Kiss and Run – Phosphoglycerol Modifications of N. Meningitidis Pili Mediate Detachment

residues bearing PG. They further report that inactivation of pptB and substitution of pilin serine residue 93 (a conserved and likely site of PG occupancy in strain 8013) led to an approximately two-fold increase in the number of bacteria found in aggregates. Likewise, overexpression of pptB resulted in a decrease in bacterial aggregation. As type IV pili are the predominant effectors of such bacterial aggregates, these results provided a connection between altered pilin modification with PG and a pilus – associated phenotype. In an effort to understand this association, molecular models of the threedimensional structure of pilin and pilus fibers were generated. Here, the data were amenable to the idea that PG site occupancy at serine 93 would negatively impact on lateral interactions between pili implicated in cellular aggregation. In line with this, induction of the de-repressible pptB allele also led to the abrogation in the expression of pili in their bundled or laterally aggregated form. The authors also report that although the initial levels and overall levels of adherence to epithelial cells are statistically indistinguishable between the wildtype, pptB, and pilin mutant carrying the serine to alanine substitution at residue 93, shedding of detached bacteria was 3.5-fold diminished in the latter two strains relative to that of the former. As a consummating result, the authors report that the pptB and pilin mutants carrying the serine to alanine substitution at residue 93 are defective (20-fold) in the capacity to migrate across the epithelial cell monolayer. Make no doubt about it, the work makes fascinating reading. The authors tout their findings as showing that “Through a regulated PTM, N. meningitidis adopts a multiply and-run strategy, presumably selected, and fine-tuned through evolution as a propagation mechanism, key for survival of the bacterium in nature.” But to what degree do the findings made in vitro relate Kiss and run – phosphoglycerol modifications of N. meningitidis pili mediate detachment