Abstract
Phenazine and its derivatives are very important secondary metabolites produced from Pseudomonas spp. and have exhibited broad-spectrum antifungal and antibacterial activities. However, till date, there are few reports about marine derived Pseudomonas and its production of phenazine metabolites. In this study, we isolated a marine Pseudomonas aeruginosa strain PA31x which produced natural product inhibiting the growth of Vibrio anguillarum C312, one of the most serious bacterial pathogens in marine aquaculture. Combining high-resolution electro-spray-ionization mass spectroscopy and nuclear magnetic resonance spectroscopy analyses, the functional compound against V. anguillarum was demonstrated to be phenazine-1-carboxylic acid (PCA), an important phenazine derivative. Molecular studies indicated that the production of PCA by P. aeruginosa PA31x was determined by gene clusters phz1 and phz2 in its genome. Electron microscopic results showed that treatment of V. anguillarum with PCA developed complete lysis of bacterial cells with fragmented cytoplasm being released to the surrounding environment. Additional evidence indicated that reactive oxygen species generation preceded PCA-induced microbe and cancer cell death. Notably, treatment with PCA gave highly significant protective activities against the development of V. anguillarum C312 on zebrafish. Additionally, the marine derived PCA was further found to effectively inhibit the growth of agricultural pathogens, Acidovorax citrulli NP1 and Phytophthora nicotianae JM1. Taken together, this study reveals that marine Pseudomonas derived PCA carries antagonistic activities against both aquacultural and agricultural pathogens, which broadens the application fields of PCA.
Highlights
There is a perpetual need for novel antibiotics to combat pathogens in the fields of public health, agriculture and aquaculture
In order to obtain potential anti-V. anguillarum compounds, over 400 bacterial strains isolated from marine sediments were evaluated by their abilities to inhibit the growth of V. anguillarum by antagonistic experiment
Phenazines are bacterial secondary metabolites that have long been recognized for their broad-spectrum antibiotic activity and been widely used in the biological control of arrange of bacterial and fungal pathogens (Pierson and Pierson, 2010)
Summary
There is a perpetual need for novel antibiotics to combat pathogens in the fields of public health, agriculture and aquaculture. The majority of microbial natural products have been isolated from terrestrial-borne microbes (Berdy, 2005), and the importance of terrestrial microbes as sources of valuable bioactive metabolites has been well established for more than half a century. With the fast development in marine related fields, recent trends in drug discovery emphasize that marine microorganisms are a potentially productive source of novel secondary metabolites and have great potential to increase the number of marine microbial natural products (Waters et al, 2010). Phenazine and its derivatives are very important secondary metabolites produced from Pseudomonas spp. and have exhibited broad-spectrum antifungal and antibacterial activities (Lee et al, 2003; Kumar et al, 2005; Morales et al, 2010). In China, PCA named Shenqinmycin has received a Pesticide Registration Certification from the Ministry of Agriculture, and widespreadly used against the plant pathogens in the land agriculture related fields because of its high fungicidal efficiency, low toxicity to humans and animals, environmental compatibility, and improvement of crop production (Su et al, 2010)
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