Siderophores and related outer membrane proteins produced by pseudomonads isolated from eels and freshwater.

A total of 46 environmental pseudomonads, together with six type strains, were examined for their siderophore-producing activity. All strains were able to grow under iron-limiting conditions, gave orange halos in the CAS agar assay, and produced hydroxamates, and some of them also produced phenolate-type compounds. Bioassays showed that all strains, except Pseudomonas aeruginosa, promoted growth of mutant strain Arthrobacter flavescens JG-9, deficient in hydroxamate production, and some of them promoted growth of Salmonella typhimurium enb-1, which requires enterobactin for growth. The presence of iron-regulated outer membrane proteins was observed, the molecular size of the main induced proteins ranged between 76 and 93 kDa.