Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal

Gene expression of bacterial collagenolytic proteases in root caries

Objective: It is unknown whether bacteria play a role in the collagen matrix degradation that occurs during caries progression. Our aim was to characterize the expression level of genes involved in bacterial collagenolytic proteases in root biofilms with and without caries. Method: we collected samples from active cavitated root caries lesions (RC, n = 30) and from sound root surfaces (SRS, n = 10). Total microbial RNA was isolated and cDNA sequenced on the Illumina Hi-Seq2500. Reads were mapped to 162 oral bacterial reference genomes. Genes encoding putative bacterial collagenolytic proteases were identified. Normalization and differential expression analysis was performed on all metatranscriptomes (FDR8) but none in SRS were Pseudoramibacter alactolyticus [HMPREF0721_RS02020; HMPREF0721_RS04640], Scardovia inopinata [SCIP_RS02440] and Olsenella uli DSM7084 [OLSU_RS02990]. Conclusion: Our findings suggest that the U32 proteases may be related to carious dentine. The contribution of a small number of species to dentine degradation should be further investigated. These proteases may have potential in future biotechnological and medical applications, serving as targets for the development of therapeutic agents

N-acetylglucosamine Regulates Virulence Properties in Microbial Pathogens

There is growing evidence that the sugar N-acetylglucosamine (GlcNAc) plays diverse roles in cell signaling pathways that impact the virulence properties of microbes and host cells. GlcNAc is already well known as a ubiquitous structural component at the cell surface that forms part of bacterial cell wall peptidoglycan, cell wall chitin in fungi and parasites, and extracellular matrix glycosaminoglycans of animal cells. Chitin and peptidoglycan have been previously linked to cell signaling as they can stimulate responses in plant and animal host cells [1–3]. Recent studies now indicate that GlcNAc released from these polymers can also activate cell signaling via several different mechanisms [4–6]. The role of these new GlcNAc signaling pathways in the regulation of virulence factors will be the focus of this review

Effect of dietary sugars on dual-species biofilms of Streptococcus mutans and Streptococcus sobrinus – a pilot study

AbstractIntroduction Frequent consumption of sugars and the presence of Streptococcus mutans and Streptococcus sobrinus are correlated with higher caries experience.Objective The aim of this pilot study was to elucidate the effect of different fermentable carbohydrates on biomass formation and acidogenicity of S. mutans and S. sobrinus biofilms.Material and method Single and dual-species biofilms of S. mutans ATCC 25175 and S. sobrinus ATCC 27607 were grown at the bottom of microtiter plates at equal concentrations for 24 h at 37 °C under micro-aerobic atmosphere. Carbohydrates were added at 2% concentration: maltose, sucrose, glucose and lactose. BHI Broth (0.2% glucose) was used as negative control. Acidogenicity was assessed by measuring the pH of spent culture medium after 24 h, immediately after refreshing the culture medium and for the next 1 h and 2 h. Crystal violet staining was used as an indicator of the total attached biofilm biomass after 24 h incubation. Data were analyzed by two-way ANOVA followed by Bonferroni post hoc test. Significance level was set at 5%.Result All carbohydrates resulted in higher biomass formation in single- and dual-species biofilms when compared to the control group. Sucrose, lactose and maltose showed higher acidogenicity than the control group in both single- and dual-species biofilms after 24 h.Conclusion These findings indicate that the type of biofilm (single- or dual-species) and the carbohydrate used may influence the amount of biomass formed and rate of pH reduction.ResumoIntrodução O consumo frequente de açucares e a presença de Streptococcus mutans e Streptococcus sobrinus estão correlacionados com maior experiência de cárie.Objetivo Elucidar o efeito de diferentes carboidratos fermentáveis na biomassa e acidogenicidade de biofilmes formados por S. mutans e S. sobrinus.Material e método Biofilmes única e dupla- espécie de S. mutans ATCC 25175 e S. sobrinus ATCC 27607 em concentrações iguais cresceram no fundo de placas de microtitulação por 24 h a 37 °C em microaerofilia. Maltose, sacarose, glicose e lactose foram adicionados a 2%. BHI caldo (0.2% glicose) foi usado como controle negativo. Acidogenicidade foi avaliada por meio da medição do pH do meio de cultura após 24 h, imediatamente após troca de meio e nas próximas 1 h e 2 h. Coloração por cristal violeta foi usada como indicador do total de biomassa aderida, após 24 h de incubação. Os dados foram analisados por teste ANOVA two way e Teste de Bonferroni. O nível de significância foi de 5%.Resultado Todos os carboidratos resultaram em maior formação de biomassa em ambos os tipos de biofilme (única ou dupla- espécie), quando comparado ao grupo controle. Sacarose, lactose e maltose mostraram maior acidogenicidade que o grupo controle após 24 h nos biofilmes única ou dupla-espécie, apenas após 24 h.Conclusão Os achados indicam que o tipo de biofilme (única ou dupla- espécie) e o tipo de carboidrato usado podem influenciar tanto na quantidade de biomassa formada quanto na taxa de redução do pH