“…According to their primary structure and molecular architecture, the sensor histidine kinases of these two-component regulatory systems can be classified in at least three different phylogenetic groups, i.e., the TodS, TdiS and BphS groups ( Figure 7A ). Hybrid histidine kinases of the TodS family are complex enzymes that contain two sensor PAS domains, i.e., PAS1, that recognizes aromatic hydrocarbons ( Busch et al, 2007 ), and PAS2, involved in dimerization ( Koh et al, 2016 ), two transmitter (autokinase) domains, and a response regulator receiver domain ( Figure 7A ) ( Busch et al, 2009 ). They are involved in the control of the genes for the aerobic degradation of toluene in Pseudomonas putida (TodS) ( Busch et al, 2007 ), P. mendocina (TmoS) ( Silva-Jiménez et al, 2012 ) and, probably, in T. aromatica (TutC) ( Leuthner and Heider, 1998 ), and styrene in some Pseudomonas strains (StyS) ( Velasco et al, 1998 ; Leoni et al, 2003 ).…”