP composition, while the capture efficiency obtained by using a single-monomer CIP composition was 30 ± 5%. Our results indicated a higher binding capacity of fourplex CIP-MWs to target bacteria, while nonsignificant binding was obtained using single-monomer CIP-MWs. The addition of N-vinylpyrrolidone significantly increased the binding performance due to its hydrophobic–hydrophilic functional groups interacting with counterparts on the surface of bacterial cells. The developed CIP-MWs can be integrated with microfluidic sensing systems as low-cost and stable working electrodes for future transduction of CIP-target binding events to an electrical read-out in CIP-based electrochemical biomimetic sensors.