Using Copper-Doped Mesoporous Bioactive Glass Nanospheres to Impart Anti-Bacterial Properties to Dental Composites

Experimental dental resin composites containing copper-doped mesoporous bioactive glass nanospheres (Cu-MBGN) were developed to impart anti-bacterial properties. Increasing amounts of Cu-MBGN (0, 1, 5 and 10 wt%) were added to the BisGMA/TEGDMA resin matrix containing micro- and nano-fillers of inert glass, keeping the resin/filler ratio constant. Surface micromorphology and elemental analysis were performed to evaluate the homogeneous distribution of filler particles. The study investigated the effects of Cu-MBGN on the degree of conversion, polymerization shrinkage, porosity, ion release and anti-bacterial activity on S. mutans and A. naeslundii. Experimental materials containing Cu-MBGN showed a dose-dependent Cu release with an initial burst and a further increase after 28 days. The composite containing 10% Cu-MBGN had the best anti-bacterial effect on S. mutans, as evidenced by the lowest adherence of free-floating bacteria and biofilm formation. In contrast, the 45S5-containing materials had the highest S. mutans adherence. Ca release was highest in the bioactive control containing 15% 45S5, which correlated with the highest number of open porosities on the surface. Polymerization shrinkage was similar for all tested materials, ranging from 3.8 to 4.2%, while the degree of conversion was lower for Cu-MBGN materials. Cu-MBGN composites showed better anti-bacterial properties than composites with 45S5 BG

BC4707 Is a Major Facilitator Superfamily Multidrug Resistance Transport Protein from Bacillus cereus Implicated in Fluoroquinolone Tolerance

Transcriptional profiling highlighted a subset of genes encoding putative multidrug transporters in the pathogen Bacillus cereus that were up-regulated during stress produced by bile salts. One of these multidrug transporters (BC4707) was selected for investigation. Functional characterization of the BC4707 protein in Escherichia coli revealed a role in the energized efflux of xenobiotics. Phenotypic analyses after inactivation of the gene bc4707 in Bacillus cereus ATCC14579 suggested a more specific, but modest role in the efflux of norfloxacin. In addition to this, transcriptional analyses showed that BC4707 is also expressed during growth of B. cereus under non-stressful conditions where it may have a role in the normal physiology of the bacteria. Altogether, the results indicate that bc4707, which is part of the core genome of the B. cereus group of bacteria, encodes a multidrug resistance efflux protein that is likely involved in maintaining intracellular homeostasis during growth of the bacteria.Peer reviewe

The Role of Digital Technologies in Responding to the Grand Challenges of the Natural Environment:The Windermere Accord

Digital technology is having a major impact on many areas of society, and there is equal opportunity for impact on science. This is particularly true in the environmental sciences as we seek to understand the complexities of the natural environment under climate change. This perspective presents the outcomes of a summit in this area, a unique cross-disciplinary gathering bringing together environmental scientists, data scientists, computer scientists, social scientists, and representatives of the creative arts. The key output of this workshop is an agreed vision in the form of a framework and associated roadmap, captured in the Windermere Accord. This accord envisions a new kind of environmental science underpinned by unprecedented amounts of data, with technological advances leading to breakthroughs in taming uncertainty and complexity, and also supporting openness, transparency, and reproducibility in science. The perspective also includes a call to build an international community working in this important area

Characterization of c-di-GMP signaling in Salmonella typhimurium

Signal transduction via cyclic nucleotides is a general mechanism utilized by cells from all kingdoms of life. Identification of cyclic diguanosine monophosphate (c-di-GMP) as an allosteric activator of the cellulose synthase in Gluconacetobacter xylinus 20 years ago, paved the way for the discovery of a novel general signalling system which is unique to bacteria. In this thesis, the c-di-GMP signalling network leading to the formation of a biofilm behavior in Salmonella enterica serovar Typhimurium (S. Typhimurium), the rdar morphotype, is described. The rdar morphotype is characterized by the expression of the extracellular matrix components cellulose and curli, which are controlled by the transcriptional regulator CsgD. Curli production is directly activated by CsgD, whereas cellulose biosynthesis is indirectly activated by CsgD via the expression of the GGDEF domain protein AdrA. AdrA is one of 20 proteins carrying a GGDEF and/or EAL domain. The development of a detection method for c-di-GMP based on high pressure liquid chromatography and mass spectrometry (MS) and structural characterisation of c-di-GMP by MS-MS analysis allowed the characterisation of the c-di-GMP pathway in S. Typhimurium.We demonstrate that the GGDEF domain synthesizes c-di-GMP, whereas the EAL domain is responsible for c-di-GMP degradation. A high c-di-GMP concentration positively regulates the biosynthesis of adhesive matrix components and biofilm formation, whereas it inversely regulates motility in S. Typhimurium, Escherichia coli and Pseudomonas aeruginosa. These findings indicate that c-di-GMP is a general regulator of the transition from motility to sessility in Bacteria. Overexpression of AdrA in the wild type strain S. Typhimurium UMR1 resulted in upregulation of cellulose and curli. The effect of c-di-GMP on curli expression was finally mapped to the level of CsgD transcription or mRNA stability. We further demonstrate that at least two subsets of GGDEF domain proteins are involved in CsgD expression. Chromosomally encoded AdrA controls cellulose production, but is not involved in CsgD expression, whereas the GGDEF-EAL domain proteins STM2123 and STM3388 control CsgD expression, but cannot functionally replace AdrA. Since all three proteins display apparent diguanylate cyclase activity, there are separate c-di-GMP pools dedicated to regulation of CsgD expression and cellulose biosynthesis. Further on, four of 15 EAL domain proteins, STM3611, STM1827, STM1703 and STM 4264, are involved in CsgD expression. All EAL domain proteins displayed apparent phosphodiesterase activity in vivo, which is, however, not directly correlated with the effect on CsgD expression, Therefore, the c-di-GMP pools degraded by the four EAL domain proteins are dedicated to CsgD expression to different extends. Other subsets of EAL domain proteins regulate pellicle formation, biofilm in liquid culture and flagella mediated motility. Although molecular mechanisms of c-di-GMP synthesis and degradation are unraveling, major questions regarding the targets of c-di-GMP signaling are still open. Bioinformatic studies predicted that the PilZ domain may function as a c-di-GMP binding domain. We experimentally demonstrate that c-di-GMP binds to the PilZ domains of the cellulose synthase from G. xylinus and YcgR from Escherichia coli. By inactivation and over expression of YcgR in S. Typhimurium we showed that this protein regulated motility in a c-di-GMP dependent way when c-di-GMP levels were enhanced. In summary, this work shows that c-di-GMP is a central regulator of a biofilm behaviour in S. Typhimurium. Although many details about the c-di-GMP metabolism were unravelled in this work, the molecular mechanisms how c-di-GMP excerts its function remain to be discovered

Bacterial biofilm and its role in the pathogenesis of disease

Recognition of the fact that bacterial biofilm may play a role in the pathogenesis of disease has led to an increased focus on identifying diseases that may be biofilm-related. Biofilm infections are typically chronic in nature, as biofilm-residing bacteria can be resilient to both the immune system, antibiotics, and other treatments. This is a comprehensive review describing biofilm diseases in the auditory, the cardiovascular, the digestive, the integumentary, the reproductive, the respiratory, and the urinary system. In most cases reviewed, the biofilms were identified through various imaging technics, in addition to other study approaches. The current knowledge on how biofilm may contribute to the pathogenesis of disease indicates a number of different mechanisms. This spans from biofilm being a mere reservoir of pathogenic bacteria, to playing a more active role, e.g., by contributing to inflammation. Observations also indicate that biofilm does not exclusively occur extracellularly, but may also be formed inside living cells. Furthermore, the presence of biofilm may contribute to development of cancer. In conclusion, this review shows that biofilm is part of many, probably most chronic infections. This is important knowledge for development of effective treatment strategies for such infections

Quantitative determination of cyclic diguanosine monophosphate concentrations in nucleotide extracts of bacteria by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry.

The physiological response to small molecules (secondary messengers) is the outcome of a delicate equilibrium between biosynthesis and degradation of the signal. Cyclic diguanosine monophosphate (c-di-GMP) is a novel secondary messenger present in many bacteria. It has a complex cellular metabolism whereby usually more than one enzyme synthesizing and degrading c-di-GMP is encoded by a bacterial genome. To assess the in vivo conditions of c-di-GMP signaling, we developed a high-performance liquid chromatography (HPLC)-mass spectrometry-based method to detect c-di-GMP with high sensitivity and to quantify the c-di-GMP concentration in the bacterial cell as described here in detail. We successfully used the methodology to determine and compare the c-di-GMP concentrations in bacterial species such as Salmonella typhimurium, Escherichia coli, Pseudomonas aeruginosa, and Vibrio cholerae. We describe the use of the methodology to assess the change in c-di-GMP concentration during the growth phase and the contribution of a point mutation in S. typhimurium to the overall cellular c-di-GMP concentration

Role of EAL-Containing Proteins in Multicellular Behavior of Salmonella enterica Serovar Typhimurium

GGDEF and EAL domain proteins are involved in turnover of the novel secondary messenger cyclic di(3′→5′)-guanylic acid (c-di-GMP) in many bacteria. The rdar morphotype, a multicellular behavior of Salmonella enterica serovar Typhimurium characterized by the expression of the extracellular matrix components cellulose and curli fimbriae is controlled by c-di-GMP. In this work the roles of the EAL and GGDEF-EAL domain proteins on rdar morphotype development were investigated. Knockout of four of 15 EAL and GGDEF-EAL domain proteins upregulated rdar morphotype expression and expression of CsgD, the central regulator of the rdar morphotype, and partially downregulated c-di-GMP concentrations. More-detailed analysis showed that the EAL domain protein STM4264 and the GGDEF-EAL domain protein STM1703, which highly downregulated the rdar morphotype, have overlapping yet distinct functions. Another subset of EAL and GGDEF-EAL domain proteins influenced multicellular behavior in liquid culture and flagellum-mediated motility. Consequently, this work has shown that several EAL and GGDEF-EAL domain proteins, which act as phosphodiesterases, play a determinative role in the expression level of multicellular behavior of Salmonella enterica serovar Typhimurium

A Role for the EAL-Like Protein STM1344 in Regulation of CsgD Expression and Motility in Salmonella enterica Serovar Typhimurium▿

The bacterial second messenger cyclic di-GMP (c-di-GMP) regulates the transition between sessility and motility. In Salmonella enterica serovar Typhimurium, the expression of CsgD, the regulator of multicellular rdar morphotype behavior, is a major target of c-di-GMP signaling. CsgD expression is positively regulated by at least two diguanylate cyclases, GGDEF domain proteins, and negatively regulated by at least four phosphodiesterases, EAL domain proteins. Here, we show that in contrast to EAL domain proteins acting as phosphodiesterases, the EAL-like protein STM1344 regulated CsgD expression positively and motility negatively. STM1344, however, did not have a role in c-di-GMP turnover and also did not bind the nucleotide. STM1344 acted upstream of the phosphodiesterases STM1703 and STM3611, previously identified to participate in CsgD downregulation, where it repressed their expression. Consequently, although STM1344 has not retained a direct role in c-di-GMP metabolism, it still participates in the regulation of c-di-GMP turnover and has a role in the transition between sessility and motility