[Effect of different levels of environmental oxygen on the biofilm production of Pseudomonas aeruginosa].
OBJECTIVE
To investigate the relationship among oxygen concentration, quorum sensing system, type secretion system, and biofilm production of Pseudomonas aeruginosa.


METHODS
A total of 23 clinical strains of Pseudomonas aeruginosa were cultured at different levels of environmental oxygen for three days. Then biofilm mass and alginate were quantified. The expression levels of LasI and RhlI were detected by real time polymerase chain reaction (PCR). The secretion of exoenzyme S was examined by Western blot.


RESULTS
Both the biofilm mass (R=0.455, P=0.000) and alginate (R=0.367, P=0.000) were positively correlated with oxygen concentration. Real time PCR showed that the expression levels of LasI and RhlI were not significantly correlated with oxygen concentration (R=0.025, P=0.794; R=-0.044, P=0.653), the production of biofilm (R=0.001, P=0.990; R=0.011, P=0.909), or alginate(R=0.029, P=0.770; R=0.193, P=0.064). Western blot showed that the optimal oxygen concentration range for exoenzyme S secretion of Pseudomonas aeruginosa ranged 10% to 30%.


CONCLUSIONS
Hyperoxia can promote the production of biofilm and alginate by Pseudomonas aeruginosa. Las/Rhl system may not participate in biofilm production at the early stage due to the low bacteria amount. The increased production of biofilm may inhibit the expression of Type Secretion system and thus inhibit bacterial virulence.
Cui
Dong-Qing
DQ
Graduate School, CAMS and PUMC, Beijing 100730, China.
Sun
Tie-Ying
TY
Li
Jian
J
Huang
Xiu-Qing
XQ
D000464:Alginates / Q000378:metabolism; D018441:Biofilms / Q000187:drug effects*; D010100:Oxygen / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000378:metabolism / Q000502:physiology*; D053038:Quorum Sensing / Q000187:drug effects / Q000502:physiology
D000464:Alginates; D010100:Oxygen