Effect of hmuY and hmuR or husA and husB genes deletion on Porphyromonas gingivalis gene expression

Porphyromonas gingivalis is one of the main etiological agents responsible for initiating and progressing periodontal diseases in humans. P. gingivalis does not synthesize heme, and it uses host hemoproteins as a source of this molecule. The main heme uptake mechanism utilized by P. gingivalis is the Hmu system composed of six proteins where HmuY (hemophore-like protein) and HmuR (TonB-dependant outer membrane heme receptor) play a crucial role in heme supply. The second heme uptake mechanism is the Hus system composed of four proteins, with HusA (hemophore-like protein) and HusB (TonB-dependant outer membrane receptor) supporting heme uptake. Heme and iron starvation influence the P. gingivalis phenotype, therefore the aim was to determine the influence of deletion of HmuY and HmuR (ΔhmuYR strain) or HusA and HusB (ΔhusAB strain) encoding genes on P. gingivalis gene expression. Porphyromonas gingivalis was cultured in heme and iron-rich conditions (Basal medium supplemented with 7.7 µM heme; Hm) or heme and iron-depleted conditions (Basal medium supplemented with 160 μM 2,2-dipyridyl; DIP) until the mid-exponential growth phase (OD600 = 0.5-0.6). Samples were analyzed in three independent biological replicates. Wild-type A7436 strain was cultured in Hm and DIP conditions. ΔhmuYR and ΔhusAB strains were cultured in Hm conditions.