When all three separate quorum-sensing signals act in concert in Vibrio harveyi, they maximize
bioluminescence and fully repress type III secretion.
V. harveyi has five qrr loci encoding small RNA regulatory molecules, each consisting of about
100 nucleotides; several of them are involved in repressing bioluminescence.
Small RNAs also play roles in population density-dependent activities, including regulation
of virulence factors, for bacterial pathogens such as Pseudomonas fluorescens, V. cholerae, Salmonella enterica, Pseudomonas aeruginosa, and Erwinia spp.
Although some bacteria appear to carry redundant copies of small RNA genes with which to finely tune expression