um ines cent ▁B acter ia : ▁H ast ings ▁investig ations ▁of ▁l umin ous ▁b acter ia ▁acted ▁as ▁a ▁catal yst ▁for ▁the ▁discover ies ▁of ▁the ▁bio chem ical ▁mechan isms ▁involved ▁in ▁their ▁light ▁production , ▁the ▁discovery ▁of ▁a ▁fla vin ▁to ▁be ▁a ▁substr ate ▁in ▁its ▁luc ifer ase ▁reaction , ▁the ▁determ ination ▁of ▁gene ▁reg ulation ▁of ▁the ▁luc ifer ases , ▁and ▁the ▁first ▁evidence ▁for ▁qu orum ▁sens ing , ▁a ▁form ▁of ▁b acter ial ▁communication . ▁In ▁qu orum ▁sens ing ▁( initial ly ▁term ed ▁auto indu ction ), ▁the ▁b acter ia ▁release ▁a ▁subst ance ▁into ▁the ▁medium , ▁the ▁auto ind uc er . ▁Once ▁the ▁concentration ▁of ▁this ▁subst ance ▁reaches ▁a ▁critical ▁level ▁( a ▁measure ▁of ▁the ▁number ▁of ▁b acter ia ▁in ▁a ▁limited ▁area ), ▁trans cription ▁of ▁specific ▁other ▁gen es ▁that ▁had ▁been ▁repr essed ▁are ▁turned ▁on . ▁Once ▁the ▁sequ enced ▁auto ind uc er ▁gene ▁was ▁found ▁to ▁occur ▁widely ▁in ▁gram - negative ▁b acter ia ▁qu orum ▁sens ing ▁became ▁accepted ▁in ▁the ▁early ▁ 1 9 9 0 s . ▁It ▁is ▁now ▁known ▁that ▁in ▁many ▁path ogen ic ▁b acter ia , ▁there ▁is ▁delayed ▁production ▁of ▁to x ins , ▁which ▁serve ▁to ▁greatly ▁augment ▁their ▁path ogen icity , ▁this ▁is ▁similar ▁to ▁what ▁happens ▁for ▁luc ifer ase ▁prote ins . ▁By ▁cur tail ing ▁their ▁to