Assuntos
Listeria monocytogenes/metabolismo , Proteômica/métodos , Ácidos , Proteínas de Bactérias/química , Eletroforese em Gel Bidimensional , Microbiologia de Alimentos , Concentração de Íons de Hidrogênio , Modelos Biológicos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizAssuntos
Proteínas de Bactérias/química , Concentração de Íons de Hidrogênio , Listeria monocytogenes/química , Proteoma , Sequência de Aminoácidos , Autorradiografia/métodos , Proteínas de Bactérias/isolamento & purificação , Técnicas Bacteriológicas/métodos , Meios de Cultura , Eletroforese em Gel Bidimensional/métodos , Indicadores e Reagentes , Focalização Isoelétrica/métodos , Dados de Sequência Molecular , Peso Molecular , Mapeamento de Peptídeos , Análise de Sequência de ProteínaRESUMO
The physiological aspects of the response to acidic conditions and the correlated protein synthesis were studied by using Listeria monocytogenes grown in a chemically defined synthetic medium. This growth was greatly affected by pH of the medium. It decreased when pH declined and was arrested at pH 4. When pH went under 4, the bacteria began to die. If the bacteria had been adapted to an intermediary sublethal pH before imposition of lethal pH stress, they would have resisted better lethal pH. A prolonged treatment at intermediary pH, however, rendered the bacteria more sensitive to subsequent lethal pH. Organic volatile acids exerted a more deleterious effect on L. monocytogenes than inorganic acids at the same stressing pH. The acquired acid tolerance was conserved after several weeks of storage of the adapted bacteria at 4 degrees C. Acid stress and acid adaptation (tolerance) affected the synthesis patterns of bacterial proteins: Many proteins were repressed and several others increased in expression level. These acid-induced proteins were separated by two-dimensional (2D-) electrophoresis and analyzed by a computer-aided 2D-gel analysis system. The results obtained suggested that acid tolerance and acid stress responses require the synthesis of a certain number of shared proteins and that additional acid-induced proteins are needed when the bacteria must face more severe acidic pH.
RESUMO
The proteomes of Listeria monocytogenes expressed in suspension and biofilm state, in the presence and absence of a carbon source, were analysed by two-dimensional electrophoresis with the help of computer software. The up-regulated proteins in each case were identified by peptide sequencing using electrospray ionisation tandem mass spectrometry and a database search against the Listeria genome was performed. Relevant functions could be attributed to a number of the induced proteins which contribute to the understanding of the mechanisms of starvation survival of L. monocytogenes in planktonic state and in biofilm.