Towards an easy production of novel pyoverdines by an antarctic Pseudomonas strain: a spectroscopic and HPLC-MS/MS characterization study

Bacterial secondary metabolites are fundamental molecules not only in several microbial processes, but also in various sectors of today's economy, especially in human health and agriculture. Siderophores are important secondary metabolites produced by various bacterial strains, including Pseudomonas species, under iron-deficient conditions. Pyoverdines are fluorescent types of siderophores with molecular mass between 889 and 1764 Da that have strong affinity to iron and other metals. In this study, Pseudomonas sp. ef1, isolated from a consortium associated with the Antarctic psychrophilic ciliate Euplotes focardii, was cultured under iron-deficiency conditions to induce pyoverdine production, in the presence of 1 % w/v glucose as a sole carbon source. The produced pyoverdines were purified and characterized by UV–Vis, fluorescence spectroscopy and HPLC-MS/MS analysis. The isolated and characterized compounds were represented by two different Group 1 Pyoverdines, both containing six amino acids peptide chain, with the following sequence: cOHOrn-Ala-Thr-Ala-OHAsp-Lys. The two pyoverdines differ only in the sidechain dicarboxylic acid, called RSC, that usually consists either of succinic/malic acid or their monoamide analogues, or glutamic/α-ketoglutaric acid. One of the two pyoverdines produced by Pseudomonas sp. ef1 is reported for the first time. The study of novel pyoverdines contribute to understand the role of secondary metabolites in modulating bacterial consortia. Furthermore, it opens new perspective in different possible applications.