In Silico Selection and In Vitro Evaluation of New Molecules That Inhibit the Adhesion of <i>Streptococcus mutants</i> through Antigen I/II

Streptococcus mutans is the main early colonizing cariogenic bacteria because it recognizes salivary pellicle receptors. The Antigen I/II (Ag I/II) of S. mutans is among the most important adhesins in this process, and is involved in the adhesion to the tooth surface and the bacterial co-aggregation in the early stage of biofilm formation. However, this protein has not been used as a target in a virtual strategy search for inhibitors. Based on the predicted binding affinities, drug-like properties and toxicity, molecules were selected and evaluated for their ability to reduce S. mutans adhesion. A virtual screening of 883,551 molecules was conducted; cytotoxicity analysis on fibroblast cells, S. mutans adhesion studies, scanning electron microscopy analysis for bacterial integrity and molecular dynamics simulation were also performed. We found three molecules ZINC19835187 (ZI-187), ZINC19924939 (ZI-939) and ZINC19924906 (ZI-906) without cytotoxic activity, which inhibited about 90% the adhesion of S. mutans to polystyrene microplates. Molecular dynamic simulation by 300 nanoseconds showed stability of the interaction between ZI-187 and Ag I/II (PDB: 3IPK). This work provides new molecules that targets Ag I/II and have the capacity to inhibit in vitro the S. mutans adhesion on polystyrene microplates

Influence of microbial adherence on corrosion of UNS 1008 carbon steel and hybrid nano-structured coatings

Purpose Microbes that are able to grow on different surfaces can cause the deterioration of the underlying layers because of their metabolic activity. The purpose of this study is report the ability of fungi-bacteria consortium (FBC) in anaerobic media, and marine strain bacteria, to attach onto UNS 1008 carbon steel and zinc epoxy coats. Design/methodology/approach Impedance analysis, scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to evaluate the adherence, biofilm formation and corrosion effect of FBC and marine bacteria onto UNS1008 carbon steel in anaerobic and aired conditions, respectively. In a similar way, the anticorrosive performance of hybrid coats on UNS 1008 carbon steel against marine bacteria. Findings In aerobic conditions, the outer layer shows a micro-crack appearance and several semi-sphere products that could be because of spore formation. In anaerobic conditions, evidence of iron sulfide surrounded by a mixture of sulfur-containing extracellular polymer substance was observed by SEM images and EDS analysis. The presence of hybrid coats (zinc epoxy with carbon nanotubes CNT content) affected the level of microbial adherence and the concentration of corrosion products (Fe2O3, Fe(OH)2 and FeS); the cell attachment was lower when the steel surface was coated with Zn/CNTs. Originality/value This study opens a window for further evaluations of CNTs associated with metals as active materials to assess the corrosion on extreme corrosive environments, like in oil and gas industries the microorganisms play an important role either to increase or reduce the corrosion processes

Influence of microbial adherence on corrosion of UNS 1008 carbon steel and hybrid nano-structured coatings

Purpose – Microbes that are able to grow on different surfaces can cause the deterioration of the underlying layers because of their metabolic activity. The purpose of this study is report the ability of fungi-bacteria consortium (FBC) in anaerobic media, and marine strain bacteria, to attach onto UNS 1008 carbon steel and zinc epoxy coats. Design/methodology/approach – Impedance analysis, scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to evaluate the adherence, biofilm formation and corrosion effect of FBC and marine bacteria onto UNS1008 carbon steel in anaerobic and aired conditions, respectively. In a similar way, the anticorrosive performance of hybrid coats on UNS 1008 carbon steel against marine bacteria. Findings – In aerobic conditions, the outer layer shows a micro-crack appearance and several semi-sphere products that could be because of spore formation. In anaerobic conditions, evidence of iron sulfide surrounded by a mixture of sulfur containing extracellular polymer substance was observed by SEM images and EDS analysis. The presence of hybrid coats (zinc epoxy with carbon nanotubes CNT content) affected the level of microbial adherence and the concentration of corrosion products (Fe2O3, Fe(OH)2 and FeS); the cell attachment was lower when the steel surface was coated with Zn/CNTs. Originality/value This study opens a window for further evaluations of CNTs associated with metals as active materials to assess the corrosion on extreme corrosive environments, like in oil and gas industries the microorganisms play an important role either to increase or reduce the corrosion processes