Hydroxamate production by Aquaspirillum magnetotacticum.

Spent culture fluids from Aquaspirillum magnetotacticum MS-1 grown at high (20 microM) but not low (5 microM) iron concentration contained material yielding a positive hydroxamate test. Cells possessed six major outer membrane proteins. Three outer membrane proteins ranging from 72,000 to 85,000 daltons were coordinately produced at iron concentrations conducive to hydroxamate production. A 55,000-dalton iron-repressible outer membrane protein was also present in strain MS-1 cultured at low but not high ferric quinate concentration. Culture fluids from strain MS-1 which were hydroxamate positive augmented growth of a Salmonella typhimurium siderophore-deficient (enb-7) mutant in low-iron medium, suggesting a role of hydroxamate in uptake of iron by the cell.