Differential protein expression by Pseudomonas fragi submitted to various stresses

Abstract

We have analyzed the impact of various stressing conditions on the physiological and molecular responses of the main psychrotrophic spoilage bacterium of refrigerated meat and meat products, Pseudomonas fragi. A survival study using conventional plating was first performed to select the stressing agents and parameters. Some of these mimicked cleaning-disinfection processes but with less drastic conditions in order to keep alive enough bacterial cells for the protein expression characterization. Cultures of P. fragi, at the beginning of the stationary phase of growth, were submitted to individual pH (5.4, 10.5), osmotic (8% Na2SO4, pH 7.0), biocide (fatty amine) shocks or combined treatments (8% Na2SO4, pH 10.5; 8% Na2SO4, pH 10.5 + biocide; pH 5.4 + pH 10.5 and pH 10.5 + pH 5.4) and the molecular responses were investigated by comparing autoradiograms of two-dimensional gel electrophoresis (2-DE) patterns of proteins radiolabeled with L-[35S]methionine. The observation of qualitative and relative quantitative variations in protein expression, determined with Melanie II image analysis software (Bio-Rad), revealed the overexpression of a total of 91 proteins for the eight challenges by comparison with the nonshocked controls. Some proteins appeared to be more or less general stress proteins whereas others were specific for one chemical treatment. The appraisal of the type of molecular response according to the type of treatment was analyzed statistically.

Two-dimensional gel electrophoresis of Mytilus galloprovincialis differences in protein expression between intertidal and cultured mussels

“…2). An identical approach has also been applied to other species (Higginbotham et al 1991, Heinke et al 1998, Tsuji et al 1999, Vasseur et al 1999) and similar results were obtained.…”

Altered Protein Expression of Streptococcus oralis Cultured at Low pH Revealed by Two-Dimensional Gel Electrophoresis

“…The overwhelming difference between the growth conditions was the initial pH of the media, however, although it maybe that the difference in growth rate had an effect on the expression of some of the proteins described here and that biofilm or continuous culture grown cells will also express different proteins. Numerous studies have used the high resolving power of 2-D electrophoresis to monitor changes in protein expression during the adaptation of microorganisms to environmental stress (4,22,28,30,41,44). We have used this technique to investigate the regulation of gene product expression of S. oralis grown under conditions of differing pH and used peptide mass fingerprinting to identify those proteins with altered expression.…”

Search and Discovery Strategies for Biotechnology: the Paradigm Shift

“…Proteome analysis of stress responses is important here because it reveals global regulation of gene expression under different stress conditions. Thus, a recent analysis of the psychrotolerant food spoilage organism Pseudomonas fragi revealed overexpression of 91 stress proteins in response to challenge from cleaning-disinfection treatments in food plants (457). Such information is highly germane to the development of effective treatment procedures where organisms are known to counteract simultaneous adverse conditions by coordinated changes in gene expression.…”