RESUMEN
Despite dramatic advances in genomics, connecting genotypes to phenotypes is still challenging. Sexual genetics combined with linkage analysis is a powerful solution to this problem but generally unavailable in bacteria. We build upon a strong negative selection system to invent mass allelic exchange (MAE), which enables hybridization of arbitrary (including pathogenic) strains of Escherichia coli. MAE reimplements the natural phenomenon of random cross-overs, enabling classical linkage analysis. We demonstrate the utility of MAE with virulence-related gain-of-function screens, discovering that transfer of a single operon from a uropathogenic strain is sufficient for enabling a commensal E. coli to form large intracellular bacterial collections within bladder epithelial cells. MAE thus enables assaying natural allelic variation in E. coli (and potentially other bacteria), complementing existing loss-of-function genomic techniques.
Asunto(s)
Infecciones por Escherichia coli , Proteínas de Escherichia coli , Infecciones Urinarias , Escherichia coli Uropatógena , Humanos , Escherichia coli Uropatógena/genética , Infecciones Urinarias/microbiología , Infecciones por Escherichia coli/microbiología , Proteínas de Escherichia coli/genética , Virulencia/genética , Factores de Virulencia/genéticaRESUMEN
Circulating Ly6Chi monocytes often undergo cellular death upon exhaustion of their antibacterial effector functions, which limits their capacity for subsequent macrophage differentiation. This shrouds the understanding on how the host replaces the tissue-resident macrophage niche effectively during bacterial invasion to avert infection morbidity. Here, we show that proliferating transitional premonocytes (TpMos), an immediate precursor of mature Ly6Chi monocytes (MatMos), were mobilized into the periphery in response to acute bacterial infection and sepsis. TpMos were less susceptible to apoptosis and served as the main source of macrophage replenishment when MatMos were vulnerable toward bacteria-induced cellular death. Furthermore, TpMo and its derived macrophages contributed to host defense by balancing the proinflammatory cytokine response of MatMos. Consequently, adoptive transfer of TpMos improved the survival outcome of lethal sepsis. Our findings hence highlight a protective role for TpMos during bacterial infections and their contribution toward monocyte-derived macrophage heterogeneity in distinct disease outcomes.