Vibrio cholerae is the responsible agent of the acute diarrhoeal disease cholera. Previous work has shown that V. cholerae possesses several grazing resistance mechanisms against protozoa. For example, V. cholerae survives intracellularly and escapes as viable cells inside protozoan expelled food vacuoles (EFVs). We previously reported that V. cholerae encased in EFVs are hyperinfectious, establishing an important link between anti-protozoal strategies and bacterial virulence. However, the molecular mechanisms behind grazing resistance remain poorly understood. To address this gap in knowledge, this work used the novel single cell RNA-transcriptomics of V. cholerae in coincubation experiments with the ciliated protozoan Tetrahymena pyriformis.
Recent results captured a total of 5,344 bacterial cells with heterogeneous gene expression. Cells with the same pattern of gene expression were grouped, resulting in eleven clusters of cells with a unique gene expression profile. Genes encoding outer membrane proteins, F1F0-Na+/H+ ATPase, metabolites and toxins showed differential expression among the clusters. Furthermore, the motility-associated killing factor (Mak) toxins (makA, makB and makC) were differentially expressed. A V. cholerae ΔmakA strain was not capable of killing T. pyriformis and showed reduced survival inside EFVs compared to the wild type. Our findings reveal new insights into the grazing resistance mechanisms of V. cholerae, identifies factors associated with the survival of V. cholerae within EFVs and more broadly, highlights the connection between antiprotozoal and virulence factors displayed by pathogenic bacteria.