RESUMEN
Antibiotic-resistant infections are a major threat to global public health and there is an urgent need to develop new drugs and interventions to treat and prevent infections caused by antibiotic-resistant bacteria. The human gut microbiota harbours both commensals and opportunistic pathogens which can acquire resistance to antibiotics through mutation and horizontal gene transfer. The powerful combination of modern high-throughput DNA sequencing and microbiological culture methods is providing novel insights into the mechanisms of antibiotic resistance among, up to recently poorly studied, commensal bacteria in the gut. Interventions to minimise the abundance of antibiotic-resistant commensals and opportunistic pathogens include faecal microbiota transplantation and the use of live biotherapeutics, but the efficacy of these treatments remains elusive.
Asunto(s)
Microbioma Gastrointestinal , Antibacterianos/farmacología , Bacterias/genética , Farmacorresistencia Bacteriana/genética , Microbioma Gastrointestinal/genética , Transferencia de Gen Horizontal , Humanos , SimbiosisRESUMEN
Infections caused by antibiotic-resistant bacteria are a major threat to public health. The pathogens causing these infections can acquire antibiotic resistance genes in a process termed horizontal gene transfer (HGT). HGT is a common event in the human gut microbiome, that is, the microbial ecosystem of the human intestinal tract. HGT in the gut microbiome can occur via different mechanisms of which transduction and conjugation have been best characterised. Novel bioinformatic tools and experimental approaches have been developed to determine the association of antibiotic resistance genes with their microbial hosts and to quantify the extent of HGT in the gut microbiome. Insights from studies into HGT in the gut microbiome may lead to the development of novel interventions to minimise the spread of antibiotic resistance genes among commensals and opportunistic pathogens.
Asunto(s)
Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Bacterias/genética , Farmacorresistencia Bacteriana , Microbioma Gastrointestinal/efectos de los fármacos , Animales , Bacterias/aislamiento & purificación , Bacterias/metabolismo , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Transferencia de Gen Horizontal , HumanosRESUMEN
In Escherichia coli, the marRAB operon is a determinant for antibiotic resistance. Such phenotypes require the encoded transcription factor MarA that activates efflux pump expression. To better understand all genes controlled by MarA, we recently mapped binding of the regulator across the E. coli genome. As expected, many MarA targets were adjacent to genes encoding stress response systems. Surprisingly, one MarA-binding site overlapped the lac operon regulatory region. Here, we show that MarA specifically targets this locus and can block transcription of the lac genes. Repression is mediated by binding of MarA to a site overlapping the lacP1 promoter -35 element. Control of the lac operon by MarA does not impact antibiotic resistance.
Asunto(s)
Escherichia coli/genética , Operón Lac/genética , Antibacterianos/farmacología , Farmacorresistencia Microbiana/genética , Escherichia coli/efectos de los fármacos , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Regiones Promotoras Genéticas/efectos de los fármacos , Regiones Promotoras Genéticas/genética , Transcripción Genética/efectos de los fármacos , Transcripción Genética/genéticaRESUMEN
The spatial organization of genomes is based on their hierarchical compartmentalization in topological domains. There is growing evidence that bacterial genomes are organized into insulated domains similar to the Topologically Associating Domains (TADs) detected in eukaryotic cells. Chromosome conformation capture (3C) technologies are used to analyze in vivo DNA proximity based on ligation of distal DNA segments crossed-linked by bridging proteins. By combining 3C and high-throughput sequencing, the Hi-C method reveals genome-wide interactions within topological domains and global genome structure as a whole. This chapter provides detailed guidelines for the preparation of Hi-C sequencing libraries for bacteria.
Asunto(s)
Cromosomas Bacterianos/química , Cromosomas Bacterianos/genética , Genoma Bacteriano , Genómica , Secuenciación de Nucleótidos de Alto Rendimiento , Conformación Molecular , Escherichia coli/genética , Biblioteca de Genes , Genómica/métodos , Imagenología TridimensionalRESUMEN
Horizontal gene transfer permits rapid dissemination of genetic elements between individuals in bacterial populations. Transmitted DNA sequences may encode favourable traits. However, if the acquired DNA has an atypical base composition, it can reduce host fitness. Consequently, bacteria have evolved strategies to minimize the harmful effects of foreign genes. Most notably, xenogeneic silencing proteins bind incoming DNA that has a higher AT content than the host genome. An enduring question has been why such sequences are deleterious. Here, we showed that the toxicity of AT-rich DNA in Escherichia coli frequently results from constitutive transcription initiation within the coding regions of genes. Left unchecked, this causes titration of RNA polymerase and a global downshift in host gene expression. Accordingly, a mutation in RNA polymerase that diminished the impact of AT-rich DNA on host fitness reduced transcription from constitutive, but not activator-dependent, promoters.
