Binding of the extracellular matrix laminin-1 to Clostridioides difficile strains

BACKGROUND Clostridioides difficile is the most common cause of nosocomial diarrhea associated with antibiotic use. The disease's symptoms are caused by enterotoxins, but other surface adhesion factors also play a role in the pathogenesis. These adhesins will bind to components of extracellular matrix. OBJECTIVE There is a lack of knowledge on MSCRAMM, this work set-out to determine the adhesive properties of several C. difficile ribotypes (027, 133, 135, 014, 012) towards laminin-1 (LMN-1). METHODS A binding experiment revealed that different ribotypes have distinct adhesion capabilities. To identify this adhesin, an affinity chromatography column containing LMN-1 was prepared and total protein extracts were analysed using mass spectrometry. FINDINGS Strains from ribotypes 012 and 027 had the best adhesion when incubated with glucose supplementations (0.2%, 0.5%, and 1%), while RT135 had a poor adherence. The criteria were not met by RT014 and RT133. In the absence of glucose, there was no adhesion for any ribotype, implying that glucose is required and plays a significant role in adhesion. MAIN CONCLUSIONS These findings show that in the presence of glucose, each C. difficile ribotype interacts differently with LMN-1, and the adhesin responsible for recognition could be SlpA protein.

Organização estrutural do taquizoíto de toxoplasma gondii: [revisão] / Structural organization of the tachyzoite of toxoplasma gondii: [review]

Objetivos: fazer uma revisão dos aspectos básicos da ultraestrutura do taquizoíto de Toxoplasma gondii, agente etiológico da toxoplasmose. Fonte de dados: os dados apresentados tomam como referência resultados recentes obtidos pelos principais grupos de pesquisadores no mundo, que se dedicam ao estudo do Toxoplasma gondii, incluindo-se dados do próprio grupo de autores. Síntese dos dados: os taquizoítos de Toxoplasma gondii são responsáveis pela fase aguda da infecção, penetrando ativamente, através do complexo apical, em células dos hospedeiros onde se multiplicam. São abordadas características ultraestruturais e moleculares particulares da película, do citoesqueleto, de organelas secretórias (róptrias, micronemas e grânulos densos) e não secretórias (apicoplasto) exclusivas do filo Apicomplexa, além das peculiaridades do núcleo, mitocôndria, acidocalcisomas, retículo endoplasmático e complexo de Golgi desses parasitos intracelulares. Conclusões: estas características confirmam que o sucesso nas etapas de adesão, invasão e multiplicação do parasito possui clara correlação com suas características morfofuncionais.

Aims: To review basic aspects on the ultrastructure of the tachyzoite of Toxoplasma gondii, the causative agent of toxoplasmosis. Source of data: The data presented are based on recent publications by the most distinguished research groups in the area dedicated to the study of Toxoplasma gondii, including studies from the present authors. Summary of findings: The tachyzoites are responsible for the acute phase of the infection by actively penetrating, through the parasites? apical complex, the host cells where they multiply. Both ultrastructural and molecular particularities of the pellicle, the cytoskeleton, secretory (rhoptries, micronemas and dense granules) and non secretory (apicoplast) organelles, specific to Apicomplexa phylum, besides peculiar features of the nucleus, mitochondrion, acidocalcisomes, endoplasmic reticulum and Golgi complex of these intracellular parasites. Conclusions: These characteristics confirm that the success in the process of adhesion, invasion and multiplication of this parasite is clearly correlated to its morphology.

The redox potential interferes with the expression of laminin binding molecules in Bacteroides fragilis

The Bacteroides fragilis ATCC strain was grown in a synthetic media with contrasting redox potential (Eh) levels [reduced (-60 mV) or oxidised (+100mV)] and their adhesion capacity to extracellular matrix components was evaluated. The strain was capable of adhering to laminin, fibronectin, fibronectin + heparan sulphate and heparan sulphate. A stronger adherence to laminin after growing the strain under oxidising conditions was verified. Electron microscopy using ruthenium red showed a heterogeneous population under this condition. Dot-blotting analyses confirmed stronger laminin recognition by outer membrane proteins of cells cultured at a higher Eh. Using a laminin affinity column, several putative laminin binding proteins obtained from the cultures kept under oxidising (60 kDa, 36 kDa, 25 kDa and 15 kDa) and reducing (60 kDa) conditions could be detected. Our results show that the expression of B. fragilis surface components that recognise laminin are influenced by Eh variations.