Regulation of Growth and Biofilm Formation of Pseudomonas aeruginosa by Exogenous Hydrogen Sulfide under Oxidative Stress
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Abstract:
The effect of exogenous hydrogen sulfide (H2S) on Pseudomonas aeruginosa (PAO1) growth under hydrogen peroxide (H2O2)-induced oxidative stress conditions was investigated using sodium sulfide hydride (NaHS) as the exogenous H2S-releasing agent. Two groups of Pseudomonas aeruginosa were grown: a control and an experimental group with no NaHS and with 0.2 mmol/L NaHS added to the medium, respectively. The survival rate, cell morphology, DNA extravasation volume, and biofilm growth of the strain in both groups were observed under the oxidative stress induced by 0, 1, 2, and 2.5 mmol/L H2O2. The results showed that with the passage of time (i.e., from 0.5 h to 1 h through to 1.5 h), the survival rate of the cells in the experimental group was significantly lower than that in the control group (p<0.05); i.e., at 0.5, 1, and 1.5 h, the survival rates of the experimental group were reduced by 24.83%, 15.69%, and 11.36%, respectively, under 1 mmol/L H2O2 treatment; by 4.92%, 11.16%, and 5.75%, respectively, under 2 mmol/L H2O2 treatment; and by 6.83%, 2.98%, and 0.39%, respectively, under 2.5 mmol/L H2O2 treatment, relative to those of the control group. The experimental group demonstrated more severe cell morphology damage and DNA extravasation than the control group did. Variations in biofilm formation under different H2O2-induced stress conditions were examined using crystal violet staining, scanning electron microscopy, and confocal laser scanning microscopy. The results showed a significant reduction in biofilm formation by the experimental group compared with that by the control group after 48 and 72 h of culture in Luria-Bertani medium containing 1 or 2 mmol/L H2O2. These results suggest that H2S enhances H2O2-induced PAO1 cell damage in this bacterial strain.
