Invasive meningococcal disease is a life-threatening infection caused by Neisseria
meningitidis (Nme). During infection, Nme encounters many niches with differences in
nutrient availability and environmental stressors. Thus, the ability to adapt in response to
these changes is important for bacterial survival and pathogenicity. One way Nme adapts to
its environment is through utilisation of the two-component regulatory system (TCS), MisRS.
The MisRS TCS is implicated in multiple stages of meningococcal virulence and has been
shown to regulate genes implicated in stress response, protein folding, metabolism, and
virulence. However, the signal(s) to which MisRS responds remains unknown. To address
this, we performed a meta-analysis of the putative MisRS regulons from four transcriptomic
studies to identify enriched pathways. We then constructed a reporter system for screening
MisRS signalling. The meta-analysis showed that a total 582 genes were dysregulated in
Neisseria misR mutants. A total of 32 and 23 genes were shared between the two Nme and
two N. gonorrhoeae studies, respectively. Only three genes were common to all four studies:
dsbD which encodes a disulfide reductase essential in pathogenic Neisseria, NEIS1560 which
encodes a putative hemolysin and NEIS1757 (unknown hypothetical).
To elucidate the signal to identify the true regulon, a reporter system which incorporates the
misR promoter upstream of a β-galactosidase reporter was constructed, in addition to a signal
blind MisS mutant. We identified and constructed three mutants based on alignments with E.
coli CpxA signal blind mutants: two amino acid (aa) substitutions (W27C and S250P) and one
partial deletion (MisSΔaa83-121). The mutated MisS alleles were then re-introduced into the
wild-type locus in Nme and reporter assays performed to determine the sensor’s activity. Both
aa substitution mutants resulted in reporter activity equivalent to misS deletion mutants.
However, the MisSΔaa83-121 expressed three to four times more β-galactosidase than wildtype.
In conclusion, we identified key residues in MisS which allowed the construction of a signal
blind sensor. This tool will allow us to identify the inducing signal(s) of MisRS as well as the
regulon to gain a more complete understanding of how Nme can adapt to its human-restricted
environment and cause disease.