Iron-chelating Hydroxamic Acid (Schizokinen) Active in Initiation of Cell Division in Bacillus megaterium

Abstract

Bacillus megaterium ATCC 19213 secretes a cell division-initiating “schizokinen” (SK) which accumulates during its culture cycle to a concentration inversely proportional to the iron added to a sucrose-mineral salts medium. Secreted SK was purified from culture filtrates as a red Fe (III) chelate, and a fraction with similar biological properties was obtained from whole cells. Infrared spectra of SK, and analyses of unhydrolyzed and acid-hydrolyzed preparations indicated it to be a secondary hydroxamate; visible absorption maxima of the ferric complex showed p H dependency typical of ferric monohydroxamates. Schizokinen preparations from cultures grown at “normal” and at low Fe concentrations were similar biologically and in certain of their chemical properties, but their R F values and infrared spectra suggested nonidentity. Significant lag reduction of B. megaterium was effected by 0.2 mμg of SK per ml; the Fe (III)-SK chelate and “iron-free” SK were equally effective. A 50-mμg amount produced half-maximal growth response of the siderochrome auxotroph, Arthrobacter JG-9. Schizokinen also overcame ferrimycin A inhibition of three Bacillus species. These properties relate the B. megaterium schizokinen to the trihydroxamate siderochromes, although SK appears to be a monohydroxamate.