[Isolation, identification and over- siderophores production of Pseudomonas fluorescens sp-f]

Strain sp-f was isolated, a siderophores over producing bacterium, using an improved universal Chrome Azurol S(CAS)-agar plate method from Donghu Lake. The result of the CAS solution siderophores quantitative determination showed the lowest As/Ar (OD680) ratio could be as low as 0.09 with Su (Siderophore Unit) of 90%. Some more experiments were made to make out the pertinence between its growth and siderophores production, indicating that its siderophores quantity reached maximum amount during the prophase of logarithmic growth. After then, siderophores concentration stopped accumulating and turned to be stable at stationary phase. Based on the characteristics of morphology, cultivation, physiology, (G + C) mol % content, 16S rDNA sequence and BIOLOG Station system analysis, it was identified as Pseudomonas fluorescens sp-f strain. RP-HPLC analysis showed there exist at least 3 kinds of catecholate siderophores, including fluorescent and non-fluorescent pyoverdins. But only fluorescent pyoverdin's excretion was completely repressed by the 200 micromol/L Fe2+ in the medium. And the non-pyoverdin siderophores excretion was induced at the same time, contrarily.