Fig. 7: Phage enrichment in adherent bacteria.
a Schematic representation of the methodology used in (b). An initial population of the ZΔMDA expressing the PilEZ4 was transduced with MDA(orf6-aadA1)Φ and recovered without selection to have both transduced and non-transduced bacteria in the same population. The population was then incubated in cell culture media and collected or incubated in the presence of epithelial or endothelial cells and only adherent bacteria were collected. The three populations were then plated on agar containing spectinomycin to quantify the percentage of bacteria infected by MDA(orf6-aadA1)Φ. b The proportion of bacteria with MDA(orf6-aadA1) prophage was determined for the three populations. b Experiments were performed three times in duplicate (n = 3). Statistical analyses were performed using a Kruskal–Wallis test with Dunn’s correction for b, and data were expressed as mean ± SEM. Source data are provided as a Source Data file. c Schematic representation of our proposed model of the amplification loop between MDAΦ infection, biofilm formation and enrichment in adhesive PilE variants. The top panel shows the expression of eight possible PilE variants following antigenic variation and coloured according to their PilE charge. Bottom left: a human carrying strains of N. meningitidis with different pili variants and not infected by the MDA phage will spread any PilE expressing bacteria. Bottom right: when an isolate expressing the MDA phage is present in the population, the phage infects bacteria expressing the most adherent PilE variants, which are able to promote themselves in the niche and produce phages. These phage-producing bacteria will form a biofilm at the top of the population11 and will be preferentially disseminated by the host.
