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• NPs entered the intracellular region and caused plasmolysis and cytoplasm outflow. • NPs stimulated the initial cell attachment and aggravated NF membrane biofouling. • Low NPs exposure promoted cell secretion, quorum sensing and homologous recombination. • High NPs condition induced cell lysis, metabolic inactivation and genomic DNA damage. The release of nanoplastics (NPs) into the environment is growing due to the extensive use of plastic products. Numerous studies have confirmed the negative effects of NPs on microorganisms, which poses uncertainties concerning their impact on nanofiltration (NF) membrane biofouling. This study investigated the initial cell adhesion process, NF membrane biofouling kinetic processes and bacterial responses of Pseudomonas aeruginosa (P. aeruginosa) exposed to varied NPs concentrations (0–50 mg·L−1). Transcriptome analysis demonstrated that low concentration of NPs (0.1 mg·L−1) promoted bacterial quorum sensing, energy metabolism, exopolysaccharide biosynthesis and bacterial secretion systems. Correspondingly, the polysaccharide content increased remarkably to 2.77 times the unexposed control, which served as a protective barrier for bacteria to avoid the impact of NPs-induced stress. Suppressed homologous recombination, microbial metabolic potentials and flagellar assembly were detected in bacteria exposed to a high concentration (50 mg·L−1) of NPs, mainly due to the triggered reactive oxygen species (ROS) generation, genomic DNA damage, and decreased energy production. Overall, enhanced formation of the extracellular polymeric substances (EPS) and aggravated membrane flux decline were observed when NPs interacted with the membrane surface by cell secretions (low NPs levels) or cell lysis (high NPs levels). These findings shed light on understanding the microbial metabolism mechanism and membrane biofouling propensity with NPs stress at both the molecular and gene levels. [Display omitted] [ABSTRACT FROM AUTHOR]

Staphylococcus epidermidis is well recognized nosocomial pathogen in clinical settings for their implants associated infections. Biofilm and virulence production executes a S. epidermidis pathogenesis against host. Hence, interfering of biofilm formation has become an auspicious to control the pathogenesis of S. epidermidis. The present study evaluates antibiofilm potential of Rhizophora mucronata against S. epidermidis biofilms. Rhizophora mucronata leaves extract significantly inhibited the biofilm formation and quebrachitol was identified as an active compound responsible for the biofilm inhibition. Quebrachitol significantly inhibited biofilm formation at concentration dependent manner without exhibit non-bactericidal property. And, quebrachitol reduced the biofilm building components such as exopolysaccharides, lipase and proteins production. Confocal laser scanning microscopic studies obtained quebrachitol surface independent biofilm efficacy against S. epidermidis. Notably, quebrachitol significantly reduced S. epidermidis adherence on biotic (coated with type I collagen and fibrinogen) and abiotic (hydrophobic and hydrophilic) surfaces. Addition of quebrachitol inhibits autolysis mediated initial attachment and accumulation associated aggregation process. Moreover, quebrachitol significantly reduced the hydrolases virulence production which supports S. epidermidis invasion into the host. Furthermore, gene expression analysis revealed the ability of quebrachitol to downregulate the virulence genes expression which are mainly involved in biofilm formation and virulence production. The results obtained from the present study suggest that quebrachitol as an ideal candidate for the therapeutic action against S. epidermidis pathogenesis. [ABSTRACT FROM AUTHOR]

Staphylococcus epidermidis is an opportunistic human pathogen, which is involved in numerous nosocomial and implant associated infections. Biofilm formation is one of the prime virulence factors of S. epidermidis that supports its colonization on biotic and abiotic surfaces. The global dissemination of three lineages of S. epidermidis superbugs highlights its clinical significance and the imperative need to combat its pathogenicity. Thus, in the current study, the antibiofilm activity of umbelliferone (UMB), a natural product of the coumarin family, was assessed against methicillin-resistant S. epidermidis (MRSE). UMB exhibited significant antibiofilm activity (83%) at 500 μg/ml concentration without growth alteration. Microscopic analysis corroborated the antibiofilm potential of UMB and unveiled its potential to impair intercellular adhesion, which was reflected in auto-aggregation and solid phase adherence assays. Furthermore, real time PCR analysis revealed the reduced expression of adhesion encoding genes (icaD, atlE, aap, bhp, ebh, sdrG , and sdrF). Down regulation of agrA and reduced production of secreted hydrolases upon UMB treatment were speculated to hinder invasive lifestyle of MRSE. Additionally, UMB hindered slime synthesis and biofilm matrix components, which were believed to augment antibiotic susceptibility. In vivo assays using Caenorhabditis elegans divulged the non-toxic nature of UMB and validated the antibiofilm, antivirulence, and antiadherence properties of UMB observed in in vitro assays. Thus, UMB impairs MRSE biofilm by turning down the initial attachment and intercellular adhesion. Altogether, the obtained results suggest the potent antibiofilm activity of UMB and the feasibility of using it in clinical settings for combating S. epidermidis infections. [ABSTRACT FROM AUTHOR]

The attachment of bacteria and other microbes to natural and artificial surfaces leads to the development of biofilms, which can further cause nosocomial infections. Thus, an important field of research is the development of new materials capable of preventing the initial adhesion of pathogenic microorganisms. In this work, novel polymer/particle composite materials, based on a polythiourethane (PTU) matrix and either spherical (s-ZnO) or tetrapodal (t-ZnO) shaped ZnO fillers, were developed and characterized with respect to their mechanical, chemical and surface properties. To then evaluate their potential as anti-fouling surfaces, the adhesion of two different pathogenic microorganism species, Staphylococcus aureus and Candida glabrata, was studied using atomic force microscopy (AFM). Our results show that the adhesion of both S. aureus and C. glabrata to PTU and PTU/ZnO is decreased compared to a model surface polydimethylsiloxane (PDMS). It was furthermore found that the amount of both s-ZnO and t-ZnO filler had a direct influence on the adhesion of S. aureus, as increasing amounts of ZnO particles resulted in reduced adhesion of the cells. For both microorganisms, material composites with 5 wt.% of t-ZnO particles showed the greatest potential for anti-fouling with significantly decreased adhesion of cells. Altogether, both pathogens exhibit a reduced capacity to adhere to the newly developed nanomaterials used in this study, thus showing their potential for bio-medical applications.

Human beta-defensin-3 (hBD3) acts as a first line of defense against both Gram-positive and Gram-negative bacteria infection. Streptococci are the significant cause for oral biofilm associated diseases. We synthesized three fragments (hBD3-1, hBD3-2, hBD3-3) from the hBD3 and evaluated the antibacterial efficacy on oral streptococci. All of the three fragments from hBD3 had good estimated solubility and hBD3-3 had a higher net positive charge than others. Structure analysis showed that the three fragments shared stable β-sheet structure, but tyrosine were not found in hBD3-2 and hBD3-3 by using Raman and circular dichroism spectroscopy. The inhibition ability of the peptides was examined on the bioactivity of Streptococcus oralis (S.oralis), Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) by minimal inhibitory concentration, minimum bactericidal concentration and anti-biofilm formation test. Three fragments had antimicrobial activity on planktonic state of streptococci, and S. oralis had much more sensitive to the three peptides. Results of antibiofilm experiment showed that streptococci biofilm formation was more sensitive to hBD3-3. Confocal laser scanning microscopy and scanning electron microscopy showed the decrease of biomass and bacterial morphology destruction, which indicated that the antimicrobial mechanism of hBD3-3 might involve an electrostatic charge-based impact on membrane permeability. In conclusion, hBD3-3 possessed the potential capacity for depressing the growth of bacteria, especially first colonizers during the development of oral biofilm. Powerful, endogenous antimicrobial peptide provides the potential to interfere with biofilm by disorganizing early biofilm formation and thereby inhibiting biofilm-associated diseases. [ABSTRACT FROM AUTHOR]

Oral bacteria initiate biofilm formation by attaching to tooth surfaces via an interaction of a lectin-like bacterial protein with carbohydrate chains on the pellicle. This study aimed to find naturally derived lectins that inhibit the initial attachment of a cariogenic bacterial species, Streptococcus mutans (S. mutans), to carbohydrate chains in saliva in vitro. Seventy kinds of lectins were screened for candidate motifs that inhibit the attachment of S. mutans ATCC 25175 to a saliva-coated culture plate. The inhibitory effect of the lectins on attachment of the S. mutans to the plates was quantified by crystal violet staining, and the biofilm was observed under a scanning electron microscope (SEM). Surface plasmon resonance (SPR) analysis was performed to examine the binding of S. mutans to carbohydrate chains and the binding of candidate lectins to carbohydrate chains, respectively. Moreover, binding assay between the biotinylated-lectins and the saliva components was conducted to measure the lectin binding. Lectins recognizing a salivary carbohydrate chain, Galβ1-3GalNAc, inhibited the binding of S. mutans to the plate. In particular, Agaricus bisporus agglutinin (ABA) markedly inhibited the binding. This inhibition was confirmed by SEM observation. SPR analysis indicated that S. mutans strongly binds to Galβ1-3GalNAc, and ABA binds to Galβ1-3GalNAc. Finally, the biotinylated Galβ1-3GalNAc-binding lectins including ABA demonstrated marked binding to the saliva components. These results suggest that ABA lectin inhibited the attachment of S. mutans to Galβ1-3GalNAc in saliva and ABA can be useful as a potent inhibitor for initial attachment of oral bacteria and biofilm formation. [ABSTRACT FROM AUTHOR]

At the industrial scale, bioleaching of metal sulfides includes two main technologies, tank leaching and heap leaching. Fluctuations in temperature caused by the exothermic reactions in a heap have a pronounced effect on the growth of microbes and composition of mixed microbial populations. Currently, little is known on the influence of pre-colonized mesophiles or moderate thermophiles on the attachment and bioleaching efficiency by thermophiles. The objective of this study was to investigate the interspecies interactions of the moderate thermophile Sulfobacillus thermosulfidooxidans DSM 9293T and the thermophile Acidianus sp. DSM 29099 during initial attachment to and dissolution of pyrite. Our results showed that: (1) Acidianus sp. DSM 29099 interacted with S. thermosulfidooxidansT during initial attachment in mixed cultures. In particular, cell attachment was improved in mixed cultures compared to pure cultures alone; however, no improvement of pyrite leaching in mixed cultures compared with pure cultures was observed; (2) active or inactivated cells of S. thermosulfidooxidansT on pyrite inhibited or showed no influence on the initial attachment of Acidianus sp. DSM 29099, respectively, but both promoted its leaching efficiency; (3) S. thermosulfidooxidansT exudates did not enhance the initial attachment of Acidianus sp. DSM 29099 to pyrite, but greatly facilitated its pyrite dissolution efficiency. Our study provides insights into cell-cell interactions between moderate thermophiles and thermophiles and is helpful for understanding of the microbial interactions in a heap leaching environment. [ABSTRACT FROM AUTHOR]

Biofilm formation is a complex and time-consuming process, especially the attachment and growth of anaerobic biofilm, which fundamentally determines the start-up of biofilm reactor. In this study, biosurfactant, rhamnolipid, was introduced into an anaerobic moving bed biofilm reactor (AnMBBR) to promote its start-up, and the results showed that AnMBBR with rhamnolipid (RMBBR) could be successfully started within 25 days. Compared to the control AnMBBR without rhamnolipid, the start-up time was shortened by about half, the attached biomass on biocarriers was increased to 1.5 times, and the pollutants removal efficiencies were all greatly improved in the start-up phase, especially NO 3 − increased from 86.76 ± 1.04% to 96.93 ± 0.73%, and then these gaps were reduced in the steady-state phase. Under the action of rhamnolipid, the adhesion force of the biofilm increased from 18.9 nN to 27.4 nN eventually, and the interfacial energy between biofilm and biocarriers was transformed from repulsion (6200 KT) to weak attraction (−100 KT) by the evaluation of the extended Derjaguin–Landau–Verwey–Overbeek theory, which significantly promoted the initial attachment of biofilm. The increased metabolic activity, key enzyme activity, extracellular polymeric substances (EPS) and quorum sensing behaviors evidenced that rhamnolipid stimulated microbial internal activities and then regulated biofilm growth process. Moreover, rhamnolipid also significantly enhanced the abundance of functional bacteria in terms of metabolism or quorum sensing, including Thauera , Methylomonas , Desulfomicrobium , Azoarcus , Leptonema. Rhamnolipid would also stimulate the expression of genes that related to membrane transport, biofilm formation and nitrogen metabolism. This work provided a promising strategy for the rapid start-up of anaerobic biofilm reactor. [Display omitted] •Rhamnolipid accelerated the start-up of anaerobic MBBR by promoting biofilm formation. •Multiple regulatory mechanisms of rhamnolipid on biofilm formation were first proposed. •Rhamnolipid changed functional and structural characteristics of cell membrane. •The interfacial energy between biofilm and biocarriers was reduced by rhamnolipid. [ABSTRACT FROM AUTHOR]

Exposure of Salmonella to environmental stress, prior to its adherence to a food contact surface, may change the cell surface properties and consequently affect its initial attachment and biofilm formation. This study investigated the influence of temperature and pH preacclimation on the initial attachment of Salmonella Enteritidis to acrylic and stainless steel. Besides, changes in physicochemical properties of cells were examined; and their surface attachment was modeled by xDLVO theory. Results showed that control cells pre-grown at 37 °C had significantly ( P < 0.05) higher initial attachment, followed by those pre-grown at 25, 42, and 10 °C. The initial attachment of cells pre-grown at pH 5.3 or 6.3 was not significantly ( P > 0.05) different from control cells pre-grown at pH 7.3, but they were significantly higher compared to cells pre-grown at pH 8.3 and 9.0. No significant difference was observed between cell attachment to acrylic and stainless steel, although they had different physicochemical properties. The xDLVO theory successfully explained higher attachment for cells pre-grown at optimal condition on both contact surfaces. However, the xDLVO theory could not explain the similar attachment of cells to acrylic and stainless steel. This study elucidates that commonly used intervention technologies including cold storage, thermal treatment, and alkaline antimicrobial agents might alter the physicochemical properties of S . Enteritidis cells and result in varied initial attachment levels. [ABSTRACT FROM AUTHOR]

Initial attachment of human oral keratinocytes (HOKs) cultured on mirror-surfaced commercially pure titanium (Ti) or yttria-stabilized tetragonal zirconia polycrystals (TZP) was investigated. Numbers of viable attached HOKs, their mRNAs and proteins expression of laminin y2 and integrin β4 were evaluated using the WST-1 assay, quantitative real-time PCR and enzyme-linked immunosorbent assay, respectively. Localization of laminin y2 and integrin β4 was observed using immunofluorescent staining. Cell spreading was evaluated by measuring the perimeter of actin on fluorescent stained images, and cell morphology was examined using scanning electron microscopy. At 1 h TZP elicited less of initial attachment than Ti in terms of mRNAs expression and proteins expression of laminin y2 and integrin β4 (p<0.05). However, at 48 h TZP was showed similar initial attachment in comparison to Ti. Therefore, it was suggested that TZP has a potential to form epithelial attachment like Ti. [ABSTRACT FROM AUTHOR]

Abstract: Although Escherichia coli is an indicator of fecal contamination in aquifers, limited research has been devoted to understanding the biological processes involved in the initial attachment of E. coli transported in abiotic porous media. The roles of the various surface structures of E. coli, like lipopolysaccharides (LPS), autotransporter proteins, and fimbriae are unknown. The objective of this research was to establish the effects of variations in surface characteristics of the outer membrane of E. coli on the attachment efficiency of 54 E. coli strains upon transport in saturated quartz sand under identical flow conditions. We used column experiments to assess retention of the E. coli strains, and we determined sphericity, motility, zeta-potential, and aggregation of all strains. LPS composition was determined based on known serotypes, and the presence/absence of 22 genes encoding surface characteristics was determined with qualitative PCR. The results indicated that under identical flow conditions, there was a variation of two orders of magnitude in the maximum breakthrough concentrations of the 54 E. coli strains. Of all factors we investigated, no single factor was able to explain attachment efficiency variations statistically significantly. However, low attachment efficiencies were associated (p =0.13) with LPS containing saccharides with phosphate and/or carboxyl groups. These saccharide groups are acidic and likely charged with a negative O-atom, which reduced attachment to the negatively charged quartz surface. In addition, of the 22 genes tested, Afa was most associated (p =0.21) with attachment efficiency. The work presented here bridges knowledge on colloid transport and molecular microbiology, and tries to offer a more holistic view on the attachment of planktonic E. coli bacteria to (abiotic) quartz grain surfaces. Future research should involve the use of microbiological techniques in order to be able to map the unique or grouped characteristics of E. coli in aquifers, and to assess the usefulness of E. coli as a fecal indicator in aquifers. [Copyright &y& Elsevier]

Summary: This study was designed to immunodetect proteoglycans (PGs) and the noncollagenous glycoproteins, bone sialoprotein (BSP) and osteopontin (OPN) on developing alveolar bone surface in rat molars by the indirect immunoperoxidase method, and to discuss the roles of these molecules at the initial principal fiber (PF) attachment. To characterize PGs, antibodies against five species of glycosaminoglycans (GAGs), chondroitin-4-sulfate (C4S), chondroitin-6-sulfate (C6S), unsulfated chondroitin (C0S), dermatan sulfate (DS), and keratan sulfate (KS) were used. Maxillary alveolar bone facing the distal root of the second molar was examined in 20- and 25-day-old male Wistar rats. Routine histological staining was also used. A hematoxylin-stained, fibril-poor layer always appeared on the alveolar bone surface just prior to the initial PF organization. This layer was strongly immunoreactive for C4S, C0S, OPN, and BSP, and weakly for C6S, but not for DS and KS. Then the initial PFs were attached to this layer. When new bone containing Sharpey''s fibers covered this layer, it remained as a hematoxylin-stained, fibril-poor layer between Sharpey''s fiber-containing and -lacking bone. The layer was consistently immunoreactive for OPN and BSP but had no immunoreactivity for GAGs. The results suggest that the accumulation of C4S-, C0S-, and C6S-carrying PGs, and of BSP and OPN is a primary event at the initial PF attachment, and is involved in the adhesion of PFs and mineralization of the initial attachment layer. The BSP and OPN act to maintain the interface integrity between Sharpey''s fiber-containing and Sharpey''s fiber-lacking alveolar bone after the PF attachment is established. [Copyright &y& Elsevier]

This study was designed to observe the principal fibers and alveolar bone in various developmental stages in rat molar using light and transmission electron microscopy and to elucidate the mechanisms of initial principal fiber attachment to the alveolar bone surface. Maxillary alveolar bone between the 2nd and 3rd molars of 20- and 25-day-old rats was used. A proteoglycan-rich, fiber-poor, and election dense layer formed on the alveolar bone surface before the principal fiber organization. This layer was not seen before principal fibers had started to develop. Principal fibers first contracted and then became embedded in this layer. With further development, new bone deposited on this layer and around already attached principal fibers. These findings suggest that this electron dense, proteoglycan-rich layer may act as an adhesive factor to mediate the initial attachment of principal fibers to the alveolar bone surface. [ABSTRACT FROM AUTHOR]

The attachment of bacteria and other microbes to natural and artificial surfaces leads to the development of biofilms, which can further cause nosocomial infections. Thus, an important field of research is the development of new materials capable of preventing the initial adhesion of pathogenic microorganisms. In this work, novel polymer/particle composite materials, based on a polythiourethane (PTU) matrix and either spherical (s-ZnO) or tetrapodal (t-ZnO) shaped ZnO fillers, were developed and characterized with respect to their mechanical, chemical and surface properties. To then evaluate their potential as anti-fouling surfaces, the adhesion of two different pathogenic microorganism species, Staphylococcus aureus and Candida glabrata, was studied using atomic force microscopy (AFM). Our results show that the adhesion of both S. aureus and C. glabrata to PTU and PTU/ZnO is decreased compared to a model surface polydimethylsiloxane (PDMS). It was furthermore found that the amount of both s-ZnO and t-ZnO filler had a direct influence on the adhesion of S. aureus, as increasing amounts of ZnO particles resulted in reduced adhesion of the cells. For both microorganisms, material composites with 5 wt.% of t-ZnO particles showed the greatest potential for anti-fouling with significantly decreased adhesion of cells. Altogether, both pathogens exhibit a reduced capacity to adhere to the newly developed nanomaterials used in this study, thus showing their potential for bio-medical applications. [ABSTRACT FROM AUTHOR]