FIG 4 .

A model for the regulation of biofilm formation in Paracoccus denitrificans based on the work described in this paper. Abbreviations: H-NOX, heme NO and oxygen binding; REC, receiver domain; HK, histidine kinase. GGDEF and EAL are sequence motifs associated with the diguanylate cyclase and phosphodiesterase, respectively. Enzymes and enzyme-catalyzed reactions are shown in black, signaling interactions in blue and gray (the latter indicating pathways that are likely to be indirect). We suggest that Hmp is the dominant pathway for NO metabolism in the static cultures used for biofilm assays.