Anaerobe/aerobe environmental flux determines protein expression profiles of Bacteroides fragilis, a redox pathogen.

The oxidation-reduction (redox) of the environment characterizes the Bacteroides fragilis pathogenic potential. Previously, using 3D confocal laser scanning microscopy, the bacteria prepared from cultures grown under oxidizing conditions (Eh(7)ca. + 100 mV) were able to penetrate into Hela cell monolayers. In contrast, when grown under reducing conditions (Eh(7)ca. - 60 mV), there were no bacteria evident within Hela cells. The influence of the anaerobe/aerobe environmental flux during the process of the anaerobe infection could be significant. In B. fragilis peritonitis, this may depend on the occurrence of aerobiosis as opposed to anaerobiosis. To this end, three clinical B. fragilis strains, two infectious and one non-infectious, were grown under oxidizing and reducing conditions; then, the outer membrane protein expressions derived from these strains were assessed, following sarcosyl extraction and SDS-PAGE. The differences between the protein profiles from these strains when cultured under oxidizing and reducing conditions were found to be statistically significant for the two infectious strains, but not for the non-infectious strain. OMP profiles under aerobic conditions compared to anaerobic conditions exhibited products with a range of apparent molecular weights suggestive of unique participation in the interaction with the host cell.

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 (+100 mV)] 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.

Adherence of bacteroides fragilis strains to a primary cell culture

Foi avaliada a capacidade de aderência de cepas de dBacteroides fragilis a várias linhagens de células de mamíferos. Algumas cepas, definidas como capazes de aglutinar eritrócitos humanso, foram capazes de aderir a células primárias, obtidas de carcaça de cobaio, nas näo às demais células testadas. Apenas uma cepa, näo aglutinante, näo demonstrou qualquer capacidade de aderência às linhagens celulares testadas.

Atividade de hemaglutinante de Bacteroides fragilis como marcador de virulência / Hemagglutination activity of Bacteroides fragilis as a virulence marker

Atividade hemaglutinante (AH) de Bacteroides fragilis foi estudada. Vários padröes de comportamento foram encontrados com eritrócitos de diferentes espécies (humano, cobaio, carneiro) e 4 grupos distintos foram formados. A perda da AH, após tratamento com calor, de algumas cepas demonstrou ter, provavelmente, as adesinas de B. fragilis, uma natureza proteica. Por outro lado, tratamentos com algumas proteases e neuraminidase näo interferiram na AH. Estudos ao microscópio ótico e eletrônico, com as mesmas cepas, sugeriram que as adesinas estejam associadas com proteínas de membrana externa ou com a presença de uma estrutura definida como "microcápsula". Parece improvável o envolvimento de estruturas como cápsula e fimbrias nesta atividade, uma vez que tanto cepas hemaglutinantes como näo hemaglutinantes apresentaram cápsula, e, fimbrias näo foram encontradas em todas as cepas hemaglutinantes. A maior freqüência de isolamento de cepas hemaglutinantes a partir de especimens clínicos (84.2 por cento) do que a partir de flora normal (15.8 por cento), e, a diferença observada na capacidade de induçäo de abscesso sub-cutâneo em camundongos por cepas hemaglutinantes e näo hemaglutinantes sugerem a AH de B. fragilis como um marcador de virulência.