RESUMO
Nitrofurans (nitrofurazone, nitrofurantoin, furazidin, nifuroxazide), and nitric oxide generators (sodium nitroprusside and isosorbide mononitrate) in subinhibitory concentrations were shown to significantly increase the bioluminescence of the sensor Escherichia coli strains used for detecting N-acyl-homoserine lactones, signaling molecules of Quorum Sensing (QS) regulatory systems. The highest activation of bioluminescence (up to 250-400 fold) was observed in the presence of nitrofurazone on E. coli DH5alpha biosensors containing lux-reporter plasmids pSB401 or pSB536. However, this activation was not specifically associated with the functioning of QS systems. We suggest that the effect observed results from a direct action of nitrofurans and NO donors on the process of bioluminescence. The data indicate the necessity of using the biosensors that make it possible to detect specific effects of substances tested on QS regulation.
Assuntos
Acil-Butirolactonas/análise , Técnicas Biossensoriais , Escherichia coli/efeitos dos fármacos , Doadores de Óxido Nítrico/farmacologia , Nitrofuranos/farmacologia , Percepção de Quorum/efeitos dos fármacos , Acil-Butirolactonas/metabolismo , Escherichia coli/metabolismo , Humanos , LuminescênciaRESUMO
The control of gene expression in response to an increase in the bacterial population density (Quorum Sensing) involves low-molecular-weight signal molecules (autoinducers, AI). AI-2 and synthase LuxS mediating its synthesis are widely distributed in Gram-negative and Gram-positive bacteria. In this work, the data were obtained on the role of global regulators of gene expression in AI-2 synthesis in Escherichia coli cells. The mutation inactivating gene rpoS (encodes sigma S subunit of RNA polymerase) was shown to drastically decrease an amount of active AI-2 in the culture medium. Mutations at gene rpoN that encodes sigma N subunit of RNA polymerase and also at gene lon, which encodes Lon proteinase, on the contrary, increase an amount of active AI-2 in supernatants of cultures. Mutant strains lacking histone-like proteins H-NS and StpA accumulate a slightly higher amount of AI-2 than the isogenic wild-type strain: however, an amount of AI-2 decreased in the culture medium of the double mutant devoid of both these proteins.
Assuntos
Escherichia coli K12/metabolismo , Homosserina/análogos & derivados , Mutação , Percepção de Quorum/fisiologia , Transcrição Gênica/fisiologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Liases de Carbono-Enxofre/genética , Liases de Carbono-Enxofre/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Escherichia coli K12/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Homosserina/biossíntese , Lactonas , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Protease La/genética , Protease La/metabolismo , RNA Polimerase Sigma 54/genética , RNA Polimerase Sigma 54/metabolismo , Fator sigma/genética , Fator sigma/metabolismoRESUMO
More than 99% of bacteria exist in natural ecosystems as specifically organized biofilms adhering to solid surfaces. Biofilms have a typical architecture and are enclosed in exopolymeric matrix. Bacteria living in biofilms are extremely resistant to antibacterial factors. In this work we studied the role of some global regulators of gene expression on biofilm formation by Escherichia coli K12. The Histone-like proteins H-NS and StpA were shown to play an essential role in the regulation of biofilm formation. Mutant strains deficient in HNS or StpA had lower levels of biofilm formation than the wild-type isogenic strain. A double mutant deficient in the two proteins was virtually incapable of forming the biofilms. The mutations in the rpoN gene encoding for the sigma N subunit of RNA-polymerase and in lon gene encoding for Lon-proteinase induced a 40-60% increase in the biofilm formation.
