1,721,106 research outputs found
Should I stay or should I go? Biofilm vs. planktonic lifestyle in bacteria
No full textSwitch between single-cell (planktonic) to biofilm growth is regulated by a variety of environmental and physiological cues, often related to stress responses, thus suggesting direct cross-talk stress responses and biofilm formation. Regulatory mechanisms presiding to this process involve the master stress regulation factor sigmaS and the biosynthesis of the cyclic di-GMP signal molecule by diguanylate cyclase enzymes (DGCs), in a tight and complex interplay
Regolazione di geni di adesione cellulare e formazione del biofilm nel batterio Escherichia coli
No full textCross-talk mechanisms between biofilm formation and response to environmental and physiological stresses in Escherichia coli
No full textSwitch between single-cell (planktonic) to biofilm growth (and vice versa) is regulated by a variety of environmental and physiological cues. Signals leading to activation of stress responses often lead to biofilm formation, which, in turn, can trigger induction of stress response mechanisms, suggesting direct cross-talk between the two cellular processes. Regulatory mechanisms presiding to this process include two-component regulatory systems, master regulators such as the rpoS gene, and signal molecules such as cyclic di-GMP, in a tight and complex interplay
Co-regulation of iron uptake system and exopolysaccharide biosynthetic operons in a biofilm-forming mutant of E.coli
No full text
Detection of the bacterial second messenger cyclic-di-GMP and evaluation of diguanylate cyclise function by microbiological assays suitable for High-Throughtput-Screening of biofilm inhibitors
No full textBiofilms are microbial communities embedded in a self-produced polymeric matrix, mainly composed by extracellular polysaccharides, which confers resistance to environmental stresses and tolerance to antibiotic treatments. In Gram negative bacteria, production of the cyclic-di-GMP (c-di-GMP) signal molecule is the main trigger for exopolysaccharides (EPS) and adhesion factors’ production: indeed, mutants affected in c-di-GMP biosynthesis are impaired in biofilm formation. In this report, we describe a simple microbiological assay to detect c-di-GMP biosynthesis by bacterial diguanylate cyclase enzymes (DGC’s). The assay relies on expression of a DGC-encoding gene from a multicopy plasmid and detection of c-di-GMP-dependent extracellular factors on agar medium supplemented with Congo red (CR), a dye which binds amyloid fibers and polysaccharides. The CR assay can be performed in 96-well microtiter plates, making it suitable for High-Throughput Screening for chemical inhibitors of c-di-GMP biosynthesis. In addition, it can be used for functional studies of diguanylate cyclases and for the elucidation of their role in production of extracellular structures. We have used the CR assay to assess the effects of five different DGC-encoding genes: adrA, ycdT, ydaM and yddV from Escherichia coli and wspR from Pseudomonas aeruginosa, in a set of E. coli strains deficient in production of EPS and/or adhesion factors. Results of the CR assays suggest that, even when expressed ectopically from a multicopy plasmid, DGC’s affect production of cell surface-associated factors in a specific manner. Different effects of the various DGC’s on production of extracellular structures, cell motility and gene expression could be confirmed by specific assay
Biofilm formation-gene expression relay system in Escherichia coli: modulation of sigma(S)-dependent gene expression by the CsgD regulatory protein via sigma(S) protein stabilization
No full textBacteria can switch from a single-cell (planktonic) mode to a multicellular community (biofilm) mode via production of cell-cell aggregation and surface adhesion factors. In this report, we present evidence that the CsgD protein, a transcription regulator involved in biofilm formation in Escherichia coli, modulates the expression of the rpoS (sigmaS) regulon. Protein pattern analysis of E. coli cells in stationary phase shows that CsgD affects the expression of several proteins encoded by sigmaS-dependent genes. CsgD regulation of sigmaS-dependent genes takes place at gene transcription level, does not by-pass the need for rpoS and is abolished in an rpoS null mutant. Consistent with these results, we find that CsgD expression leads to an increase in sigmaS intracellular concentration. Increase in sigmaS cellular amount is mediated by CsgD-dependent transcription activation of iraP, encoding a factor involved in sigmaS protein stabilization. Our results strongly suggest that the CsgD regulatory protein plays a major role as a relay between adhesion factors production and sigmaS-dependent gene expression via sigmaS protein stabilization. Direct co-ordination between biofilm formation and expression of the rpoS regulon could positively impact important biological processes, such as host colonization or response to environmental stresses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
