Suchergebnisse

Extracellular proteins of Bifidobacterium longum may mediate important interactions with the host. Here, we report on a comprehensive analysis of such proteins by using protein-free culture conditions and two-dimensional gel electrophoresis followed by mass spectrometry for protein identification. Seventeen proteins were detected in the culture supernatant, and 14 of them could be identified. Among these were 3 hypothetical solute-binding proteins of ABC transporters, an invasion-associated protein homolog, putative enzymes catalyzing cell wall turnover, several polypeptides with similarity to bacterial conjugation proteins, and 3 proteins of unknown function. Surprisingly, aldolase, usually considered as a cytoplasmic protein, was found in the culture supernatant. All proteins, excluding aldolase, were predicted to contain a signal peptide and a signal peptide cleavage site in their immature form. Some of the excreted proteins are interesting targets for further genetic and physiological studies ; This work was financed by European Union FEDER funds and the Spanish Plan Nacional de I+D (project AGL2004-06727-C02). B.S. was the recipient of a pre-doctoral fellowship from the Spanish Ministerio de Ciencia y Tecnologia and from the MICA Department of the National Institute for Research in Agronomy (INRA) ; Peer reviewed

Bifidobacteria are one of the main microbial inhabitants of the human colon. Usually administered in fermented dairy products as beneficial microorganisms, they have to overcome the acidic pH found in the stomach during the gastrointestinal transit to be able to colonize the lower parts of the intestine. The mechanisms underlying acid response and adaptation in Bifidobacterium longum biotype longum NCIMB 8809 and its mutant resistant to acid pH B. longum biotype longum 8809dpH, were studied. Comparison of protein maps, and protein identification by MALDI-TOF mass spectrometry analysis, allowed us to identify 9 different proteins whose production largely changed in the mutant strain. Furthermore, the production of 47 proteins was modulated by pH in one or both strains. These included general stress response chaperones, proteins involved in transcription and translation, as well as in the carbohydrate and nitrogen metabolism, among others. Significant differences in the levels of metabolic end-products and in the redox status of the cells were also detected between the wild type strain and its acid pH resistant mutant in response, or as a result of, adaptation to acid. Remarkably, the results of this work indicated that adaptation and response to low pH in B. longum biotype longum involves changes in the glycolytic flux and in the ability to regulate the internal pH. These changes were accompanied by a higher content of ammonium in the cytoplasm, likely coming from amino acid deamination, and a decrease of the bile salt hydrolase activity ; This work was financed by European Union FEDER funds and the Spanish Plan Nacional de I + D (project AGL2004-06727-C02-01/ALI and AGL2005-05788-C02-01/ALI). B. Sánchez was the recipient of a FPI predoctoral fellowship from the Spanish Ministerio de Ciencia y Tecnología and from the MICA department of the National Institute for Research in Agronomy (INRA). ; Peer reviewed

Bile salts are natural detergents that facilitate the digestion and absorption of the hydrophobic components of the diet. However, their amphiphilic nature makes them very inhibitory for bacteria and strongly influences bacterial survival in the gastrointestinal tract. Adaptation to and tolerance of bile stress is therefore crucial for the persistence of bacteria in the human colonic niche. Bifidobacterium animalis subsp. lactis, a probiotic bacterium with documented health benefits, is applied largely in fermented dairy products. In this study, the effect of bile salts on proteomes of B. animalis subsp. lactis IPLA 4549 and its bile-resistant derivative B. animalis subsp. lactis 4549dOx was analyzed, leading to the identification of proteins which may represent the targets of bile salt response and adaptation in B. animalis subsp. lactis. The comparison of the wild-type and the bile-resistant strain responses allowed us to hypothesize about the resistance mechanisms acquired by the derivative resistant strain and about the bile salt response in B. animalis subsp. lactis. In addition, significant differences in the levels of metabolic end products of the bifid shunt and in the redox status of the cells were also detected, which correlate with some differences observed between the proteomes. These results indicate that adaptation and response to bile in B. animalis subsp. lactis involve several physiological mechanisms that are jointly dedicated to reduce the deleterious impact of bile on the cell's physiology. ; This work was financed by European Union FEDER funds and the Spanish Plan Nacional de I + D (project AGL2004-06727-C02-01/ALI). B. Sánchez was the recipient of an FPI predoctoral fellowship from the Spanish Ministerio de Ciencia y Tecnología and from the MICA Department of the National Institute for Research in Agronomy (INRA). ; Peer reviewed