Virulence genes and previously unexplored gene clusters in four commensal Neisseria spp. isolated from the human throat expand the neisserial gene repertoire

Commensal non-pathogenicNeisseriaspp. live within the human host alongside the pathogenicNeisseria meningitidisandNeisseria gonorrhoeaeand due to natural competence, horizontal gene transfer within the genus is possible and has been observed. Four distinctNeisseriaspp. isolates taken from the throats of two human volunteers have been assessed here using a combination of microbiological and bioinformatics techniques. Three of the isolates have been identified asNeisseria subflavabiovarperflavaand one asNeisseria cinerea. Specific gene clusters have been identified within these commensal isolate genome sequences that are believed to encode a Type VI Secretion System, a newly identified CRISPR system, a Type IV Secretion System unlike that in otherNeisseriaspp., a hemin transporter, and a haem acquisition and utilization system. This investigation is the first to investigate these systems in either the non-pathogenic or pathogenicNeisseriaspp. In addition, theN. subflavabiovarperflavapossess previously unreported capsule loci and sequences have been identified in all four isolates that are similar to genes seen within the pathogens that are associated with virulence. These data from the four commensal isolates provide further evidence for aNeisseriaspp. gene pool and highlight the presence of systems within the commensals with functions still to be explored.