Streptococcus pneumoniae is a causal agent of otitis media, pneumonia, meningitis and severe cases of septicemia. This human pathogen infects elderly people and children with a high mortality rate of approximately one million deaths per year worldwide. Antibiotic-resistance of S. pneumoniae strains is an increasingly serious health problem; therefore, new therapies capable of combating pneumococcal infections are indispensable. The application of gold nanoparticles has emerged as an option in the control of bacterial infections; however, the mechanism responsible for bacterial cell lysis remains unclear. Specifically, it has been observed that gold nanoparticles are capable of crossing different structures of the S. pneumoniae cells, reaching the cytosol where inclusion bodies of gold nanoparticles are noticed. In this work, a novel process for the separation of such inclusion bodies that allowed the analysis of the biomolecules such as carbohydrates, lipids and proteins associated with the gold nanoparticles was developed. Then, it was possible to separate and identify proteins associated with the gold nanoparticles, which were suggested as possible candidates that facilitate the interaction and entry of gold nanoparticles into S. pneumoniae cells.

Streptococcus pneumoniae is a human pathogen whose principal virulence factor is its capsule. This structure allows the bacterium to evade the human immune system. Treatment of infections caused by this bacterium is based on antibiotics; however, the emergence of antibiotic-resistant strains makes this task increasingly difficult. Therefore, it is necessary to investigate new therapies, such as those based on gold nanoparticles, for which unfortunately the mechanisms involved have not yet been investigated. As far as we know, this study is the first that attempts to explain how gold nanoparticles destroy the bacterium Streptococcus pneumoniae. We found that the mean particle size was an important issue, and that the effect on the bacterium was dose-dependent. Cellular growth was inhibited by the presence of the nanoparticles, as was cell viability. The pH of the bacterial growth media was acidified, but interestingly the reactive species were not affected. A transmission electron microscopy analysis revealed the presence of inclusion bodies of gold nanoparticles within the bacterium. We present the first findings that attempt to explain how gold nanoparticles lyse Gram-positive bacteria.

Streptococcus pneumoniae is a Gram-positive microorganism that is the cause of bacterial pneumonia, sinusitis and otitis media. This human pathogen also can cause invasive diseases such as meningitis, bacteremia and septicemia. Haemoglobin (Hb) and haem can support the growth and viability of S. pneumoniae as sole iron sources. Unfortunately, the acquisition mechanism of Hb and haem in this bacterium has been poorly studied. Previously we identified two proteins of 37 and 22 kDa as putative Hb- and haem-binding proteins (Spbhp-37 and Spbhp-22, respectively). The sequence of Spbhp-37 protein was database annotated as lipoprotein without any function or localization. Here it was immunolocalized in the surface cell by transmission electron microscopy using specific antibodies produced against the recombinant protein. The expression of Spbhp-37 was increased when bacteria were grown in media culture supplied with Hb. In addition, the affinity of Sphbp-37 for Hb was determined. Thus, in this work we are presenting new findings that attempt to explain the mechanism involved in iron acquisition of this pathogen. In the future these results could help to develop new therapy targets in order to avoid the secondary effects caused by the traditional therapies.

Pseudomonas aeruginosa (P. aeruginosa) es una bacteria Gram negativa de gran relevancia clínica, responsable de infecciones nosocomiales graves, especialmente en pacientes inmunocomprometidos. Su capacidad para adquirir hierro es crucial para su patogenicidad, en este trabajo de investigación se buscó identificar proteínas de membrana clave involucradas en la captación del grupo hemo como posibles blancos terapéuticos. Para lograrlo, se realizó un análisis in silico, evaluando 47 proteínas de membrana potenciales mediante Expasy BLAST. Se identificaron 7 proteínas de membra candidatas que contienen los motivos conservados FRAP y NPNL, esenciales para la unión al hemo. Además, se analizó la presencia de secuencias FurBox en las regiones promotoras para evaluar su regulación por hierro. Nuestros hallazgos muestran que las proteínas de membrana encontradas contienen los motivos necesarios para permitir su interacción con el grupo hemo. Además, presentan secuencias FurBox, sugiriendo que son reguladas por hierro. En conclusión, estas proteínas representan prometedores blancos terapéuticos; su inhibición podría reducir la virulencia de P. aeruginosa al limitar la adquisición de hierro y la formación de biofilms, sentando las bases para futuros estudios sobre inhibidores dirigidos a estas proteínas.