SRA

Intracellular bacterial pathogens can exhibit large heterogeneity in growth rate inside host cells with major consequences for the infection outcome. If and how the host responds to this heterogeneity remains poorly understood. Here, we combined a fluorescent reporter of bacterial cell division with single-cell RNA-seq analysis to study the macrophage response to different intracellular states of the model pathogen Salmonella enterica serovar Typhimurium. The transcriptomes of individual infected macrophages revealed a spectrum of functional host response states to dividing and non-dividing bacteria. Intriguingly, macrophages harboring non-dividing Salmonella display hallmarks of the pro-inflammatory M1 polarization state and differ little from bystander cells, suggesting that non-dividing bacteria evade recognition by intracellular immune receptors. By contrast, macrophages containing dividing bacteria have turned into an anti-inflammatory, M2-like state, as if fast-growing intracellular Salmonella overcome host defense by reprogramming macrophage polarization. Additionally, our clustering approach reveals intermediate host functional states between these extremes. Altogether our data suggest that gene expression variability in infected host cells shapes different cellular environments, some of which may favor a growth arrest of Salmonella facilitating immune evasion and the establishment of a long-term niche; while others allow Salmonella to escape intracellular antimicrobial activity and proliferate. Overall design: 60 samples