Effect of Pyocyanin on a Crude-Oil-Degrading Microbial Community

Abstract

Pseudomonas aeruginosa is an n-alkane degrader that is frequently isolated from petroleum-contaminated sites and produces factors that enhance its competitiveness and survival in many environments. In this study, one such factor, pyocyanin, has been detected in an oil-degrading culture containing P. aeruginosa and is a redox-active compound capable of inhibiting microbial growth. To examine the effects of pyocyanin further, an oil-degrading culture was grown with and without 9.5 M pyocyanin and microbial community structure and oil degradation were monitored for 50 days. Denaturing gradient gel electrophoresis (DGGE) analysis of cultures revealed a decrease in the microbial community diversity in the pyocyanin-amended cultures compared to that of the unamended cultures. Two members of the microbial community in pure culture exhibited intermediate and high sensitivities to pyocyanin corresponding to intermediate and low levels of activity for the antioxidant enzymes catalase and superoxide dismutase, respectively. Another member of the community that remained constant in the DGGE gels over the 50-day culture incubation period exhibited no sensitivity to pyocyanin, corresponding to a high level of catalase and superoxide dismutase when examined in pure culture. Pyocyanin also affected the overall degradation of the crude oil. At 50 days, the culture without pyocyanin had decreased polycyclic aromatic hydrocarbons compared to the pyocyanin-amended culture, with a specific reduction in the degradation of dibenzothiophenes, naphthalenes, and C 29 and C 30 hopanes. This study demonstrated that pyocyanin influenced the diversity of the microbial community and suggests the importance of understanding how interspecies interactions influence the degradation capability of a microbial community.

Discovery of a biofilm electrocline using real-time 3D metabolite analysis

“…If this hypothesis is true, we predict that addition of another extracellular electron acceptor such as NO 3 − would reduce flux of electrons to PYO, thereby resulting in collapse of the PYO electrocline. To test this prediction, the impact of NO 3 − on the PYO electrocline produced by P. aeruginosa Δphz1/2 in the presence of exogenous PYO was assessed. As expected, in the presence of excess NO 3 − , the PYO electrocline collapsed (Fig.…”

“…To definitively assess whether the collapse of the PYO electrocline was due to diversion of electron flux away from PYO to NO 3 − , the impact of NO 3 − on the PYO electrocline was assessed by using biofilms of a P. aeruginosa napA mutant. NapA is the periplasmic NO 3 − reductase important for reduction of NO 3 − under aerobic conditions (35); thus, the P. aeruginosa napA mutant is unable to divert electrons to NO 3 − under aerobic conditions.…”

“…PYO was chosen for study because it is a multifunctional molecule, serving both as a QS signal (26), a potent antimicrobial in vitro and in situ (3,27), and as a virulence factor important for P. aeruginosa pathogenesis (28,29). Our data reveal that P. aeruginosa biofilms produce high levels of PYO that is actively maintained in the reduced state proximal to the biofilm.…”

“…Cues are chemically and functionally diverse and include primary metabolites arising from central metabolism as well as secondary metabolites. Although dedicated signals have been the focus of significant research over the last 20 y, it is clear that primary and secondary metabolites also impact the species composition and behaviors of microbial communities in vitro and in vivo (3)(4)(5). In some cases, once-presumed dedicated signals have been shown to also act as cues, suggesting that many small molecules may be multifunctional (1,(6)(7)(8).…”

Antibiotic Action of Pyocyanin on Some Pathogenic Bacteria Isolated From Wound Infection.

“…with 31 mm, E. coli with 12 mm, Candida sp. with 12 mm (diameter of inhibition zone) with no antifungal effect (Özyürek Sezen et al, 2016 Norman, 2002). In addition to this, it has been recorded that Gram positive bacilli and cocci are more sensitive to antibacterial effect of pyocyanin than Gram negative bacilli, while all strains P. aeruginosa were highly resistant to pyocyanin (Baront and Rowe, 1981).…”