Proteïna FNR : un pas endavant en la investigació antimicrobiana

Al laboratori de Genètica Molecular Bacteriana, de l'Institut de Biotecnologia i de Biomedicina de la UAB, han estudiat quins són els mecanismes de regulació genètica que han permès que alguns bacteris, fins el dia d'avui, puguin desenvolupar-se en ambients anòxics. Sembla que la resposta està en la proteïna FNR, la qual, en cas de manca d'oxigen, s'encarrega d'activar l'enzim anaeròbic (una ribonucleotidil reductasa), essencial per al manteniment de la viabilitat cel·lular. Aquesta observació pot ser clau per al futur control farmacològic del creixement bacterià durant processos infecciosos

Confondre per vèncer : interferir en la comunicació bacteriana com estratègia per a combatre els patògens resistents a antibiòtics

Investigadors del grup de recerca en Patogènesi Bacteriana i Antimicrobians de l'Institut de Biotecnologia i de Biomedicina i del Departament de Genètica i de Microbiologia de la UAB, en col·laboració amb el grup de Química Farmacèutica de la University College Cork (Irlanda), han dissenyat i avaluat noves molècules capaces d'interferir amb la comunicació bacteriana alterant-ne la formació de biofilm i potenciant l'activitat de la colistina, un dels antibiòtics d'últim recurs.Investigadores del grupo de investigación en Patogénesis Bacteriana y Antimicrobianos del Instituto de Biotecnología y de Biomedicina y del Departamento de Genética y Microbiología de la UAB, en colaboración con el grupo de Química Farmacéutica de la University College Cork (Irlanda), han diseñado y evaluado nuevas moléculas capaces de interferir con la comunicación bacteriana alterando la formación de biofilm y potenciando la actividad de la colistina, uno de los antibióticos de último recurso.Researchers from the Bacterial Pathogenesis and Antimicrobials group of the Institut de Biotecnologia i de Biomedicina (IBB) and the Department of Genetics and Microbiology at UAB, in collaboration with the Pharmaceutical Chemistry group of the University College Cork (Ireland), have designed and evaluated new molecules capable of interfering with bacterial communication by altering biofilm formation and enhancing the activity of colistin, one of the last resort antibiotics

antibacTR : dynamic antibacterial-drug-target ranking integrating comparative genomics, structural analysis and experimental annotation

Background : development of novel antibacterial drugs is both an urgent healthcare necessity and a partially neglected field. The last decades have seen a substantial decrease in the discovery of novel antibiotics, which combined with the recent thrive of multi-drug-resistant pathogens have generated a scenario of general concern. The procedures involved in the discovery and development of novel antibiotics are economically challenging, time consuming and lack any warranty of success. Furthermore, the return-on-investment for an antibacterial drug is usually marginal when compared to other therapeutics, which in part explains the decrease of private investment. - Results : in this work we present antibacTR, a computational pipeline designed to aid researchers in the selection of potential drug targets, one of the initial steps in antibacterial-drug discovery. The approach was designed and implemented as part of two publicly funded initiatives aimed at discovering novel antibacterial targets, mechanisms and drugs for a priority list of Gram-negative pathogens: Acinetobacter baumannii, Escherichia coli, Helicobacter pylori, Pseudomonas aeruginosa and Stenotrophomonas maltophilia. However, at present this list has been extended to cover a total of 74 fully sequenced Gram-negative pathogens. antibacTR is based on sequence comparisons and queries to multiple databases (e.g. gene essentiality, virulence factors) to rank proteins according to their potential as antibacterial targets. The dynamic ranking of potential drug targets can easily be executed, customized and accessed by the user through a web interface which also integrates computational analyses performed in-house and visualizable on-site. These include three-dimensional modeling of protein structures and prediction of active sites among other functionally relevant ligand-binding sites. - Conclusions : given its versatility and ease-of-use at integrating both experimental annotation and computational analyses, antibacTR may effectively assist microbiologists, medicinal-chemists and other researchers working in the field of antibacterial drug-discovery. The public web-interface for antibacTR is available at 'http://bioinf.uab.cat/antibactr'

Fumarate and nitrate reduction (FNR) dependent activation of the Escherichia coli anaerobic ribonucleotide reductase nrdDG promoter

The nrdDG promoter regulates transcriptional expression of the anaerobic ribonucleotide reductase of Escherichia coli, an essential enzyme required to supply the building blocks for DNA synthesis. In this work, binding of the pleiotropic FNR (fumarate and nitrate reduction) transcriptional regulator to the nrdDG promoter region and the effects of binding on transcription were investigated. Gel retardation analysis with purified FNR* demonstrated FNR interaction at two FNR sites, termed FNR-2 and FNR-1, while studies with altered FNR boxes indicated that the upstream FNR-2 site was essential for anaerobic activation of the nrdDG promoter. Although the FNR-1 site was not absolutely required, it allowed maximal expression of this promoter. These results suggest that the two sites have an additive effect in coordinating nrdDG expression in response to shifting oxygen concentrations. [Int Microbiol 2008; 11(1):49-56

Animals devoid of pulmonary system as infection models in the study of lung bacterial pathogens

Biological disease models can be difficult and costly to develop and use on a routine basis. Particularly, in vivo lung infection models performed to study lung pathologies use to be laborious, demand a great time and commonly are associated with ethical issues. When infections in experimental animals are used, they need to be refined, defined, and validated for their intended purpose. Therefore, alternative and easy to handle models of experimental infections are still needed to test the virulence of bacterial lung pathogens. Because non-mammalian models have less ethical and cost constraints as a subjects for experimentation, in some cases would be appropriated to include these models as valuable tools to explore host-pathogen interactions. Numerous scientific data have been argued to the more extensive use of several kinds of alternative models, such as, the vertebrate zebrafish (Danio rerio), and non-vertebrate insects and nematodes (e.g., Caenorhabditis elegans) in the study of diverse infectious agents that affect humans. Here, we review the use of these vertebrate and non-vertebrate models in the study of bacterial agents, which are considered the principal causes of lung injury. Curiously none of these animals have a respiratory system as in air-breathing vertebrates, where respiration takes place in lungs. Despite this fact, with the present review we sought to provide elements in favor of the use of these alternative animal models of infection to reveal the molecular signatures of host-pathogen interactions

IS200 is not a member of the IS600 family of insertion sequences

IS200 is an insertion sequence present in all Salmonella species except S. agona (1, 2). The element is absent from all other Enterobacteriaceae, with the exception of some strains of Shigella flexneri and Shigella sonnei (2). It had been hypothesized that the first mutation characterized as an IS200 insertion, hisD984::IS200 (1, 3) might actually be a deletion mutant of the Shigella insertion element IS630 (4). However, sequencing of the ends of a second mutation caused by IS200 insertion later suggested that IS200 was a distinct insertion element (5). We recently obtained the complete nucleotide sequence of the insertion element IS200 inserted in the histidine operon of S. typhimuriwn (causing the mutation hisD984::IS200). The element is 708 bp long; if this size corresponds to a wild-type element, IS200 can be considered the smallest insertion sequence known (6). A diagram of the hypothetical structure of IS200 is presente

Detecció d'activitat genotòxica a l'aigua

Ha estat estudiada l'activitat genotòxica d'extrets orgànics d'aigües del riu Llobregat durant l'època primaveral. Per a aquest estudi han estat desenvolupades les condicions de treball òptimes amb soques d'Eschcrichia coli portadores de fusions entre el gen lacZ i els gens recA, sfiA i umuC del sistema SOS. Ha estat valorada, mitjançant la quantificació de l'enzim β-galactosidasa, la inducció d'aquets tres gens SOS, i hom ha pogut determinar així la capacitat genotòxica i la mutagènesi dependent del sistema SOS dels extrets orgànics d'aigües. Aixi mateix, ha estat dut a terme complementàriament l'assaig d'Ames en aquelles mostres en les quals no havia estat detectada mutagenicitat seguint 1'assaig SOS. Hom discuteix els avantatges d'emprar conjuntament ambdós mètodes així com l'aplicació a l'estudi de la genotoxicitat i de la mutagènesi ambiental.The genotoxic activity of organic extracts of Llobregat River was studied using two bacterial methods for the assay of mutagenicity. The SOS-dependent genotoxicity and mutagenesis has been determined measuring the β-galactosidase activity; a lacZ gene fusion under the control of different SOS genes (recA, sfiA and umuC) was used. The Ames' test has been also employed as a complement when the samples were negative in the induction of the SOS-dependent mutagenesis. The advantages of using both methods and their application to the study of environmental genotoxicity are discussed

Fumarate and nitrate reduction (FNR) dependent activation of the Escherichia coli anaerobic ribonucleotide reductase nrdDG promoter

The nrdDG promoter regulates transcriptional expression of the anaerobic ribonucleotide reductase of Escherichia coli, an essential enzyme required to supply the building blocks for DNA synthesis. In this work, binding of the pleiotropic FNR (fumarate and nitrate reduction) transcriptional regulator to the nrdDG promoter region and the effects of binding on transcription were investigated. Gel retardation analysis with purified FNR* demonstrated FNR interaction at two FNR sites, termed FNR-2 and FNR-1, while studies with altered FNR boxes indicated that the upstream FNR-2 site was essential for anaerobic activation of the nrdDG promoter. Although the FNR-1 site was not absolutely required, it allowed maximal expression of this promoter. These results suggest that the two sites have an additive effect in coordinating nrdDG expression in response to shifting oxygen concentrations

Triclosan-induced genes Rv1686c-Rv1687c and Rv3161c are not involved in triclosan resistance in Mycobacterium tuberculosis

A key issue towards developing new chemotherapeutic approaches to fight Mycobacterium tuberculosis is to understand the mechanisms underlying drug resistance. Previous studies have shown that genes Rv1686c-Rv1687c and Rv3161c, predicted to encode an ATP-binding cassette transporter and a dioxygenase respectively, are induced in the presence of triclosan and other antimicrobial compounds. Therefore a possible role in drug resistance has been suggested for the products of these genes although no functional studies have been done. The aim of the present study was to clarify the role of Rv1686c-Rv1687c and Rv3161c in M. tuberculosis resistance to triclosan and other drugs. To this end, deficient mutants and overproducing strains for both systems were constructed and their minimal inhibitory concentration (MIC) against over 20 compounds, including triclosan, was evaluated. Unexpectedly, no differences between the MIC of these strains and the wild-type H37Rv were observed for any of the compounds tested. Moreover the MIC of triclosan was not affected by efflux pump inhibitors that inhibit the activity of transporters similar to the one encoded by Rv1686c-Rv1687c. These results suggest that none of the two systems is directly involved in M. tuberculosis resistance to triclosan or to any of the antimicrobials tested