Protein expression in Escherichia coli S17-1 biofilms: impact of indole

Abstract

Bacteria undergo significant changes during adherence to surfaces and biofilm development. Cell-to-cell signalling molecules are known to be involved in these phenotypic adaptations to the sessile mode of life. We demonstrated previously that indole can act as an extracellular signal to regulate biofilm formation in E. coli. To identify proteins over- or under-expressed in response to E. coli biofilm formation and indole signalling, we compared the proteomes of the E. coli S17-1 wild-type and 3714 (S17-1 tnaA::Tn5) tryptophanase-negative mutant cells (which don't produce indole) grown as suspensions or biofilms in the presence or absence of exogenous indole. From computer-assisted image analysis, 407 spots were discriminated on two-dimensional electropherograms. Principal component analysis (PCA) of the electropherograms did not discriminate between the proteomes of the wild-type and mutant cells grown as suspensions indicating that indole has a limited impact onto protein expression of planktonic cells. The first principal component extracted by PCA, after standardization of the observations, opposed planktonic and biofilm cells confirming the existence of changes in protein expression during E. coli biofilm formation. Among proteins over- or under-expressed by both sessile wild-type and mutant cells, we identified metabolic enzymes, transporters, proteins involved in the translation and transcription machinery, stress response and regulation, and signalling proteins. The wild-type and mutant strains grown as biofilms in the presence of indole were discriminated by the second component. The role of some proteins whose expression was altered in biofilm bacteria compared to suspended counterparts is discussed.

Production of Indole froml-Tryptophan and Effects of These Compounds on Biofilm Formation byFusobacterium nucleatumATCC 25586

“…This is probably because the importance of indole had not been recognized, except for its usefulness as a common diagnostic marker. However, increasing evidence suggests that indole mediates cell-to-cell signaling, similar to the N-acyl derivatives of homoserine lactone, cyclic peptide, and quinolones (9,34,41,55). The goal of this study was to gain insight into indole production by F. nucleatum, a key microorganism for dental biofilm formation, and to evaluate the effects of tryptophan and indole on biofilm formation.…”

Biofilm Formation-Gene Expression Relay System inEscherichia coli: Modulation of σS-Dependent Gene Expression by the CsgD Regulatory Protein via σSProtein Stabilization

“…Such coordination would relay the transition from single cell to biofilm to expression of the rpoS regulon, i.e., one of the main stress responses in bacteria (29). Interestingly, biofilm formation in E. coli, even when independent of CsgD and of curli production, appears to be tightly connected to S -dependent gene expression (1,4,17,34,62) and to general induction of stress responses (4, 54), possibly FIG. 7. S turnover experiments.…”

Signals, Regulatory Networks, and Materials That Build and Break Bacterial Biofilms

“…The challenge of the researcher is to determine which of the conditions studied in the lab are relevant to environments experienced by the bacterium in the wild. Conditions such as the nutritional status of the environment and even the presence of conjugative plasmids can lead to quorum-sensing cues being bypassed or overridden (56,105,113,264,267). Presumably, all of these signals feed into intricate cellular signaling networks that ultimately results in the appropriate response to the prevailing conditions.…”